This document provides a 3-sentence summary of the key information from the given document:
The document is a white paper from Power Engineers, Inc. that was prepared for CTC Global to discuss conductor performance, reactive power, and voltage management on electric transmission lines. It covers concepts of real and reactive power, the impact of resistance, inductance, and capacitance on transmission lines, and compares the performance of different conductor designs for managing reactive power and voltages. The white paper also includes a case study example to illustrate reactive power and voltage performance on transmission lines.
The Performance Tuning of Seven Level Diode Clamped Multi Level Inverter Mr.M.Madhivhanan
PG Scholar,
Department of Electrical and Electronics Engineering,
Arignar Anna Institute of Science and Technology, Chennai
E-mail: madhivhanan@gmail.com
MODELING OF HYBRID WIND AND PHOTOVOLTAIC ENERGY SYSTEM USING A NEW CONVERTER ...elelijjournal
Renewable energy technologies offers clean, abundant energy gathered from self-renewing resources such as the sun, wind etc. As the power demand increases, power failure also increases. So, renewable energy sources can be used to provide constant loads. A new converter topology for hybrid wind/photovoltaic energy system is proposed. Hybridizing solar and wind power sources provide a realistic form of power generation.
A Comparative Study of Various AC-DC Converters for Low Voltage Energy Harves...paperpublications3
This document compares various AC-DC converters for low voltage energy harvesting applications. It summarizes the operation and simulation results of several bridgeless converter topologies including a standard H-bridge converter, dual polarity boost converter, parallel boost and buck-boost converter, and integrated bridgeless boost rectifier. Simulation results show that the integrated bridgeless boost rectifier provides the highest average output voltage and boost ratio compared to the other converters, making it the most efficient topology for low voltage energy harvesting applications. It also has the advantage of requiring fewer passive components due to the integrated boost and buck-boost operation.
SOLID STATE TRANSFORMER - USING FLYBACK CONVERTERAbhin Mohan
FUTURISTIC ELECTRICAL ENGINEERING PROJECT.
A Device that can step up as well as step down coltage and get output as both DC or AC. Total flexibility of Power using DC link by Flyback Coverter.
IRJET- Review on Various Topologis used for Decoupling of Fluctuating Power i...IRJET Journal
This document reviews various topologies used for decoupling fluctuating power in single-phase AC circuits. It discusses how active power decoupling techniques can help mitigate issues caused by power fluctuations, such as distorted power factor correction and reduced maximum power point tracking efficiency in applications like solar inverters. Specifically, it analyzes a symmetrical half-bridge circuit topology that uses minimal passive components to absorb power surges. The document also reviews several past studies on active power decoupling methods, capacitive energy storage approaches, and the benefits of film capacitors over electrolytic capacitors for power decoupling applications.
A Two-Input Dual Active Bridge Converter for a Smart User Network Using Integ...Alessandro Burgio
The current on the low voltage side of the high
frequency transformer of a dual active bridge converter is
subject to rapid rising and falling edge; in designing the
converter, the peak current is a key factor to achieve robustness
and reliability. To limit the peak current, the adoption of a
further inductor in series with the transformer is a feasible
solution. In this paper the authors propose a novel topology for a
DAB converter useful to deeply reduce the peak current. The
authors also present a 1kW prototype of a DAB converter
implementing the proposed topology and built using integrated
power modules in place of discrete ones. The results of a
laboratory test clearly demonstrated the good dynamic response
of the DAB converter considering a deep step change in power
balancing.
Voltage Control of Dual Active Bridge Converter for CO-Amorphous Core Materia...kuldeep12555
Solid-State Transformer (SST) provides versatile power system operation. In the smart world, there are technologies where everything is incorporated that reduce the size and eventually save time in delivering a fast process. It has been seen that solid-state transformer voltage begins to decrease during operation that needs to be regulated through some control strategy. In this paper, a Dual Active Bridge (DAB) converter has been used to control the voltage of SST that employs the Single-Phase Shift (SPS) technique. For further efficiency improvement Co73(Si, B)27 co-amorphous material has been used for the core of SST because co-amorphous alloy has much lower loss compared with Fe-amorphous cores and have limited saturation flux density. Real-time parameters of core have been used in the analysis. It has been evident from the results that DAB dc-dc converter-based SST with SPS control technique is simple and offers better performance compared to stand-alone SST. It improves the overall performance and efficiency of the system. This paper has been accomplished in Matlab® / Simulink environment.
Keywords: Co73 (Si, B)27 Amorphous Core Material; Solid-State transformer (SST); Dual Active Bridge (DAB); High
voltage (HV) Application.
The document discusses the use of solid state transformers (SST) in wind energy systems. SST can effectively replace conventional transformers and reactive power compensators, increasing the flexibility of wind energy systems. SST integrate rectification, isolation, and inversion stages to provide voltage conversion as well as reactive and active power compensation. The document also describes how SST can be interfaced with wind energy systems to provide benefits such as power factor control, fast isolation during faults, and regulation of both AC and DC loads.
The Performance Tuning of Seven Level Diode Clamped Multi Level Inverter Mr.M.Madhivhanan
PG Scholar,
Department of Electrical and Electronics Engineering,
Arignar Anna Institute of Science and Technology, Chennai
E-mail: madhivhanan@gmail.com
MODELING OF HYBRID WIND AND PHOTOVOLTAIC ENERGY SYSTEM USING A NEW CONVERTER ...elelijjournal
Renewable energy technologies offers clean, abundant energy gathered from self-renewing resources such as the sun, wind etc. As the power demand increases, power failure also increases. So, renewable energy sources can be used to provide constant loads. A new converter topology for hybrid wind/photovoltaic energy system is proposed. Hybridizing solar and wind power sources provide a realistic form of power generation.
A Comparative Study of Various AC-DC Converters for Low Voltage Energy Harves...paperpublications3
This document compares various AC-DC converters for low voltage energy harvesting applications. It summarizes the operation and simulation results of several bridgeless converter topologies including a standard H-bridge converter, dual polarity boost converter, parallel boost and buck-boost converter, and integrated bridgeless boost rectifier. Simulation results show that the integrated bridgeless boost rectifier provides the highest average output voltage and boost ratio compared to the other converters, making it the most efficient topology for low voltage energy harvesting applications. It also has the advantage of requiring fewer passive components due to the integrated boost and buck-boost operation.
SOLID STATE TRANSFORMER - USING FLYBACK CONVERTERAbhin Mohan
FUTURISTIC ELECTRICAL ENGINEERING PROJECT.
A Device that can step up as well as step down coltage and get output as both DC or AC. Total flexibility of Power using DC link by Flyback Coverter.
IRJET- Review on Various Topologis used for Decoupling of Fluctuating Power i...IRJET Journal
This document reviews various topologies used for decoupling fluctuating power in single-phase AC circuits. It discusses how active power decoupling techniques can help mitigate issues caused by power fluctuations, such as distorted power factor correction and reduced maximum power point tracking efficiency in applications like solar inverters. Specifically, it analyzes a symmetrical half-bridge circuit topology that uses minimal passive components to absorb power surges. The document also reviews several past studies on active power decoupling methods, capacitive energy storage approaches, and the benefits of film capacitors over electrolytic capacitors for power decoupling applications.
A Two-Input Dual Active Bridge Converter for a Smart User Network Using Integ...Alessandro Burgio
The current on the low voltage side of the high
frequency transformer of a dual active bridge converter is
subject to rapid rising and falling edge; in designing the
converter, the peak current is a key factor to achieve robustness
and reliability. To limit the peak current, the adoption of a
further inductor in series with the transformer is a feasible
solution. In this paper the authors propose a novel topology for a
DAB converter useful to deeply reduce the peak current. The
authors also present a 1kW prototype of a DAB converter
implementing the proposed topology and built using integrated
power modules in place of discrete ones. The results of a
laboratory test clearly demonstrated the good dynamic response
of the DAB converter considering a deep step change in power
balancing.
Voltage Control of Dual Active Bridge Converter for CO-Amorphous Core Materia...kuldeep12555
Solid-State Transformer (SST) provides versatile power system operation. In the smart world, there are technologies where everything is incorporated that reduce the size and eventually save time in delivering a fast process. It has been seen that solid-state transformer voltage begins to decrease during operation that needs to be regulated through some control strategy. In this paper, a Dual Active Bridge (DAB) converter has been used to control the voltage of SST that employs the Single-Phase Shift (SPS) technique. For further efficiency improvement Co73(Si, B)27 co-amorphous material has been used for the core of SST because co-amorphous alloy has much lower loss compared with Fe-amorphous cores and have limited saturation flux density. Real-time parameters of core have been used in the analysis. It has been evident from the results that DAB dc-dc converter-based SST with SPS control technique is simple and offers better performance compared to stand-alone SST. It improves the overall performance and efficiency of the system. This paper has been accomplished in Matlab® / Simulink environment.
Keywords: Co73 (Si, B)27 Amorphous Core Material; Solid-State transformer (SST); Dual Active Bridge (DAB); High
voltage (HV) Application.
The document discusses the use of solid state transformers (SST) in wind energy systems. SST can effectively replace conventional transformers and reactive power compensators, increasing the flexibility of wind energy systems. SST integrate rectification, isolation, and inversion stages to provide voltage conversion as well as reactive and active power compensation. The document also describes how SST can be interfaced with wind energy systems to provide benefits such as power factor control, fast isolation during faults, and regulation of both AC and DC loads.
PV Cell Fed High Step-up DC-DC Converter for PMSM Drive ApplicationsIJMTST Journal
In this concept novel high step-up dc–dc converter with an active coupled-inductor network is presented for
a sustainable energy system. The proposed converter contains two coupled inductors which can be
integrated into one magnetic core and two switches. The primary sides of coupled inductors are charged in
parallel by the input source, and both the coupled inductors are discharged in series with the input source to
achieve the high step-up voltage gain with appropriate duty ratio, respectively. In addition, the passive
lossless clamped circuit not only recycles leakage energies of the coupled inductor to improve efficiency but
also alleviates large voltage spike to limit the voltage stresses of the main switches. The reverse-recovery
problem of the output diode is also alleviated by the leakage inductor and the lower part count is needed;
therefore, the power conversion efficiency can be further upgraded. The voltage conversion ratios, the effect of
the leakage inductance and the parasitic parameters on the voltage gain are discussed. The voltage stress
and current stress on the power devices are illustrated and the comparisons between the proposed converter
and other converters are given. The simulation results are presented by using Mat lab/Simulink software.
