This document provides an overview of commonly used protective relay functions and their ANSI device numbers. It discusses instantaneous overcurrent (50), time overcurrent (51), directional overcurrent (67), reclosing relay (79), and under/over frequency (81O/U) functions. It explains how these functions work, their settings, and considerations for coordination between devices to ensure selective tripping during faults. Microprocessor relays allow for customized curves and grouping of protective functions.
This document discusses power system protection settings and provides information on calculating protection settings. It covers the functions of protective relays and equipment protection, the required information for setting calculations such as line parameters and fault studies, and the process of calculating, checking, and implementing protection settings. The goal is to set protections to operate dependably, securely, and selectively during faults while meeting clearance time requirements.
This document discusses resistance potential dividers for measuring high voltages. It describes the circuit diagram of a potential divider, which consists of two resistors R1 and R2 connected in series. The construction of potential dividers is also outlined, noting the use of voltage controlling capacitors across the resistors to avoid damage from sudden voltage changes. Potential dividers allow accurate measurement of high DC voltages by applying the voltage across R1 and measuring the smaller voltage drop across R2.
Static relays use electronic components like semiconductors instead of mechanical parts to detect faults and operate. They have components like rectifiers to convert AC to DC, level detectors to compare values to thresholds, and amplifiers and output devices to trigger trips. The document discusses the components, types, and applications of various static relays like overcurrent, directional, differential, distance and instantaneous relays used in power system protection.
Relays are electromagnetic switches that are designed to detect faults on electrical circuits and trip circuit breakers. They use a low amperage control circuit to operate a high amperage tripping circuit. Relays can be classified based on their construction, applications, or time of operation. Common types include impedance, reactance, mho, and digital protective relays. Impedance relays have an overcurrent operative torque and a voltage-restraining torque. Reactance relays have a current operative torque and a directional restraining torque. Mho relays induce operative torque from both voltage and current and have a voltage-restraining torque. Digital protective relays use microprocessors to analyze voltages, currents, and
this is useful for peoples interested in power quality problems and their mitigation. it provides causes, effects of voltage sag and their mitigation techniques.
This document discusses different types of firing angle control schemes for HVDC converters, including individual phase control (IPC) and equidistant phase control (EPC). IPC allows independent control of each phase's firing angle based on commutation voltages. EPC generates firing angles at equal intervals through a ring counter. Higher-level controllers are also discussed that can control DC power modulation for frequency regulation, emergency control, reactive power control, and damping of sub-synchronous oscillations. Voltage source converter control is mentioned, where the modulation index and phase angle are used to regulate active and reactive power flow.
Generator Protection By - Er Rahul Sharma Rahul Ruddra
This document discusses generator protection systems. It describes how differential protection uses CTs to detect faults by measuring differences in current. Modified differential protection is discussed as a way to protect the full winding. Other protections mentioned include restricted earth fault protection, stator protection against phase and interturn faults, rotor earth fault protection using dc injection, loss of excitation detection, overload protection using temperature sensors, and negative sequence protection to prevent rotor overheating. The conclusion emphasizes that protective relays act after a fault occurs to ensure safety and equipment protection.
This document discusses power system protection settings and provides information on calculating protection settings. It covers the functions of protective relays and equipment protection, the required information for setting calculations such as line parameters and fault studies, and the process of calculating, checking, and implementing protection settings. The goal is to set protections to operate dependably, securely, and selectively during faults while meeting clearance time requirements.
This document discusses resistance potential dividers for measuring high voltages. It describes the circuit diagram of a potential divider, which consists of two resistors R1 and R2 connected in series. The construction of potential dividers is also outlined, noting the use of voltage controlling capacitors across the resistors to avoid damage from sudden voltage changes. Potential dividers allow accurate measurement of high DC voltages by applying the voltage across R1 and measuring the smaller voltage drop across R2.
Static relays use electronic components like semiconductors instead of mechanical parts to detect faults and operate. They have components like rectifiers to convert AC to DC, level detectors to compare values to thresholds, and amplifiers and output devices to trigger trips. The document discusses the components, types, and applications of various static relays like overcurrent, directional, differential, distance and instantaneous relays used in power system protection.
Relays are electromagnetic switches that are designed to detect faults on electrical circuits and trip circuit breakers. They use a low amperage control circuit to operate a high amperage tripping circuit. Relays can be classified based on their construction, applications, or time of operation. Common types include impedance, reactance, mho, and digital protective relays. Impedance relays have an overcurrent operative torque and a voltage-restraining torque. Reactance relays have a current operative torque and a directional restraining torque. Mho relays induce operative torque from both voltage and current and have a voltage-restraining torque. Digital protective relays use microprocessors to analyze voltages, currents, and
this is useful for peoples interested in power quality problems and their mitigation. it provides causes, effects of voltage sag and their mitigation techniques.
This document discusses different types of firing angle control schemes for HVDC converters, including individual phase control (IPC) and equidistant phase control (EPC). IPC allows independent control of each phase's firing angle based on commutation voltages. EPC generates firing angles at equal intervals through a ring counter. Higher-level controllers are also discussed that can control DC power modulation for frequency regulation, emergency control, reactive power control, and damping of sub-synchronous oscillations. Voltage source converter control is mentioned, where the modulation index and phase angle are used to regulate active and reactive power flow.
Generator Protection By - Er Rahul Sharma Rahul Ruddra
This document discusses generator protection systems. It describes how differential protection uses CTs to detect faults by measuring differences in current. Modified differential protection is discussed as a way to protect the full winding. Other protections mentioned include restricted earth fault protection, stator protection against phase and interturn faults, rotor earth fault protection using dc injection, loss of excitation detection, overload protection using temperature sensors, and negative sequence protection to prevent rotor overheating. The conclusion emphasizes that protective relays act after a fault occurs to ensure safety and equipment protection.
Generator and Transformer Protection (PART 1)Dr. Rohit Babu
Part 1. Generator Protection
Protection of generators against stator faults
Rotor faults and abnormal conditions
Restricted earth fault and inter-turn fault protection
Numerical examples
1) Over current occurs when electric current exceeds intended levels, potentially causing equipment damage from excess heat. It can be caused by short circuits, overloading, design flaws, or ground faults.
2) Over current relays contain a current coil. During normal operation, the magnetic effect is insufficient to trigger the relay. During over currents, the increased magnetic effect overcomes the restraint, moving the contact to isolate the circuit.
3) Over current relays come in instantaneous, definite time, and inverse time variations depending on their time of operation. Inverse time relays isolate faults faster for more severe over currents.
SWICTH GEAR AND PROTECTION (2170906)
DISTANCE RELAY
• There are mainly Three types of distance relay
1) Impedance Relay
2) Reactance Relay
3) Mho Relay
This presentation is brief introduction to the transient disturbances(how they occur and reason behind that) and its classification(Oscillatory and Impulsive).
This document discusses different types of directional over current relays. It explains that directional over current relays operate when fault current flows in a particular direction and will not operate if power flows in the opposite direction. It provides details on 30 and 90 degree connections for directional relays and describes the construction and operation of non-directional over current relays and shaded pole type directional over current relays.
