The document discusses electromagnetic relays used in power systems. It describes two main operating principles for electromagnetic relays: electromagnetic attraction and electromagnetic induction. Electromagnetic attraction relays operate using an armature attracted to magnet poles, and include attractor-armature, solenoid, and balanced beam types. Electromagnetic induction relays operate on induction motor principles using a pivoted disc and alternating magnetic fields, and include shaded-pole, watt-hour meter, and induction cup structures. The document also defines important relay terms like pick-up current, current setting, and time-setting multiplier.
This PPT About The Double Line To Ground Fault Analysis in electrical power system.in that PPT derive the equation of double line to ground fault step by step.in this PPT show the circuit diagram of double line to ground fault.
Directional and differential relays operate based on the direction and magnitude of current flow in a circuit. Directional relays only operate when power flows in a specific direction, typically away from a protected zone. Differential relays compare current magnitudes at both ends of a protected zone and operate when there is a difference, indicating an internal fault. Percentage or biased beam differential relays include a restraining coil to prevent operation under heavy load conditions by requiring a higher differential current threshold. Translay systems use voltage balance between relay windings rather than current transformer secondaries to protect long cable runs while avoiding accuracy issues of traditional voltage balance schemes.
This document discusses transformer protection philosophy and methods. It describes various types of faults that can occur in transformers like ground faults, phase-to-phase faults, interturn faults, and core faults. It also discusses mechanical protections like Buchholz relay, sudden pressure relay, pressure relief valve, and temperature indicators. Electrical protections discussed include biased differential relay protection and harmonic restraint. The document provides details on how these protections work and their settings.
Representation of power system componentsPrasanna Rao
This document discusses the representation of power system components in circuit models for analysis. It introduces the key components of a power system, including generators, transmission lines, and distribution systems. It then covers circuit models for representing synchronous machines, transformers, transmission lines, and static and dynamic loads. The rest of the document discusses additional modeling techniques like one-line diagrams, impedance diagrams, per-unit systems, and calculating base values for analysis.
This document discusses underground cables for electrical power distribution. It covers the construction of cables including conductors, insulation, metallic sheathing, bedding, armouring and serving. Common insulating materials like XLPE are described. Cables are classified based on voltage level. Methods of laying cables underground include direct laying, draw-in systems and solid systems. Potential cable faults include open circuits, short circuits and earth faults. Underground cables have advantages over overhead systems like better appearance, lower maintenance needs and fewer faults, but the installation costs are higher.
The document discusses electromagnetic relays used in power systems. It describes two main operating principles for electromagnetic relays: electromagnetic attraction and electromagnetic induction. Electromagnetic attraction relays operate using an armature attracted to magnet poles, and include attractor-armature, solenoid, and balanced beam types. Electromagnetic induction relays operate on induction motor principles using a pivoted disc and alternating magnetic fields, and include shaded-pole, watt-hour meter, and induction cup structures. The document also defines important relay terms like pick-up current, current setting, and time-setting multiplier.
This PPT About The Double Line To Ground Fault Analysis in electrical power system.in that PPT derive the equation of double line to ground fault step by step.in this PPT show the circuit diagram of double line to ground fault.
Directional and differential relays operate based on the direction and magnitude of current flow in a circuit. Directional relays only operate when power flows in a specific direction, typically away from a protected zone. Differential relays compare current magnitudes at both ends of a protected zone and operate when there is a difference, indicating an internal fault. Percentage or biased beam differential relays include a restraining coil to prevent operation under heavy load conditions by requiring a higher differential current threshold. Translay systems use voltage balance between relay windings rather than current transformer secondaries to protect long cable runs while avoiding accuracy issues of traditional voltage balance schemes.
This document discusses transformer protection philosophy and methods. It describes various types of faults that can occur in transformers like ground faults, phase-to-phase faults, interturn faults, and core faults. It also discusses mechanical protections like Buchholz relay, sudden pressure relay, pressure relief valve, and temperature indicators. Electrical protections discussed include biased differential relay protection and harmonic restraint. The document provides details on how these protections work and their settings.
Representation of power system componentsPrasanna Rao
This document discusses the representation of power system components in circuit models for analysis. It introduces the key components of a power system, including generators, transmission lines, and distribution systems. It then covers circuit models for representing synchronous machines, transformers, transmission lines, and static and dynamic loads. The rest of the document discusses additional modeling techniques like one-line diagrams, impedance diagrams, per-unit systems, and calculating base values for analysis.
This document discusses underground cables for electrical power distribution. It covers the construction of cables including conductors, insulation, metallic sheathing, bedding, armouring and serving. Common insulating materials like XLPE are described. Cables are classified based on voltage level. Methods of laying cables underground include direct laying, draw-in systems and solid systems. Potential cable faults include open circuits, short circuits and earth faults. Underground cables have advantages over overhead systems like better appearance, lower maintenance needs and fewer faults, but the installation costs are higher.
This document describes a three phase inverter that converts DC voltage to AC voltage. There are two main modes of conduction for a three phase inverter - 180 degree conduction and 120 degree conduction. 180 degree conduction involves three switches being on at a time, while 120 degree conduction only has two switches on at a time. The document provides circuit diagrams and equations to calculate the output voltages under each conduction mode. Waveforms are also shown to illustrate the phase and line voltages.
Design Development and Testing of an Overvoltage and Undervoltage Protection ...Kunal Maity
This voltage protection circuit is designed to develop a low-voltage and high-voltage tripping mechanism to protect a load from any damage. The electronic devices get easily damaged due to fluctuation in AC means supply take place frequently.
Representation of short & medium transmission linesvishalgohel12195
This document discusses the classification and modeling of overhead transmission lines. It notes that short transmission lines only consider resistance and inductance due to their lower voltages and distances. Medium and long transmission lines must account for capacitance effects. The document presents models for short lines using lumped resistance and inductance and models for medium lines using end condenser, nominal T, and nominal π methods which lump the distributed capacitance for simplified analysis. It also discusses voltage regulation and transmission efficiency calculations.
Sphere gaps can be used to measure high voltages up to 2500 kV. They work by measuring the sparkover voltage between two conductive spheres. The standard diameters for the spheres are between 6.25 cm to 200 cm. Various factors like humidity, temperature, and pressure can influence the sparkover voltage. Sphere gaps are accurate to within 3% for measurements if the spacing between the spheres is less than half the sphere diameter.
Application of Capacitors to Distribution System and Voltage RegulationAmeen San
Application of Capacitors to
Distribution System and Voltage
Regulation
POWER FACTOR IMPROVEMENT,
System Harmonics
Voltage Regulation
Methods of Voltage Control
This document defines and compares active power, reactive power, and apparent power in AC circuits. It states that active power is responsible for useful work, is represented by P, and is given by the relation P=VICosθ. Reactive power oscillates between the source and load, does not contribute to useful work, and is represented by Q=VISinθ. Apparent power is represented by S=VI and is equal to the square root of the sum of the squares of active and reactive power.
A microgrid is a small-scale power supply network designed to provide power for a small community. It enables local power generation and is connected to both local generating units and the utility grid to prevent outages. Excess power can be sold back to the grid. Microgrids use various small power sources, making them flexible and efficient. They can reduce transmission losses and provide reliable energy to critical loads. DC microgrids in particular are more efficient and can interface naturally with renewable energy sources. Microgrids have applications for households, renewable energy parks, energy storage, and electric vehicle charging stations. Controlling techniques include linear, non-linear, active and passive controls. Future trends involve making microgrids more intelligent and robust through improved interaction with
1) The document discusses inductance in electrical conductors and transmission lines. It defines internal and external inductance and provides formulas to calculate them.
2) Formulas are provided for the inductance of a single-phase two-wire transmission line, as well as a three-phase line with symmetrical and unsymmetrical conductor spacing.
3) Bundled conductors are described as having multiple sub-conductors to reduce losses at high voltages and transmit more power efficiently.
Construction & E.M.F. eqn. of transformerJay Baria
In this ppt, construction and emf equation of transformer is shown and also the types of transformer and its various losses and its application is given in the presentation.
The document discusses phase control rectifiers, including:
- Single phase half wave control with resistive and resistive-inductive loads, including the use of a freewheeling diode.
- Performance parameters such as average output voltage, power factor, current distortion factor, and more.
- Single phase full wave converters using midpoint and bridge configurations. Waveforms and operation of each are described.
The document summarizes the different generations of electrical relays used in digital protection systems. It discusses fuse relays, electromechanical relays, solid state relays, digital relays, adaptive digital relays, multifunction relays, and intelligent relays. Electromechanical relays were prone to failures over time but newer digital and solid state relays are more reliable with no moving parts. Digital relays allow for more complex functions, self-testing, and communication compared to earlier relay technologies. Adaptive digital relays can automatically adjust settings based on changes in power system conditions. Multifunction relays provide multiple protection functions in a single unit to reduce space and wiring needs. Intelligent relays allow customers to change
Voltage characteristics of grid electricity (EN 50160)Leonardo ENERGY
Three parties exert an influence on the power quality in the electric network: the network operator, the network user and the manufacturer of the network equipment. Standard EN 50160 represents a compromise between those three parties.