Reactive Power Compensation and Control via Shunt Reactors and Under Ground P...IJERA Editor
In this paper we will cover the techniques used locally to accomplish the reactive power compensation. First, the importance of reactive power compensation is explained through defining the different types of electrical power and showing the effect of power compensation on the electric power network quality. The power under ground cable is the first technique used to compensate for the inductance of overhead transmission lines and power transformers during heavy loading of the network. Then, we explore the application of the two types of shunt reactors in different locations of the network to compensate for the capacitance of the network during light loading. Finally, a conclusion is presented.
Z - Source Multi Level Inverter Based PV Generation SystemIJERA Editor
This document summarizes a research paper on a Z-source multi-level inverter based PV generation system. The paper proposes using a Z-source multi-level inverter instead of a conventional voltage source inverter to improve system performance. It presents mathematical models of the PV panel, Z-source inverter, and MPPT technique. Simulation results show that the Z-source multi-level inverter provides boosting capability, reduces harmonics, and improves efficiency compared to a conventional voltage source inverter for solar energy conversion. The system is able to efficiently supply both linear and non-linear loads.
Generator electricals for slideshare (wecompress.com)David P
Generator or Genset electrical components
Generator electrical calculations
Generator type of loads
what is power factor & how it affects the Generator performance
Generator load calculations
Hardware Implementation of Solar Based Boost to SEPIC Converter Fed Nine Leve...IJPEDS-IAES
Multi level inverters are widely used in high power applications because of
low harmonic distortion. This paper deals with the simulation
and implementation of PV based boost to SEPIC converter with multilevel
inverter. The output of PV system is stepped up using boost to sepic
converter and it is converted into AC using a multilevel inverter.
The simulation and experimental results with the R load is presented in this
paper. The FFT analysis is done and the THD values are compared. Boost to
SEPIC converter is proposed to step up the voltage to the required value. The
experimental results are compared with the simulation results. The results
indicate that nine level inverter system has better performance than seven
level inverter system.
Development and Deployment of Saturated-Core Fault Current Limiters in Distri...Franco Moriconi
Zenergy Power has been developing an inductive-type of fault current limiter (FCL) for electric power grid applications. The FCL employs a magnetically saturating reactor concept which acts as a variable inductor in an electric circuit. In March 2009 Zenergy Power, with funding from the California Energy Commission and the U.S. Department of Energy (DOE), installed an FCL in the Avanti distribution circuit of Southern California Edison’s Shandin substation in San Bernardino, CA. Rated at 15 kV and 1,250 amperes steady-state, the “Avanti” device is the first superconductor FCL installed in a US utility. In January 2010, the “Avanti” device successfully limited its first series of real-world faults when the circuit experienced multiple single-phase and three-phase faults. After successfully validating the performance of a new “compact” saturated-core FCL, Zenergy Power received contracts to install a 12 kV, 1,250 amperes compact FCL in the CE Electric UK grid in early 2011 and a 138 kV, 1,300 amperes FCL at the Tidd substation of American Electric Power in late 2011.
A Novel Three Phase Multi-string Multilevel Inverter with High DC-DC Closed o...rnvsubbarao koppineni
This document proposes and analyzes a novel three-phase multi-string multilevel inverter for photovoltaic systems. The inverter uses a high step-up DC-DC converter to boost and stabilize the output DC voltage from multiple renewable energy sources. It then uses a simplified multilevel inverter topology with only six switches instead of the eight switches used in conventional cascaded H-bridge multilevel inverters, reducing losses. Simulation and experimental results show the inverter provides improved output waveforms, lower harmonics, reduced size and cost compared to other topologies.
Performance of FACTS Devices for Power System Stabilityijeei-iaes
When a power grid is connected to an induction type wind electric generator (WEG), when there is variation in load and wind speed, grid voltage also vary. In this paper, we study what is the impact when there is a variation of load and wind by variation of real power and reactive power consumed by WEG effect of load and wind speed variations on real power supplied and reactive power consumed by the WEG as well as voltage on the grid are studied. The voltage variation in the grid is controlled by reactive power compensation using shunt connected Static VAR Compensator (SVC) comprising Thyristor Controlled Reactor (TCR) and Fixed Capacitor (FC). With the help of Fuzzy Logic Controller (FLC), TCR is operated automatically.
Modeling of solar array and analyze the current transientEditor Jacotech
Spacecraft bus voltage is regulated by power
conditioning unit using switching shunt voltage regulator having
solar array cells as the primary source of power. This source
switches between the bus loads and the shunt switch for fine
control of spacecraft bus voltage. The effect of solar array cell
capacitance [5][6] along with inductance and resistance of the
interface wires between solar cells and power conditioning
unit[1], generates damped sinusoidal currents superimposed on
the short circuit current of solar cell when shunted through
switch. The peak current stress on the shunt switch is to be
considered in the selection of shunt switch in power conditioning
unit. The analysis of current transients of shunt switch in PCU
considering actual spacecraft interface wire length by
illumination of solar panel (combination of series and parallel
solar cells) is difficult with hardware simulation. Software
simulation by modeling solar cell is carried out for a single string
(one parallel) in Pspice [6]. Since in spacecrafts number of
parallels and interface cable length are variable parameters the
analysis of current transients of shunt switch is carried out by
modeling solar array with the help of solar cell model[6] for the
actual spacecraft condition.
Abstract: A traditional boost converter cannot provide high voltage gain because of the equivalent series resistance present in the circuit. Studies are going on to develop high gain boost converters without extremely high duty ratio. Coupled inductor or transformer link can be used in to get a high step up converter. Transformer links make the circuit bulkier. A dual switch step up converter is a compact solution to get high conversion ratio. High voltage gain can be obtained in a dual switch boost converter, with a low voltage and current stress on the switches. Here a method to further improve the voltage gain of a dual switch converter is presented. A dual switch step up DC/DC converter circuit with high voltage gain is explained. The converter achieves high voltage gain with a low duty cycle. For the same conversion ratio, voltage stress across the switches is also low compared to the traditional dual switch converter. Simulation results in MATLAB/Simulink are also presented.
Voltage Flicker Mitigation in Electric Arc Furnace using D-STATCOMIAES-IJPEDS
This article discusses using a D-STATCOM to mitigate voltage flicker caused by an electric arc furnace load. An electric arc furnace is modeled as a time-varying nonlinear resistance controlled by current. Simulation results show that without a D-STATCOM, voltage flicker of 8.8% occurs when the furnace is connected. With Icosφ control of the D-STATCOM, voltage flicker and total harmonic distortion are reduced, and power factor is improved to near unity. The D-STATCOM successfully mitigates the power quality issues caused by the electric arc furnace load.
In this project, main focus is to develop high power density and high efficiency converter with closed loop control for attaining load and line regulation. Complete converter was simulated in PSIM and implemented hardware in CEERI lab.
Design of a Single Phase Isolated Bidirectional AC to DC Converter for Batter...Tom Gibson
This document summarizes the design of a 3 kW bidirectional AC-DC converter for a battery energy storage system. It analyzes a dual active bridge topology with a 100 kHz transformer to interface a 300 V battery bank to a 110 V, 60 Hz grid. The dual active bridge design is presented, showing how the phase shift between bridges can control both the power flow direction and magnitude. Simulation results validate the design and control approach. The grid interface stage is also briefly discussed.
Filter Based Solar Power Generation System with a Seven Level InverterIJMTST Journal
This paper proposes a new solar power generation system, which is composed of a DC/DC power converter and a new seven-level inverter. The DC/DC power converter integrates a DC-DC boost converter and a transformer to convert the output voltage of the solar cell array into two independent voltage sources with multiple relationships. This new seven-level inverter is configured using a capacitor selection circuit and a full-bridge power converter, connected in cascade. The capacitor selection circuit converts the two output voltage sources of DC-DC power converter into a three-level DC voltage and the full- bridge power converter further converts this three- level DC voltage into a seven-level AC voltage. In this way, the proposed solar power generation system generates a sinusoidal output current that is in phase with the utility voltage and is fed into the utility. The salient features of the proposed seven-level inverter are that only six power electronic switches are used and only one power electronic switch is switched at high frequency at any time. A prototype is developed and tested to verify the performance of this proposed solar power generation system.
- The document describes a Matlab/Simulink model of a photovoltaic (PV) array fed multilevel boost converter.
- It includes modeling of the PV array and its voltage-current and power-voltage characteristics, as well as modeling of the multilevel boost converter topology.
- The proposed multilevel boost converter uses one inductor, one switch, and multiple diodes and capacitors to achieve multiple voltage levels at its output and regulate the output voltage.
Modeling and Analysis of a Maximum Power Point Tracking Control for Double St...IRJET Journal
This document presents a mathematical model and analysis of a maximum power point tracking (MPPT) control scheme for a double-stage solar photovoltaic system connected to the power grid. It derives the mathematical model for a boost converter used to increase the voltage from the solar panels and sizes the inductor and capacitor values. It then introduces, models, and compares three MPPT techniques - perturb and observe, incremental conductance, and fuzzy logic control - using MATLAB/Simulink software to optimize the efficiency of extracting power from the solar panels. The goal is to track the maximum power point without oscillations and properly design the passive components of the boost converter to operate in continuous conduction mode and extract maximum power over a range of weather conditions
IRJET - Hybrid Renewable Energy Sources for Power Quality Improvement with In...IRJET Journal
This document discusses hybrid renewable energy sources and power quality improvement using an intelligent controller. It proposes using a hybrid system of renewable energy sources along with a shunt active power filter (APF) controlled by an intelligent controller to improve power quality issues like harmonics. The APF compensates for harmonic current in the system. The document provides details on the various components involved like the choke, linear and non-linear loads, three-phase voltage and current measurement, bridge amplifier, hysteresis control, and power quality (PQ) theory. It also discusses control strategies for the shunt APF like synchronous detection and instantaneous power (p-q) theory methods.
