1. Transmission lines are vital for power transfer but operate close to limits, so faults must be detected and isolated quickly. Protection systems identify fault locations and isolate only faulted sections.
2. Factors influencing line protection include criticality, fault clearing times, line configuration, loading conditions, and equipment failure modes. Protection redundancy and backup schemes are important.
3. GE Multilin relays provide advantages for applications like single pole tripping, communications schemes, and security for dual breaker terminals through dedicated logic and direct measurement of circuit breaker currents.
The switchyard functions to transmit power from generating stations to the electrical grid at incoming voltages and allow for switching via switchgears. It interfaces between the power plant and grid. There are two main types of switchyards: air insulated and gas insulated. The switchyard contains various equipment like busbars to distribute power, insulators to support conductors, surge arresters to protect from overvoltage, isolators to isolate lines, wave traps to prevent communication interference, and circuit breakers and relays to isolate faulty lines. Differential protection relays compare currents at the boundaries of protected equipment like power lines or transformers to accurately and quickly detect internal faults.
The document discusses busbar protection, including the need for busbar protection, types of busbar protections like high impedance, medium impedance and low impedance protections. It describes the requirements of busbar protection like short tripping time and stable operation during external faults. The document discusses different busbar arrangements and applications of numerical busbar protection systems like RADSS. It provides examples of busbar protection schemes for different bus configurations. The document also includes excerpts from technical manuals providing recommendations on busbar protection in substations.
The document provides information about switchyard protection, powerline carrier communication, and SCADA application in substation control from Power Grid Corporation of India. It includes single line diagrams of substation equipment, descriptions of circuit breakers, lightning arrestors, isolators, and other components. It also explains power line carrier communication using PLCC, and line traps to block carrier waves. Finally, it outlines the architecture and functionality of SCADA systems for data collection, transmission, monitoring, control, and network supervision in power grids.
IRJET- Distance Algorithm for Transmission Line with Mid-Point Connected ...IRJET Journal
This document discusses distance protection of a transmission line with a STATCOM installed at the mid-point. It begins with an introduction to FACTS devices and their impact on transmission line protection schemes. It then reviews the modeling and operation of STATCOM and distance relays. The performance of a two-zone distance protection scheme is evaluated for different fault conditions using EMTDC/PSCAD simulation. To address misoperations of the conventional distance relay when the line is compensated by STATCOM, an adaptive distance protection algorithm is presented and its flow diagram is shown. The algorithm adaptively selects the protection zones based on the STATCOM injection current and measured relay quantities to improve the reliability of distance protection.
The slide is basically to show the general knowledge about the System Works for this Electrified Double Track Project between Ipoh & Padang Besar, the Equipments & its Functions.I have presented this slide to my college in Commercial Department and I want to share this little of my contribution to all linked in members.Hope we can get some benefit from this slide.Thank You
Study and comparison of various communication based protective relaying schem...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Study and comparison of various communication based protective relaying schem...eSAT Journals
Abstract The relay communication system is the heart of the protective scheme. The independent operation of the relays scheme for the protection of transmission line is not adequate in some cases where the time delay to clear faults beyond the zone1 reach for distance relays may be considered unacceptable. The need for additional intelligence in the protection of some transmission lines arises due to the failing of Distance protection. As the future may see more global the protection designs also require high-bandwidth communications in order to achieve the required speed. In this paper there is the study and comparison of various communication based protective relaying schemes which utilize a communications path to send signals from the relaying system at one end of the line to that at the other end. Key words: Wire Pilot, PLCC, Microwave channel
This document discusses pilot protection schemes for transmission lines. Pilot schemes use communication channels between line terminals to provide instantaneous clearing of faults over the entire line length. Common pilot schemes described include permissive overreaching transfer trip (POTT), directional comparison blocking (DCB), and directional comparison unblocking (DCUB). Redundant pilot channels and protection principles are recommended to improve the reliability and security of pilot schemes. Desirable relay features include integrated functions for weak infeed conditions as well as sensitive directional overcurrent elements to key the pilot communications.
The switchyard functions to transmit power from generating stations to the electrical grid at incoming voltages and allow for switching via switchgears. It interfaces between the power plant and grid. There are two main types of switchyards: air insulated and gas insulated. The switchyard contains various equipment like busbars to distribute power, insulators to support conductors, surge arresters to protect from overvoltage, isolators to isolate lines, wave traps to prevent communication interference, and circuit breakers and relays to isolate faulty lines. Differential protection relays compare currents at the boundaries of protected equipment like power lines or transformers to accurately and quickly detect internal faults.
The document discusses busbar protection, including the need for busbar protection, types of busbar protections like high impedance, medium impedance and low impedance protections. It describes the requirements of busbar protection like short tripping time and stable operation during external faults. The document discusses different busbar arrangements and applications of numerical busbar protection systems like RADSS. It provides examples of busbar protection schemes for different bus configurations. The document also includes excerpts from technical manuals providing recommendations on busbar protection in substations.
The document provides information about switchyard protection, powerline carrier communication, and SCADA application in substation control from Power Grid Corporation of India. It includes single line diagrams of substation equipment, descriptions of circuit breakers, lightning arrestors, isolators, and other components. It also explains power line carrier communication using PLCC, and line traps to block carrier waves. Finally, it outlines the architecture and functionality of SCADA systems for data collection, transmission, monitoring, control, and network supervision in power grids.
IRJET- Distance Algorithm for Transmission Line with Mid-Point Connected ...IRJET Journal
This document discusses distance protection of a transmission line with a STATCOM installed at the mid-point. It begins with an introduction to FACTS devices and their impact on transmission line protection schemes. It then reviews the modeling and operation of STATCOM and distance relays. The performance of a two-zone distance protection scheme is evaluated for different fault conditions using EMTDC/PSCAD simulation. To address misoperations of the conventional distance relay when the line is compensated by STATCOM, an adaptive distance protection algorithm is presented and its flow diagram is shown. The algorithm adaptively selects the protection zones based on the STATCOM injection current and measured relay quantities to improve the reliability of distance protection.
The slide is basically to show the general knowledge about the System Works for this Electrified Double Track Project between Ipoh & Padang Besar, the Equipments & its Functions.I have presented this slide to my college in Commercial Department and I want to share this little of my contribution to all linked in members.Hope we can get some benefit from this slide.Thank You
Study and comparison of various communication based protective relaying schem...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Study and comparison of various communication based protective relaying schem...eSAT Journals
Abstract The relay communication system is the heart of the protective scheme. The independent operation of the relays scheme for the protection of transmission line is not adequate in some cases where the time delay to clear faults beyond the zone1 reach for distance relays may be considered unacceptable. The need for additional intelligence in the protection of some transmission lines arises due to the failing of Distance protection. As the future may see more global the protection designs also require high-bandwidth communications in order to achieve the required speed. In this paper there is the study and comparison of various communication based protective relaying schemes which utilize a communications path to send signals from the relaying system at one end of the line to that at the other end. Key words: Wire Pilot, PLCC, Microwave channel
This document discusses pilot protection schemes for transmission lines. Pilot schemes use communication channels between line terminals to provide instantaneous clearing of faults over the entire line length. Common pilot schemes described include permissive overreaching transfer trip (POTT), directional comparison blocking (DCB), and directional comparison unblocking (DCUB). Redundant pilot channels and protection principles are recommended to improve the reliability and security of pilot schemes. Desirable relay features include integrated functions for weak infeed conditions as well as sensitive directional overcurrent elements to key the pilot communications.