The important advantages of the EN 50160 standard are:
The definition of the voltage parameters important for power quality
The quantitative determination of reference values that can be used in the power quality evaluation
EN 50160 deals with the voltage characteristics in statistical or probabilistic terms. It gives recommendations that, for a percentage of measurements (e.g. 95%) over a given time, the value must be within the specified limits. This boundary value will be accepted as the compatibility level between the level of disturbances in the network and the level of immunity of equipment.
If the customer has higher requirements than the minimum performance criteria prescribed in this standard, they should instigate their own mitigation measures. Another option is to negotiate a separate agreement for a higher supply quality with the power supplier.
In this way, the responsibilities of the network operator, equipment manufacturer and user are matched and clarified.
This document discusses fundamentals of alternating current (AC), including:
- AC voltage is generated as sinusoidal waves by power plants and used worldwide.
- Key definitions for AC waves include waveform, instantaneous value, peak amplitude, peak-to-peak value, cycle, period, and frequency.
- The basic mathematical form for a sinusoidal AC waveform is y = A sin(ωt), where A is the amplitude and ωt represents angular displacement over time.
- Root mean square (RMS) value represents the effective or heating value of AC and is calculated as the square root of the mean of the squares of the instantaneous values over one cycle.
- Average value of a symmetrical AC waveform is
The document discusses shunt reactors used in power systems. Shunt reactors are installed to reduce grid voltage during off-peak periods when excess reactive power leads to high voltages. They absorb reactive power through magnetizing currents, thereby reducing voltage. The document recommends installing 25 additional shunt reactors of 63 MVAR each in the southern grid to maintain voltages between 416-420 kV during off-peak hours. It provides background on why reactors are needed and describes the basic operating principles and components of shunt reactors.
This document discusses the various types of testing required for protection equipment, including:
- Type tests to prove the relay meets specifications and standards under abnormal power conditions.
- Routine factory production tests to check for defects during manufacturing.
- Commissioning tests to prove correct installation of a protection scheme before use.
- Periodic maintenance tests to identify equipment failures or degradation over time.
Electrical type tests are described in detail, including functional, rating, thermal withstand, burden, input, output, and insulation resistance tests. The purpose is to thoroughly evaluate performance and safety.
This presentation discusses transmission lines, including overhead power lines and underground cables. It classifies transmission lines as overhead or underground, and further divides them based on voltage and construction. Overhead lines are cheaper but can be affected by the environment, while underground cables are more expensive to install and maintain but are safer and not impacted by the environment. The presentation also covers nominal T and Pi circuit models that can be used to analyze medium transmission lines, and provides equations for calculating voltages and currents at the sending and receiving ends.
This document discusses various types of three-phase transformer connections including:
- Delta-delta, which produces no phase shift between input and output voltages.
- Delta-wye, which produces a 30 degree phase shift.
- Wye-delta, which also produces a 30 degree phase shift with primary and secondary connections reversed from delta-wye.
- Wye-wye requires special precautions like connecting the neutral or using a tertiary winding to prevent voltage distortion.
- Open-delta can transform voltage using only two transformers in an emergency situation but has lower capacity.
- Autotransformers are more economical than conventional transformers for moderate voltage changes between 0.5-2 times.
Protection against overvoltage
overvoltage
causes of overvoltage
lightning
types of lightning strokes
harmful effect of lightning
protection against lightning
Tugas Kelompok 4 - Teknik Tegangan Tinggi - Prof.Ir. Syamsir Abduh , MM, Ph.D...Rio Afdhala
Dokumen tersebut membahas tentang tegangan tinggi DC, termasuk fungsi pengujian tegangan tinggi DC, fenomena yang terjadi pada tegangan tinggi seperti sparkover dan korona, kelebihan sistem transmisi menggunakan tegangan tinggi DC seperti kapasitas penyaluran yang lebih besar, dan contoh rangkaian pembangkit tegangan tinggi DC seperti rangkaian Greinacher dan Cockroft-Walton.
This document provides information about the fourth edition of the textbook "Electric Machinery Fundamentals" by Stephen J. Chapman. It includes details about the author's background and qualifications. The book is dedicated to the author's mother and contains brief contents, table of contents, and information about the publisher. It provides a high-level overview of the textbook's coverage of fundamental principles of electric machinery, transformers, power electronics, AC and DC machines.
Transient overvoltages and currents: detection and measurementBruno De Wachter
This document discusses power quality monitoring for transients and overvoltages. It describes the purposes of monitoring as contractual verification, troubleshooting, and statistical surveys. It also discusses considerations for instrumentation, noting that transients can occur in the low-frequency millisecond range or high-frequency microsecond range. Monitoring in the low-frequency domain requires selecting voltage and current transducers to provide adequate signal levels and frequency response. Instrumentation selection depends on factors like the monitoring location and ability to interrupt the circuit being monitored.
This document describes a three phase inverter that converts DC voltage to AC voltage. There are two main modes of conduction for a three phase inverter - 180 degree conduction and 120 degree conduction. 180 degree conduction involves three switches being on at a time, while 120 degree conduction only has two switches on at a time. The document provides circuit diagrams and equations to calculate the output voltages under each conduction mode. Waveforms are also shown to illustrate the phase and line voltages.
Design Development and Testing of an Overvoltage and Undervoltage Protection ...Kunal Maity
This voltage protection circuit is designed to develop a low-voltage and high-voltage tripping mechanism to protect a load from any damage. The electronic devices get easily damaged due to fluctuation in AC means supply take place frequently.
Representation of short & medium transmission linesvishalgohel12195
This document discusses the classification and modeling of overhead transmission lines. It notes that short transmission lines only consider resistance and inductance due to their lower voltages and distances. Medium and long transmission lines must account for capacitance effects. The document presents models for short lines using lumped resistance and inductance and models for medium lines using end condenser, nominal T, and nominal π methods which lump the distributed capacitance for simplified analysis. It also discusses voltage regulation and transmission efficiency calculations.
Sphere gaps can be used to measure high voltages up to 2500 kV. They work by measuring the sparkover voltage between two conductive spheres. The standard diameters for the spheres are between 6.25 cm to 200 cm. Various factors like humidity, temperature, and pressure can influence the sparkover voltage. Sphere gaps are accurate to within 3% for measurements if the spacing between the spheres is less than half the sphere diameter.
Application of Capacitors to Distribution System and Voltage RegulationAmeen San
Application of Capacitors to
Distribution System and Voltage
Regulation
POWER FACTOR IMPROVEMENT,
System Harmonics
Voltage Regulation
Methods of Voltage Control
This document defines and compares active power, reactive power, and apparent power in AC circuits. It states that active power is responsible for useful work, is represented by P, and is given by the relation P=VICosθ. Reactive power oscillates between the source and load, does not contribute to useful work, and is represented by Q=VISinθ. Apparent power is represented by S=VI and is equal to the square root of the sum of the squares of active and reactive power.
A microgrid is a small-scale power supply network designed to provide power for a small community. It enables local power generation and is connected to both local generating units and the utility grid to prevent outages. Excess power can be sold back to the grid. Microgrids use various small power sources, making them flexible and efficient. They can reduce transmission losses and provide reliable energy to critical loads. DC microgrids in particular are more efficient and can interface naturally with renewable energy sources. Microgrids have applications for households, renewable energy parks, energy storage, and electric vehicle charging stations. Controlling techniques include linear, non-linear, active and passive controls. Future trends involve making microgrids more intelligent and robust through improved interaction with
1) The document discusses inductance in electrical conductors and transmission lines. It defines internal and external inductance and provides formulas to calculate them.
2) Formulas are provided for the inductance of a single-phase two-wire transmission line, as well as a three-phase line with symmetrical and unsymmetrical conductor spacing.
3) Bundled conductors are described as having multiple sub-conductors to reduce losses at high voltages and transmit more power efficiently.
Construction & E.M.F. eqn. of transformerJay Baria
In this ppt, construction and emf equation of transformer is shown and also the types of transformer and its various losses and its application is given in the presentation.
The document discusses phase control rectifiers, including:
- Single phase half wave control with resistive and resistive-inductive loads, including the use of a freewheeling diode.
- Performance parameters such as average output voltage, power factor, current distortion factor, and more.
- Single phase full wave converters using midpoint and bridge configurations. Waveforms and operation of each are described.
The document summarizes the different generations of electrical relays used in digital protection systems. It discusses fuse relays, electromechanical relays, solid state relays, digital relays, adaptive digital relays, multifunction relays, and intelligent relays. Electromechanical relays were prone to failures over time but newer digital and solid state relays are more reliable with no moving parts. Digital relays allow for more complex functions, self-testing, and communication compared to earlier relay technologies. Adaptive digital relays can automatically adjust settings based on changes in power system conditions. Multifunction relays provide multiple protection functions in a single unit to reduce space and wiring needs. Intelligent relays allow customers to change
Voltage characteristics of grid electricity (EN 50160)Leonardo ENERGY
Three parties exert an influence on the power quality in the electric network: the network operator, the network user and the manufacturer of the network equipment. Standard EN 50160 represents a compromise between those three parties.
The important advantages of the EN 50160 standard are:
The definition of the voltage parameters important for power quality
The quantitative determination of reference values that can be used in the power quality evaluation
EN 50160 deals with the voltage characteristics in statistical or probabilistic terms. It gives recommendations that, for a percentage of measurements (e.g. 95%) over a given time, the value must be within the specified limits. This boundary value will be accepted as the compatibility level between the level of disturbances in the network and the level of immunity of equipment.