This document discusses power factor improvement. It begins by defining power factor as the cosine of the angle between the voltage and current in an AC circuit. Power factor can be lagging if the current lags the voltage in an inductive circuit, or leading if the current leads the voltage in a capacitive circuit. Low power factor is undesirable as it results in higher equipment ratings, conductor sizes, copper losses and poorer voltage regulation. Power factor can be improved by adding capacitors in parallel with inductive loads to provide a leading reactive current. This reduces the phase angle between voltage and current, increasing the power factor. Other methods of power factor improvement include using synchronous condensers and phase advancers. Improving power factor is important for both
Reactive Power Compensation in 132kv & 33kv Grid of Narsinghpur Areaijceronline
Power Sector is considered to be very important and priority sector as it leads to overall development of country. The cost of installation of new generating units is rising; hence generated electrical energy has to be utilized carefully and efficiently, which changes through each AC cycle. It is proposed to study the effect of group shunt compensation provided for the mix of rural and urban loads, catered from grid sub-stations in the district of Narsinghpur, to assess its adequacy and saving in transmission losses. An optimum combination of compensators which yields maximum benefits in the system shall be worked out. Load Flow Study for the effect of group shunt compensation provided on 132KV bus of 220KV sub-station Narsinghpur and on 33KV buses of 132KV sub stations Srinagar, Narsinghpur, Gadarwara and Burman sub-stations for the mix of rural and urban loads, catered from partial grid network in Narsinghpur district. If reactive power is supplied near the load, the line current can be reduced or minimized, reducing power losses and improving voltage regulation at the load terminals. The leading current drawn by the shunt capacitors compensates the lagging current drawn by the load. The selection of shunt capacitors depends on many factors, the most important of which is the amount of lagging reactive power taken by the load. Objective was to study the effect of group shunt compensation provided for the mix of rural and urban loads, catered from grid sub-stations in the district of Narsinghpur and to assess the adequacy and saving in transmission losses & to work out an optimum combination of compensators which yields maximum benefits in the system. Depending on the stages of 'ON' and 'OFF', operations to be carried out in various permutations and combinations of shunt compensators i.e. switchable capacitor banks provided on 132 KV bus of 220KV substation Narsinghpur and on 33KV buses of 132 KV substations
This document discusses power relationships in electrical systems. It begins by defining key terms like active power, reactive power, apparent power and power factor. It explains that active power is the rate of usable energy transfer while reactive power supplies stored energy in reactive elements. Apparent power is the product of voltage and current and comprises both active and reactive power. Power factor is the ratio of active to apparent power. Inductive loads cause current to lag voltage, lowering the power factor. The document then discusses power factor correction using capacitors and its benefits like increasing system capacity and reducing losses. It provides examples of calculating current, power and load impedance in wye-delta systems.
power factor correction using smart relayHatem Seoudy
This document summarizes active, reactive, and apparent power. It defines these three types of power and provides equations to calculate them for different load types, including resistive, reactive, and resistive/reactive loads. It explains power factor as the ratio of active power to apparent power and discusses causes of low power factor. Typical power factor values are provided for different load types. Improving power factor provides benefits like reduced electricity bills and equipment costs.
This document summarizes a research article that proposes using a Unified Power Quality Compensator (UPQC) device to regulate voltage and mitigate fluctuations at a weak grid connection to a wind farm. The UPQC uses internal control strategies to regulate the voltage at the wind farm terminals using its series converter, and uses its shunt converter to filter wind farm power and prevent voltage fluctuations. The control strategy manages active and reactive power sharing between the series and shunt converters through a common DC link. Simulation results showed the UPQC approach effectively regulated voltage during load changes and rejected power fluctuations from tower shadow effects at the wind turbines.
PV Cell Fed High Step-up DC-DC Converter for PMSM Drive ApplicationsIJMTST Journal
In this concept novel high step-up dc–dc converter with an active coupled-inductor network is presented for
a sustainable energy system. The proposed converter contains two coupled inductors which can be
integrated into one magnetic core and two switches. The primary sides of coupled inductors are charged in
parallel by the input source, and both the coupled inductors are discharged in series with the input source to
achieve the high step-up voltage gain with appropriate duty ratio, respectively. In addition, the passive
lossless clamped circuit not only recycles leakage energies of the coupled inductor to improve efficiency but
also alleviates large voltage spike to limit the voltage stresses of the main switches. The reverse-recovery
problem of the output diode is also alleviated by the leakage inductor and the lower part count is needed;
therefore, the power conversion efficiency can be further upgraded. The voltage conversion ratios, the effect of
the leakage inductance and the parasitic parameters on the voltage gain are discussed. The voltage stress
and current stress on the power devices are illustrated and the comparisons between the proposed converter
and other converters are given. The simulation results are presented by using Mat lab/Simulink software.
Reactive Power Compensation and Control via Shunt Reactors and Under Ground P...IJERA Editor
In this paper we will cover the techniques used locally to accomplish the reactive power compensation. First, the importance of reactive power compensation is explained through defining the different types of electrical power and showing the effect of power compensation on the electric power network quality. The power under ground cable is the first technique used to compensate for the inductance of overhead transmission lines and power transformers during heavy loading of the network. Then, we explore the application of the two types of shunt reactors in different locations of the network to compensate for the capacitance of the network during light loading. Finally, a conclusion is presented.
Z - Source Multi Level Inverter Based PV Generation SystemIJERA Editor
This document summarizes a research paper on a Z-source multi-level inverter based PV generation system. The paper proposes using a Z-source multi-level inverter instead of a conventional voltage source inverter to improve system performance. It presents mathematical models of the PV panel, Z-source inverter, and MPPT technique. Simulation results show that the Z-source multi-level inverter provides boosting capability, reduces harmonics, and improves efficiency compared to a conventional voltage source inverter for solar energy conversion. The system is able to efficiently supply both linear and non-linear loads.
Generator electricals for slideshare (wecompress.com)David P
Generator or Genset electrical components
Generator electrical calculations
Generator type of loads
what is power factor & how it affects the Generator performance
Generator load calculations
Hardware Implementation of Solar Based Boost to SEPIC Converter Fed Nine Leve...IJPEDS-IAES
Multi level inverters are widely used in high power applications because of
low harmonic distortion. This paper deals with the simulation
and implementation of PV based boost to SEPIC converter with multilevel
inverter. The output of PV system is stepped up using boost to sepic
converter and it is converted into AC using a multilevel inverter.
The simulation and experimental results with the R load is presented in this
paper. The FFT analysis is done and the THD values are compared. Boost to
SEPIC converter is proposed to step up the voltage to the required value. The
experimental results are compared with the simulation results. The results
indicate that nine level inverter system has better performance than seven
level inverter system.
Development and Deployment of Saturated-Core Fault Current Limiters in Distri...Franco Moriconi
Zenergy Power has been developing an inductive-type of fault current limiter (FCL) for electric power grid applications. The FCL employs a magnetically saturating reactor concept which acts as a variable inductor in an electric circuit. In March 2009 Zenergy Power, with funding from the California Energy Commission and the U.S. Department of Energy (DOE), installed an FCL in the Avanti distribution circuit of Southern California Edison’s Shandin substation in San Bernardino, CA. Rated at 15 kV and 1,250 amperes steady-state, the “Avanti” device is the first superconductor FCL installed in a US utility. In January 2010, the “Avanti” device successfully limited its first series of real-world faults when the circuit experienced multiple single-phase and three-phase faults. After successfully validating the performance of a new “compact” saturated-core FCL, Zenergy Power received contracts to install a 12 kV, 1,250 amperes compact FCL in the CE Electric UK grid in early 2011 and a 138 kV, 1,300 amperes FCL at the Tidd substation of American Electric Power in late 2011.
A Novel Three Phase Multi-string Multilevel Inverter with High DC-DC Closed o...rnvsubbarao koppineni
This document proposes and analyzes a novel three-phase multi-string multilevel inverter for photovoltaic systems. The inverter uses a high step-up DC-DC converter to boost and stabilize the output DC voltage from multiple renewable energy sources. It then uses a simplified multilevel inverter topology with only six switches instead of the eight switches used in conventional cascaded H-bridge multilevel inverters, reducing losses. Simulation and experimental results show the inverter provides improved output waveforms, lower harmonics, reduced size and cost compared to other topologies.
Performance of FACTS Devices for Power System Stabilityijeei-iaes
When a power grid is connected to an induction type wind electric generator (WEG), when there is variation in load and wind speed, grid voltage also vary. In this paper, we study what is the impact when there is a variation of load and wind by variation of real power and reactive power consumed by WEG effect of load and wind speed variations on real power supplied and reactive power consumed by the WEG as well as voltage on the grid are studied. The voltage variation in the grid is controlled by reactive power compensation using shunt connected Static VAR Compensator (SVC) comprising Thyristor Controlled Reactor (TCR) and Fixed Capacitor (FC). With the help of Fuzzy Logic Controller (FLC), TCR is operated automatically.
Modeling of solar array and analyze the current transientEditor Jacotech
Spacecraft bus voltage is regulated by power
conditioning unit using switching shunt voltage regulator having
solar array cells as the primary source of power. This source
switches between the bus loads and the shunt switch for fine
control of spacecraft bus voltage. The effect of solar array cell
capacitance [5][6] along with inductance and resistance of the
interface wires between solar cells and power conditioning
unit[1], generates damped sinusoidal currents superimposed on
the short circuit current of solar cell when shunted through
switch. The peak current stress on the shunt switch is to be
considered in the selection of shunt switch in power conditioning
unit. The analysis of current transients of shunt switch in PCU
considering actual spacecraft interface wire length by
illumination of solar panel (combination of series and parallel
solar cells) is difficult with hardware simulation. Software
simulation by modeling solar cell is carried out for a single string
(one parallel) in Pspice [6]. Since in spacecrafts number of
parallels and interface cable length are variable parameters the
analysis of current transients of shunt switch is carried out by
modeling solar array with the help of solar cell model[6] for the
actual spacecraft condition.
Abstract: A traditional boost converter cannot provide high voltage gain because of the equivalent series resistance present in the circuit. Studies are going on to develop high gain boost converters without extremely high duty ratio. Coupled inductor or transformer link can be used in to get a high step up converter. Transformer links make the circuit bulkier. A dual switch step up converter is a compact solution to get high conversion ratio. High voltage gain can be obtained in a dual switch boost converter, with a low voltage and current stress on the switches. Here a method to further improve the voltage gain of a dual switch converter is presented. A dual switch step up DC/DC converter circuit with high voltage gain is explained. The converter achieves high voltage gain with a low duty cycle. For the same conversion ratio, voltage stress across the switches is also low compared to the traditional dual switch converter. Simulation results in MATLAB/Simulink are also presented.
Voltage Flicker Mitigation in Electric Arc Furnace using D-STATCOMIAES-IJPEDS
This article discusses using a D-STATCOM to mitigate voltage flicker caused by an electric arc furnace load. An electric arc furnace is modeled as a time-varying nonlinear resistance controlled by current. Simulation results show that without a D-STATCOM, voltage flicker of 8.8% occurs when the furnace is connected. With Icosφ control of the D-STATCOM, voltage flicker and total harmonic distortion are reduced, and power factor is improved to near unity. The D-STATCOM successfully mitigates the power quality issues caused by the electric arc furnace load.