Protection of transmission lines(encrypted)Rohini Haridas
This document discusses protection methods for transmission lines. It describes:
1. Transmission lines require more protective schemes than other equipment due to their long lengths and exposure, making faults more common.
2. Key methods of transmission line protection include time-graded overcurrent protection, differential protection, current-graded overcurrent protection, and distance protection.
3. Distance protection uses impedance relays that can discriminate between faults along the line and those near the end, providing more selective operation than overcurrent protection alone. It describes implementations using simple impedance, reactance, and mho relays.
Need for protection
Nature and causes of faults
Types of faults
Fault current calculation using symmetrical components
Zones of protection
Primary and back up protection
Essential qualities of protection
Typical protection schemes.
(1) Five classical types of busbar protection systems are discussed: system protection, frame-earth protection, differential protection, phase comparison protection, and directional blocking protection. System protection and phase comparison protection are only suitable for small substations, while frame-earth and differential protection are discussed in more detail.
(2) Frame-earth protection measures fault current flowing from the switchgear frame to earth. Differential protection compares currents flowing into and out of the busbar and trips if they are not equal.
(3) Modern digital differential algorithms aim to improve filtering, response time, restraint techniques, and transient blocking compared to classical schemes.
This document provides an overview of power grid design. It discusses the key components of an electrical grid including power generation, transmission, and distribution. Power is generated at stations and stepped up for transmission over long distances via transmission lines before being stepped down for distribution. Grid design involves selecting sites and bus bar schemes, determining bill of materials, ensuring safety clearances, designing earth mats, and laying out control rooms and equipment. Factors like proximity to load centers, accessibility, and avoidance of obstructions must be considered for site selection. Common bus bar schemes include single, main-auxiliary, double, and one-and-a-half breaker configurations. Proper grid design is important for reliably and safely delivering power.
The document discusses a SCADA system for electrical distribution implemented by Jamshedpur Utilities and Services Company (JUSCO). JUSCO uses a SCADA system monitored from its Network Monitoring and Control Centre (NMCC) to automate power distribution. The document outlines various field equipment in the electrical distribution network like transformers, breakers, buses that are monitored by the SCADA system. It also discusses the communication infrastructure and control room setup used for the SCADA system.
The 7SR23 DAD is a numeric high impedance circulating current relay has four current inputs, it is used as a unit protection to detect phase and earth faults.
The relay can be applied to busbars, connections, transformers, reactors and motors.
This document discusses switch-on-to-fault (SOTF) protection schemes. It describes the purpose of SOTF schemes, which is to trip a transmission line breaker when closed onto a faulted line. It outlines three common SOTF scheme applications and details the internal logic and settings of SOTF schemes in numerical relays. The document compares internal dead line detection logic to external trigger methods and discusses merits and limitations of different SOTF implementation methods. It also provides examples of SOTF logic for different breaker arrangements like one and a half breaker, double bus, and double bus transfer schemes.
7SA522 Distance Protection Relay For Transmission Linesashwini reliserv
The SIPROTEC 7SA522 relay provides full-scheme distance protection and incorporates all functions usually required for the protection of a power line. The relay is designed to provide fast and selective fault clearance on transmission and subtransmission cables and overhead lines with or without series capacitor compensation. The power system star point can be solid or resistance grounded (earthed), resonant-earthed via Peterson coil or isolated. The SIPROTEC 7SA522 is suitable for single-pole and three-pole tripping applications with and without tele (pilot) protection schemes.
IRJET- Design of Single Phase Transformerless InverterIRJET Journal
The document describes the design of a single-phase transformerless inverter for use in grid-connected photovoltaic systems. It discusses how such inverters can induce leakage currents due to the lack of galvanic isolation and unstable common mode voltages. The paper then presents the H5 inverter topology as a way to reduce these leakage currents by keeping the common mode voltage constant during all operating modes. Simulation results from MATLAB show that the H5 topology achieves lower leakage currents than other topologies like H6 and HERIC. The document concludes that the H5 inverter design meets the requirements for eliminating leakage currents in transformerless photovoltaic systems.
The document discusses the design of a microcontroller-based system for parameter measurement and protection of electrical transformers using power line communication. It aims to monitor transformer parameters like voltage, current, temperature and protect against overcurrent and overvoltage faults. The system uses current and voltage sensors connected to a microcontroller to measure parameters. If a fault is detected, the microcontroller sends a trip signal to a relay to disconnect the transformer. It is intended to provide improved reliability compared to traditional electromechanical protection techniques.
The 7SR12 includes for directional control of the overcurrent and earth fault functionality and is typically installed where fault current can flow in either direction i.e. on interconnected systems.
The document discusses the design and components of electrical power grids. It begins with an introduction to power grids, noting their three main components: power stations, transmission lines, and transformers. It then covers various topics related to designing a power grid substation including selecting the site, layout designs, busbar schemes, safety clearances, earth mat design, and control rooms. Key equipment for grids are also discussed such as lighting arrestors, current and potential transformers, circuit breakers, and isolators. The presentation concludes that grids are important for supplying reliable and economic power from sources to loads and maintaining efficiency, though their design and components make them costly.
This document provides an overview of the key components and functions of an electrical substation. It discusses how transformers are used to increase or decrease voltages, how current transformers and capacitor voltage transformers are used for measurements. It also describes circuit breakers, disconnect switches, surge arresters, protective relays, wave traps, battery backups, control rooms and the protection systems used to quickly detect faults.
This document discusses fault level calculations in electric power systems. It explains that fault level calculations are necessary to select protective devices, circuit breakers, and equipment that can withstand short circuit currents. The document outlines the procedure for calculating fault levels, which involves representing the system with a single line diagram, choosing a base MVA, calculating per unit reactances, determining the equivalent reactance to the fault point, and using formulas to calculate fault MVA and current. It also discusses how current limiting reactors can be used to insert additional reactance and reduce short circuit currents to match circuit breaker ratings.
Seminar Report on 220 KV Grid Sub Station on Bundi SahilQureshi14
This document provides an overview of a 220kV grid substation in Bundi, Rajasthan, India. It discusses the purpose and components of grid substations, including transformers, circuit breakers, isolators, buses, current transformers, and other key equipment. It also describes the selection process for the substation site and lists considerations like proximity to load centers, accessibility, and avoidance of flood-prone areas. Various types of substations and transformers are defined. An index lists the topics covered in the document.
This document provides an overview of power system protection. It discusses why protection systems are needed, the basic principles and elements, and common protection schemes. Protection systems must maintain reliable power system operation during both small and severe disturbances. The key components of a protection system are protective relays, circuit breakers, current and voltage sensors, and communication channels. Common protection schemes discussed include overcurrent, distance, differential, and pilot protection using transfer trip schemes. Digital relays offer advantages like multifunctionality, adaptability, and reliability.
The document differentiates between substations and grid stations. It states that a substation is a conversion point between transmission and distribution voltages using transformers to serve a regional area. Substations are connected by transmission lines. A grid station interconnects two transmission circuits, often between regions, and may contain transformers. The interconnected network of grid stations forms the electrical grid.