These slides are all about Phasor Measurement Units (PMUs). An introduction to PMU is presented as a preliminary knowledge for the course 'Distribution Generation and Smart Grid'. Your valuable suggestions are welcome.
Microcontroller based multifunction_relayRajeev Kumar
This document discusses a microcontroller-based relay system for detecting faults in a power system. It describes how the microcontroller monitors electrical parameters in real-time, detects abnormal conditions, and sends a trip signal to circuit breakers. The microcontroller converts analog signals to digital using an ADC and detects faults based on programmed conditions. It also discusses using the system to implement overvoltage/undervoltage protection and the advantages of microcontroller-based relays over electromechanical relays.
This document provides an overview of power system engineering concepts related to unbalanced system analysis. It begins with an introduction to symmetrical and unsymmetrical faults on three-phase systems. It then discusses percentage reactance and base KVA, the steps for symmetrical fault calculations, and an introduction to symmetrical components and sequence impedances. The document proceeds to explain single line-to-ground faults, line-to-line faults, and double line-to-ground faults. It provides examples of calculating fault currents and sequence components. In summary, the document covers fundamental concepts for analyzing faults in three-phase power systems, including symmetrical and unsymmetrical faults, sequence components, and example calculations.
This PPT explains about the circuit breaker, and its types. Then about the need and purpose of the circuit breaker. And finally the testing and types of testing of circuit breakers.
This document provides an overview of power system stability analysis. It defines power system stability as the ability of a system to maintain equilibrium during normal operation and regain equilibrium after disturbances. It discusses different types of stability including rotor angle stability and voltage stability. Key factors that influence stability like operating conditions, faults, and clearing times are also summarized. Methods for enhancing stability such as high-speed fault clearing and controlled load shedding are briefly mentioned. Models for analyzing stability like the swing equation and equal area criterion are defined in less than 3 sentences.
Current Transformer and Potential TransformerRidwanul Hoque
One of the major difference between them is that the current transformer converts the high value of current into low value whereas the potential or voltage transformer converts the high value of voltages into low voltage.
Grounding or earthing offers two principal advantages. First, it provides protection to the power system. Secondly, earthing of electrical equipment ensures the safety of the persons handling the equipment.
Generation shift factor and line outage factorViren Pandya
This is animated presentation to let students have an idea about use of generation shift factor and line outage distribution factor to assess power system security by contingency analysis. Entire presentation is prepared from a very nice book authored by Wood.
This document provides guidance on setting calculations for transformer differential protection. It discusses examining CT performance, calculating winding "tap" values, and determining pickup points for the 87T, 87H, and 87GD elements. Key steps include checking CT and relay ratings, selecting tap settings, setting the 87T minimum pickup and slope settings, setting harmonic restraint values, and setting the 87H unrestrained high set differential pickup and delay. The goal is to provide high-speed protection while avoiding misoperation during conditions like inrush current.
The document discusses protection of alternators from various faults. It describes 7 types of faults that alternators require protection from: (1) failure of prime mover, (2) failure of field, (3) overcurrent, (4) overspeed, (5) overvoltage, (6) stator winding faults, and (7) unbalanced loading. It then provides details on differential protection and the Merz-Price circulating current scheme, which is commonly used to protect against stator winding faults. It also discusses limitations of this scheme and modified schemes for protection in other situations.
Unit 04 Protection of generators and transformers PremanandDesai
The document discusses faults and protection methods for alternators and transformers. For alternators, common faults include failure of the prime mover, field failure, overcurrent, overspeed, overvoltage, and unbalanced or stator winding faults. Differential and inter-turn protection are described. For transformers, faults include open circuits, overheating, and winding short-circuits. Buchholz devices, earth fault relays, overcurrent relays, and differential systems provide protection. Earth fault protection for transformers uses a core-balance leakage scheme.
This document discusses generator protection techniques. It begins by explaining why protective systems are needed to protect expensive power system elements like generators. It then describes different types of generator faults and various protection schemes. These include stator protection using differential protection and its modifications. Rotor faults and their protections like rotor earth fault protection are also explained. The document provides details on other protections like overcurrent, overvoltage, vibration and overheating protections. It concludes by stating that protective devices help detect faults, notify maintenance, and disconnect faulty elements to ensure continuous and safe operation of power systems.
This document discusses fundamentals of power system protection. It explains that protection systems are needed to isolate faults and maintain stable operation. The key components of a protection system are described as protective relays, circuit breakers, current and voltage transformers. Common protection schemes like overcurrent, distance, differential and their applications are outlined. Digital relays are noted to provide advantages like adaptability, selectivity and integration with communication systems.
Generator and Transformer Protection (PART 1)Dr. Rohit Babu
Part 1. Generator Protection
Protection of generators against stator faults
Rotor faults and abnormal conditions
Restricted earth fault and inter-turn fault protection
Numerical examples
1) Over current occurs when electric current exceeds intended levels, potentially causing equipment damage from excess heat. It can be caused by short circuits, overloading, design flaws, or ground faults.
2) Over current relays contain a current coil. During normal operation, the magnetic effect is insufficient to trigger the relay. During over currents, the increased magnetic effect overcomes the restraint, moving the contact to isolate the circuit.
3) Over current relays come in instantaneous, definite time, and inverse time variations depending on their time of operation. Inverse time relays isolate faults faster for more severe over currents.
SWICTH GEAR AND PROTECTION (2170906)
DISTANCE RELAY
• There are mainly Three types of distance relay
1) Impedance Relay
2) Reactance Relay
3) Mho Relay
This presentation is brief introduction to the transient disturbances(how they occur and reason behind that) and its classification(Oscillatory and Impulsive).
This document discusses different types of directional over current relays. It explains that directional over current relays operate when fault current flows in a particular direction and will not operate if power flows in the opposite direction. It provides details on 30 and 90 degree connections for directional relays and describes the construction and operation of non-directional over current relays and shaded pole type directional over current relays.
These slides are all about Phasor Measurement Units (PMUs). An introduction to PMU is presented as a preliminary knowledge for the course 'Distribution Generation and Smart Grid'. Your valuable suggestions are welcome.
Microcontroller based multifunction_relayRajeev Kumar
This document discusses a microcontroller-based relay system for detecting faults in a power system. It describes how the microcontroller monitors electrical parameters in real-time, detects abnormal conditions, and sends a trip signal to circuit breakers. The microcontroller converts analog signals to digital using an ADC and detects faults based on programmed conditions. It also discusses using the system to implement overvoltage/undervoltage protection and the advantages of microcontroller-based relays over electromechanical relays.
This document provides an overview of power system engineering concepts related to unbalanced system analysis. It begins with an introduction to symmetrical and unsymmetrical faults on three-phase systems. It then discusses percentage reactance and base KVA, the steps for symmetrical fault calculations, and an introduction to symmetrical components and sequence impedances. The document proceeds to explain single line-to-ground faults, line-to-line faults, and double line-to-ground faults. It provides examples of calculating fault currents and sequence components. In summary, the document covers fundamental concepts for analyzing faults in three-phase power systems, including symmetrical and unsymmetrical faults, sequence components, and example calculations.