In this project, main focus is to develop high power density and high efficiency converter with closed loop control for attaining load and line regulation. Complete converter was simulated in PSIM and implemented hardware in CEERI lab.
Design of a Single Phase Isolated Bidirectional AC to DC Converter for Batter...Tom Gibson
This document summarizes the design of a 3 kW bidirectional AC-DC converter for a battery energy storage system. It analyzes a dual active bridge topology with a 100 kHz transformer to interface a 300 V battery bank to a 110 V, 60 Hz grid. The dual active bridge design is presented, showing how the phase shift between bridges can control both the power flow direction and magnitude. Simulation results validate the design and control approach. The grid interface stage is also briefly discussed.
Filter Based Solar Power Generation System with a Seven Level InverterIJMTST Journal
This paper proposes a new solar power generation system, which is composed of a DC/DC power converter and a new seven-level inverter. The DC/DC power converter integrates a DC-DC boost converter and a transformer to convert the output voltage of the solar cell array into two independent voltage sources with multiple relationships. This new seven-level inverter is configured using a capacitor selection circuit and a full-bridge power converter, connected in cascade. The capacitor selection circuit converts the two output voltage sources of DC-DC power converter into a three-level DC voltage and the full- bridge power converter further converts this three- level DC voltage into a seven-level AC voltage. In this way, the proposed solar power generation system generates a sinusoidal output current that is in phase with the utility voltage and is fed into the utility. The salient features of the proposed seven-level inverter are that only six power electronic switches are used and only one power electronic switch is switched at high frequency at any time. A prototype is developed and tested to verify the performance of this proposed solar power generation system.
- The document describes a Matlab/Simulink model of a photovoltaic (PV) array fed multilevel boost converter.
- It includes modeling of the PV array and its voltage-current and power-voltage characteristics, as well as modeling of the multilevel boost converter topology.
- The proposed multilevel boost converter uses one inductor, one switch, and multiple diodes and capacitors to achieve multiple voltage levels at its output and regulate the output voltage.
Modeling and Analysis of a Maximum Power Point Tracking Control for Double St...IRJET Journal
This document presents a mathematical model and analysis of a maximum power point tracking (MPPT) control scheme for a double-stage solar photovoltaic system connected to the power grid. It derives the mathematical model for a boost converter used to increase the voltage from the solar panels and sizes the inductor and capacitor values. It then introduces, models, and compares three MPPT techniques - perturb and observe, incremental conductance, and fuzzy logic control - using MATLAB/Simulink software to optimize the efficiency of extracting power from the solar panels. The goal is to track the maximum power point without oscillations and properly design the passive components of the boost converter to operate in continuous conduction mode and extract maximum power over a range of weather conditions
IRJET - Hybrid Renewable Energy Sources for Power Quality Improvement with In...IRJET Journal
This document discusses hybrid renewable energy sources and power quality improvement using an intelligent controller. It proposes using a hybrid system of renewable energy sources along with a shunt active power filter (APF) controlled by an intelligent controller to improve power quality issues like harmonics. The APF compensates for harmonic current in the system. The document provides details on the various components involved like the choke, linear and non-linear loads, three-phase voltage and current measurement, bridge amplifier, hysteresis control, and power quality (PQ) theory. It also discusses control strategies for the shunt APF like synchronous detection and instantaneous power (p-q) theory methods.
This document discusses power factor improvement. It begins by defining power factor as the cosine of the angle between the voltage and current in an AC circuit. Power factor can be lagging if the current lags the voltage in an inductive circuit, or leading if the current leads the voltage in a capacitive circuit. Low power factor is undesirable as it results in higher equipment ratings, conductor sizes, copper losses and poorer voltage regulation. Power factor can be improved by adding capacitors in parallel with inductive loads to provide a leading reactive current. This reduces the phase angle between voltage and current, increasing the power factor. Other methods of power factor improvement include using synchronous condensers and phase advancers. Improving power factor is important for both
Reactive Power Compensation in 132kv & 33kv Grid of Narsinghpur Areaijceronline
Power Sector is considered to be very important and priority sector as it leads to overall development of country. The cost of installation of new generating units is rising; hence generated electrical energy has to be utilized carefully and efficiently, which changes through each AC cycle. It is proposed to study the effect of group shunt compensation provided for the mix of rural and urban loads, catered from grid sub-stations in the district of Narsinghpur, to assess its adequacy and saving in transmission losses. An optimum combination of compensators which yields maximum benefits in the system shall be worked out. Load Flow Study for the effect of group shunt compensation provided on 132KV bus of 220KV sub-station Narsinghpur and on 33KV buses of 132KV sub stations Srinagar, Narsinghpur, Gadarwara and Burman sub-stations for the mix of rural and urban loads, catered from partial grid network in Narsinghpur district. If reactive power is supplied near the load, the line current can be reduced or minimized, reducing power losses and improving voltage regulation at the load terminals. The leading current drawn by the shunt capacitors compensates the lagging current drawn by the load. The selection of shunt capacitors depends on many factors, the most important of which is the amount of lagging reactive power taken by the load. Objective was to study the effect of group shunt compensation provided for the mix of rural and urban loads, catered from grid sub-stations in the district of Narsinghpur and to assess the adequacy and saving in transmission losses & to work out an optimum combination of compensators which yields maximum benefits in the system. Depending on the stages of 'ON' and 'OFF', operations to be carried out in various permutations and combinations of shunt compensators i.e. switchable capacitor banks provided on 132 KV bus of 220KV substation Narsinghpur and on 33KV buses of 132 KV substations
This document discusses power relationships in electrical systems. It begins by defining key terms like active power, reactive power, apparent power and power factor. It explains that active power is the rate of usable energy transfer while reactive power supplies stored energy in reactive elements. Apparent power is the product of voltage and current and comprises both active and reactive power. Power factor is the ratio of active to apparent power. Inductive loads cause current to lag voltage, lowering the power factor. The document then discusses power factor correction using capacitors and its benefits like increasing system capacity and reducing losses. It provides examples of calculating current, power and load impedance in wye-delta systems.
power factor correction using smart relayHatem Seoudy
This document summarizes active, reactive, and apparent power. It defines these three types of power and provides equations to calculate them for different load types, including resistive, reactive, and resistive/reactive loads. It explains power factor as the ratio of active power to apparent power and discusses causes of low power factor. Typical power factor values are provided for different load types. Improving power factor provides benefits like reduced electricity bills and equipment costs.
This document summarizes a research article that proposes using a Unified Power Quality Compensator (UPQC) device to regulate voltage and mitigate fluctuations at a weak grid connection to a wind farm. The UPQC uses internal control strategies to regulate the voltage at the wind farm terminals using its series converter, and uses its shunt converter to filter wind farm power and prevent voltage fluctuations. The control strategy manages active and reactive power sharing between the series and shunt converters through a common DC link. Simulation results showed the UPQC approach effectively regulated voltage during load changes and rejected power fluctuations from tower shadow effects at the wind turbines.
A Fault Current Limiter Circuit to Improve Transient Stability in Power SystemIAES-IJPEDS
Short circuit current limitation in distribution system utilities can be an operational approach to improve power quality, since the estimated voltage sag amplitude during faults may be intensely reduced. The application of superconducting fault current limiter (SFCL) is projected here to limit the fault current that occurs in power system. SFCL utilizes superconductors to instantaneously decrease the unanticipated electrical surges that happen on utility distribution and power transmission networks. SFCL considerably decrease the economic burden on the utilities by reducing the wear on circuit breakers and protecting other expensive equipment. The designed SFCL model is used for determining an impedance level of SFCL according to the fault current limitation necessities of different types of the smart grid system. The representation of this paper about to see the optimum resistive value of SFCL for enhancing the transient stability of a power system. The assessment of optimal resistive value of the SFCL connected in series in a transmission line with a conductor throughout a short circuit fault is consistently determined by applying the equal-area criterion supported by power-angle curves. A Simulink based primary model is developed and additionally the simulation results for the projected model are achieved by using MATLAB.
1. The document discusses issues related to bulk power transmission and the need for Flexible AC Transmission Systems (FACTS) controllers to enhance system controllability and power transfer capacity. It covers topics such as analysis of uncompensated transmission lines, passive reactive power compensation, and voltage control using static var compensators.
2. It provides an overview of various FACTS controllers and their benefits in improving power flow control capability, transient stability, and steady-state voltage stability of power systems. Specific controllers discussed include thyristor controlled series capacitors, static var compensators, and phase shifting transformers.
3. The document presents models and equations for analyzing power flow in AC transmission lines and explains how FACTS controllers can
This document summarizes a research paper that proposes and evaluates a novel interleaved ZCS boost DC-DC converter topology for photovoltaic interfaces. The converter uses two quasi-resonant switch blocks and lossless snubbers to achieve soft switching. Simulation results show the converter achieves reduced voltage and current ripple compared to conventional designs. A dual loop control scheme with an outer voltage loop and inner current loop is used to regulate the output. Coupling inductors between converter cells further improve transient response and reduce ripple. The proposed converter design and control scheme effectively interfaces photovoltaic systems with loads.
Reactive power is necessary to support voltage in AC electrical systems but does no useful work. It is caused by devices with inductive or capacitive properties and can lead to higher electricity costs if not properly managed. Insufficient reactive power can also cause blackouts by leading to voltage collapses. While residential customers are typically not charged for reactive power directly, correcting poor power factor through devices can lower electricity bills by reducing losses from unnecessary current on distribution systems. Proper reactive power management is important for reliability of electricity grids.
This document proposes and validates an equivalent circuit model for a wireless power transfer system capable of transferring 220W of power over a 30cm air gap with 95% efficiency. The model represents the transmitter and receiver coils as inductors with low mutual coupling. Analytical expressions for the model are derived and validated using finite element analysis and experimental results. Loss analysis is also performed to investigate skin effect and proximity effect losses at high operating frequencies. A new coil spatial design is proposed to reduce such losses compared to conventional coil designs.
Power Circuits and Transforers-Unit 5 Labvolt Student Manualphase3-120A
* Active power (P) = 3 kW = 3,000 W
* Inductive reactive power (Q) = 4 kvar
* Using the power triangle:
* Apparent power (S) = √(P^2 + Q^2)
* = √(3,000^2 + 4,000^2)
* = √(9,000,000 + 16,000,000)
* = √25,000,000
* = 5,000 VA = 5 kVA
The apparent power is 5 kVA. The answer is b.
Load switches in power systems may cause oscillations in active and reactive power flow.