If the customer has higher requirements than the minimum performance criteria prescribed in this standard, they should instigate their own mitigation measures. Another option is to negotiate a separate agreement for a higher supply quality with the power supplier.
In this way, the responsibilities of the network operator, equipment manufacturer and user are matched and clarified.
This document discusses fundamentals of alternating current (AC), including:
- AC voltage is generated as sinusoidal waves by power plants and used worldwide.
- Key definitions for AC waves include waveform, instantaneous value, peak amplitude, peak-to-peak value, cycle, period, and frequency.
- The basic mathematical form for a sinusoidal AC waveform is y = A sin(ωt), where A is the amplitude and ωt represents angular displacement over time.
- Root mean square (RMS) value represents the effective or heating value of AC and is calculated as the square root of the mean of the squares of the instantaneous values over one cycle.
- Average value of a symmetrical AC waveform is
The document discusses shunt reactors used in power systems. Shunt reactors are installed to reduce grid voltage during off-peak periods when excess reactive power leads to high voltages. They absorb reactive power through magnetizing currents, thereby reducing voltage. The document recommends installing 25 additional shunt reactors of 63 MVAR each in the southern grid to maintain voltages between 416-420 kV during off-peak hours. It provides background on why reactors are needed and describes the basic operating principles and components of shunt reactors.
This document discusses the various types of testing required for protection equipment, including:
- Type tests to prove the relay meets specifications and standards under abnormal power conditions.
- Routine factory production tests to check for defects during manufacturing.
- Commissioning tests to prove correct installation of a protection scheme before use.
- Periodic maintenance tests to identify equipment failures or degradation over time.
Electrical type tests are described in detail, including functional, rating, thermal withstand, burden, input, output, and insulation resistance tests. The purpose is to thoroughly evaluate performance and safety.
This presentation discusses transmission lines, including overhead power lines and underground cables. It classifies transmission lines as overhead or underground, and further divides them based on voltage and construction. Overhead lines are cheaper but can be affected by the environment, while underground cables are more expensive to install and maintain but are safer and not impacted by the environment. The presentation also covers nominal T and Pi circuit models that can be used to analyze medium transmission lines, and provides equations for calculating voltages and currents at the sending and receiving ends.
This document discusses various types of three-phase transformer connections including:
- Delta-delta, which produces no phase shift between input and output voltages.
- Delta-wye, which produces a 30 degree phase shift.
- Wye-delta, which also produces a 30 degree phase shift with primary and secondary connections reversed from delta-wye.
- Wye-wye requires special precautions like connecting the neutral or using a tertiary winding to prevent voltage distortion.
- Open-delta can transform voltage using only two transformers in an emergency situation but has lower capacity.
- Autotransformers are more economical than conventional transformers for moderate voltage changes between 0.5-2 times.
Protection against overvoltage
overvoltage
causes of overvoltage
lightning
types of lightning strokes
harmful effect of lightning
protection against lightning
Tugas Kelompok 4 - Teknik Tegangan Tinggi - Prof.Ir. Syamsir Abduh , MM, Ph.D...Rio Afdhala
Dokumen tersebut membahas tentang tegangan tinggi DC, termasuk fungsi pengujian tegangan tinggi DC, fenomena yang terjadi pada tegangan tinggi seperti sparkover dan korona, kelebihan sistem transmisi menggunakan tegangan tinggi DC seperti kapasitas penyaluran yang lebih besar, dan contoh rangkaian pembangkit tegangan tinggi DC seperti rangkaian Greinacher dan Cockroft-Walton.
This document provides information about the fourth edition of the textbook "Electric Machinery Fundamentals" by Stephen J. Chapman. It includes details about the author's background and qualifications. The book is dedicated to the author's mother and contains brief contents, table of contents, and information about the publisher. It provides a high-level overview of the textbook's coverage of fundamental principles of electric machinery, transformers, power electronics, AC and DC machines.
Transient overvoltages and currents: detection and measurementBruno De Wachter
This document discusses power quality monitoring for transients and overvoltages. It describes the purposes of monitoring as contractual verification, troubleshooting, and statistical surveys. It also discusses considerations for instrumentation, noting that transients can occur in the low-frequency millisecond range or high-frequency microsecond range. Monitoring in the low-frequency domain requires selecting voltage and current transducers to provide adequate signal levels and frequency response. Instrumentation selection depends on factors like the monitoring location and ability to interrupt the circuit being monitored.
Evaluating the Arc-Flash Protection Benefits of IEC 61850 CommunicationSchneider Electric
The goal of arc-flash protection is to minimize the damaging effects of released energy, which requires very fast and reliable communication among protection system components. In addition to discussing communication requirements and options for sensors, current transformers, relays, circuit breakers, and upper level control systems, this paper introduces and evaluates the benefits and drawbacks of new IEC 61850-based communication options.
Behavioral studies of surge protection componentsjournalBEEI
In our daily life, almost all the items we used, being a computer, television, lift or vehicle we drive consist of some kind of electrical or electronics component inside. The operation of these devices could be severely affected by lightning activity or electrical switching events, as there are more than 2000 thunderstorms in progress at any time resulting in 100 lightning flashes to ground per second. In practice, any device using electricity will subject to surge damages induced from the lightning or switching of heavy load. Surge protection device (SPD) is added at the power distribution panel and critical process loop to prevent damage subsequently cause plant shutdown. There are many questions raised on the SPD. How can this small device protect the equipment from large energy release by the lightning? What is inside the device? How does it work? This paper provides comprehensive detail in revealing the science and engineering behind the SPD, its individual component characteristic and how does it work. The technical information presented is limited to surge protection on equipment; surge protection for building structure will not be discussed here.
IRJET- Embedded System based Multi-Source Leakage Current Protection for Low ...IRJET Journal
1. The document discusses the development of a microcontroller-based residual current circuit breaker (RCCB) that can detect faults even when the main power supply fails and a backup inverter is providing power.
2. Conventional RCCBs only protect against faults in the main power supply and not the backup inverter. This leaves users at risk of electric shock if a fault occurs when the inverter is operating.
3. The proposed microcontroller-based RCCB aims to address this issue by detecting faults under any power conditions, whether the main supply or backup inverter is providing power, in order to protect users.
This is a great guide to surge protection from Hager and if you would like Hager Surge Protection fitted to your Bypass Switches Input for mains one or two please call us on 0800 978 8988 or email sales@criticalpowersupplies.co.uk
Critical Power Supplies provide a range of surge protection kits that can be fitted to any of our bypass switches or consumer units to meet Amendment 1 of the 17th Edition.
The surge protection devices in the kit offer type 2 protection to the BS EN 61643 standard, to ensure conformity with the current edition of BS 7671.
Amendment 1 of the 17th Edition requires electricians to conduct a risk assessment of properties to see if they require surge protection.
When you consider that many homes have a lot of sensitive electronic equipment, such as TVs, Hi-Fis, PCs and printers that would be adversely affected by a voltage surge, then the need for such devices increases.
Transient overvoltages are not just caused by a direct lightning strike, a nearby strike, within a kilometre, can cause substantial damage. Other causes can be fluctuations in the power supply or from equipment such as microwaves or showers being switched.
Our surge protection kit can prevent the spread of overvoltages in electrical installations and protect the equipment connected to it. It is characterised by an 8/20us current wave.
To gain a greateer understanding of Surge Protection and our Surge Protection Kit & Devices download a copy of our Guide to Surge Protection Devices.
Early warning surge&lightning (electrical safety ) for valuable equipment...Mahesh Chandra Manav
Surge protection devices (SPDs) are important for protecting electrical equipment from overvoltage events like lightning strikes. The key points are:
1. SPDs consist of nonlinear components that suppress transient overvoltages, as well as indicators and short circuit protection. Common technologies are varistors, gas discharge tubes, and zener diodes.
2. For electrical installations, SPDs should be selected based on factors like the level of lightning exposure, the maximum discharge current, and distance from sensitive loads. A Type 1 SPD is installed at the main switchboard while additional Type 2 or 3 SPDs provide finer protection closer to equipment.
3. Proper SPD installation is also important, with short
Control of Dvr with Battery Energy Storage System Using Srf TheoryIJERA Editor
One of the best solutions to improve power quality is the dynamic voltage restorer (DVR). DVR is a kind of
custom power devices that can inject active/reactive power to the power grids. This can protect loads from
disturbances such as sag and swell. Usually DVR installed between sensitive loads feeder and source in
distribution system. Its features include lower cost, smaller size, and its fast dynamic response to the
disturbance. In this project SRF technique is used for conversion of voltage from rotating vectors to the
stationary frame. SRF technique is also referred as park’s transformation. In this the reference load voltage is
estimated using the unit vectors. The real power exchanged at the DVR output ac terminal is provided by the
DVR input dc terminal by an external energy source or energy storage system. In this project three phase
parallel or series load may be used along with SRF technique to compensate voltage sag and voltage swell. And
also wind generator is also used as a load. This project presents the simulation of DVR system using
MATLAB/SIMULINK.