This PPT explains about the circuit breaker, and its types. Then about the need and purpose of the circuit breaker. And finally the testing and types of testing of circuit breakers.
This document provides an overview of power system stability analysis. It defines power system stability as the ability of a system to maintain equilibrium during normal operation and regain equilibrium after disturbances. It discusses different types of stability including rotor angle stability and voltage stability. Key factors that influence stability like operating conditions, faults, and clearing times are also summarized. Methods for enhancing stability such as high-speed fault clearing and controlled load shedding are briefly mentioned. Models for analyzing stability like the swing equation and equal area criterion are defined in less than 3 sentences.
Current Transformer and Potential TransformerRidwanul Hoque
One of the major difference between them is that the current transformer converts the high value of current into low value whereas the potential or voltage transformer converts the high value of voltages into low voltage.
Grounding or earthing offers two principal advantages. First, it provides protection to the power system. Secondly, earthing of electrical equipment ensures the safety of the persons handling the equipment.
Generation shift factor and line outage factorViren Pandya
This is animated presentation to let students have an idea about use of generation shift factor and line outage distribution factor to assess power system security by contingency analysis. Entire presentation is prepared from a very nice book authored by Wood.
This document provides guidance on setting calculations for transformer differential protection. It discusses examining CT performance, calculating winding "tap" values, and determining pickup points for the 87T, 87H, and 87GD elements. Key steps include checking CT and relay ratings, selecting tap settings, setting the 87T minimum pickup and slope settings, setting harmonic restraint values, and setting the 87H unrestrained high set differential pickup and delay. The goal is to provide high-speed protection while avoiding misoperation during conditions like inrush current.
The document discusses protection of alternators from various faults. It describes 7 types of faults that alternators require protection from: (1) failure of prime mover, (2) failure of field, (3) overcurrent, (4) overspeed, (5) overvoltage, (6) stator winding faults, and (7) unbalanced loading. It then provides details on differential protection and the Merz-Price circulating current scheme, which is commonly used to protect against stator winding faults. It also discusses limitations of this scheme and modified schemes for protection in other situations.
Unit 04 Protection of generators and transformers PremanandDesai
The document discusses faults and protection methods for alternators and transformers. For alternators, common faults include failure of the prime mover, field failure, overcurrent, overspeed, overvoltage, and unbalanced or stator winding faults. Differential and inter-turn protection are described. For transformers, faults include open circuits, overheating, and winding short-circuits. Buchholz devices, earth fault relays, overcurrent relays, and differential systems provide protection. Earth fault protection for transformers uses a core-balance leakage scheme.
This document discusses generator protection techniques. It begins by explaining why protective systems are needed to protect expensive power system elements like generators. It then describes different types of generator faults and various protection schemes. These include stator protection using differential protection and its modifications. Rotor faults and their protections like rotor earth fault protection are also explained. The document provides details on other protections like overcurrent, overvoltage, vibration and overheating protections. It concludes by stating that protective devices help detect faults, notify maintenance, and disconnect faulty elements to ensure continuous and safe operation of power systems.
This document discusses fundamentals of power system protection. It explains that protection systems are needed to isolate faults and maintain stable operation. The key components of a protection system are described as protective relays, circuit breakers, current and voltage transformers. Common protection schemes like overcurrent, distance, differential and their applications are outlined. Digital relays are noted to provide advantages like adaptability, selectivity and integration with communication systems.
The document provides information on grading procedures for various power system protection schemes including:
1. Parallel feeders where directional relays are needed at each feeder terminal to prevent unnecessary tripping under fault conditions.
2. Ring main circuits which require directional relays since fault current can flow in both directions; grading is done by opening the ring at different locations.
3. Non-directional relays can be used on ring circuits if the source substation relays and relays with higher time settings are at load substations.
This document provides an overview of microprocessors and microcontrollers. It discusses the major components of microcontrollers, including the microprocessor, memory, and input/output ports. It also covers microprocessor architecture, data formats, software, and example applications of microprocessor-based and microcontroller-based systems. The purpose is to introduce students in an digital systems engineering course to fundamental concepts of microprocessors and microcontrollers.
The document defines a microprocessor as a small integrated circuit that functions as a digital data processor. It discusses the history and components of microprocessors, including the arithmetic logic unit, control unit, registers, and buses. It also covers characteristics like bandwidth, clock speed, and instruction sets. The document classifies processors and microprocessors and lists some common microprocessor producers.
The document discusses power system protection. It defines the objectives of power system protection as detecting and isolating faults instantaneously while minimizing the number of circuits isolated and restoring the system quickly. It also discusses criteria for proper protection systems, including reliability, selectivity, speed of operation, and discrimination. Detection methods like current transformers and potential transformers are explained. Common protection relays like electromagnetic attraction, balance beam, and electromagnetic induction types are also summarized.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
International Journal of Engineering Research and DevelopmentIJERD Editor
This document summarizes the performance evaluation of a modern numerical protective relay (NPR) using a microcontroller for overcurrent protection. It describes the design and implementation of an overcurrent relay using a microcontroller-based system-on-chip approach. The relay is tested according to IEEE standards and shown to operate within acceptable time limits. Test results demonstrate that the microcontroller-based design provides adequate reliability and security for overcurrent protection while improving performance compared to conventional designs.
This document provides an overview of microprocessors and microcontrollers. It discusses the evolution of microprocessors from discrete components to integrated circuits. The key components of a microprocessor like the CPU, ALU, and memory are described. Microcontroller fundamentals like PIC microcontrollers and their architecture are also covered. Common applications of microprocessors and microcontrollers are in devices like appliances, automobiles, and industrial control systems. Leading manufacturers of microprocessors and microcontrollers are mentioned.
The document provides information about the Intel 8085 microprocessor. Some key details include:
- It is an 8-bit processor that operates on a 5V power supply with a maximum clock frequency of 3MHz.
- It has 40 pins and uses a multiplexed address/data bus. It can access 64KB of memory space and 256 I/O ports.
- It has one accumulator, flag, and six general purpose registers. It supports various addressing modes and 74 instructions.
- Interrupts include TRAP, RST 5.5, RST 6.5, RST 7.5, and INTR. Serial I/O is also supported directly.
-
A protective device coordination study involves organizing the time-current characteristics of protective devices from the utility to downstream devices. The study determines device ratings, settings, and ensures minimum load is interrupted during faults while protecting devices. Results include instrument transformer ratios, relay settings, fuse ratings, and circuit breaker ratings. The study should be revised every 5 years or when devices are added or modified.
The document summarizes research on using space vector modulation (SVM) for speed control of an induction motor driven by a three-phase inverter. It compares SVM to sine triangle pulse width modulation (SPWM) and finds that SVM provides better harmonic performance, higher DC bus utilization, and a more sinusoidal output voltage. The document simulates v/f control of an induction motor using SVM for both open-loop and closed-loop speed control systems. It is observed that the induction motor's performance is improved with SVM compared to SPWM modulation.