The document discusses different types of electrical bus bar arrangements used in power systems. It defines a bus bar as a conductor that collects electric power from incoming feeders and distributes it to outgoing feeders. The main types discussed are single bus bar, single bus bar with sectionalization, main and transfer bus, double bus double breaker, sectionalized double bus bar, one and a half breaker, ring main, and mesh arrangements. Each has advantages like reliability, flexibility and cost considerations, but also disadvantages related to complexity, maintenance costs, and ability to isolate faults.
1) Multi-terminal HVDC systems can connect non-synchronous power systems and integrate offshore renewable energy sources more efficiently than AC solutions.
2) The document discusses control schemes for multi-terminal HVDC systems to allow them to provide ancillary services like frequency control to connected AC areas.
3) Two control schemes are analyzed - one that modulates active power injections and one that modulates DC voltages - and theoretical analysis and simulations show they can help stabilize frequency deviations between areas after disturbances.
Protection of transmission lines(encrypted)Rohini Haridas
This document discusses protection methods for transmission lines. It describes:
1. Transmission lines require more protective schemes than other equipment due to their long lengths and exposure, making faults more common.
2. Key methods of transmission line protection include time-graded overcurrent protection, differential protection, current-graded overcurrent protection, and distance protection.
3. Distance protection uses impedance relays that can discriminate between faults along the line and those near the end, providing more selective operation than overcurrent protection alone. It describes implementations using simple impedance, reactance, and mho relays.
Need for protection
Nature and causes of faults
Types of faults
Fault current calculation using symmetrical components
Zones of protection
Primary and back up protection
Essential qualities of protection
Typical protection schemes.
(1) Five classical types of busbar protection systems are discussed: system protection, frame-earth protection, differential protection, phase comparison protection, and directional blocking protection. System protection and phase comparison protection are only suitable for small substations, while frame-earth and differential protection are discussed in more detail.
(2) Frame-earth protection measures fault current flowing from the switchgear frame to earth. Differential protection compares currents flowing into and out of the busbar and trips if they are not equal.
(3) Modern digital differential algorithms aim to improve filtering, response time, restraint techniques, and transient blocking compared to classical schemes.
This document provides an overview of power grid design. It discusses the key components of an electrical grid including power generation, transmission, and distribution. Power is generated at stations and stepped up for transmission over long distances via transmission lines before being stepped down for distribution. Grid design involves selecting sites and bus bar schemes, determining bill of materials, ensuring safety clearances, designing earth mats, and laying out control rooms and equipment. Factors like proximity to load centers, accessibility, and avoidance of obstructions must be considered for site selection. Common bus bar schemes include single, main-auxiliary, double, and one-and-a-half breaker configurations. Proper grid design is important for reliably and safely delivering power.
The document discusses a SCADA system for electrical distribution implemented by Jamshedpur Utilities and Services Company (JUSCO). JUSCO uses a SCADA system monitored from its Network Monitoring and Control Centre (NMCC) to automate power distribution. The document outlines various field equipment in the electrical distribution network like transformers, breakers, buses that are monitored by the SCADA system. It also discusses the communication infrastructure and control room setup used for the SCADA system.
The 7SR23 DAD is a numeric high impedance circulating current relay has four current inputs, it is used as a unit protection to detect phase and earth faults.
The relay can be applied to busbars, connections, transformers, reactors and motors.
This document discusses switch-on-to-fault (SOTF) protection schemes. It describes the purpose of SOTF schemes, which is to trip a transmission line breaker when closed onto a faulted line. It outlines three common SOTF scheme applications and details the internal logic and settings of SOTF schemes in numerical relays. The document compares internal dead line detection logic to external trigger methods and discusses merits and limitations of different SOTF implementation methods. It also provides examples of SOTF logic for different breaker arrangements like one and a half breaker, double bus, and double bus transfer schemes.
7SA522 Distance Protection Relay For Transmission Linesashwini reliserv
The SIPROTEC 7SA522 relay provides full-scheme distance protection and incorporates all functions usually required for the protection of a power line. The relay is designed to provide fast and selective fault clearance on transmission and subtransmission cables and overhead lines with or without series capacitor compensation. The power system star point can be solid or resistance grounded (earthed), resonant-earthed via Peterson coil or isolated. The SIPROTEC 7SA522 is suitable for single-pole and three-pole tripping applications with and without tele (pilot) protection schemes.
IRJET- Design of Single Phase Transformerless InverterIRJET Journal
The document describes the design of a single-phase transformerless inverter for use in grid-connected photovoltaic systems. It discusses how such inverters can induce leakage currents due to the lack of galvanic isolation and unstable common mode voltages. The paper then presents the H5 inverter topology as a way to reduce these leakage currents by keeping the common mode voltage constant during all operating modes. Simulation results from MATLAB show that the H5 topology achieves lower leakage currents than other topologies like H6 and HERIC. The document concludes that the H5 inverter design meets the requirements for eliminating leakage currents in transformerless photovoltaic systems.
The document discusses the design of a microcontroller-based system for parameter measurement and protection of electrical transformers using power line communication. It aims to monitor transformer parameters like voltage, current, temperature and protect against overcurrent and overvoltage faults. The system uses current and voltage sensors connected to a microcontroller to measure parameters. If a fault is detected, the microcontroller sends a trip signal to a relay to disconnect the transformer. It is intended to provide improved reliability compared to traditional electromechanical protection techniques.
The 7SR12 includes for directional control of the overcurrent and earth fault functionality and is typically installed where fault current can flow in either direction i.e. on interconnected systems.
The document discusses the design and components of electrical power grids. It begins with an introduction to power grids, noting their three main components: power stations, transmission lines, and transformers. It then covers various topics related to designing a power grid substation including selecting the site, layout designs, busbar schemes, safety clearances, earth mat design, and control rooms. Key equipment for grids are also discussed such as lighting arrestors, current and potential transformers, circuit breakers, and isolators. The presentation concludes that grids are important for supplying reliable and economic power from sources to loads and maintaining efficiency, though their design and components make them costly.
This document provides an overview of the key components and functions of an electrical substation. It discusses how transformers are used to increase or decrease voltages, how current transformers and capacitor voltage transformers are used for measurements. It also describes circuit breakers, disconnect switches, surge arresters, protective relays, wave traps, battery backups, control rooms and the protection systems used to quickly detect faults.
This document discusses fault level calculations in electric power systems. It explains that fault level calculations are necessary to select protective devices, circuit breakers, and equipment that can withstand short circuit currents. The document outlines the procedure for calculating fault levels, which involves representing the system with a single line diagram, choosing a base MVA, calculating per unit reactances, determining the equivalent reactance to the fault point, and using formulas to calculate fault MVA and current. It also discusses how current limiting reactors can be used to insert additional reactance and reduce short circuit currents to match circuit breaker ratings.
Seminar Report on 220 KV Grid Sub Station on Bundi SahilQureshi14
This document provides an overview of a 220kV grid substation in Bundi, Rajasthan, India. It discusses the purpose and components of grid substations, including transformers, circuit breakers, isolators, buses, current transformers, and other key equipment. It also describes the selection process for the substation site and lists considerations like proximity to load centers, accessibility, and avoidance of flood-prone areas. Various types of substations and transformers are defined. An index lists the topics covered in the document.