1) The document provides guidance on selecting and installing surge protection devices (SPDs) to protect electrical equipment from damage caused by transient overvoltages.
2) It recommends using a Type 1 SPD at the origin of an installation, Type 2 SPDs at distribution boards, and Type 3 SPDs near sensitive terminal equipment as part of a cascading protection scheme.
3) Key factors in selecting SPDs include the installation's exposure to lightning, the sensitivity of equipment to be protected, and BS 7671 requirements for impulse withstand voltages and surge current ratings.
This document provides an overview of surge protection devices (SPDs), including their selection, application and operating theory. It discusses the sources and types of transient overvoltages that can damage electrical equipment. SPDs help mitigate these dangers by limiting transient voltage spikes. The document reviews relevant lightning and surge protection standards like BS EN 62305 and BS 7671. It examines SPD types, design considerations, installation best practices, inspection and testing procedures. Protection against overcurrents and coordination of multiple SPDs is also covered.
This document summarizes a research paper that proposes a microcontroller-based system to monitor and protect electric distribution transformers. The system would detect faults like single line-ground faults, line-to-line faults, double line-ground faults, overvoltage, and undervoltage. It would send fault alerts via GSM network to a control station. A user interface using MATLAB would display the distribution system status. The aim is to minimize equipment damage from faults and improve power distribution monitoring and management. Key components include step-down transformers, a microcontroller, GSM module, and bridge rectifier.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
The document is a project report on an Uninterruptible Power Supply (UPS) system. It includes sections on the problem identification, circuit diagram and components, and project work completed. The project involves designing a UPS that can provide regulated DC power from batteries during power outages or disturbances. Key components include a transformer, rectifier, battery, voltage regulator, and static switch. The project work done so far includes collecting data, analyzing the circuit diagram, and preparing the report. Future work will involve building the circuit, testing it, and submitting the final report.
This document is a seminar report on power system protection. It includes an introduction to power system protection and its objectives. It describes the key components of a protection system including current transformers, potential transformers, protective relays, circuit breakers, lightning arresters, and isolators. It provides details on the purpose and operation of each component. The document is submitted to fulfill the requirements for a bachelor's degree in electrical engineering.
Switchgear and Protection ...........................MANOJ KHARADE
1. Circuit breakers are used in power systems to interrupt faults by opening and breaking the circuit. They can operate manually or automatically under normal and abnormal load conditions.
2. When the contacts of a circuit breaker open during a fault, an electric arc is struck which must be extinguished quickly to interrupt the current. Various circuit breaker designs employ different mechanisms and mediums to rapidly elongate, chop, or dissipate the arc to achieve interruption.
3. Common circuit breaker types include oil, air, SF6, and vacuum breakers which differ in the insulating medium used. Proper selection of breakers based on voltage ratings and interrupting capabilities is important for power system protection and reliability.
Switchgear and Protection.................MANOJ KHARADE
This document provides an overview of circuit breakers and power system protection. It discusses the need for protection systems due to faults that can occur in power systems. Faults are classified as short circuits or open circuits, with short circuits being more common and serious. The protection system aims to reliably and quickly isolate faults while maintaining supply to unaffected sections. It divides the system into protective zones so that primary protection clears faults within a zone, with backup protection in case of primary failure. Selectivity is important to isolate only the faulty section. Circuit breakers are used to define zone boundaries and isolate faults.
The document discusses standards for motor control center design, including those established by UL, NEMA, and the National Electrical Code. It also summarizes several other organizations that develop relevant standards, such as IEEE, IEC, and ANSI. Proper overcurrent protection of motor control centers is required for safety, as it prevents equipment damage from overloads, short circuits, and ground faults.
This document provides guidance on electrical safety in the construction sector. It covers basic concepts of electricity including circuits, voltage, resistance and current. It describes common electrical accidents in construction and their consequences. Recommendations are given for safe use of temporary electrical installations, tools and equipment. An annex includes an inspection checklist for electrical safety and a model for electrical safety management. The overall aim is to prevent electrical risks and accidents in construction work.
Similar to Transient overvoltages and currents: mitigation and protection techniques (20)
This Application Note describes the technology and applications of infrared heating. The basic principles behind the technology and its important characteristics, such as the effect of emissivity and shape coefficient on the rate of transfer of thermal energy, are described.
Infrared heating is characterized by high energy densities, rapid heating, and relative ease of installation. All these advantages offer the possibility of higher production speeds, more compact installations, and lower investment costs. Thus, in many industrial production processes, infrared heating offers advantages with respect to conventional heating techniques such as convection or hot air ovens.
Induction heating is used for the direct heating of electrically conducting materials. The primary advantage is that the heat is generated within the material itself, giving very fast cycle times, high efficiency, and the potential for localized heating. On the downside, because of the desired coupling between inductor and load, there are restrictions on the size and geometry of the work piece. However, there are many applications in the field of heating or melting of metals.
This application note illustrates the use and advantages of dielectric heating, which as the name implies, is used for materials that are non-conducting. The essential advantage of dielectric heating is that the heat is generated within the material to be heated. In comparison with more conventional heating techniques (hot air, infrared, et cetera) in which the material is heated via the outer surface, dielectric heating is much more rapid. This is because electrical insulating materials, i.e. the domain of dielectric heating, are usually also poor conductors of heat.
Other interesting characteristics of radio frequency and microwave heating are the high power density and the potential for selectively heating materials. However, dielectric heating is an expensive technique and its application is generally limited to the heating of products with high added value, or to products that cannot be heated by other means.
Introduction to industrial electrical process heatingBruno De Wachter
This application note provides an introduction to a series of papers on industrial electric process heating technologies, hereinafter referred to as electro-heat or electro-heating technologies.
It briefly describes the basic principles of each of the various electro-heating technologies and explores their common ground. The economic and process related advantages of electro-heat are discussed. In the majority of cases, electro-heat has a better environmental performance than an industrial heating system utilizing natural gas or other fossil fuels. This application note provides some insight into why this is the case.
Finally, this paper provides an overview of the most appropriate applications as well as a short overview of the specific areas of technological development for each of the electro-heat technologies.
Leonard is evaluating investment options for replacing an existing system. He performed a basic LCC analysis but wants to strengthen his analysis by accounting for uncertainties. A stochastic LCC analysis using Monte Carlo simulation can model uncertain inputs as distributions rather than single values. This allows Leonard to identify risks and see how robust his decision is to changes in inputs. The document discusses key statistical concepts needed to model inputs as distributions, including probability mass functions, cumulative distribution functions, means, modes and standard deviations. It also introduces a running example to illustrate applying these concepts to Leonard's investment problem.
Leonard is considering replacing his company's aging pump system with one of two newer options. He performs a life cycle cost analysis to determine the lowest total cost alternative over a 9-year period. The summary outlines the 6 steps of the analysis: 1) Define the objective as choosing the lowest cost of the three options over 9 years. 2) Identify relevant costs as investment, maintenance, energy, downtime, salvage value. 3) Gather data on these costs from sources and estimate costs for each year. 4) Calculate key financial indicators like net present value and internal rate of return. 5) Perform risk analysis on uncertain inputs. 6) Make the optimal decision.
The intention of this application note is to look at various aspects of generator sets (gensets) utilized globally to provide medium to long term backup power, and to improve system availability and reliability. Critical locations and applications depend on generators for back-up power. Examples of such critical locations are hospitals, airports, government buildings, telecommunications facilities, data centers, and nuclear power plants. Within this paper we intend to cover the main components of gensets, general applications, different fuels utilized, size selection, environmental issues, maintenance and noise pollution. The main emphasis of this document will be towards selection of gensets for critical loads and system availability.
This application note is intended to be a source of guidance and to help reduce confusion pertaining to the design, configuration, selection, sizing, and installation of Uninterruptable Power Supply (UPS) systems. This document is a useful information source for electrical consultants, electrical engineers, facility managers, and design and build contractors.
In the recent past, many design engineers have tried to create the perfect UPS solution for supporting critical loads. However, these designs have generally overlooked coverage for changing load profiles (e.g. leading power factor), sleep mode, and advanced scalability solutions. Such solutions and/or options can assist in gaining higher system efficiency, without exposing the critical load to disruptions from the utility.
This paper presents information related to various generic types of current UPS units, complete with their merits and demerits. It covers different topologies and various system solutions for clients. Auxiliary items, such as the battery bank, diesel generator set, and switchgear are included in the document since they also form an integral part of a UPS system.
To aid in the reduction of the carbon footprint, the paper has indicated achievable operational efficiency figures for different solutions.
A typical generic UPS Specification has been included as an Appendix to this paper to support electrical engineering professionals.
Replacement decisions for ageing physical assetsBruno De Wachter
The moment an asset will no longer be fit for use can seldom be determined when the asset is put in place. It invariably depends upon criticality and operational conditions. This is the reason there is a very large spread in useful asset life, even with the same type of assets within the same company.
Asset owners should periodically determine the remaining useful life (RUL) of their assets. An asset generally starts to deteriorate as it gets older. There are two main reasons why an organization needs to replace a deteriorated asset:
The operational costs (e.g. maintenance or energy costs) are rising to the point that it is economically better to invest in a new asset
The risk of critical failure is increasing to an unacceptable level
These are two different reasons that must be analyzed in two different ways.