A Comparative Analysis Among PWM Control Z-source Inverter with Conventional ...Mustafa Xaved
The document compares conventional PWM inverters and Z-source inverters for induction motor drive applications. It finds that Z-source inverters provide advantages over conventional current source and voltage source inverters. Specifically, Z-source inverters can operate as either a voltage source or current source inverter. They also provide buck-boost capability and contain lower harmonics compared to conventional inverters. Simulation results show that induction motors driven by Z-source inverters have higher starting torque, quicker operation, and reduced settling time for rotor and stator currents.
Digital signal processing based on motor control pptboga manisha
This document discusses digital signal processing (DSP) based motor control using the TMS320C240 DSP controller. It provides an overview of DSP and motor control trends, describes the TMS320 family and TMS320C240 controller, and discusses AC induction motors and different control methods like scalar and vector control. Vector control methods like field oriented control are highlighted as providing faster response, four quadrant speed control, and reduced motor size and power consumption. The conclusion states that the TMS320C240 DSP controller allows for intelligent control approaches to reduce system costs and improve drive system reliability.
Speed control of induction motor using vf dsAli Hassan
This document discusses variable frequency drives (VFDs) and how they are used to control the speed of induction motors. It describes the main components of a VFD - the rectifier, DC bus, and inverter - and how they work together to convert incoming AC power to DC and then invert it back to AC at a variable frequency that controls motor speed. The document notes that VFDs are used in boilers at a company to control induced draft fans, forced draft fans, and bagasse feeders. It explains that VFDs provide energy savings of 25-30% by consuming only the power needed, with a return on investment period of 6 months to 2 years. Advantages include efficient motor speed control while
Abstract
This report focuses on controlling the speed of a DC motor using PWM technique.
Direct current (DC) motors have been widely used in many industrial applications such as electric vehicles, steel rolling mills, electric cranes, and robotic manipulators due to precise, wide, simple, and continuous control characteristics
The dc motor speed in general is directly proportional to the supply voltage, so if reduce the voltage from 12 volts to 6 volts then our speed become half of what it originally had. But in practice, for changing the speed of a dc motor we cannot go on changing the supply voltage all the time. Rather than simply adjusting the voltage sent to the motor, we can switch the motor supply on and off where switching is done so much fast that the motor only notices the average voltage effect and not the switching operation.
This study guide is intended to provide those pursuing the CCNA certification with a framework of what concepts need to be studied. This is not a comprehensive document containing all the secrets of the CCNA, nor is it a “braindump” of questions and answers.
I sincerely hope that this document provides some assistance and clarity in your studies.
In this project we will be controlling the speed of Dc motor using Arduino controller. Dc motor is drive by using PWM technique and then using encoder to sense the rpm of DC motor. Encoder produces pulses in the output, which is feed into Arduino and Arduino controls the speed of DC motor. So we have implemented the feedback system which controls the speed of DC motor.
Speed Control of DC Motor using MicrocontrollerSudip Mondal
This document discusses a project to control the speed of a DC motor using a microcontroller and pulse width modulation. Specifically, it aims to vary the speed-torque relationship of a DC motor electronically using a microcontroller to generate high and low pulses that control motor speed. Pulse width modulation is identified as a technique that can be used to simulate variable voltages through variations in pulse width to achieve variable analog speed control. The document outlines the components used, including an H-bridge circuit and microcontroller, and discusses some limitations such as susceptibility to electromagnetic interference.
Short Circuit, Protective Device Coordinationmichaeljmack
This document discusses short-circuit calculations, protective device coordination, and arc flash analysis. It covers topics such as short-circuit fault types and calculations, the purpose of short-circuit studies, system components involved, and protective device coordination principles. Methods to perform arc flash analysis and mitigate incident energy exposure are also presented, such as improving protective device coordination settings, installing current limiting fuses or circuit breakers, and using Type 50 protective devices.
This document discusses short-circuit calculations, protective device coordination, and arc flash analysis. It covers topics such as short-circuit fault types and calculations, the purpose of short-circuit studies, system components involved, and protective device coordination principles. Methods to perform arc flash analysis and mitigate incident energy exposure are also examined, such as improving coordination settings, installing current limiting fuses or circuit breakers, and using Type 50 protective devices.
The document discusses various components and principles of power system protection. It describes the objectives of protection systems as keeping the power system stable by isolating only faulted components. The main components of protection systems are listed as current and voltage transformers, protective relays, circuit breakers, batteries, and communication channels. Key qualities of protection systems are described as reliability, selectivity, fastness of operation, and discrimination. Common types of relays and their operating principles are also outlined.
This document provides an overview of protective relaying principles and the career path for young protection engineers. It discusses the need to protect power systems from faults, the different types of relays and their functions. It also outlines the challenges facing young protection engineers such as gaining practical experience and developing a solid understanding of power systems. Mentorship and continuous learning are emphasized as important for success in this field.
Protection of lines
Overcurrent Protection schemes
PSM, TMS
Numerical examples
Carrier current and three-zone distance relay using impedance relays
Protection of bus bars by using Differential protection
This document discusses power system protection schemes, including:
- Zones of protection with protective relays coordinated between zones
- Attributes of reliable, selective, and fast relaying
- Fault clearing times of relays and circuit breakers
- Protection of system components like feeders, transmission lines, transformers, generators
It provides examples of overcurrent protection design using time-graded and current-graded discrimination. Directional relays, differential protection, and power line carrier communication are also summarized.
This document provides information about key components of electrical substations. It discusses substations, their purpose of transforming voltage for local use. It describes components like buses that carry current, disconnects that isolate equipment, circuit breakers that interrupt current, current and voltage transformers that detect and transform current and voltage, earthing switches that provide a ground path for safety, and surge arrestors that protect from overvoltage. It provides specifications for common equipment and gives an overview of typical preventative maintenance activities for various substation components.
This document discusses protections for alternators and busbars. It describes mechanical protections like failure of prime mover, failure of field, overcurrent, overspeed, and overvoltage. Electrical protections discussed include unbalanced loading and stator winding faults. Differential protection and balanced earth fault protection are described for protecting alternators. Busbar protection requires short tripping times, sensitivity to internal faults, and selectivity. Differential and high/low impedance schemes are used for busbar protection.
This document discusses power system analysis using ETAP software. It provides background on why system studies are important during project design and modification phases. Common parameters considered in studies include short circuit analysis, load flow, relay coordination, arc flash, and motor starting. ETAP is used to model the electrical system and perform these analyses. Key aspects covered are load flow study methodology, short circuit analysis methodology, and relay coordination methodology. Relay coordination is important to protect the system by having the nearest relay trip first followed by backup protection.
This presentation will discuss how the use and need for voltage transformers has changed over the last twenty years. With the introduction of auto-ranging electric meters, meter technicians need to be prepared, use the appropriate tools and PPE for high capacity circuits (without VT's), as this method has become increasingly popular.