Such oscillations can be damped by synthetic inertia provided by smart inverters providing power
from DC sources such as photovoltaic or battery storage. However, AC current provided by inverters
is inherently non-sinusoidal, making measurements of active and reactive power subject to harmonic
distortion. As a result, transient effects due to load switching can be obscured by harmonic distortion.
An RLC circuit serves as a reference load. The oscillation caused by switching in the load presents as
a dual-sideband suppressed-carrier signal. The carrier frequency is available via voltage data but the
phase is not. Given a group of candidate signals formed from phase voltages, an algorithm based on
Costas Loop that can quickly quantify the phase difference between each candidate and carrier (thus
identifying the best signal for demodulation) is presented. Algorithm functionality is demonstrated
in the presence of inverter-induced distortion.
The document discusses power quality issues in power systems. It defines various power quality issues such as voltage fluctuations, sags, swells, interruptions, harmonic distortion, and current and voltage imbalances. It states that power quality is concerned with deviations from ideal sinusoidal voltages and currents. The sources of power quality issues are described as nonlinear loads containing power electronic devices, capacitor banks, and static converters, which can cause problems like harmonic resonance.
Power Flow Control using Quadrature Boostersbalasubu2k
This document discusses using quadrature boosters (QBs) to control real power flows on transmission lines. QBs are similar to phase shifters but allow control of both voltage magnitude and angle. The author proposes modifying power flow equations to include the voltage injected by QBs. Simulations on 5-bus, 30-bus, and 115-bus test systems showed the calculated QB voltages achieved desired real power flows. Optimal power flow control using QBs is also discussed to meet thermal limits and scheduled loads while maintaining voltages.
Design of Shunt Active Power Filter to eliminate harmonics generated by CFLpaperpublications3
Abstract: The use of non-linear loads; such as TV sets and computer, microwave ovens, multiple low power diode rectifier, fluorescent lamps and electric drives, draw very distorted currents. These non-linear loads lead to generation of current/voltage harmonics and draw reactive power. This paper presents the three-phase shunt active power filter (SAPF) to compensate harmonics generated by non-linear load (compact fluorescent lamp). The instantaneous active and reactive power theory (called p-q theory) is used to design the control of SAPF. The harmonic distortion and the active filter control scheme have been verified by MATLAB simulation.
An all-electric driveline based on a double wound flywheel, connected in series between main energy storage and a wheel motor, is presented. The flywheel works as a power buffer, allowing the battery to deliver optimized power. It also separates electrically the system in two sides, with the battery connected to the low voltage side and the wheel motor connected to the high voltage side. This paper presents the implementation and control of the AC/DC/AC converter, used to connect the flywheel high voltage windings to the wheel motor. The converter general operation and the adopted control strategy are discussed. The implementation of the AC/DC/AC converter has been described from a practical perspective. Results from experimental tests performed in the full-system prototype are presented. The prototype system is running with satisfactory stability during acceleration mode. Good efficiency and unity power factor could be achieved, based on vector control and space vector modulation
The document summarizes information about power factor correction. It defines key terms like working power, reactive power, and apparent power. It then explains that power factor is a measure of efficiency and discusses common causes of low power factor like induction motors. The document lists devices used for power factor improvement like static capacitors and synchronous condensers. It outlines issues with low power factor like higher utility bills and lower system capacity. Finally, it discusses benefits of power factor correction like reduced electricity bills and environmental benefits from improved energy efficiency.
Improved Power Quality by using STATCOM Under Various Loading ConditionsIJMTST Journal
This document discusses improving power quality using a STATCOM under various loading conditions. It first provides background on power quality issues and defines STATCOM. It then describes the system topology which includes a wind energy generation system connected to the grid along with a STATCOM and battery energy storage system. Two control schemes for the STATCOM are proposed: Bang-Bang current control and fuzzy logic control. Simulation results using MATLAB/Simulink are presented for various cases including balanced/unbalanced linear and non-linear loads, showing the STATCOM is able to mitigate power quality issues and regulate voltage.
the ratio of the actual electrical power dissipated by an AC circuit to the product of the r.m.s. values of current and voltage. The difference between the two is caused by reactance in the circuit and represents power that does no useful work.
This document summarizes reactive power management in India. It begins by defining the different types of power: active power, which does actual work; reactive power, which doesn't do work but is needed to support voltage; and apparent power, which is the combination of active and reactive power. It then discusses the necessity of reactive power to support voltage and enable the transmission of active power. The document outlines issues India faced with an electricity blackout in 2012 due to underestimating the importance of reactive power. It describes various methods to compensate for reactive power, such as shunt compensation, series compensation, and FACTS devices. It concludes by discussing India's growing need to strengthen its transmission network through improved reactive power management to meet increasing power
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Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
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CTC Global ACCC Conductor Performance
1. October 9, 2013
CTC GLOBAL
Conductor Performance
White Paper
Revision 0
PROJECT NUMBER:
131411
PROJECT CONTACT:
Larry Henriksen
EMAIL:
lhenriksen@powereng.com
PHONE:
208.788.3456
2. POWER ENGINEERS, INC.
HLY 099-1887 (SR-06) CTCG (10/09/13) LLH 131411 REV. 0
Conductor Performance White Paper
PREPARED FOR:
CTC GLOBAL
PREPARED BY:
LARRY HENRIKSEN, P.E. – 208.788.3456 – LHENRIKSEN@POWERENG.COM
JON LEMAN, P.E. – 509.758.6029 – JON.LEMAN@POWERENG.COM
SIVASIS PANIGRAHI, P.E. – 503.892.6742 – SPANIGRAHI@POWERENG.COM
REVISION HISTORY
REV.
ISSUE
DATE
ISSUED
FOR
PREP
BY
CHKD
BY
APPD
BY
NOTES
0 10/09/13 Impl LLH JTL SP For use
“Issued For” Definitions:
- “Prelim” means this document is issued for preliminary review, not for implementation
- “Appvl” means this document is issued for review and approval, not for implementation
- “Impl” means this document is issued for implementation
- “Record” means this document is issued after project completion for project file
3. POWER ENGINEERS, INC.
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i
TABLE OF CONTENTS
INTRODUCTION................................................................................................................................1
EXECUTIVE SUMMARY..................................................................................................................1
THEORY...............................................................................................................................................2
ENERGY AND POWER..........................................................................................................................2
REAL (ACTIVE) POWER AND REACTIVE POWER ................................................................................2
RESISTANCE, INDUCTANCE, AND CAPACITANCE ...............................................................................5
Resistance and Real Power Conversion .........................................................................................5
Inductance and Reactive Power Consumed....................................................................................6
Capacitance and Reactive Power Supplied ....................................................................................6
Inductance Cancels Capacitance ....................................................................................................7
ELECTRIC TRANSMISSION LINES ..............................................................................................8
REAL POWER LOSSES .........................................................................................................................8
REACTIVE POWER LOSS .....................................................................................................................9
REACTIVE POWER SUPPLY ...............................................................................................................10
REACTIVE POWER AND LINE LOADING ............................................................................................11
REACTIVE POWER FLOW AND VOLTAGE..........................................................................................13
CONDUCTOR COMPARISON .......................................................................................................13
REACTIVE POWER AND VOLTAGE MANAGEMENT ...........................................................20
OVERVIEW ........................................................................................................................................20
EXAMPLE ..........................................................................................................................................22
CONCLUSIONS.................................................................................................................................26
4. POWER ENGINEERS, INC.
HLY 099-1887 (SR-06) CTCG (10/09/13) LLH 131411 REV. 0
1
INTRODUCTION
This white paper was prepared for CTC Global by POWER Engineers, Inc. to address:
Real (active) and reactive power concepts
The creation and consumption of reactive power in electric transmission lines
The effect of reactive power on system voltages
Equipment for managing reactive power and system voltages
Comparison of reactive power performance of different conductor designs
A simple case study illustrating reactive power and voltage performance
EXECUTIVE SUMMARY
Replacing conventional conductors such as aluminum conductor steel reinforced (ACSR) with one of
the high temperature conductors such as aluminum conductor composite core (ACCC) or aluminum
conductor steel supported (ACSS) of the same diameter can be a cost effective way to increase the
transfer capacity of transmission lines. Maintaining the same conductor diameter makes it likely that
existing structures can be used and with proper conductor selection and application ground clearances
can normally be maintained.
Increasing power transfer will impact reactive power consumption, and therefore voltage, as well as
real power losses. Voltage drop and reactive power flow are related and interdependent. Reactive
power flows from high voltage to low voltage. Adding shunt capacitors to increase the supply of
reactive power will increase voltage.
The internal construction of conductors does not have a significant impact on the amount of reactive
power supplied and consumed or voltage performance. So long as voltage remains constant the
reactive power supply and consumption in an electric transmission line are primarily determined by
the number of subconductors per phase, their diameter, and their spacing; along with the phase to
phase spacing. Reactive power losses will be the same regardless of conductor type selected so long
as the conductor diameters are the same.
Adding shunt capacitors or other reactive power sources can increase the ability to transfer power
over transmission lines significantly, however reactive power losses vary with the square of current
(or power transmitted) and this imposes practical upper limits on the ability to increase power transfer
through the addition of shunt capacitors.
Real power losses vary directly with the resistance of the conductor, which is heavily influenced by
the internal construction of the conductor as well as by the material used in the conductor.
Conductors with relatively small cores using trapezoidal strands will have a larger cross sectional area
of aluminum compared to other designs with the same overall diameter and will have significantly
lower resistances and lower electrical losses as a result.
5. POWER ENGINEERS, INC.
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2
THEORY
Energy and Power
Energy is defined in IEEE 100, The Authoritative Dictionary of IEEE Standards Terms, Seventh
Edition (IEEE Dictionary), as “That which does work or is capable of doing work.”. In the
International System of Units (SI) the unit for energy is a Joule (J), which in usual electrical units can
be defined as a Watt-second. (W-s). One J can also be defined as a Newton-meter (N-m) which is
force times distance. In either definition energy is the ability to do a defined amount of work.
Power is defined in the IEEE Dictionary as “The rate of generating, transferring, or using energy.”.
In the SI system it is expressed in Joules/sec or Watts.
Energy is power summed over a period of time. In mathematical terms:
Equation 1)
In the case where Power is constant over time:
Equation 2)
Real (Active) Power and Reactive Power
In alternating current (AC) electrical systems power is classified as real power (also referred to as
active power) and reactive power.