A clear insight is necessary in the past and current costs of the asset, and in the age and condition of the asset, in order to correctly analyze the costs and to judge if replacement is economically a sound choice.
It is not possible, however, to use only past data to judge if the risk of continuing to use an asset is acceptable. Some critical failures could have such a significant impact that an organization should avoid them at all cost. For those assets, methodologies like criticality ranking and failure mode and effect analysis (FMEA) apply. Based on these, countermeasures and inspection programs can be put in place to mitigate the risks and determine when an asset should be replaced.
Developing preventive maintenance plans with RCMBruno De Wachter
Preventive maintenance has a great impact on performance, risk, costs and energy consumption of assets. It should be customised for each asset, because every asset works under different circumstances and has another criticality. One of the major shifts in point of view in preventive maintenance within these last few decades is that it should be aimed at fulfilling the organisational strategy.
Maintenance involves all the activities needed to keep an asset functioning according to the demands of the organisation. It includes not only overhauls or exchange of parts, but also calibration, inspection, cleaning, lubrication, functional tests and more. Simply replacing or restoring components after fixed intervals is called predetermined maintenance. This is often not an effective strategy, because only a minor part of all failure modes are time related. Most failure modes do not have a rising probability with rising component age. In these cases condition monitoring or function test may provide a good solution.
RCM is a good and generally accepted methodology to select preventive maintenance tasks. Because it is too time consuming to conduct it for every asset in an organisation, faster methods have been developed, such as Industrial RCM, which uses templates with failure modes and preventive maintenance actions for standard components.
This Application Note describes how to select the right mix of preventive maintenance tasks for an asset system, using RCM, Industrial RCM and Preventive Maintenance Set Up (PM Set Up).
Electrical storage systems: efficiency and lifetimeBruno De Wachter
This application note discusses the technical aspects of battery energy storage system design and operation and their influence upon system efficiency and lifetime. The various roles of electrical energy storage systems are discussed first in order to gain appreciation of the way these systems are used. This is followed by a discussion of the most common battery technologies and their aging mechanisms. Factors which affect the efficiency and lifetime of power electronics are also discussed, since power converter(s) and associated switchgear are essential elements and determine in part the performance of energy storage systems.
A common factor which affects both the lifetime of batteries and (power) electronics is heat: the higher the temperature, the faster a component ages. Energy losses result mostly in heat production. Striving for high energy efficiency in both the battery and power electronics thus gives a double payoff: in addition to the energy savings, the lowered heat production results in lowered cooling requirements and longer life of components due to a lower operating temperature.
Unleashing the limitless possibilities of electricity in technological applications requires proper caution and care. Handling vast amounts of energy—in any form—comes with significant hazards. When energy is released in an undesired way, the results can be devastating. One only needs to consider some manifestations of unwanted energy release in nature such as lightning strikes or earthquakes, to realize that handling energy requires due care.
Fortunately, the manifestation of energy in the form of electricity can be controlled—and thus can be made safe—relatively easily. Since its discovery, numerous methods and systems have been developed for harnessing electricity. This has enabled the benefits of electricity in everyday use and avoided its hazards.
The first section presents the most important and common hazards associated with the use of electricity, along with some basic concepts on hazard, risk, and risk reduction.
The second section gives an overview of common and standard design solutions, with a focus on the safety aspects of the particular techniques cited.
Transformers can be more than just static devices that transfer electrical energy. Separation transformers, isolation and extra isolation transformer play a major role in the protection of people and equipment. They come in all ranges, from very small (a few VA) to quite large (a few MVA), and although more expensive than autotransformers or transformers with simple separate windings, they are an easy way to solve problems that could arise concerning:
Protecting individuals from electrical shock
Avoiding critical equipment from losing power in the case of a first insulation fault
Protecting sensitive equipment from electrical noise
Creating a star point for equipment that require it
Given that the core business of a hospital is the welfare of its patients, it is easy to understand why the intricacies of electricity are not a high priority. However, ensuring patient welfare requires a huge variety of medical appliances, which in turn, require electricity. Electricity is therefore a vital utility and any malfunction or interruption can quickly lead to disastrous consequences.
This combination—being absolutely vital but far from the primary concern of the organization—entails a certain risk.
Standards and regulations prescribe how a hospital’s electrical installations should be conceived and installed to ensure safety and reliability. Those regulations are complemented by the prescriptions of the equipment manufacturers. All these rules, however, create a complex tangle of information for the user, often making it difficult to figure out which rule has to be applied where and exactly how it has to be implemented. In this tutorial, we will try to shed light on those regulations and give a comprehensive overview.
Once safety and reliability are taken care of, the focus can shift to energy efficiency. The fact that efficiency is only of secondary priority for a hospitals’ electrical installation does not mean its impact cannot be significant. By focusing on energy efficiency, hospitals can often make surprisingly large savings on the total cost of ownership (TCO) of their installations and thus on the cost of the medical aid they render. This paper addresses a few of the major energy efficiency topics relevant to medical building management.
Cables that are exposed to fire while being expected to retain their functionality and provide power to essential equipment at another location must be appropriately selected and sized to take account of the increased electrical resistance at elevated temperature. Manufacturers offer cables and accessories that will survive a standard cellulose fire for 30, 60 or 90 minutes when correctly specified and installed.
Cables, including fire safety cables, are specified in terms that reflect their normal duty conditions; design parameters under fire conditions are rarely, if ever, specified. The objective of this paper is to provide a clear methodology for designing fire safety circuits based on the derivation and application of correction factors and standard cable parameters.
Cables that are exposed to fire while being expected to retain their functionality and provide power to essential equipment at another location must be appropriately selected and sized. This is not only a question of an appropriate insulation. Designers must take account of the increased electrical resistance at elevated temperature.
Manufacturers offer cables and accessories that will survive a standard cellulose fire for 30, 60 or 90 minutes when correctly specified and installed.
A first step to specifying a suitable fire safety cable is a good knowledge of the temperature rise characteristic in areas affected by the fire.
A second step is the correct selection and erection of the cable. This includes the correct sizing of the conductor. Cables, including fire safety cables, are specified in terms that reflect their normal duty conditions; design parameters under fire conditions are rarely, if ever, specified. The designer must take into account the consequent effects of the increased resistance on current carrying capacity, voltage drop, and short circuit capacity of the conductors. Special care should go to the current carrying capacity of the conductor if it is to supply electrically driven fire pumps drawing high starting currents. The circuit protection should also be adapted to fire conditions, as it must be designed to function with significant higher loop impedance than normal.
This paper provides a clear methodology for designing fire safety circuits based on the derivation and application of correction factors and standard cable parameters.
Having selected the appropriate cable, it must be installed properly, using suitable accessories and following the manufacturer’s restrictions.
Safety in non-residential electrical installationsBruno De Wachter
Statistics regarding electrical accidents worldwide indicate that thousands of people are injured or killed every year. Electrical professionals working on the installation, maintenance, repair, and construction of electrical facilities are in fact the very people most likely to experience an electrical accident. Of these, electricians are the most vulnerable. Contact with electrical wiring or other electrical equipment is the most common cause of an electrical accident.
Achieving a zero number of electrical accidents will require a safe electrical installation, properly maintained over its lifetime, and an emphasis on the good condition of the measures protecting against electric shock and burns. This, together with a proper training of employees, will go a long way towards achieving this goal.
Earth resistance is a key parameter in determining the efficiency of earthing systems. In this application note we look at the measurement of earth resistance.
After a description of some universal fundamentals (e.g. standards, error margins and the influence of the weather), various measurement methods are discussed. A common feature of all the methods is that they determine the earth impedance by measuring the voltage across the earthing system for a known test current. Apart from that, there is a wide degree of variation in the internal circuitry of the measuring instruments used and the layout and arrangement of the external measuring circuit. A major distinction can be made between methods that draw current directly from the supply, and those methods that don’t.
Each method has its own particular disadvantages such as limited applicability, electric shock hazard, larger measurement errors, or requiring more time and effort to complete. The various advantages and disadvantages of the individual measurement techniques are described in the final chapters of this application note.
Power quality (PQ) is a major concern for a large number of industrial sites and buildings. This guide provides an easy-reference to the major power quality phenomena, the problems they are causing, and measures to avoid those problems. It is unlikely that a single solution will be effective. Careful design of a solutions mix, tailored to the PQ problems experienced, and based on a detailed understanding of the causes of the PQ problems, is needed.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
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
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
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%.
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
Car accident rates have increased in recent years, resulting in losses in human lives, properties, and other financial costs. An embedded machine learning-based system is developed to address this critical issue. The system can monitor road conditions, detect driving patterns, and identify aggressive driving behaviors. The system is based on neural networks trained on a comprehensive dataset of driving events, driving styles, and road conditions. The system effectively detects potential risks and helps mitigate the frequency and impact of accidents. The primary goal is to ensure the safety of drivers and vehicles. Collecting data involved gathering information on three key road events: normal street and normal drive, speed bumps, circular yellow speed bumps, and three aggressive driving actions: sudden start, sudden stop, and sudden entry. The gathered data is processed and analyzed using a machine learning system designed for limited power and memory devices. The developed system resulted in 91.9% accuracy, 93.6% precision, and 92% recall. The achieved inference time on an Arduino Nano 33 BLE Sense with a 32-bit CPU running at 64 MHz is 34 ms and requires 2.6 kB peak RAM and 139.9 kB program flash memory, making it suitable for resource-constrained embedded systems.