The document discusses electromagnetic protection relays. It begins by covering the syllabus and providing background on relays. The key types of relays discussed are electromechanical relays, including attracted armature relays like hinged armature and plunger types, and induction relays like induction disc and cup relays. Induction disc relays can be of the shaded pole or wattmeter type, while an induction cup relay operates similarly to an induction motor.
1. The document discusses various aspects of power system protection including relay types, relay elements, relay characteristics, and relay terminology.
2. Key relay types discussed are definite time, inverse time, and instantaneous relays. Relay elements include measuring, comparing, and tripping elements.
3. Important relay characteristics are sensitivity, selectivity, reliability, and speed of operation. Relays can also be categorized by characteristic, logic, or actuating parameter.
4. Terminology discussed includes pickup level, reset level, operating time, and plug and time setting multipliers which are used to adjust relay settings.
Gate Pulse Triggering of Single Phase Thyristor Circuit through Opto-CouplingNusrat Mary
The document discusses a thyristor-based controlled rectifier circuit for high voltage DC transmission. It uses opto-couplers to isolate the thyristor triggering circuit from the high voltage AC input. Simulation results using Proteus show that varying the firing angle of the thyristors produces rectified outputs with different voltage levels and ripple factors. Thyristors allow controlled rectification with benefits of efficiency and reliability over uncontrolled rectification for applications like HVDC transmission.
The document provides a summary of Ernst de Villiers' training at Eskom over a 6-month period from July 2014 to January 2015. It describes the various departments visited, including Control Plant Maintenance (CPM) covering DC, telecontrol, and protection systems, as well as Network Engineering Design. Specific training content for each department is outlined, with examples of battery testing and commissioning procedures, recloser maintenance, protection relay testing, and preliminary design work for the Khotana electrification project.
There are three main aspects of power system protection: normal operation, prevention of electrical failures, and mitigation of failure effects. Protective relaying is one feature aimed at minimizing equipment damage and service interruptions when failures occur. Relays have evolved from electromechanical to static and digital types. Overcurrent protection is used for phase and earth faults, with inverse-time curves allowing coordination between relays. Adequate grading margins must be provided between relay operations.
The document discusses different methods for testing circuit breakers. It describes synthetic testing methods, which use separate sources for the short-circuit current and transient recovery voltage. The two main synthetic test circuits are the parallel current-injection method and series voltage injection method. The parallel current-injection method uses a current source for the short-circuit current and capacitors to inject additional high-frequency current. The series voltage injection method uses a voltage source to apply the transient recovery voltage. Synthetic testing allows testing of higher voltage circuit breakers than direct testing methods.
Similar to Fundamentals of Microprocessor Based Relays (20)
Auburn, NY - 200 Years of History 1793-1993michaeljmack
Auburn, New York celebrated its 200th anniversary in 1993. The city has a rich history dating back to its founding in 1792 by John L. Hardenbergh. Early settlers established homes, churches, mills and prioritized education. Auburn grew into an economic center, gaining a village charter in 1815. The state prison and Auburn Theological Seminary brought prestige. During the Civil War, Auburn supported the Union and industries like manufacturing flourished afterwards. While the economy has changed, Auburn looks to build on its cultural and educational strengths as it enters its third century.
Auburn High School, Auburn, NY, 1982 Yearbookmichaeljmack
This document is the yearbook from Auburn High School for the class of 1982. It contains photos, quotes, and information about various events and members of the senior class. The yearbook staff proudly presents "Images of Yesterday" to capture memories from the past year at A.H.S. It includes sections on beach day, typical school days, homecoming, and memories from the class of '82 as they prepare to graduate and go their separate ways.
Auburn High School, Auburn, NY, 1980 Yearbookmichaeljmack
This document appears to be from a high school yearbook. It lists various superlatives voted on by the graduating class such as "Most Humorous", "Best Looking", and "Most Likely to Succeed". It also includes photos and quotes from individual graduating students. The document celebrates the class of 1979 and recognizes various achievements and personalities of the students.
This document provides an overview of surge protection and transient surges. It defines a transient surge as a brief high-voltage spike lasting millionths of a second. The document discusses how surges can damage equipment and cost businesses billions annually. It describes how surge protective devices (SPDs) work by diverting damaging currents away from equipment. The document emphasizes that proper SPD location and installation is important for effective protection. It provides guidance on selecting appropriate protection levels based on surge risk and discusses relevant industry codes and standards.
Diesel Particulate Filters Control Systemsmichaeljmack
This document discusses diesel particulate filter systems from Rypos, Inc. for stationary diesel generators and port equipment. It provides an overview of regulatory requirements for particulate matter emissions in California, describes Rypos' active regeneration filter technology using electrical heating elements, and lists some customer installations of their diesel particulate filter systems on generators and rubber-tired gantries at various ports.
Five to 10 arc flash explosions occur daily in the US, often requiring specialized burn treatment. There are two types of faults that can cause arcs: bolted faults where current flows through a solid connection, and arcing faults where current arcs through ionized air. Arcing faults are more dangerous as the energy is released into the environment. Standards like NFPA 70E and OSHA requirements aim to protect workers by enforcing safety practices like arc flash analyses and requiring personal protective equipment suitable for the estimated incident energy levels. Proper maintenance and use of protective equipment can reduce arc flash exposure hazards.
This document provides information on Siemens medium-voltage gas-insulated arc-resistant switchgear. It discusses the switchgear's increased safety, reliability, and flexibility features. The document includes technical specifications, diagrams, and benefits such as its compact design, high personnel safety, minimized fire load, and maintenance-free components due to its SF6 gas insulation. It also describes innovative features like its video camera system for viewing the selector switch position and capacitive voltage indicators.
This document discusses transformer inrush current and its impact on differential relays. Transformer inrush occurs when the flux in the transformer core needs to be established, causing a large magnetizing current to flow. This inrush current appears as a differential current that can cause misoperation of transformer differential relays. The document examines characteristics of inrush current like the switching point, remnant flux, system impedance, and transformer design. It also discusses various harmonic-based methods for restraining differential relays during inrush like percentage of total harmonic, percentage of 2nd harmonic, and adaptive 2nd harmonic methods. The considerations for applying these methods include reliability, security, and speed of operation.
This document discusses Building Information Modeling (BIM) and its implications for electrical engineers. It begins with an overview of BIM, explaining that BIM provides a digital representation of a facility and its physical and functional characteristics. It then discusses how BIM can benefit owners, design engineers, and contractors by improving coordination, reducing risks and costs, and streamlining processes. The remainder of the document focuses on a case study of a large hospital project where BIM was used, highlighting lessons learned around project setup, managing limitations, and the importance of communication and proper planning when adopting BIM.
15 years of experience stator ground fault protectionmichaeljmack
The document discusses different methods for 100% stator ground fault protection on generators based on 15 years of experience. It describes conventional 59G protection that only covers 90-95% of the stator, as well as 3rd harmonic schemes that can provide full coverage but have limitations. Subharmonic injection was also used in Europe and provides full coverage independently of generator loading. While 3rd harmonic schemes require testing the generator's harmonic signature, subharmonic injection is preferable as it works regardless of loading and can detect faults offline or throughout the entire winding.