This document provides an overview of power system protection. It discusses why protection systems are needed, the basic principles and elements, and common protection schemes. Protection systems must maintain reliable power system operation during both small and severe disturbances. The key components of a protection system are protective relays, circuit breakers, current and voltage sensors, and communication channels. Common protection schemes discussed include overcurrent, distance, differential, and pilot protection using transfer trip schemes. Digital relays offer advantages like multifunctionality, adaptability, and reliability.
The document differentiates between substations and grid stations. It states that a substation is a conversion point between transmission and distribution voltages using transformers to serve a regional area. Substations are connected by transmission lines. A grid station interconnects two transmission circuits, often between regions, and may contain transformers. The interconnected network of grid stations forms the electrical grid.
The document discusses different types of electrical bus bar arrangements used in power systems. It defines a bus bar as a conductor that collects electric power from incoming feeders and distributes it to outgoing feeders. The main types discussed are single bus bar, single bus bar with sectionalization, main and transfer bus, double bus double breaker, sectionalized double bus bar, one and a half breaker, ring main, and mesh arrangements. Each has advantages like reliability, flexibility and cost considerations, but also disadvantages related to complexity, maintenance costs, and ability to isolate faults.
1) Multi-terminal HVDC systems can connect non-synchronous power systems and integrate offshore renewable energy sources more efficiently than AC solutions.
2) The document discusses control schemes for multi-terminal HVDC systems to allow them to provide ancillary services like frequency control to connected AC areas.
3) Two control schemes are analyzed - one that modulates active power injections and one that modulates DC voltages - and theoretical analysis and simulations show they can help stabilize frequency deviations between areas after disturbances.
This document discusses power system protection components and devices. It describes the key elements which include current and voltage transformers, protective relays, circuit breakers, batteries, and fuses. These components work together to isolate faults and protect different elements of the electrical network. The document also discusses primary and backup protection methods, types of backup protection, and measures for evaluating protection system performance such as reliability, selectivity, speed and economy.
An Overview Of Agbami Fpso Electrical Power Systemvkmalik
The document provides an overview of the electrical power system protection on the AGBAMI FPSO. It describes the main, essential, and emergency power systems on board including generator capacity and configuration. It also discusses the various studies conducted on the power system model to determine protection requirements, including load flow analysis, short circuit study, and protective device coordination study. The document outlines the zoning of protection on the power system and the types of protection relays used. It provides examples of protection functions for generators, transformers, switchgear, feeders, and motors.
This document provides an overview of relays. It begins with an introduction to Minda Furukawa Electric Pvt. Ltd, a joint venture company that produces wiring harnesses and relay components. It then defines relays as switches that open and close circuits electromechanically or electronically to control one circuit by another. The document outlines the basic design of relays including their electromagnet, armature and contacts. It describes the main types of relays as electromechanical or solid state. Applications of relays include amplifying signals, isolating faults, and time delay functions. Advantages are their ability to control high voltage circuits with low signals and provide safety. A brief history of relays dates them back
protection of transmission lines[distance relay protection scheme]moiz89
The document discusses various aspects of transmission line protection including classification of transmission lines, types of faults, protection schemes, requirements of distance protection, over current protection, phase comparison protection, and distance protection schemes. It also covers autoreclose philosophy, power swings, fuse failure function, and other protection functions.
This document is a project report on relays by Sheshadri Shekhar Rauth for his Bachelor of Technology degree in Electrical Engineering. It discusses the history and holding capacity of Diesel Loco Shed in Kharagpur, the basic design and operation of relays, and the types of relays used in the shed including wheel slip relays, general purpose relays, and contactor relays. It also provides references and concludes that the training opportunities at the shed were helpful for gaining knowledge about machinery and instruments.
Relays sense abnormal voltage and current conditions and send signals to circuit breakers to isolate faulty parts of a power system. Electromagnetic induction relays use eddy currents produced in a disc to generate torque. There are different types of overcurrent and directional relays. Distance relays use impedance, reactance, or mho principles. Transformer and feeder protection uses overcurrent, distance, or pilot wire schemes. Circuit breakers use oil, air, sulfur hexafluoride, or vacuum to extinguish arcs and open faulty circuits. Instrument transformers reduce high voltages and currents to safer, measurable levels for meters and relays.
This document discusses power system protection settings and provides information on calculating protection settings. It covers the functions of protective relays and equipment protection, the required information for setting calculations such as line parameters and fault studies, and the process of calculating, checking, and implementing protection settings. The goal is to set protections to operate dependably, securely, and selectively during faults while meeting clearance time requirements.
A thermal power plant converts the heat from coal into electrical energy. Coal is burned in a boiler to produce high pressure steam, which spins turbines connected to generators. This generates electricity. The steam is then condensed in a condenser using cooling water, which is cooled in cooling towers or ponds and recycled. Thermal power plants currently contribute the majority of electricity production in India.
This document discusses transmission line protection principles. It begins by introducing transmission lines and the importance of quickly detecting and isolating faults on lines. It then discusses factors that influence line protection design like line criticality, fault clearing times, line configuration, and loading. The document focuses on advantages of GE Multilin relays for transmission line protection, including their ability to handle single pole tripping, communicate between line terminals reliably, and operate securely at dual breaker terminals by directly measuring individual breaker currents.
Current differential line protection setting considerationsAsim Ihsan
1) Current-only line differential relays have advantages over other protection schemes like directional comparison, including simpler settings. Settings for early electromechanical pilot wire relays were easy, using factory defaults or a few tap settings based on estimated fault current.
2) For digital current differential relays, the simple setting principles of early pilot wire relays seem to have been forgotten. Applying the most sensitive setting of 10-20% without considering fault levels contradicts relay principles of balancing security, sensitivity, dependability and speed. Higher sensitivity increases dependability but decreases security, and could cause false trips.
3) This paper reviews setting criteria for current differential line protection, focusing on charge comparison relays. Operating time
1) The document describes the performance of a quadrilateral relay for protection of extra high voltage transmission lines during faults with high resistance.
2) A PSCAD/EMTDC model of a 300km transmission line is developed and a quadrilateral relay scheme with two zones is designed and tested under different fault conditions.
3) Simulation results show that the quadrilateral relay can accurately detect faults located in zones 1 and 2 and is well-suited for providing flexible protection during high resistance faults on EHV transmission lines.
This document describes various principles of relay operation used in power systems. It discusses several categories of relays including level detection relays, magnitude comparison relays, differential relays, phase angle comparison relays, distance relays, pilot relays, harmonic content relays, and frequency sensing relays. It also describes some common relay designs such as plunger-type electromechanical relays and their operating characteristics. Relay principles can be based on detecting changes in current, voltage, phase angles, harmonic components, or frequency during fault conditions.
1. Microprocessor-based current differential relays can provide superior protection for transmission lines but applying them to lines with tapped transformers presents challenges. Currents are not measured at tap points.
2. Key issues are the load current from taps appearing as a differential error, faults at the low voltage side of taps misleading the relay, and magnetizing inrush current. Distance elements and removing zero-sequence current can help address these issues.