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.
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
2. Operations Strategy in a Global Environment.ppt
Transient overvoltages and currents: mitigation and protection techniques
1. APPLICATION NOTE
TRANSIENTS & OVERVOLTAGES: MITIGATION AND
PROTECTION TECHNIQUES
UIE
August 2015
ECI Publication No Cu0141
Available from www.leonardo-energy.org
3. Publication No Cu0141
Issue Date: August 2015
Page ii
CONTENTS
Summary ........................................................................................................................................................ 1
Fundamentals of surge protection.................................................................................................................. 2
General ..................................................................................................................................................................2
Types of surge-protective device components.......................................................................................................3
Types of surge-protective devices..........................................................................................................................3
Function of SPDs............................................................................................................................................. 6
Performance under surges .....................................................................................................................................6
Performance under steady-state variations...........................................................................................................6
Durability (Endurance)............................................................................................................................................6
Modes and mode conversion at the power port....................................................................................................6
Selection of limiting levels .............................................................................................................................. 7
Mitigate surges at the origin........................................................................................................................... 9
Mitigation of capacitor-switching transients................................................................................................. 10
General ................................................................................................................................................................10
Timing control.......................................................................................................................................................10
Pre-insertion devices ............................................................................................................................................11
Fixed inductors .....................................................................................................................................................11
MOV arresters ......................................................................................................................................................12
Inherent or built-in equipment protection.................................................................................................... 13
Add-On protection........................................................................................................................................ 14
SPD application at service entrance or point of use.............................................................................................14
Cascade coordination ...........................................................................................................................................14
General objective of coordination .........................................................................................................14
Assessment of coordination...................................................................................................................15
System interaction protection ...................................................................................................................... 16
Non-metallic links.................................................................................................................................................16
Equalizing reference potentials ............................................................................................................................16
4. Publication No Cu0141
Issue Date: August 2015
Page 1
SUMMARY
This is the eighth publication in a series of Application Notes on transient overvoltages and transient currents
in AC power systems and customer installations. For a general introduction to the subject, first read Cu0134 –
Transients and Overvoltages: Introduction.
This application note provides insight into the fundamentals of surge protection and mitigation.
It describes the basic characteristics of Surge Protective Devices (SPDs) which divert surges by offering a low-
impedance path to return the surge current to its source. The different types of SPDs are presented, based on
their internal circuitry and their components. This application note also discusses the various functions of an
SPD and the conditions it should be able to withstand as well as insight into how to select the SPD limiting
levels.
Different techniques for the mitigation of capacitor-switching transients are discussed in this application note.
In the final part of this note, built-in equipment protection, add-on protection, and system interaction
protection are discussed in greater detail.
5. Publication No Cu0141
Issue Date: August 2015
Page 2
FUNDAMENTALS OF SURGE PROTECTION
GENERAL
In the low-voltage (end-user) environment, SPDs serve to divert impinging surges by offering a low-impedance
path to return the surge current to its source. This function can be accomplished in a single or several stages,
depending on the system configuration and the degree of freedom available to the user in connecting SPDs at
different points of the system.
Large surges originating outside of the user's facility – usually associated with lightning or major power-system
events – are best diverted at the service entrance of a facility. Surges generated within the premises can be
diverted by SPDs located close to the internal surge source or close to the sensitive equipment in need of
protection. Figure 1 shows the principle of a two-stage protection scheme. The first stage provides diversion of
impinging high-energy surges
*
through the arrester, typically installed at the service entrance, or by a device
permanently connected at the service panel. Some restriction of the propagation of surge currents in branch
circuits is inherently provided by the inductance of the premises wiring. The second stage of voltage limiting is
provided by an SPD of lesser surge-handling capability which is typically located close to the equipment in
need of protection as an add-on, plug-in device, or incorporated within the equipment by the manufacturer.
This second stage completes the scheme for dealing with surges of external origin as well as for surges
originating within the building.
Figure 1 – A two stage protection scheme.
*
The term high-energy surge is used here as short-hand for the more accurate term surge with high energy-
delivery capability. Some power-quality surveys reports make reference to the concept of and term energy in
the surge as an abstract characteristic of the surge itself, which could be derived from measuring only the
voltage and duration of a surge occurring in the power system Such characterization is meaningless and
misleading (Standler, 1989); (Key et al., 1996].
6. Publication No Cu0141
Issue Date: August 2015
Page 3
TYPES OF SURGE-PROTECTIVE DEVICE COMPONENTS
Providing detailed information on SPDs is not within the scope of this Guide; however, some knowledge about
the components involved in the protective function will assist in making engineering judgements about their
selection and application. SPD components can be classified into two types: voltage-limiting devices and
voltage-switching devices (also called crowbars). A low-pass filter will attenuate the high frequency portion of
a surge and thus act in a manner similar to an SPD. However, according to the formal definition of an SPD, such
a low-pass filter is not in fact a proper SPD because it does not include a non-linear device.
A voltage-switching (crowbar) device involves a switching action as the voltage across the terminals rises. This
switching can be either the breakdrown of a gas between electrodes or the activation of a solid-state device.
After its activation, the device presents a low impedance to divert the transient current through some low-
impedance path back toward its source. A voltage-limiting device can be based on the technology of avalanche
(zener) diodes or varistors. Both avalanche diodes and varistors exhibit a monotonic and non-linear current-
voltage characteristic, in contrast with the abrupt change of impedance associated with voltage-switching
devices.
TYPES OF SURGE-PROTECTIVE DEVICES
Several types of internal configuration are found in commercial SPDs. This variety is due to the internal
circuitry as well as the SPD components used in the circuits. Recent IEEE and IEC standards have now
designated SPDs as being one-port SPD or two-port SPD. These two terms are explained below.
One-port SPDs – The protective function of a one-port SPD is provided by a shunt connection (Figure 2) to the
circuit to be protected, seen as one or more pairs, such as line-to-neutral, line-to-ground, and neutral-to-
ground.
Figure 2
7. Publication No Cu0141
Issue Date: August 2015
Page 4
The issue of providing protection to one, two, or three of these pairs is discussed later in this application note.
For the one-port SPD, the limiting voltage is measured at the terminals, either screw terminals or leads. This
configuration opens the possibility of misapplying the device by using long leads for the connection, which
results in an inductive voltage being added to the intended limiting voltage of the device. This possibility must
be recognized in guidance on SPD applications as well as in details of the lead configuration when performing
tests.
Two-port SPDs – In two-port SPDs, there is a power input port and a power output port that are distinct.
Depending upon the design, some components can be inserted in series between the input and output port.
The motivation for this configuration is generally to provide the two-stage protection scheme illustrated in
Figure 1a within a single package.
Another motivation is to remedy the lead length problem: Some manufacturers offer the so-called in-line
configuration for permanently connected SPDs, with four terminals and the requirement that the power flow
be through the SPD. Figure 3 shows typical arrangements of two-port SPDs. These configurations make it
necessary to design and rate the device for a specific value of the power-frequency current.
Figure 3
8. Publication No Cu0141
Issue Date: August 2015
Page 5
From the point of view of surge suppression, a two-port SPD is intended for one and only one direction of
impinging surges. Typically, the SPD component connected nearest to the input terminals has a greater
current-handling capacity than the component connected nearest to the output terminals. This asymmetry
must be recognized in the application.
Note in Figure 3 that the designation of two-port applies whether the SPD has a three-terminal or a four-
terminal configuration. Correct operation of this SPD is based on the following assumptions:
1) The impinging surge comes from the left of the figure
2) The series impedance separating the two SPD components will produce a sufficient voltage drop,
added to the limiting voltage of the varistor at right to cause the gas tube at left to sparkover and
relieve the varistor from the stress of conducting the tail of the surge
Such a design might operate quite well at the maximum stress level, but not at intermediate current levels, or
slow-rising surges, for which the voltage drop in the series impedance would be insufficient to produce
sparkover of the gas tube. Such a situation is referred to as blind spot and should be recognized when
specifying selection or tests for SPDs.
9. Publication No Cu0141
Issue Date: August 2015
Page 6
FUNCTION OF SPDS
The primary function of an SPD is the diversion of impinging surges away from sensitive loads without causing
immediate or long-term failure of the SPD. However, the SPD must also withstand the normal and abnormal
variations in steady-state conditions of the power system. This dual requirement focuses on characteristics
discussed in the following paragraphs. Particular emphasis must be given to the failure modes of a sound SPD
under abnormal system conditions, as well as failure modes under normal system conditions of an SPD, which,
for whatever reason, might have reached the end of its useful life.
PERFORMANCE UNDER SURGES
This characteristic is of course the very purpose of an SPD. Various severity levels of surges should be
stipulated for candidate SPDs depending upon the location of the SPD. The 0.5 µs 100 kHz Ring Wave and the
1.2/50 µs 8/20 µs Combination Wave provide basic information on the limiting voltage and energy-handling
capability of an SPD for single surges as well as for cumulative effects over the life of the device. The purpose
of an SPD is to limit transient overvoltages to values that downstream equipment can withstand without
damage, or in certain cases without upset.