Real power is power that is being generated, consumed, or transported that can be used to perform
“real” work, for example heating a building or pumping water. Real power is expressed in units of
Watts (W), kilowatts (kW) which is 1000 W, and megawatts (MW) which is 1,000,000 W. Real
power is also referred to as active power. The symbol “P” is used for real power.
Reactive power can be present in alternating current (AC) power systems. Reactive power is power
which is stored in or being transported to be stored in electric or magnetic fields. Reactive power is
expressed in units of Volt-Ampere reactive (VAr), kilo Volt Ampere reactive (kVAr) or mega Volt
Ampere reactive (MVAr) to differentiate it from real power. Please note that in terms of fundamental
SI units W and VAr (or VA) are equivalent and can be used together in mathematical equations so
long as proper mathematical accommodations are made. The symbol “Q” is used for reactive power.
Real power and reactive power are related by the equation:
Equation 3)
6. POWER ENGINEERS, INC.
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3
Where S is total power, P is real power, Q is reactive power and j is defined as the square root of -1.
The bar above the symbol S indicates that in this formulation S is a vector, with both magnitude and
angle. S is usually expressed in VA, kVA or MVA.
The magnitude of total power is:
Equation 4)
The magnitude of current flowing through a conductor in a balanced three phase system is:
Where I is the magnitude of current in amperes (A), S is the magnitude of total power and Vll is the
line to line voltage of the system in Volts (V), or kV. S and Vll need to be expressed in matching
units (e.g. kVAr and kV).
It is important to note that reactive power flow results from the exchange of energy between electric
and magnetic fields at system frequency, usually 50 or 60 times per second (50 or 60 Hz). Electric
current results from this flow of energy. However in an ideal system (a system without resistance and
therefore without real power losses) no real power is consumed in the transfer and temporary storage
of the energy. Stated differently no fuel would have to be supplied to the electric generator prime
mover to support the flow of reactive power in an ideal lossless system.
The energy transferred in reactive power flow would be capable of doing work, but is not accessible.
It is either trapped in the capacitive (electric field) and inductive (magnetic field) elements of the AC
electrical system, or is in transit between the capacitive and inductive elements of the system.
Reactive power flow does affect system voltage and can be managed by application of equipment
which will offset or supplement reactive power flow occurring in the electrical system.
Refer to Figure 1 for a graphical summary of this discussion.
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Figure 1 – Real Power (P) and Reactive Power (Q)
Reactive power is normally described as being:
“consumed” or “lost” in inductive circuit elements, typically shunt (line to line or line to
ground) connected inductors (usually referred to as shunt reactors) or the series inductive
impedance in electric transmission lines. Inductive elements store energy in magnetic fields.
An under excited synchronous generator will consume reactive power.
“supplied” by capacitive circuit elements, typically shunt connected capacitors or the shunt
capacitive impedance in electric transmission lines. Capacitive elements store energy in
electric fields. An over excited synchronous generator will supply reactive power.
The phase angle of current into inductive circuit elements is 180 degrees out of phase with the current
into capacitive elements. Consequently the current from inductive and capacitive elements cancel.
Reactive power supplied by capacitive circuit elements leads to a voltage rise on an electrical system,
while reactive power consumed by inductive elements leads to reduced voltage.
In an electric transmission system reactive power flows from system buses that have higher voltage
towards system buses that have lower voltage.
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Reactive power consumed by an inductive element is often referred to as reactive power loss. In this
report either term may be used and the reader should be aware that these terms are synonymous.
The use of the terms “supply”, “consume” or “loss” as they apply to reactive power are not precise
technical terms but are commonly used as a matter of convenience. In an ideal (no real power loss)
system reactive power is not consumed, lost or supplied. Instead it is stored and released at system
frequency (usually 50 or 60 times per second) as electric and magnetic fields build up and collapse.
Resistance, Inductance, and Capacitance
Resistor
Inductor (Often Called a Reactor)
Capacitor
Figure 2 – Symbols for Resistors, Inductors, and Capacitors
Resistance, inductance and capacitance are properties used to mathematically describe behavior of
electrical systems. The circuit elements for these properties are resistors, inductors and capacitors.
See Figure 2 for the drawing symbols for these circuit elements.
Resistance and Real Power Conversion
This discussion applies to both AC and DC circuits.
Resistance is the property associated with real power consumption. Real power consumption can
occur intentionally (as in the following space heater example) or unintentionally (as with real power
losses in a transmission line). An everyday example of a resistor is the coil in an electric space
heater. When the heater is turned on voltage is applied across coil of the heater, current flows, and
the rate that electrical energy is converted to thermal energy is described by the following equation:
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Where P is the electrical power converted to heat in W, I is the electrical current in A, V is the voltage
across the resistor (heater coil in this case) in Volts (V) and R is the resistance of the heater coil in
Ohms (Ω).
It is important to note that P is proportional to the square of the current (or alternatively with the
voltage across the resistor), with the result that if the current is doubled the rate electrical energy is
converted to heat quadruples.
Inductance and Reactive Power Consumed
This discussion applies only to AC circuits.
Inductance is the property associated with energy storage in magnetic fields. The reactive power
consumed in an inductor, which is the rate that power is stored and released every power system
cycle, is:
Where Q is the reactive power in VAr, I is the current through the inductor in A, π is the constant pi
(3.14159 . . . .), f is the system frequency in Hertz (Hz), L is the inductance in Henries (H) and V is
the voltage across the inductor in V.
Equation 7) can be simplified to:
Where XL is the inductive reactance which is defined as 2π f L and has the units of Ω. The inductive
reactance is a convenient and regularly used unit for expressing inductance for AC systems. Note the
form of the equation is the same as equation 6).
The amount of reactive power consumed by an inductive element varies with the square of the
electrical current passing through the element or alternatively with the voltage across the element.
For example if the current doubles then the reactive power consumed will quadruple.
Capacitance and Reactive Power Supplied
Capacitance is the property associated with energy storage in electric fields. The reactive power
supplied by a capacitor, which is the rate at which power stored and released every power system
cycle, is:
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Where Q is the reactive power in VAr, V is the voltage across the capacitor in V, π is the constant pi
(3.14159 . . . .), f is the system frequency in Hertz (Hz), C is the capacitance in Farads (F) and I is the
current through the capacitor in A.
Equation 9) can be simplified to:
Where XC is the capacitive reactance which is defined as 1/(2πfC) and has the units of Ω. The
capacitive reactance is a convenient and regularly used unit for expressing capacitance for AC
systems. Note the form of this equation is the same as equations 6) and 8).
When transmission line shunt capacitance is involved equation 10) is often restated as:
Where BC is the capacitive susceptance (usually just called susceptance) and is usually expressed in
Siemens (S) or microSiemens (μS); or alternatively in mhos (mhos is Ohms spelled backwards) or
micromhos. Susceptance is the inverse of XC or 2 π f C. It is a convenient unit in transmission line
performance analysis and will be used in subsequent discussions.
The amount of reactive power supplied by a capacitor varies with the square of the voltage energizing
the capacitor (or alternatively with the square of the current flowing through the capacitor). For
example if the voltage increases 10% then the amount of reactive power supplied by a capacitor will
increase 21%.
Inductance Cancels Capacitance
It is important that the current through an inductor is most positive when the current through a
capacitor is most negative (180 degrees out of phase). Consequently the current from a capacitor and
inductor, when added together, will cancel one another.
Stated differently a capacitor will supply the reactive power consumed in an inductor (often referred
to as a reactor in power systems).
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ELECTRIC TRANSMISSION LINES
Electric transmission lines have resistance, inductance and capacitance. Figure 3 shows a simplified
equivalent circuit for an overhead transmission line, including series (in line) resistance, series
inductance, and shunt capacitance. Connecting one side of the capacitor symbol to ground, denoted
by the ground ( ) symbol, identifies this as a shunt (line to line or line to ground) capacitance.
For illustration resistances, inductances and capacitances are shown as discrete elements, however in
reality they are continuously distributed along the transmission line.
Figure 3 – Overhead Transmission Line Equivalent Circuit
Real Power Losses
Real power losses are caused by electrical current flowing through the series resistance ( ) in the
transmission conductors (resistance losses) and by electricity discharging into the air (corona).
Corona losses are very low except at EHV voltages and even there are less than 10% of total losses.
Additionally corona losses are much higher during foul weather making them statistical in nature.
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They are related to subconductor diameter and bundling but not conductor type, as they are a surface
area, surface condition, voltage and weather related phenomenon. Corona losses should not normally
be a factor in selecting the type of conductor and won’t be discussed further.
Resistance losses vary directly with the resistance of the conductor. Resistance is primarily a
function of:
Cross sectional area of conducting material – Resistance is nearly proportional to the cross
sectional area of conductor(s). A two subconductor bundle will have half the resistance of a
single conductor and a three subconductor bundle one-third the resistance of a single
conductor.
Conductor material – Aluminum and its alloys used in electrical conductors can vary in
resistivity by 20% or more, from about 64% International Annealed Copper Standard (IACS)
to 52.5% IACS.
Temperature of conductor – The resistivity of aluminum used in conductor will vary about
0.4% per °C. For example raising conductor temperature from 25 C to 100 C would increase
resistance by about 30%.
Frequency – AC current tends to flow toward the outside of the conductor. This is called skin
effect and is higher at higher frequencies. For a homogenous conductor (no core) the
difference in resistance between 50 Hz and 60 Hz could be negligible while for a large high
strength ACSR conductor with a large core the resistance at 60 Hz could be on the order of
3% higher than at 50 Hz.
There are other factors aside from conductor characteristics that impact line losses. Obviously but
importantly line resistance and losses vary directly with the length of the line. In addition 1) the
presence of overhead ground wire(s) will also increase losses slightly due to circulating currents in
the ground wire(s) and 2) unequal current distribution between phases can also cause a slight increase
in losses. The losses for these two causes can rise to the level where mitigation in the form of
insulated and segmented overhead ground wires and adding transposition structures can be cost
effective. These issues are independent of conductor selection and will not be discussed further.
As described in the earlier calculations real power losses vary with the square of the current flowing
through the line. For example if current were doubled real power losses would quadruple.
Line losses vary directly with the length of the line.
Reactive Power Loss
Reactive power losses are caused by electrical current flowing through the series inductance
( ) in the transmission line.
As noted in the theory section inductance is an electrical property associated with the storage of
energy in magnetic fields. Reactive power consumption in AC circuits varies directly with the
inductive reactance of the circuit which is a function of:
Frequency – Inductive reactance varies directly with frequency in Hz. See equation 8).