Emergency, Legally Required and Optional Standby Systemsmichaeljmack
The document discusses the differences between emergency, legally required standby, and optional standby systems according to the 1999 NEC. Emergency systems are for life safety and are subject to more stringent requirements than standby systems. Legally required standby systems serve equipment important for safety but not critical for life, while optional standby systems are intended to minimize economic losses and protect facilities. The document provides detailed comparisons of the categories and guidance on proper system design and component selection.
Lighting Control Solutions for Daylit Spacesmichaeljmack
This document provides an overview of a webinar on lighting control solutions for daylit spaces. The webinar aims to teach participants how architectural daylighting design can impact daylight penetration and occupant comfort, how to circuit electric lighting to work with daylight, and how to design daylight-responsive lighting controls to save energy. The webinar covers topics like daylight benefits, linking daylighting design with electric lighting systems, control strategies, photosensor characteristics, and examples of control designs for different daylighting configurations.
COPS: An Arresting Look at NEC Article 708michaeljmack
The document discusses an arresting look at NEC Article 708 which establishes requirements for critical operations power systems. It provides an overview of a webcast on the topic with multiple presenters discussing key aspects of Article 708 such as operational availability, how it relates to other NEC articles, and ensuring public acceptance. The presenters aim to provide takeaways on several learning objectives related to understanding and implementing Article 708.
Seismic Compliance of Electrical Distributionmichaeljmack
This document discusses changes in seismic code requirements for electrical equipment from 2006 IBC and ASCE/SEI 7-05 standards. It highlights key events like the 1985 Mexico City earthquake that revealed issues with site effects and building resonances, driving later code revisions. The document outlines equipment qualification options in current codes including analysis, testing on a shake table, and presents considerations for developing a testing protocol aligned with building code seismic performance goals.
The document discusses generator set transient response to load changes. It notes that voltage level is more consistent than utilities but frequency control is poorer in responding to load changes. When load changes, both the frequency and voltage will change until the governor and AVR can increase fuel and excitation levels. The size of the load change and speed of responding fuel/excitation systems impact how much the voltage and frequency change. Proper transient response is important for motor starting and UPS operation. Test data is presented showing voltage dips and recovery times for different sized generator sets and loads. The conclusions emphasize specifying generator set performance according to NFPA 110 standards and testing at factory and jobsite to verify transient response capabilities.
Modeling of a digital protective relay in a RT Digital Simulatormichaeljmack
1. The document describes modeling a digital protective relay in a real-time digital simulator (RTDS) to test the relay's performance under various system disturbances without needing physical hardware.
2. Key modules of the simulated relay include differential protection, external fault detection, internal fault detection, directional logic, and open current transformer detection.
3. Testing results found the simulated relay responded within reasonable tolerance of an actual hardware relay for various faults like internal faults, evolving faults, and open current transformers. This allows protective algorithms to be developed and verified in software first before hardware realization.
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1) Many power plant events are complex to analyze and often involve human error, especially during commissioning of new plants. Accurately documenting events and sharing lessons learned is important.
2) Protective relays and their coordination, along with oscillographic records, play a key role in preventing damage and speeding return to service after events occur.
3) Common event types discussed include multi-phase faults, stator ground faults, inadvertent energizing, overexcitation, loss-of-field, and generator breaker failures. Close attention to relay settings and logic is needed to mitigate risks.
1) Voltage collapse is a major cause of recent blackouts due to increased reliance on remote generation and lack of transmission expansion. As transmission lines trip, reactive power losses increase, reducing voltage.
2) Generators provide reactive power (VARs) to support system voltage through their automatic voltage regulators (AVRs). During low voltage events, AVRs and generator protection systems may not be able to maintain stable operation.
3) Undervoltage load shedding is used to prevent total system collapse by automatically removing certain loads if voltage drops below a threshold for a set time period. This helps restore the balance between generation and load.
Transformers transfer energy from one circuit to another through magnetic coupling and are used to transform voltage levels for transmission and distribution. They operate on the principles that voltage in equals voltage out and turns ratio determines the voltage transformation. Transformers are widely used throughout power systems and come in different configurations, ratings, and winding arrangements to serve various applications including generation, transmission, distribution, and end use.
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
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Batteries -Introduction – Types of Batteries – discharging and charging of battery - characteristics of battery –battery rating- various tests on battery- – Primary battery: silver button cell- Secondary battery :Ni-Cd battery-modern battery: lithium ion battery-maintenance of batteries-choices of batteries for electric vehicle applications.
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ACEP Magazine edition 4th launched on 05.06.2024Rahul
This document provides information about the third edition of the magazine "Sthapatya" published by the Association of Civil Engineers (Practicing) Aurangabad. It includes messages from current and past presidents of ACEP, memories and photos from past ACEP events, information on life time achievement awards given by ACEP, and a technical article on concrete maintenance, repairs and strengthening. The document highlights activities of ACEP and provides a technical educational article for members.
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELgerogepatton
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
6. Interrupting Methods
• Fuse
Fusible element melts to disconnect faulty
zone/equipment
I2T law
• Recloser
Single or three-phase, 15 to 38kV
Line or substation
• Circuit Breaker
• Indoor switchgear
• Outdoor breaker or switchgear
• Air, Oil, SF6, Vacuum, Magnetic blast
8. 50 – Instantaneous OC
Instantaneous Overcurrent (function 50)
• The instantaneous overcurrent protective element operates with no intentional time delay
when the current has exceeded the relay setting
• There is a pickup setting.
• 50P – phase inst. overcurrent. Pickup usually set at 25% higher than the maximum current
seen by the relay for a three-phase fault at the end of the circuit.
• 50N – neutral inst. overcurrent
(The phasor summation of phase currents Ia, Ib, Ic equals In)
• 50G – ground inst. overcurrent – low pickup setting
(Uses separate or zero sequence CT)
12. 51 – Time Overcurrent
• Where it is desired to have more time delay before the element operates for the purpose of
coordinating with other protective relays or devices, the time overcurrent protective element is
used. The trip time varies inversely with current magnitude.
• Characteristic curves most commonly used are called “inverse,””very inverse,” and “extremely
inverse.” The user must select the curve type. They are said to be a family of curves and selected
by the time dial.
• Curve type and time dial are separate settings. Time dial adjusts the time delay of the characteristic
to achieve coordination between downstream and upstream overcurrent devices.
• There is a minimum pickup setting. The pickup setting should be chosen such that the protective
device will be operating on the most inverse part of its time curve over the range of current for
which must operate.
• 51P – phase time overcurrent
• 51N – neutral time overcurrent
(The phasor summation of phase currents Ia, Ib, Ic equals In)
• 51G – ground time overcurrent ‐ low pickup setting (uses separate or zero sequence CT)
17. 51 ‐ Fuses
• The time verses current characteristics of a fuse
has two curves.
• The first curve is called the minimum melt curve
• The minimum melt curve is the time between
the initiation of a current large enough to
cause the fusible element(s) to melt and the
instant when arcing occurs.