PERFORMANCE UNDER STEADY-STATE VARIATIONS
As discussed in Cu0136, low-voltage AC power systems can experience temporary overvoltages that can stress
SPDs. The concept and specification of a maximum continuous operating voltage (MCOV) has been developed
to assess the ability of an SPD to withstand such abnormal conditions. Proper selection of an SPD requires
reconciliation of the MCOV of the SPD and the various scenarios for the occurrence of temporary overvoltages
at the point of interest.
DURABILITY (ENDURANCE)
An SPD is expected to provide reliable operation for a number of years. This durability is generally not
specified by the SPD manufacturer (except, indirectly, by those offering a lifetime guarantee on their package)
because of the dominant effect of undefined environmental stresses on the aging process.
MODES AND MODE CONVERSION AT THE POWER PORT
Depending upon the design and application philosophy of manufacturers, commercial SPDs are offered with
surge protection provided between all pairs of conductors or between only some selected pairs. In North
American practice where the equipment grounding conductor is bonded to the neutral and local earth at the
service entrance, only differential mode surges can emerge from the service panel. However, surge currents
associated with a differential mode surge, when flowing in the conductors of a branch circuit, can produce
voltage drops along the neutral conductor or the equipment grounding conductor. This results in a significant
difference of voltages with respect to other grounded structures (a form of mode conversion). The diversity of
approaches must be recognized, and any test schedule must be established, taking into consideration the
specific design of the SPD under test.
10. Publication No Cu0141
Issue Date: August 2015
Page 7
SELECTION OF LIMITING LEVELS
Under the perception that it is necessary – or at least desirable – to provide the lowest possible level for the
limiting (clamping) voltage, some SPD manufacturers have been offering SPDs with a limiting level as low as
330 V for 120 V circuits. These manufacturers claim superior performance over competing SPDs that achieve
somewhat higher levels (such as 400 V or 500 V) under the same specified applied surge current. A similar
downward auction for limiting voltage selection is likely to occur for other system voltages.
During the development of the seminal standard UL 1449 and IEC Publication 664 in the late seventies and
early eighties, a table of overvoltage categories was under consideration with levels that included the 330 V
value. However, it is noteworthy that this level was not cited in IEC 664 as a level for systems rated at 120 V,
but rather as a level for systems rated at 50 V. Thus, the understandable desirability of effective protection
through low limiting voltage became biased toward considering (advertising) a limiting voltage of 330 V as a
plus factor in evaluating the performance of SPDs for 120 V circuit applications.
A better perspective of the issue was reached in the nineties, but the outmoded perceptions and advertising
claims linger. Against these, the following facts and considerations should be kept in mind:
- Among published papers on immunity testing of appliances [Anderson & Bowes, 1990, Smith &
Standler, 1992], and surge immunity tests performed on a wide range of appliances, no adverse
effects have been reported until the applied surges exceed thresholds of 600 V to 1,000 V
- The well-accepted CBEMA Curve (now renamed ITIC Curve) did not require limiting voltages of 330 V
(for 120 V loads) for durations of less than 0.5 ms, and allowed limiting voltages with increasing levels
at shorter durations
- A low limiting level can result in premature aging of the SPD when it is called upon to more frequently
clamp surges that would not have caused any intervention of an SPD with somewhat higher limiting
voltage [Martzloff & Leedy, 1989], or swells resulting in significant shift of the nominal voltage when
applied in large numbers over the life of the device [Lagergren et al., 1992]
- Some utilities wish to select an SPD capable of withstanding twice the line-to-neutral voltage in order
to avoid device failure or fuse opening under the condition of lost neutral connection
It appears then that the advantage of a low limiting voltage can in fact have undesirable side effects on the
long-term overall reliability of the application of an SPD in end-user circuits. The chart in Figure 4 summarizes
the considerations involved in selecting a suitable SPD. Clearly, the mere selection of a limiting level as a
retrofit approach to protect a piece of equipment is insufficient for a reliable application.
12. Publication No Cu0141
Issue Date: August 2015
Page 9
MITIGATE SURGES AT THE ORIGIN
The classical EMC approach to disturbance mitigation generally recommends mitigation at the origin whenever
possible. For instance, IEC 61000-5-2 offers guidelines on earthing and wiring practices that can reduce the
coupling of surges between their origin and the circuits of interest. In the case of surges however, all the
discussions presented on their origin indicate that such a sensible approach cannot apply to lightning surges
once they have been coupled into the power system.
Designing a power system for less exposure to lightning surges is not within the prerogatives of the industrial
user, and thus is not discussed in this Guide. One possible exception to this situation where the end-user is
confronted with surges that cannot be mitigated before they impact the installation is the case of capacitor-
switching surges discussed below. For surges such as these, mitigation might be possible at the origin when
the parties involved cooperate in finding a solution.
13. Publication No Cu0141
Issue Date: August 2015
Page 10
MITIGATION OF CAPACITOR-SWITCHING TRANSIENTS
GENERAL
Devices for the mitigation of capacitor-switching transients at their point of origin either attempt to minimize
the overvoltage or overcurrent at the point of application of the capacitors, or limit (clip) the overvoltage. For
the capacitor-switching transients discussed in Cu0136, several solutions or mitigation means can be applied,
as follows.
Solutions to the excessive secondary overvoltages associated with capacitor switching (described in Cu0136)
usually involve one or more of the following:
a. Detuning the primary circuit by changing capacitor bank sizes, moving banks, and/or removing banks
from service
b. Switching large banks in more than one section
c. Using an overvoltage control method such as pre-insertion resistors/inductors or synchronous closing
control
d. Converting low-voltage power factor correction banks into harmonic filters (detuning the secondary
circuit – which should be common practice today, but is not always fully implemented)
Solutions to the excessive current inrush associated with back-to-back capacitor switching (described in
Cu0136) usually involve one or more of the following:
a. Adding current-limiting reactors to decrease the peak current and frequency of the oscillatory inrush
current
b. Adding pre-insertion resistors or inductors to the switching device
c. Adding synchronous closing control to the switching device
d. Electronic switching, connecting presicely at a phase angle for which the residual voltage of the
capacitor equals the instantaneous system voltgage
Each of these methods has various advantages and disadvantages in terms of transient overvoltage mitigation,
cost, installation requirements, operating and maintenance requirements, and reliability. Some of these
factors are described in the following paragraphs.
TIMING CONTROL
Synchronous closing consists of performing the closing of the contacts of each phase near a zero voltage, as
illustrated in Figure 5. To accomplish closing at or near a zero voltage, it is necessary to use a switching device
that maintains a dielectric strength sufficient until its contacts touch.
14. Publication No Cu0141
Issue Date: August 2015
Page 11
Figure 5
Although this level of precision is difficult to achieve, closing consistency of ±0.5 ms should be possible. A
closing consistency of ±1.0 ms was found to provide overvoltage control comparable to properly sized pre-
insertion inductors. The success of a synchronous closing scheme is often determined by the ability to repeat
the process under various system and climate conditions. Adaptive, microprocessor-based control schemes
that have the ability to learn from previous events address this concern.
Grounded capacitor banks are controlled by closing the three phases at three successive zeros of the phase-to-
ground voltage (60 degree separation). Ungrounded capacitor banks are controlled by closing the first two
phases at a phase-to-phase zero voltage and then delaying the third phase 90 degrees (zero voltage of phase-
to-ground).
PRE-INSERTION DEVICES
A pre-insertion impedance (resistor or inductor) provides a means for reducing the transient currents and
voltages associated with the energization of a capacitor bank. The impedance is by-passed shortly after the
initial transient dissipates, thereby producing a second transient event. The insertion transient typically lasts
for less than one cycle of the frequency. The performance of the system pre-insertion impedance is evaluated
using magnitudes of both the insertion and the by-pass transients, as well as the capability to dissipate the
energy associated with the event, and repeat the event on a regular basis. The optimum resistor value for
controlling capacitor-switching transients depends primarily upon the capacitor size and source strength.
FIXED INDUCTORS
Fixed inductors have been used successfully to limit inrush current during back-to-back switching. The value of
these inductors is typically on the order of several hundred microhenries. In addition, inductors provided to
limit outrush current (into a nearby fault) may be applied, with typical values of 0.5 mH to 2.0 mH. However,
these fixed reactors do not provide appreciable transient overvoltage reduction.
15. Publication No Cu0141
Issue Date: August 2015
Page 12
After all, the presence of a reactor connected in series with a compensation capacitor should be common
practice today. Such a combination will act as a detuning reactor to avoid resonances between the
compensation capacitance and any inherent inductance in the system. Such resonances could be excited by
lower order harmonics present in the system. The inductance ratings of such detuning reactors, however, are
one or two orders of magnitudes higher than of those for mitigating the inrush currents. Consequently, the
current transient when connecting a capacitance is replaced by a voltage transient when disconnecting an
inductance. This needs to be dealt with accordingly.
MOV ARRESTERS
Metal oxide varistors (MOVs) can limit transient overvoltages to the protective level (typically 1.8 to 2.5 per-
unit) at the point of application. The primary concern associated with MOV application is the energy duty
during a restrike event. Although a rare occurrence, a switch restrike generally results in the highest arrester
duty for arresters located at the switched capacitor. In addition, remote arresters (including low-voltage
customer applications) can be subjected to severe energy duty if voltage magnification occurs. This condition
could be especially troublesome for distribution systems if SiC-based arresters remain in service.