Conductor diameter for single conductor designs – Larger diameter conductors reduce
inductive reactance of the line. For example going from a small conductor (336.4 kcm or
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170.5 mm2
ACSR) to a large conductor (1590 kcm or 805.7 mm2
ACSR) on a 138 kV H-
frame line would result in a reduction in series inductive reactance and reactive power losses
of approximately 11.4%.
Subconductor diameter, number of subconductors and bundle spacing for bundled circuit
designs – Larger diameter conductor, more subconductors, and larger bundle spacing reduce
inductive reactance. For example going from a large single conductor (1590 kcm or 805.7
mm2
ACSR) on a 230 kV H-Frame line to a two subconductor bundle of equivalent cross
sectional area (2 x 795 kcm or 2 x 402.8 mm2
ACSR) or to a three subconductor bundle of
approximately equivalent cross sectional area (3 x 556.5 kcm or 3 x 282 mm2
ACSR) would
result in a reduction in series inductive reactance and reactive power losses of approximately
24.6% and 33.6% respectively.
Phase to phase spacing - Reducing phase to phase spacing reduces inductive reactance. For
example a 230 kV line with a two subconductor bundle of mid-sized conductors (795 kcm or
402.8 mm2
ACSR) constructed on a compact monopole structure would have approximately
6.8% lower series inductive reactance and reactive power losses than an H-Frame design.
Line inductive reactance and losses vary directly with the length of the line.
As described in the earlier calculations reactive power losses vary with the square of the current
flowing through the line. For example if current were doubled reactive power losses would
quadruple.
Reactive Power Supply
Reactive power supply is caused by the electric transmission voltage applied across the shunt
capacitance ( ) that exists between the phase conductors of the transmission line.
As discussed in the theory section capacitance is an electrical property associated with the storage of
energy in electric fields. Reactive power supply in AC circuits varies directly with the shunt
capacitive susceptance (susceptance) of the circuit. The susceptance and therefore the amount of
reactive power supplied is a function of:
Frequency – Reactive power supplied varies directly with frequency in Hz. See equation 11).
Conductor diameter for single conductor designs – Larger diameter conductor increases
susceptance and the amount of reactive power supplied. For example going from a small
conductor (336.4 kcm or 170.5 mm2
ACSR) to a large conductor (1590 kcm or 805.7 mm2
ACSR) on a 138 kV H-frame line would result in an increase in susceptance and reactive
power supplied of approximately 13.4%.
Subconductor diameter, number of subconductors and bundle spacing for bundled circuit
designs – Larger diameter conductor, more subconductors, and larger bundle spacing increase
susceptance. For example going from a large single conductor (1590 kcm or 805.7 mm2
ACSR) on a 230 kV H-Frame line to a two subconductor bundle of equivalent cross sectional
area (2 x 795 kcm or 2 x 402.8 mm2
ACSR) or to a three subconductor bundle of
approximately equivalent cross sectional area (3 x 556.5 kcm or 3 x 282 mm2
ACSR) would
result in an increase in susceptance and reactive power supplied of approximately 31.8% and
49.5% respectively.
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Phase to phase spacing - Reducing phase to phase spacing increases susceptance. For
example a 230 kV line with a two subconductor bundle of mid-sized conductors (795 kcm or
402.8 mm2
ACSR) constructed on a compact monopole structure would have approximately
5.8% higher susceptance and reactive power supplied than an H-Frame design.
Ground clearance and sag have insignificant impact on the susceptance and the amount of reactive
power supplied by a transmission line. A 20 m (65.6 ft) increase in line clearance for the 230 kV H-
Frame two subconductor bundle line resulted in a less than 1% decrease on susceptance.
Susceptance varies directly with the length of the line.
Reactive power supplied varies with the square of the voltage on the line. For example if voltage
were increased 10% reactive power supplied would increase 21%.
The current flowing through the shunt capacitances on the line (described as a susceptance for
calculation purposes) results in current flowing on the conductors. The capacitive current flowing in
the conductors is often referred to as line charging current.
On long unloaded or lightly loaded high voltage lines there can be significant and unacceptable
increases in remote line end voltages a result of the charging current and reactive power flow.
TABLE 1 - REPRESENTATIVE TRANSMISSION LINE ELECTRICAL POSITIVE SEQUENCE REACTANCE AND SUSCEPTANCE
STRUCTURE
TYPE
EQUIVALENT
PHASE
SPACING
BUNDLE/
CONDUCTOR
CONDUCTOR
DIAMETER
AL AREA PER
CONDUCTOR
SERIES INDUCTIVE
REACTANCE
SHUNT CAPACITIVE
SUSCEPTANCE
ft m in mm kcm mm2 Ω/mi Ω/km Change μS/mi μS/km Change
138 kV H Frame 19.5 5.95 1 x Linnet ACSR 0.720 18.3 336.4 170.5 0.8096 0.5031 Base 5.277 3.279 Base
138 kV H Frame 19.5 5.95 1 x Falcon ACSR 1.545 39.2 1590.0 805.7 0.7176 0.4459 -11.4% 5.986 3.720 13.4%
230 kV H Frame 24.6 7.50 1 x Falcon ACSR 1.545 39.2 1590.0 805.7 0.7457 0.4634 Base 5.775 3.588 Base
230 kV H Frame 24.6 7.50 2 x Drake ACSR 1.108 28.1 795.0 402.8 0.5621 0.3493 -24.6% 7.614 4.731 31.8%
230 kV H Frame 24.6 7.50 3 x Dove ACSR 0.927 23.5 556.5 282.0 0.4952 0.3077 -33.6% 8.636 5.366 49.5%
230 kV H Frame 24.6 7.50 2 x Drake ACSR 1.108 28.1 795.0 402.8 0.5621 0.3493 Base 7.614 4.731 Base
230 kV Monopole 16.5 5.03 2 x Drake ACSR 1.108 28.1 795.0 402.8 0.5237 0.3254 -6.8% 8.052 5.004 5.8%
Reactive Power and Line Loading
Figure 4 illustrates the interaction between the power transmitted through a transmission line and the
supply and reactive power consumption in an electric transmission line.
The red curve represents the reactive power (Q) supplied by the shunt capacitance of the transmission
line. Q supplied is proportional to the square of voltage which results in a curve that is nearly flat,
with Q supplied decreasing a relatively small amount due to voltage drop as the line transmits more
power (P).
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The blue curve represents the Q consumption (losses) due to current flowing through the transmission
line. As a first approximation the electrical current is proportional to P transmitted making Q losses
approximately proportional to the square of the power transmitted. Q losses vary markedly with the
power transmitted, starting at zero when P is equal to zero and growing very rapidly as P increases.
Surge Impedance Loading (SIL) is the point at which the Q supplied by the shunt capacitance of the
line equals the Q lost in the series inductance of the line. For a unity power factor load at the SIL
level the voltage would be constant for the entire length of the transmission line. Transmission lines
are normally loaded in excess of the SIL; however the SIL is a useful figure of merit for the capacity
of a transmission line.
Figure 4 – Reactive Power vs. Transmission Line Loading
Changes in line design that increase shunt capacitive susceptance (BC) and consequently increase the
Q supplied (larger diameter conductor, more subconductors, larger bundle spacing, and closer phase
spacing) move the red “Q Supplied” curve up. These same changes in line design also reduce series
inductive reactance (XL) and the Q losses moving the blue “Q Lost” curve to the right. The net effect
is to increase capacity of the line, which is evidenced by the increase in the SIL, located at the
intersection of these two curves.
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Reactive Power Flow and Voltage
Figure 5 illustrates how transmission line voltages are affected by reactive power flow. Reactive
power flows from higher voltage to lower voltage. Alternatively stated supplying reactive power will
increase voltage. Devices that supply reactive power such as shunt capacitors are used to increase
voltage when voltage levels fall below acceptable levels. Similarly devices that consume reactive
power such as shunt inductors (commonly called reactors) are used to lower voltage when voltage
levels are above acceptable levels.
Figure 5 – Reactive Power Flow vs. Transmission Line Voltage
CONDUCTOR COMPARISON
The relative performances of a number of different conductors were compared for a representative
150 kV transmission line operating at 50 Hz. For this comparison transmission line parameters
(inductance, resistance and susceptance) were calculated using the Alternate Transients Program
(ATP). Single conductors and two subconductor bundles were considered. The results are
summarized in a series of charts which follow.
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Figure 6 – Conductor Diameters of Conductors Compared
Figure 7 – Inductive Reactance of Conductors Compared
0.0 0.5 1.0 1.5 2.0 2.5 3.0
INVAR (UX LC17)
ACSR Dove
ACSS Dove
ACCR Dove
ACCR/TW Oswego
ACSS/TW Oswego
GAP/TW Oryx
ACCC/TW Amsterdam
cm
Conductor Diameter
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
INVAR (UX LC17)
ACSR Dove
ACSS Dove
ACCR Dove
ACCR/TW Oswego
ACSS/TW Oswego
GAP/TW Oryx
ACCC/TW Amsterdam
Ω (Ohms)/km
Inductive Reactance (X)
Responsible for Reactive Power Loss
Single
Double
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Figure 8 – Capacitive Susceptance of Conductors Compared
Figure 9 – Surge Impedance Loading of Conductors Compared
Figures 6, 7, 8 and 9 illustrate that the inductive reactance (X), capacitive susceptance (B), and surge
impedance loading (SIL) of the transmission lines are a function of conductor diameter, all other
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
INVAR (UX LC17)
ACSR Dove
ACSS Dove
ACCR Dove
ACCR/TW Oswego
ACSS/TW Oswego
GAP/TW Oryx
ACCC/TW Amsterdam
μS (micro-Siemens or micro-mhos)/km
Capacitive Susceptance (B)
Responsible for Reactive Power Supply
Single
Double
0 20 40 60 80 100
INVAR (UX LC17)
ACSR Dove
ACSS Dove
ACCR Dove
ACCR/TW Oswego
ACSS/TW Oswego
GAP/TW Oryx
ACCC/TW Amsterdam
MW
Surge Impedance Loading (SIL)
Power Flow at which Q Lost= Q Supplied
Single
Double
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characteristics of the transmission line being held constant. These results are consistent with
discussion in the Theory section of this report.
The data also provides an example of the electrical performance improvement obtained when a two
subconductor bundle is used in lieu of a single conductor.
All of the conductors compared had very nearly the same diameter and consequently very nearly the
same X, B, and SIL values. Examining the values for INVAR (UX LC17) provides an example of
how a slightly smaller conductor diameter exhibited a slightly larger X, slightly smaller B, and
slightly lower SIL as expected.