• The second curve is called the total clearing time.
• The total clearing time is the total time
elapsing from the beginning of an
overcurrent to the final circuit interruption.
• The time current characteristic curve of a fuse
follows a I2T characteristic - that is to say as the
current goes up, the time drops by the square of
the current increase.
Total clearing
time curve
Minimum
melt
Current
Time
18. 51 – Coordinating Fuses
Load
Primary
Secondary
LoadSecondary
2I
1I 1I
Time
Current
• The operating time of a fuse is a function of the pre-arcing (melting) and arcing time
• For proper coordination, total I2T of secondary fuse shouldn’t exceed the pre-arcing
(melting) of primary fuse. This is established if current ratio of primary vs.
secondary fuse current rating is 2 or greater for fuses of the same type.
19. 51 – Coordinating Fuses & Relays
Current
Time
Minimum TCI time of
0.4s
Time Over Current Curve
Fuse curve
• The time overcurrent relay should back
up the fuse over full current range.
The time overcurrent relay
characteristic curve best suited for
coordination with fuses is the
Extremely Inverse, which is similar to
the I2t fuse curves. For Extremely
Inverse relay curves, primary pickup
current setting should be 3-times fuse
rating. For other relay curves, up to 4-
times fuse rating should be considered.
Ensure no cross over of fuse or time
overcurrent relay curves.
• To account for CT saturation and
errors, electro-mechanical relay
overshoot, timing errors and fuse
errors a minimum TCI of 0.4s should
be used.
20. 51 – Coordinating Relays
• The following is recommended TCI to ensure proper coordination.
0 1000 2000 3000 4000
0
0.5
1
1.5
2
2.5
3
Fault current at 11 kV
Timetooperate(s)
0.4 s between relay and fuse
0.3 s between digital relays
21. 51 – Reset Curves
• Reset of Time Overcurrent Element
• There are (2) different types of resets within Time Overcurrent Protection:
• EM or Timed Delay Reset – this mimics the disc travel of an
electromechanical relay moving back to the reset position.
• If the disc has not yet completely traveled back to the reset position and the
time overcurrent element picks up again, the trip time will be shorter.
• If the current picks up and then dropouts many times, the disc will “ratchet”
itself to the operate position.
• Be careful when coordinating with upstream or downstream devices.
• Instantaneous Reset – once the time overcurrent element operates,
it will reset immediately
24. 67 – How it Works
(a) To determine the direction of
current we need a reference
voltage or current that will not
change direction during the
fault. To determine the
direction of current in phase A
we will use Vbc. Digital relays
allow an offset from the
reference voltage or current to
provide better protection.
(b) The protection engineer must
look back into the system from
the fault and determine the
current fault angle (in this case
a 600 lagging in current from
phase Van is determined the
typical fault angle).
31. 79 – Reclosing Relay
• Not all Faults Are Permanent
– Most Industrial Facilities Use Insulated Cable,
Which Results in Permanent Faults
– Utilities Often Use Non‐Insulated Overhead
Conductors, Resulting in Many Temporary Faults:
• Wind Causing Conductors to Touch
• Fires Temporarily Breaking Down Air
32. 79 – Reclosing Relay
• Automatically reclose a circuit breaker or recloser which has been tripped by protective
relaying or recloser control
• Multi‐shot reclosing for distribution circuits
• Instantaneous shot (~0.25s)
• Delayed reclosures (typically two delayed , for example 3s & 15s, or 15s & 30s)
• Coordinate with branch fuses
• After initial reclose block instantaneous overcurrent functions to allow fuse to blow
• After successful reclose, the reclosing function will reset after some adjustable time delay
(typically 60s).
• If the fault is permanent, the protective device will trip and reclose several times. If
unsuccessful, the protective device will go to LOCKOUT and keep the breaker open.
Some devices have a separate reset time from lockout (for example 10s after the breaker
is manually closed).
33. 79 – Reclosing & Fuses
52
R
• Two methods:
• Fuse blowing
• Fuse blows for any fault, including temporary fault
• Fuse saving
• Use automatic reclosing to try and save fuses for temporary faults
39. • Phase instantaneous and
time-delayed overcurrent
is used.
• Ground instantaneous
overcurrent is used.
• Optionally, ground time-
delayed overcurrent is
used
Typical Industrial Feeder CB
40. Typical Utility Feeder CB
• Phase and ground
overcurrent protection
with multi-shot
reclosing relay is used.
• Both instantaneous
and time-delayed
overcurrent are used.
• Reclosing is Often
Included for Overhead
Lines
79
44. 50 – Short Circuit Protection
• The short circuit element provides
protection for excessively high overcurrent
faults
• Phase-to-phase and phase-to-ground
faults are common types of short circuits
• To avoid nuisance tripping during starting,
set the the short circuit protection pick up
to a value at least 1.7 times the maximum
expected symmetrical starting current of
motor.
• The breaker or contactor must have an
interrupting capacity equal to or greater
then the maximum available fault current
or let an upstream protective device
interrupt fault current.
50. A motor can run overloaded without a fault in motor or supply
A primary motor protective element of the motor protection relay is the
thermal overload element and this is accomplished through motor
thermal image modeling. This model must account for thermal process in
the motor while motor is starting, running at normal load, running
overloaded and stopped. Algorithm of the thermal model integrates both
stator and rotor heating into a single model.
• Main Factors and Elements Comprising
the Thermal Model are:
• Overload Pickup Level
• Overload Curve
• Running & Stopped Cooling Time Constants
• Hot/Cold Stall Time Ratio
• RTD & Unbalance Biasing
• Motor State Machine
49 – Overload Protection
51. 49 - Motor Thermal Limit Curves
Thermal Limit Curves:
B. Hot Running Overload
B
A. Cold Running Overload
A
D. Hot Locked Rotor CurveD
C
C. Cold Locked Rotor Curve
F. Acceleration curve @100%
voltage
F
E. Acceleration curve @ 80% rated
voltageE
• Thermal Limit of the model is dictated by overload curve constructed in
the motor protection device in the reference to thermal damage curves
normally supplied by motor manufacturer.
• Motor protection device is equipped with set of standard curves and
capable to construct customized curves for any motor application.
52. 49 - Thermal Overload Pickup
• Set to the maximum allowed by
the service factor of the motor.
• Set slightly above the motor
service factor by 8-10% to
account for measuring errors
• If RTD Biasing of Thermal Model
is used, thermal overload setting
can be set higher
• Note: motor feeder cables are
normally sized at 1.25 times
motor’s full load current rating,
which would limit the motor
overload pickup setting to a
maximum of 125%.
SF Thermal Overload Pickup
1.0 1.1
1.15 1.25
53. • Thermal Capacity Used (TCU) is a criterion selected in thermal model
to evaluate thermal condition of the motor.
• TCU is defined as percentage of motor thermal limit utilized during
motor operation.
• A running motor will have some level of thermal capacity used due
to Motor Losses.