3. Solutions proposed in the document include using biased characteristics, adaptive compensation for charging currents, distance supervision set to avoid taps, and removing zero-sequence current from the differential signal. Careful setting is needed to balance security and sensitivity.
This document discusses improvements to transmission line protection systems to address increasing power system requirements. It presents solutions for preventing overreach of zone 1 distance elements for series-compensated lines and preventing corruption of distance element polarization during pole-open conditions. It also introduces an efficient frequency estimation logic for single-pole tripping applications to prevent misoperation during frequency excursions when a pole is open. An algorithm is discussed to prevent single-pole reclosing while a fault is present to avoid additional damage and disturbances. The presented solutions result in a protective system suitable for heavy loading, single-pole tripping, series line compensation, and shunt line compensation.
A Performance Analysis of Statcom on Distance Protection RelayIJSRD
Legacy Transmission system protection schemes are mainly based on distance relaying. However, performance of distance relay is affected in presence of shunt Flexible AC Transmission System Devices (FACTS) like Static synchronous Compensator (STATCOM) which are mostly used to enhance the transferring capacity of transmission system. The study about the protection system like transmission protection by using Distance Relay Specially mho relay and its zone wise tripping characteristics. The detailed idea about FACTS, type of FACTS, Advantages of FACTS and application of FACTS. For various purpose like power handling capacity by injecting or absorbing reactive power. The STATCOM has adverse effect on protection like distance protection ,distance relay mal-function when STATCOM is connected to the Line, when STATCOM is in fault loop then have a great impact on relay tripping characteristics. Distance relay simulation in MATLAB plays an important role.
IRJET- Overhead Line Protection with Automatic Switch by using PLC AutomationIRJET Journal
This document describes a system to automatically protect overhead transmission lines from overload faults using a PLC-controlled air break switch. The system monitors current on the line using a sensor and can open the switch if overload is detected. This allows faulty sections to be isolated without interrupting the whole line. The automatic switch provides remote operation and is more reliable than conventional manual switches. It aims to quickly detect and resolve overload problems through automation using a PLC to control the switch based on current readings.
Double Circuit Transmission Line Protection using Line Trap & Artificial Neur...IRJET Journal
This document presents a technique for protecting double circuit transmission lines using line traps and artificial neural networks. Line traps are placed at the terminals of the protected line to detect faults based on high frequency transients. An artificial neural network is trained using the RMS voltage and current signals to classify fault types. MATLAB simulation studies were conducted to model a 300km, 25kV, 50Hz transmission system with three zones. RMS measurements from one end were used to train the neural network to classify faults. The neural network approach provides fast, secure and reliable protection for double circuit transmission lines.
This document discusses the development of protective relaying in Nigeria's power system automation. It describes how relay technology has progressed from electromechanical relays to solid-state relays to microprocessor-based relays. The implementation of microprocessor-based relays in substation automation has improved performance over electromechanical relays by eliminating manually reading meters, providing more precise load data, enabling wider communication of information, and enhancing control functions. Substation automation now includes supervisory control and data acquisition systems for remote monitoring and control of substations.
This document presents a novel technique for fault detection and classification on double circuit transmission lines using artificial neural networks (ANNs). The technique uses high frequency transients caused by faults to identify internal and external faults. ANNs with suitable numbers of neurons are used to analyze voltage and current signals and decompose them to identify faults. Extensive simulation studies show the proposed approach can accurately discriminate between internal and external faults, providing fast, effective, and efficient protection. The document describes modeling a double circuit transmission line system in MATLAB, selecting ANN input/output parameters, developing a 3-layer 45-neuron ANN structure, and presenting simulation results demonstrating the ANN can detect and classify different fault types within a few milliseconds.
A protective relay is a device that detects faults in electrical systems and operates circuit breakers to isolate faulty sections. It distinguishes normal and abnormal conditions by measuring electrical quantities like voltage, current, and frequency that change during faults. The relay components include inputs that receive measurements, settings to program decision thresholds, processing to compare inputs to settings, and outputs to operate switches. Relays ensure the safety of equipment and continuity of supply by rapidly detecting faults and automatically disconnecting the faulty section from the healthy system.
Published in the year 2014, this paper explains how interoperability and decentralized automation system can be achived in electrical distribution grid using IEC61850. Network information from neighboring nodes can help field controllers make decisions faster and more accurately thereby making the distribution network self- healing and reliable.
Consideration of Three Phase Faults on Transmission Line with Distance Protec...ijtsrd
In a modern power system, electrical energy from the generating station is delivered to the consumers through a network of transmission and distribution. Transmission lines are also important elements of electric power system and require attention of protecting for safety against the possible faults occurring on them. The detection of a fault and disconnection of a faulty section or apparatus can be achieved by using fuses or relays in conjunction with circuit breakers. Distance relay has the ability to detect a fault within a distance along a transmission line or cable from its location. Distance relay protection is the most widely used in case of high voltage and extra high voltage in the transmission line. In this paper discussion about how to protect the long transmission line with distance relay. June Tharaphe Lwin | Christ Tine Lin "Consideration of Three Phase Faults on Transmission Line with Distance Protection" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd28013.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/28013/consideration-of-three-phase-faults-on-transmission-line-with-distance-protection/june-tharaphe-lwin
The 7SD5 relay provides full scheme differential protection and incorporates all functions usually required for the protection of power lines. It is designed for all power and distribution levels and protects lines with two up to six line ends. The relay is designed to provide high-speed and phase-selective fault clearance. The relay uses fiber-optic cables or digital communication networks to exchange telegrams and includes special features for the use in multiplexed communication networks. Also, pilot wires connections can be used with an external converter.
The document describes a project report on robotics monitoring of power systems. It discusses how robots can be used to detect faults in transmission lines by using sensors like acoustic, electric field, infrared, and multi-processor control. The robot monitoring method allows faults to be detected before failures occur and is more economical than conventional human inspection methods. It also discusses the design of the robotic platform, sensor technologies for monitoring cable insulation status and energization, advantages like replacing dangerous human work and operating in hazardous environments.
This document summarizes a research paper that proposes new offline Prony and Matrix Pencil methods for phasor estimation to improve fault location accuracy on series compensated transmission lines. The techniques aim to eliminate sub-synchronous frequency components, decaying DC offsets, and noise before phasor estimation. The performance is evaluated using simulated signals in Matlab and results are compared to existing methods. Key aspects of series compensation impacts, the proposed filtering and estimation techniques, and Prony and Matrix Pencil methods are summarized.
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
This presentation includes basic of PCOS their pathology and treatment and also Ayurveda correlation of PCOS and Ayurvedic line of treatment mentioned in classics.
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
Walmart Business+ and Spark Good for Nonprofits.pdfTechSoup
"Learn about all the ways Walmart supports nonprofit organizations.
You will hear from Liz Willett, the Head of Nonprofits, and hear about what Walmart is doing to help nonprofits, including Walmart Business and Spark Good. Walmart Business+ is a new offer for nonprofits that offers discounts and also streamlines nonprofits order and expense tracking, saving time and money.
The webinar may also give some examples on how nonprofits can best leverage Walmart Business+.