Figure 10 – Reactive Power Consumption of Conductors Compared
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Figure 10a – Reactive Power Consumption of Conductors Compared, Zoomed in View
Figure 10 plots the net reactive power supply and losses for the representative 150 kV 100 km line.
Figure 10a is a zoomed in view of part of the single conductor curve to show that data for all
conductors is contained on the chart. The reactive power supplied and consumed is very nearly
identical for all conductors so they appear as a single line in Figure 10. Because all conductors have
nearly identical diameters the reactive power losses will for practical purposes be the same for all the
conductors compared.
Compare Figure 10 with Figure 4. The curves in Figure 10 combine the “Q Supplied” and “Q Lost”
curves from Figure 4 into a single trace. The reactive power losses are negative (reactive power is
being supplied) for power flow levels below the surge impedance loading (SIL) levels of 57 Mega
Watts (MW) for the single conductor case and 87 MW for the two subconductor bundle case. As
loading increases above the SIL reactive power losses quickly increase and as loading increases larger
amounts of reactive power compensation (typically shunt capacitors) will need to be applied to
maintain system voltage.
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Figure 11 – Resistance of Conductors Compared
0.00 0.05 0.10 0.15
INVAR (UX LC17)
ACSR Dove
ACSS Dove
ACCR Dove
ACCR/TW Oswego
ACSS/TW Oswego
GAP/TW Oryx
ACCC/TW Amsterdam
Ω (Ohms)/km
Resistance (R)
Responsible for Real Power Loss
Single
Double
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Figure 12 – Real Power Losses of Conductors Compared
The data in Figures 6, 7, 8, 9 and 10 confirmed that the line characteristics affecting reactive power
losses, reactive power supply and surge impedance loading were dependent upon conductor diameter
rather than internal conductor construction.
Figures 10 and 11 illustrates that real power losses are dependent upon internal conductor
construction, and that conductors with smaller cores and trapezoidal stranding, such the ACC/TW
Amsterdam, can provide more aluminum cross sectional area in the same diameter significantly
reducing resistance and real power losses. The resistances and losses of two subconductor bundles
are one half that of a single conductor.
The exponential nature of real power losses is apparent in Figure 12. Doubling the power flow
quadruples the losses.
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REACTIVE POWER AND VOLTAGE MANAGEMENT
Overview
Reactive power and voltage are closely related and interdependent. Managing reactive power is an
integral part of operating an electrical transmission system and must be done taking into account the
entire transmission system which includes but is not limited to lines characteristics and length; load
magnitude, power factor and location; generation plant size, location and ability to provide and
absorb reactive power; reactive power management devices such as shunt reactors and shunt
capacitors, including size location and switching capability; and ability to maintain voltage under
contingency conditions such as loss of a line of generation station.
To introduce the topic reactive power and voltage management will be discussed for a radial (source
on one end, load on the other) transmission line.
Figure 13 – Transmission Line Loading and Reactive Power Needs
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For a no load or lightly loaded case surplus reactive power is generated and that reactive power flows
from the end of the line back to the grid, raising the voltage on the end of the line. Refer to the
explanation accompanying Figure 5. For longer and higher voltage lines the line end voltage can
become high enough to damage equipment or risk insulation failure and shunt reactors (inductors)
will be installed at the ends of the line to consume part of the reactive power supplied by the line and
lower the voltage to an acceptable level. For a range of power transmitted, on either side of the surge
impedance loading, the line end voltage will fall within acceptable ranges and no reactive power
compensation will be required. As power transfers increase the line end voltage will fall below
acceptable limits and reactive power compensation, most typically shunt capacitors, will be installed
to supply additional reactive power and raise the line end voltage to keep it within acceptable limits.
Equipment ratings, insulation capability, government regulations and industry standards determine
acceptable voltage limits.
Figure 14 – Reactive Power Compensation Options
Options for managing reactive power control are shown in Figure 14.
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Shunt capacitors are most commonly used, due to both cost and simplicity. Shunt capacitors
are connected to the power system through a circuit breaker and may be switched in steps to
keep the change in voltage during switching to acceptable levels.
Shunt reactors are often used on the ends of longer (greater than 100 km) transmission lines
345 kV and above to reduce line end voltages when the line is being energized. They are also
commonly used in substations to manage reactive power during lightly loaded system
conditions.
Series capacitors are typically used on long (greater than 150 km) lines 345 kV and above.
The capacitors are placed in series (in line) rather than connected between phases or to
ground. The series capacitor has the effect of canceling out part of the line series inductance
reducing reactive power losses and voltage drop on the line.
Static VAr Compensators (SVCs) and Static Synchronous Compensators (STATCOMs) are
power electronic systems that can automatically adjust reactive power output in small
fractions of a second and are used when their automatic high speed operation is required to
maintain system stability. They are typically applied at transmission voltages although in
some special applications they are applied at lower voltages (e.g. managing reactive power at
wind energy plants).
Unified Power Flow Controllers (UPFCs) combine the features of a STATCOM with the
ability to inject/absorb real power. UPFCs are not generally used.
Example
The results of a voltage drop study are shown on the following figures. The voltage drop study was
based upon:
150 kV, 50 Hz AC source bus (“Grid” on diagram in Figures 15, 16 and 17).
Single ACCC/TW Amsterdam conductor
50 km and 100 km radial lines
A load varying from 0 to 300 MW at unity power factor at the end of the line. The load was
modeled as a constant impedance, with the impedance adjusted for each loading level.
Reactive power compensation using shunt capacitors
The voltage performance of the other conductors reviewed earlier in this paper would be for practical
purposes identical. The diameters of all these conductors are nearly the same resulting in nearly
identical line capacitance and inductance and therefore practically identical voltage performance.
The voltage performance of a line in a networked system, which is the more typical case, is also
dependent upon the reactive power supplied by or absorbed into the grid at the ends of the line and
requires a power flow study modeling the entire transmission system to analyze. The results of this
simple radial system voltage drop study will, however, provide an example of the concepts discussed
in this paper as well as be representative of many transmission lines that are in service.
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Figure 15 – End of Line Voltage without Reactive Compensation
Without reactive compensation the end of line voltage at zero or very light load is slightly higher than
the grid source, which is held to 1.0 per unit. The voltage rise occurs because of reactive power
supplied by the line is flowing back to the grid source, increasing the line end voltage. At maximum
load the voltage drop on the 100 km line is more than double the voltage drop on the 50 km line. This
effect becomes more apparent as line lengths are increased.
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Figure 16 – End of Line Voltage with a 50 MVAr Shunt Capacitor
With a 50 mega Volt Ampere reactive (MVAr) shunt capacitor at the line end the line end voltage at
no load exceeds the maximum allowable level indicating the capacitor would have to be switched off
during lightly loaded conditions. Adding the 50 MVAr shunt capacitors significantly increased the
amount of load that could be served without dropping below the 0.95 per unit minimum acceptable
voltage. For the 50 km line the load increased from approximately 165 MW to approximately 260
MW, a nearly 100 MW increase. For the 100 km line the load roughly doubled from approximately
85 MW to 175 MW. This case illustrates the marked improvement in transmission line performance
that can be obtained by the application of shunt capacitors.
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Figure 17 – End of Line Voltage with a 75 MVAr Shunt Capacitor
With 25 MVAr more of shunt capacitors added to the end of the line, for a total of 75 MVAr, the
effects observed with the 50 MVAr shunt capacitor are increased. The line end voltage at no load
exceeds the maximum allowable level by a greater amount and the capacitor would have to be
switched off for light and moderate loading conditions to avoid violating allowable voltage limits.
Additional load could be served but the increase from the 50 MVAr load levels is less than
proportional to the 50% increase in capacitance. For the 50 km line the load increased from
approximately 260 MW to 300 MW, only 40 more MW or 15.4%. For the 100 km line the load
increased approximately 175 MW to 210 MW, 35 more MW or 20%. The diminishing return for
added capacitance occurs because the reactive power losses that must be compensated for increase as
the square of the power transmitted through the transmission line. As a consequence there are
theoretical and practical limits to the amount of reactive power compensation that can be effectively
applied to increase power transfer through a transmission line. The selection of reactive
compensation type and size and the related decisions relating to conductor size, bundling, structure
type and so on are best made with guidance from a comprehensive analytical and economic analysis.
29. POWER ENGINEERS, INC.
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CONCLUSIONS
Real power is a concept used to explain the conversion energy from one form to another. For
example mechanical energy is converted to electrical energy in an electrical generator and electrical
energy is converted to thermal energy in a space heater. The resistance in electrical conductors
results in real power being converted to thermal energy as current flows through the line giving rise to
real power losses.
Reactive power is a concept used to explain the effect of energy storage in and the transfer of energy
between the electric and magnetic fields that surround transmission line conductors. Reactive power
is both supplied and consumed in electric transmission lines. Reactive power is supplied by the shunt
(phase to phase and phase to ground) capacitance of the transmission line. Reactive power is
consumed when current flows through the series inductance of the transmission line.
Voltage drop and reactive power flow are related and interdependent. Reactive power flows from
high voltage to low voltage. Adding shunt capacitors to increase the supply of reactive power will
increase voltage.
Replacing conventional conductors such as aluminum conductor steel reinforced (ACSR) with one of
the high temperature conductors such as aluminum conductor composite core (ACCC) or aluminum
conductor steel supported (ACSS) of the same diameter can be a cost effective way to increase the
transfer capacity of transmission lines. Maintaining the same conductor diameter makes it likely that
existing structures can be used and with proper conductor selection and application ground clearances
can normally be maintained.
Increasing power transfer will impact reactive power consumption, and therefore voltage, as well as
real power losses.
The internal construction of conductors does not have a significant impact on the amount of reactive
power supplied or lost or the voltage performance. So long as voltage remains constant the reactive
power supply and consumption in an electric transmission line are primarily determined by the
number of subconductors per phase, their diameter, and their spacing; along with the phase to phase
spacing. Reactive power consumption will be the same regardless of conductor type selected so long
as the conductor diameters are the same.
Adding shunt capacitors or other reactive power sources can increase the ability to transfer power
over transmission lines significantly, however reactive power consumption varies with the square of
current (or power transmitted) and this imposes practical upper limits on the ability to increase power
transfer through the addition of shunt capacitors.
Real power losses vary directly with the resistance of the conductor, which is heavily influenced by
the internal construction of the conductor as well as by the material used in the conductor.
Conductors with relatively small cores using trapezoidal strands will have a larger cross sectional area
of aluminum compared to other designs and will have significantly lower resistances and lower
electrical losses as a result.