The effectiveness of these mitigation methods is system dependent, and a detailed analysis is necessary to
select the optimum scheme [Mikhail et al., 1986]; [Grebe, 1995]. While often justifiable for large transmission
applications, transient analysis of distribution capacitor applications is rarely performed and, in general,
capacitor banks are installed without transient overvoltage control.
If these preventive measures against capacitor switching transients are not practical or possible for an end-
user customer to coordinate with the supplier, then remedial measures can be applied at the service entrance
and points of connection of equipment in the customer's facility. This is described in the subchapter Function
of SPDs.
16. Publication No Cu0141
Issue Date: August 2015
Page 13
INHERENT OR BUILT-IN EQUIPMENT PROTECTION
To take care of load equipment performance, well-considered specifications for the equipment should always
be presented to the potential suppliers. Inquiries should be carried out with several suppliers to obtain
comparable data for equipment performance. This should include levels of immunity to transients, among
other data. However, different protection strategies can make protection levels difficult to compare. Solutions
for protection proposed by different suppliers should be evaluated. It should be verified whether they are
using SPDs internally or base their protection strategy on providing SPDs centralized in the electrical
installation. In any event, the supplier should commit to the specified level of transient voltage immunity.
General information included in equipment specification should be the conditions defined by mutual
agreement among the parties involved. Factors to be considered include likelihood and frequency of
occurrence, magnitude, and other characteristics of the transients. Specific equipment performance
parameters to be specified may, among others, include the magnitude of standardized transients that should
not cause an abnormal operation of the equipment and the level at which the equipment should not be
damaged.
The expected outcomes for various scenarios should be specified. For instance, the IEC 61000-4-xx series
describes the level of performance expected and should be a valuable fundamental reference and support for
determining equipment specifications. More descriptions, precautions and mitigation measures can be found
in the IEC 62305 series.
17. Publication No Cu0141
Issue Date: August 2015
Page 14
ADD-ON PROTECTION
SPD APPLICATION AT SERVICE ENTRANCE OR POINT OF USE
Experience has indicated that built-in surge protection, as designed by equipment manufacturers, is not always
sufficient. Efforts have been applied to correct this situation through the development of IEC standards on
equipment immunity. However, there is much equipment in use that was built before these immunity
standards emerged. Furthermore, many users wish to ensure more reliability and therefore routinely prescribe
add-on surge protection. This desire leads to the need for selecting the most effective point of application of
SPDs – service entrance, point of use, or both.
The term service entrance is used in this Guide as a general term. The actual installation described by this term
might have different implementations, depending upon local codes and practices. The interpretation of the
term also depends on the type of service connection (overhead up to the building, underground for some
distance before the building) and voltage rating of the service connection. The following discussion is
presented for the case of power being supplied to the customer at a low voltage, and the service entrance
understood as the point of common coupling.
In such an arrangement, the user has discretionary control on what SPD may be installed at the service
entrance. The selection of a two-stage protection is also at the user's discretion. Large commercial installations
are generally implemented under the guidance or supervision of a competent facility engineer. At the lower
end of the power scale, residential installations are generally implemented with little engineering
consideration applied to the choice made by the resident on providing surge protection. An exception to this
situation is emerging, with some utilities offering a packaged whole house protection engineered with
coordinated service entrance and point-of-use (plug-in) SPDs. This engineered two-stage scheme takes into
consideration the issues of cascade coordination, a topic that is discussed in the next subsection.
Providing well-coordinated SPDs at the service entrance diverts impinging surge currents to earth at that point,
rather than allowing them to flow into the installation wiring where they can induce interfering voltages in the
circuits and equipment. The selection of SPDs installed at the service entrance, upstream from the customer's
overcurrent protection, implies that the SPDs incorporate a suitable SPD disconnector rated for the available
fault current that might develop in case of SPD failure.
CASCADE COORDINATION
GENERAL OBJECTIVE OF COORDINATION
A coordination study of SPDs and equipment is needed whenever more than one SPD is used to protect
equipment. This study should be executed after it has been verified that the protection level of the SPDs and
their location are suitable for the equipment to be protected. The general objective of the coordination study
is to reduce the overvoltages by means of SPDs to the withstand capability of the equipment to be protected
and to ensure that the surge current rating capability of the individual SPDs will not be exceeded. This
condition can be expressed as follows:
Given two SPDs connected in parallel, SPD1 and SPD2 and separated by a decoupling impedance (Figure 6), the
energy coordination is achieved if the portion of energy dissipated through SPD2 is lower than or equal to the
maximum energy-withstand of SPD2 for each surge-current level and waveform to be considered.
18. Publication No Cu0141
Issue Date: August 2015
Page 15
Figure 6
Coordination between two SPDs can be demonstrated by five different approaches, described below.
Whatever the approach, it is necessary that the end-user have control over the selection of the SPDs,
preferably both of them. If one is already given and beyond the control of the end-user, the coordination of
the second candidate SPD can be assessed and more suitable candidates identified if necessary. Most of the
time, coordination is, or might seem to be a complex situation. Some of the following five procedures might
then appear to the end-user as difficult to apply, due to lack of knowledge concerning some data, as for
example accurate SPD characteristics. Nevertheless, coordination is necessary to ensure technically effective
and cost-effective use of resources.
ASSESSMENT OF COORDINATION
The five basic different methods of assessing the coordination of two SPDs are:
1. Application of preferred SPD combinations. This is the most convenient variant for the users because
the burden of demonstration is incumbent upon the SPD manufacturer. However, this approach
implies either that a sole source manufacturer be selected, or that standard methods be developed to
allow determination that candidate devices from different sources are in fact equivalent.
2. Coordination computation. Computer simulation enables complex systems to be examined and
parametric evaluation performed over a wide range.
3. Application of the Let-Through Energy concept. In this concept, some decoupling impedance is
postulated in the upstream SPD and a computation is performed for converting the SPD
characteristics on the basis of an equivalent combination wave generator. A comparison can then be
made with the energy-withstand capability of the downstream SPD (Hasse et al., 1994]
4. Coordination test. A full-scale test is performed with candidate SPDs, for a postulated decoupling
impedance and a range of surge currents such that blind spots, if any, are revealed. Candidate devices
may include voltage-limiting SPDs, voltage-switching SPDs, or combination type SPD [voltage-
switching SPD + voltage-limiting SPD].
5. Simplified rules with margin. Simplified tables including margins for the coordination of some typical
SPDs may be used when no other data is known from the SPD manufacturers. The values given in
these tables include sufficient margins to cover discrepancies between manufacturers and
manufacturing tolerances.
19. Publication No Cu0141
Issue Date: August 2015
Page 16
SYSTEM INTERACTION PROTECTION
As discussed in Cu0138, interactions at equipment ports involving different systems can produce damaging or
upsetting shifts in reference potentials during surge events. Anecdotal information indicates that this
mechanism is probably the most frequent cause of electronic consumer equipment failure (TV receivers and
VCRs with cable signal input, computers with wired modem connection, smart telephones, etc.)
Various mitigation schemes have been proposed to remedy upsetting or damaging potential differences.
Increasing the withstand capability of the PC system by the manufacturers is unlikely to occur, given the
market economics. Moreover, it actually might not be practical for some of the voltages that can appear in
actual situations. The most effective course would be a fibre optic decoupling, inserted in the communications
link, but the expense and involvement required would be objectionable for the typical home office application.
For industrial applications where the consequences can be severe, this approach is often selected and has
been found to be both successful and cost-effective
NON-METALLIC LINKS
Consumer options are limited to either replacement of existing conducted communication and control links
with their fibre optic counterparts, or insertion of commercially available isolation devices as needed. The first
option, while appropriate for new installations, might not be cost-effective for an existing installation. Devices
manufactured specifically for various port types can be applied for existing installations. For example, RS-232
communications are often used for connecting programmable logic controllers and other devices in utility and
industrial facilities. These links are easily isolated using an optically coupled adapter that connects directly to
the RS-232 port. These devices must have a suitable voltage isolation rating (e.g. kilovolts) for the application.
Some of these devices only have isolation capability measured in hundreds of volts which might not be
sufficient. Similar devices exist for other ports.
EQUALIZING REFERENCE POTENTIALS
Theoretically, a simple way to eliminate the shifts in reference potentials during surge events would be to
bond the two reference conductors of the two systems. However, such a simple bonding might not be
acceptable from the point of view of the system operators, the local or national codes, and product listing
agencies. Therefore, this Guide cannot provide recommendations applicable to all situations in all countries,
but only describe general principles leading to a solution.
When bonding the two references directly is not permitted, it might be permissible to provide an SPD of
appropriate characteristics that will in effect bond the two references – although with some potential
difference still left – but only during a surge event. This legitimately circumvents the prohibition of a
permanent bonding under steady-state conditions. The alternative, i.e. no bond at all, is that unintended
bonding is likely to occur – with damaging results – by sparkover of the clearances separating the conductors
of the two systems. For instance, tests have shown that the isolation between the cable input and the tuner of
a typical TV receiver will flashover at about 2.5 kV [Martzloff, 2000].