The event will cover the following::
Walmart Business + (https://business.walmart.com/plus) is a new shopping experience for nonprofits, schools, and local business customers that connects an exclusive online shopping experience to stores. Benefits include free delivery and shipping, a 'Spend Analytics” feature, special discounts, deals and tax-exempt shopping.
Special TechSoup offer for a free 180 days membership, and up to $150 in discounts on eligible orders.
Spark Good (walmart.com/sparkgood) is a charitable platform that enables nonprofits to receive donations directly from customers and associates.
Answers about how you can do more with Walmart!"
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
Beyond Degrees - Empowering the Workforce in the Context of Skills-First.pptxEduSkills OECD
Iván Bornacelly, Policy Analyst at the OECD Centre for Skills, OECD, presents at the webinar 'Tackling job market gaps with a skills-first approach' on 12 June 2024
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
How to Manage Your Lost Opportunities in Odoo 17 CRM
1 transmission
1. Transmission Line
Protection Principles
1. Introduction
Transmission lines are a vital part of the electrical distribution
system, as they provide the path to transfer power between
generation and load. Transmission lines operate at voltage levels
from 69kV to 765kV, and are ideally tightly interconnected for
reliable operation.
Factors like de-regulated market environment, economics, rightof-way clearance and environmental requirements have pushed
utilities to operate transmission lines close to their operating
limits. Any fault, if not detected and isolated quickly will cascade
into a system wide disturbance causing widespread outages for a
tightly interconnected system operating close to its limits.
Transmission protection systems are designed to identify the
location of faults and isolate only the faulted section . The key
challenge to the transmission line protection lies in reliably
detecting and isolating faults compromising the security of the
system.
2. Factors Influencing line Protection
The high level factors influencing line protection include the
criticality of the line (in terms of load transfer and system stability),
fault clearing time requirements for system stability, line length, the
system feeding the line, the configuration of the line (the number
of terminals, the physical construction of the line, the presence
of parallel lines), the line loading, the types of communications
available, and failure modes of various protection equipment.
The more detailed factors for transmission line protection directly
address dependability and security for a specific application. The
protection system selected should provide redundancy to limit
the impact of device failure, and backup protection to ensure
dependability. Reclosing may be applied to keep the line in service
for temporary faults, such as lightning strikes. The maximum load
current level will impact the sensitivity of protection functions,
and may require adjustment to protection functions settings
during certain operating circumstances. Single-pole tripping
applications impact the performance requirements of distance
elements, differential elements, and communications schemes.
The physical construction of the transmission line is also a factor
in protection system application. The type of conductor, the size of
conductor, and spacing of conductors determines the impedance
of the line, and the physical response to short circuit conditions,
as well as line charging current. In addition, the number of line
terminals determines load and fault current flow, which must
be accounted for by the protection system. Parallel lines also
impact relaying, as mutual coupling influences the ground
current measured by protective relays. The presence of tapped
transformers on a line, or reactive compensation devices such
as series capacitor banks or shunt reactors, also influences the
choice of protection system, and the actual protection device
settings.
Transmission Line Protection Principles
2. 3. GE Multilin Application Advantages
Before considering using a GE Multilin relay for a specific
transmission line protection application, it is important to
understand how the relay meets some more general application
requirements for simplicity, security, and dependability. GE Multilin
relays provide simplicity and security for single pole tripping,
dependability for protection communications between line
terminals, security for dual-breaker line terminals, and simplicity
and dependability of redundant protection schemes.
3.1 Single-Pole Tripping
Single pole tripping using distance protection is a challenging
application. A distance relay must correctly identify a singlephase fault, and trip only the circuit breaker pole for the faulted
phase. The relay also must initiate the recloser and breaker failure
elements correctly on the fault event. The distance elements
protecting the unfaulted phases must maintain security during
the open-pole condition and any reclosing attempts.
The D90Plus Line Protection System and D60 Line Distance
Relay use simple, dedicated control logic for single pole tripping
applications. This control logic uses a Phase Selector, Trip Output
and Open Pole Detector in conjunction with other elements as
shown in the simplified block diagram.
The Trip Output is the central logic of single pole tripping. The Trip
Output combines information from the Open Pole Detector, Phase
Selector, and protection elements to issue a single pole or three
pole trip, and also to initiate automatic reclosing and breaker
failure. The Phase Selector is the key element for maintaining the
security of single pole tripping applications, quickly and accurately
identifying the faulted phase or phases based on measured
currents and voltages, by looking at the phase angles between
the positive sequence, negative-sequence, and zero-sequence
components.
The Open Pole Detector ensures the relay operates correctly during
a single pole trip, placing the relay in an open pole condition when
a single pole trip command is issued, or one pole of the circuit
breaker is open. The Open Pole Detector asserts on a single pole
trip command, before the circuit breaker pole actually opens, to
block protection elements that may misoperate under an open
pole condition, such as negative sequence elements, undervoltage
Reset
Open Pole
V, I
Open Pole(s)
Phase Selector
21P
Trip Output
Init BF
AR
21G
Dir. Supv.
Open Pole
Detector
Figure 1.
Single pole trip logic.
protection, and phase distance elements associated with the
faulted phase (for example, AB and CA elements for an AG fault).
The Open Pole Detector also resets and blocks the Phase Selector
so the other distance elements may operate for evolving faults.
The Open Pole Detector also accounts for line charging current
and for weak infeed conditions.
Once the Open Pole Detector operates, a further trip will cause
the Trip Output to declare a three pole fault, indicating either an
evolving fault condition or a reclose onto a permanent phaseto-ground fault. This total logic simplifies the setting of the D60
for single pole tripping, and ensures dependable and secure
operation when faced with single line-to-ground faults.
The L90 Line Differential Relay and the L60 Line Phase Comparison
Relay are both phase-segregated, current only relays. Single pole
tripping on these relays does not present any unusual challenges,
as each phase of the protection element operates independently
of the other unfaulted phases.
3.2 Communications
Often transmission lines are protected by using schemes
that require communications with relays located at other line
terminals. The reliability of the communications obviously
impacts the reliability of the protection system. GE Multilin relays
include features that maintain reliable operation of the protection
communications during power line faults, communications
channel delays, communications channel switching, and
communications channel dropout.
Pilot protection: Pilot protection schemes, such as directional
comparison blocking and permissive over-reaching transfer trip,
use simple on/off communications between relays. There are
many methods to send this signal. The most common method is to
use contact closure to an external communication circuit, such as
power line carrier, microwave, radio, or fiber optic communications.
GE Multilin relays simplify fiber optic communications method
by using internal fiber optic communications via Direct I/O,
eliminating the need for external communications devices. Direct
I/O is a reliable mechanism that is simple to configure, securely
transmits digital status points such as tripping or blocking
commands between relays via directly-connected or multiplexed
fiber optic channels. Direct I/O operates within 2ms for high speed
communications to the remote line end.
Direct I/O is available in any of the transmission line relays by
adding an internal communications card. The output of the card
can be IEEE C37.94, RS422 or G.703 communications to interface
with fiber optic multiplexers, or may be a direct fiber connection
to other relays. The communications card can be single-channel
or dual-channel, to support point-to-point communications, dual
point-to-point communications, or ring communications between
up to 16 relays.