• Thermal Trip when Thermal Capacity Used equals 100%
49 – Thermal Capacity Used
54. Overload Curve
Set the overload curve below cold thermal limit and above hot thermal limit
If only hot curve is provided by mfgr, then must set below hot thermal limit
49 - Overload Curve Selection
55. If the motor starting
current begins to
infringe on the thermal
damage curves or if the
motor is called upon to
drive a high inertia load
such that the
acceleration time
exceeds the safe stall
time, custom or voltage
dependent overload
curve may be required.
49 - Overload Curve Selection
56. 49 - Overload Curve Selection
A custom overload curve
will allow the user to
tailor the relay’s thermal
damage curve to the
motor such that a
successful start can occur
without compromising
protection while at the
same time utilizing the
motor to its full potential
during the running
condition.
57. 49 - Current Unbalance Bias
Negative sequence currents (or unbalanced phase currents) will cause
additional rotor heating that will be accounted for in Thermal Model.
Positive Sequence
Negative Sequence
• Main causes of current unbalance
• Blown fuses
• Loose connections
• Stator turn-to-turn faults
• System voltage distortion and unbalance
• Faults
58. 49 - Current Unbalance Bias
• Equivalent heating motor current is employed to bias thermal model in
response to current unbalance.
• Im - real motor current; K - unbalance bias factor; I1 & I2 -
positive and negative sequence components of motor current.
• K factor reflects the degree of extra heating caused by the negative
sequence component of the motor current.
• IEEE guidelines for typical and conservative estimates of K.
59. Thermal Model - Motor Cooling
• Motor cooling is characterized by separate cooling time constants
(CTC) for running and stopped motor states. Typical ratio of the
stopped to running CTC is 2/1
• It takes the motor typically 5 time constants to cool.
Thermal Model Cooling100% load -
Running
Thermal Model Cooling Motor
Tripped
60. 46 - Unbalance Protection
• Indication of unbalance negative sequence current / voltage
• Unbalance causes motor stress and temperature rise
• Current unbalance in a motor is result of unequal line voltages
• Unbalanced supply, blown fuse, single-phasing
• Current unbalance can also be present due to:
• Loose or bad connections
• Incorrect phase rotation connection
• Stator turn-to-turn faults
• For a typical three-phase induction motor:
• 1% voltage unbalance (V2) relates to 6% current unbalance (I2)
• For small and medium sized motors, only current transformers (CTs) are available and
no voltage transformers (VTs). Measure current unbalance and protect motor.
• The heating effect caused by current unbalance will be protected by enabling the
unbalance input to the thermal model
• For example, a setting of 10% x FLA for the current unbalance alarm with a delay of
10 seconds and a trip level setting of 25% x FLA for the current unbalance trip with a
delay of 5 seconds would be appropriate.
Motor Relay
61. 27 – Undervoltage Protection
• The overall result of an undervoltage condition is an increase
in current and motor heating and a reduction in overall motor
performance.
• The undervoltage protection element can be thought of as
backup protection for the thermal overload element. In some
cases, if an undervoltage condition exists it may be desirable
to trip the motor faster than thermal overload element.
• The undervoltage trip should be set to 90% of nameplate
unless otherwise stated on the motor data sheets.
• Motors that are connected to the same source/bus may
experience a temporary undervoltage, when one of motors
starts. To override this temporary voltage sags, a time delay
setpoint should be set greater than the motor starting time.
62. 59 – Overvoltage Protection
• The overall result of an overvoltage condition is a
decrease in load current and poor power factor.
• Although old motors had robust design, new motors are
designed close to saturation point for better utilization of
core materials and increasing the V/Hz ratio cause
saturation of air gap flux leading to motor heating.
• The overvoltage element should be set to 110% of the
motors nameplate unless otherwise started in the data
sheets.
68. Size Matters
• Small 500 to 10,000 kVA
• Medium 10,000 kVA to 100 MVA
• Large 100 MVA and above
• Less than 500kVA not considered a power transformer
• Our Discussion is mainly applicable to Medium and Large
Power Transformers
73. Transformer Phase Shifts
• H1 (A) leads X1 (a) by 30
• Currents on “H” bushings are
line-to-line quantities
• Subtract from reference
phase vector the connected
non-polarity vector
HV LV
H1
H2
H3
X1
X3
X2
A
B
C
a
b
c
a
b
c A
B
C
Assume 1:1 transformer
81. 87T ‐ Inrush Detection
• Inrush Detection and Restraint
– 2nd harmonic restraint has been employed
for years
– “Gap” detection has also been employed
– As transformers are designed to closer
tolerances, the incidence of both 2nd
harmonic and low current gaps in waveform
have decreased
– If 2nd harmonic restraint level is set too low,
differential element may be blocked for
internal fault due to generated harmonics
83. Traditional 2nd Harmonic
> Responds to the RATIO of magnitudes of 2nd Harmonic and
Fundamental Frequency Components
> Typical setting is 15-20% (dependent on transformer
construction)
Adaptive 2nd Harmonic
> Responds to both Magnitudes and Phase Angles of 2nd Harmonic
and Fundamental Frequency Component
> Use on transformers experiencing lower than normal 2nd
harmonic levels during magnetizing inrush conditions (say 5-
10%)
87T – Harmonic Restraint
86. Igd, pu
I= max( IR1, IR2,IR0 ), pu
Min. PKP
S lope
Fast detection of winding ground faults
Very secure performance on external ground
faults
Configurable pickup, slope, and time delay
87TG - Restricted Ground Fault Protection
88. 63 – Pressure Devices
• Two Main Types:
– Sudden Pressure Relay – Applied to transformers
without a Conservator Tank, uses pressure Rate of
Rise
– Bucholtz Relays – Applied to Transformers with a
Conservator Tank, uses accumulated gas pressure
• When an Arc occurs in oil, a release of various
gasses occurs.
• Sudden Pressure Increase is Detected by Relay
91. SUDDEN PRESSURE
RELAY
CHANGE PRESSURE RELIEF
DEVICE
63 - Sudden Pressure Relay (SPR)
•The SPR detects excessive rates of pressure rise within the
tank as result of internal arcing causing oil breakdown and
subsequent gas evolution
•They can operate on a change in oil or gas pressure
•Using a bellows and orifice to respond to rapid differential
pressure changes, they are an inverse-time characteristic
•The SPR should be an input on the digital transformer relay
for targeting, SOE and waveform capture
92. 63 - Buchholtz Relay
•Used on conservator type oil preservation systems
as a protective device that senses gas accumulation
•If a low level fault results in arcing, the small
amount of gas that is produced will accumulate in
this relay resulting in an alarm
•The SPR should be an input on the digital
transformer relay for targeting, SOE and waveform
capture
94. 59/81 – Overexcitation Causes
• Transmission Systems that Supply Distribution Substations
– High voltage from Generating Plants
– Voltage and Reactive Support Control Failures
• Runaway LTCs
• Capacitor banks in when they should be out
• Shunt reactors out when they should be in
• Near‐end breaker failures resulting in voltage rise on
line (Ferranti effect)