Line Current Differential: Communications is an integral piece of
a line differential relay, as the currents from one line terminal must
be sent to relays at other line terminals to perform the differential
calculation. This requires the use of a digital communications
channel, which is commonly a multiplexed channel where channel
switching may occur. The analog information must be precisely
Transmission Line Protection Principles
3. time synchronized between the line ends for the differential
calculation to be correct. Synchronization errors show up as
phase angle offset, where identical currents produce phasors
with different phase angles, and transient errors, where changes
in current are seen at different times at different measurement
points. For example, on a 60 Hz system, every 1ms of time
shift between terminals introduces a 21.6° phase shift into the
measured currents.
The L60 Line Phase Comparison Relay directly solves two common
challenges with the carrier signal. The first issue is channel delay.
The channel delay is measured during commissioning and is
entered as a setting in the phase comparison element. The
remote phase angle measurements are buffered and delayed by
this value to match the incoming pulses from the remote relays.
The L60 has two communications channels, and two independent
channel time delays, to support three-terminal lines.
There are two methods to account for the phase shift between
line terminals due to the communications channel delay. One
method is to measure the round-trip channel delay, and shift
the local current phase by an angle equal to ½ of the round-trip
delay time. This method is simple to implement, but creates a
transient error when the communications channel is switched.
In addition, the differential element will be temporarily blocked
when the communications channel switches, or noise in the
communications channel causes communications packet loss.
The other common issue is pulse asymmetry of the carrier signal.
Carrier sets may extend, either the mark (on) or space (off) signals
at the receiving end compared with the originally sent signal.
This difference is measured during commissioning by using
oscillography data, and simply entered as a setting in the phase
comparison element.
The L90 Line Differential Relay employs a different method,
using synchronous sampling by internally synchronizing the
clocks on each L90. This method achieves high reliability, as the
round-trip channel delay is not vitally important. The differential
element successfully operates during channel switching or after
packet loss, because the communications packets are precisely
synchronized.
In the L90, synchronization is accomplished by synchronizing the
clocks to each other rather than to a master clock. Each relay
compares the phase of its clock to the phase of the other clocks
and compares the frequency of its clock to the power system
frequency and makes appropriate adjustments. The frequency
and phase tracking algorithm keeps the measurements at
all relays within a plus or minus 25 microsecond error during
normal conditions for a 2 or 3 terminal system. In all cases, an
estimate of phase error is computed and used to automatically
adapt the restraint region of the differential element. The time
synchronization algorithm can also use a GPS satellite clock to
compensate for channel asymmetry. The use of a GPS clock is not
normally required, except in applications such as a SONET ring
where the communications channel delay may be asymmetric.
In addition, the L60 supports some other methods to improve
the reliability of protection communications. For short lines with
negligible charging current, the channel delay measurement can
be automated by running a loop-back test during normal system
conditions and measuring the difference between the sent and
received pulses. The L60 also supports automated check-back of
the carrier system. Under normal conditions, the relay can initiate
transmission of and modulate the analog signal to exchange small
amounts of information. This automatic loop-back can replace
the carrier guard signal, and more importantly, verifies the entire
communications path, including the relays on both ends.
3.3 Security for Dual-Breaker Terminals
Dual-breaker terminal line terminals, such as breaker-and-a-half
and ring bus terminals, are a common design for transmission
lines. The standard practice is to sum the currents from each
circuit breaker externally by paralleling the CTs, and using this
external sum as the line current for protection relays. This practice
f
Compute
Frequency
Deviation
Line Phase Comparison: As with line differential, communications
is an integral part of phase comparison relaying. Simple binary
communications, such as power line carrier or microwave, is used
to send a pulse to the remote end when the phase angle of the
measured current is positive. Coordination between the pulses
from the remote end, and the phase angle measured at the local
end, must be maintained.
f
System
Frequency
+
f - f1
This method produces synchronization accurate to within 125
microseconds between the relays on each end of the protected
line. By using internally synchronized sampling, the L90 can
accommodate 4 consecutive cycles of communications channel
loss before needing to block the differential element. If the
communications channel is restored within 5 seconds of channel
loss, the L90 differential element will restart on the first received
packet, without any time synchronization delay, due to the inertia
of the internal clocks of the relays.
Relay 2
Relay 1
+
-
f1
f2
Compute
Frequency
Deviation
f - f2
Phase Frequency
Loop Filter
Phase Frequency
Loop Filter
1
2
( 2 - 1)/2 Ping-Pong
Phase
Deviation
time stamps
Ping-Pong ( 2 - 1)/2
Phase
Deviation
GPS
Phase
Deviation
time stamps
GPS
Phase
Deviation
( 2 - 1)/2
GPS
Clock
( 2 - 1)/2
GPS
Clock
Figure 2.
Clock synchronization block diagram for a two terminal system using L90
current differential system.
Transmission Line Protection Principles
4. works well during actual line faults. However, for some external
fault events, poor CT performance may lead to improper operation
of line protection relays.
not impact the speed or sensitivity of the protection elements,
operates during all load conditions, and correctly allows tripping
during an evolving external-to-internal fault condition.
When current flows through a dual-breaker line terminal, the line
current measured by a relay using external summation matches
the actual line current only if the two CTs are accurate. The most
significant relaying problem is CT saturation in either CT. The current
measured by the relay may contain a large error current, which
can result in the relay operating due to an incorrect magnitude or
direction decision. This incorrect operation may also occur if the
linear error current of the CTs due to accuracy class is close to the
through current level. These errors appear in the measured phase
currents. As a result, relays that calculate the negative sequence
and zero sequence currents from the measured phase currents
may also see errors.
The dual-breaker line terminal supervisory logic essentially
determines if the current flow through each breaker is either
forward or reverse. Both currents should be forward for an internal
fault, and one current should be forward and one reverse for an
external line fault. The supervisory logic uses, on a per-phase
basis, a high-set fault detector (FDH), typically set at 2-3 times the
nominal rating of the CT, and a directional element for each CT
input to declare a forward fault, for each breaker. The logic also
uses, on a per-phase basis, a low-set fault detector (FDL), typically
set at 1.5-2 times the nominal rating of the CT, and a directional
element to declare a reverse fault, for each breaker.
Distance: Distance relays applied at dual-breaker line terminals
are vulnerable to mis-operation on external faults. During a closein reverse external fault, the voltage is depressed to a very low
level, and the security of the relay is maintained by directional
supervision. If one of the line CTs saturates, the current measured
by the relay may increase in magnitude, and be in the opposite
direction of the actual fault current, leading to an incorrect
operation of the forward distance element for an external fault.
The D90Plus Line Protection System and the D60 Line Distance
Relay handles the challenge of dual-breaker line terminals by
supporting two three-phase current inputs to support breaker
failure, overcurrent protection, and metering for each circuit
breaker. The relays then mathematically add these currents
together to form the total line current used for distance and
directional overcurrent relaying.
Directly measuring the currents from both circuit breakers allows
the use of supervisory logic to prevent the distance element
and directional overcurrent elements from operating incorrectly
for reverse faults due to CT error. This supervisory logic does
i2
IF + ILine
52
Relay
ILine
10 - 15 pu
with
0.1 pu error
0.1 pu error
iLine shows incorret
magnitude, direction
iLine
CT 1
ILine
The L90 Line Differential Relay supports up to four three-phase
current inputs for breaker failure, overcurrent protection, and
metering for each circuit breaker. The relay then uses these
individual currents to form the differential and restraint currents
for the differential protection element.
2
CT 1
52
Line Differential: Line differential protection is prone to tripping
due to poor CT performance on dual-breaker terminals, as the
error current from the CTs is directly translated into a differential
current. The only possible solution for traditional line differential
relays is to decrease the sensitivity of the differential element,
which limits the ability of the differential element to detect low
magnitude faults, such as highly resistive faults.
CT 1 saturates
i2 is reduced
i
IF + ILine
iLine
Tripping is permitted during all forward faults, even with weak
infeed at the dual-breaker terminal. Tripping is blocked for all
reverse faults when one breaker sees forward current and one
breaker sees reverse current. During an evolving external-tointernal fault, tripping is initially blocked, but when the second
fault appears in the forward direction, the block is lifted to permit
tripping.
0.2 pu error
52
Relay
Relay
10 - 15 pu
IF
IF
52
CT 2
Figure 3.
52
52
i1
503
52
503
10 - 15 pu
with
0.1 pu error
0.1 pu error
Figure 4.
Impact of CT saturation on two-breaker line applications
a) Accurate CTs preserve the reverse line current direction under weak
remote feed.
b) Saturation of the CT carries the reverse current may invert the line
current as measured from the externally summated CTs.
10
L90
Id 0.2 pu
Ir = 10 - 15 pu
NO TRIP
10 - 15 pu
Id 0.2 pu
Ir 0.2 pu
TRIP
CT 2
i1
52
Sensitivity of line differential system for dual-breaker applications.
Transmission Line Protection Principles
5. The L90 differential element design explicitly accounts for the
performance of the CTs for dual-breaker line terminals. Each L90
protecting a transmission line calculates differential and restraint
quantities based on local information directly measured by the
relay, and information received from relays located at the remote
line ends. Tripping decisions are made locally be each relay.
The values of ILOC and ILOC_RESTRAINT are transmitted to the L90
relays located at the other line ends. The differential and restraint
values used in the actual tripping decision combine both the
local differential and restraint current, and the differential and
restraint currents from the remote line ends. These calculations
are performed individually on each phase.
The information sent by one L90 to the other L90s on the line is
the local differential and restraint currents. The local differential
current is the sum of all the local currents on a per-phase basis.
One L90 can accept up to 4 current measurements, but only 2
currents are used for a dual-breaker application.
I DIFF = I LOC + I REMOTE 1 + I REMOTE 2
I LOC = I 1 + I 2 + I 3 + I 4
The local restraint current is defined by the following equation for
each phase.
I LOC _ RESTRAINT =
(I
LOC _ REST _ TRAD
) + MULT • (I
2
LOC _ ADA
)
2
The starting point for the restraint is the locally measured
current with the largest magnitude. This ensures the restraint is
based on one of the measured currents for all fault events, and
increases the level of restraint as the fault magnitude increases.
ILOC_REST_TRAD is this maximum current magnitude applied
against the actual differential characteristic settings. ILOC_ADA is
the sum of the squares estimate of the measurement error in the
current, and is used to increase the restraint as the uncertainty of
actual measurement increases, such as during high magnitude
fault events and CT saturation. MULT is an additional factor that
increases the error adjustment of the restraint current based
on the severity of the fault event and the likelihood the fault is
an external fault, when CT saturation is most likely to cause an
incorrect operation.
(I REST ) 2 = (I LOC _ RESTRAINT ) 2 + (I REM 1 _ RESTRAINT ) 2 + (I REM 2 _ RESTRAINT ) 2
Considering the worst case external fault with CT saturation, the
differential current IDIFF will increase due to the CT error that
appears in ILOC. However, the restraint current IREST will increase
more significantly, as the ILOC_RESTRAINT uses the maximum of
the local currents, that is increased based on the estimation of CT
errors and presence of CT saturation. The end result is a correct
restraining of the differential element.
Phase Comparison: The L60 Line Phase Comparison Relay
supports two three-phase current inputs for breaker failure,
overcurrent protection, and metering for each circuit breaker. The
relay then uses these individual currents to form the local phase
angle information for use in the phase comparison scheme.
A phase comparison relay operates by comparing the relative
phase angles of the current from each end of the transmission line.
When the measured current exceeds the level of a fault detector,
and the phase angles from each end of the line are in phase, the
phase comparison relay operates. For a dual-breaker application
using an external sum, the saturation of one CT may cause the
relay current to increase high enough to operate the fault detector.
Because the current from the unsaturated CT predominates in this
waveform, the phase angle of the relay current may change. If the
phase angle of the relay current is in phase with the relay current
at the remote end of the line, the relay will trip.
CT 1
CT 1
52
52
52
52
CT 2
CT 2
D90Plus Distance POTT Scheme
D60 Distance POTT Scheme
L90 Line
Differential
L60 Phase
Comparison
Multilplexed Fiber Optic
Multilplexed Fiber Optic
Multilplexed Fiber Optic (different channel)
Power Line Carrier
D90Plus Distance POTT Scheme
D60 Distance POTT Scheme
L90 Line
Differential
L60 Phase
Comparison
Figure 5.
Redundancy Requirements - Alternate main protection possibilities from GE Multilin.
Transmission Line Protection Principles
11
6. The L60 in dual-breaker applications selects the appropriate phase
angle, based on the information measured from the current flow
through both circuit breakers. The relay uses fault detectors on
each current input, and develops the phase angle for each current
input, and then special dual breaker logic consolidates the fault
detector flags and the phase angle pulses for the line terminal.
The fault detector flag is set for a line terminal if either fault
detector from the two breakers is picked up. The type of phase
comparison protection scheme, tripping or blocking, controls the
pulse combination logic. For a tripping scheme, a positive polarity
is declared for the terminal if one breaker displays positive polarity
with its respective fault detector picked up, while the other breaker
either does not show negative polarity or its fault detector is not
picked up.
3.4 Redundancy Considerations to Enhance
Reliability
The reliability of transmission system protection is dependent on
the reliability of the protection scheme used and the individual
components of the protection scheme. Transmission protection
systems typically use redundancy to increase the dependability
of the system. There are two general methods of implementing
redundancy. One method is to use multiple sets of protection
using the same protection scheme. The other method is to use
multiple sets of protection using different protection principles.
Depending on the voltage class, either method of redundancy
may involve using 2 or 3 sets of protection. In both cases, the goal
is to increase dependability, by ensuring the protection operates
for a fault event. Security may be improved through the use of socalled voting schemes (e.g. 2-out-of-3), potentially at the expense
of dependability.
Multiple sets of protection using the same protection scheme
involves using multiple relays and communications channels.
This is a method to overcome individual element failure. The
simplest method is to use two protection relays of the same type,
using the same scheme and communications channel. This only
protects against the failure of one relay. In some instances, relays
of different manufacturers are used, to protect against common
mode failures. It is also common to use redundant communications
channels, in case of failure on one communications channel.
Often, the communications channels use different methods, such
as power line carrier and fiber optic. This is especially true due to
the concerns of power line carrier operation during internal fault
events.
12
An alternative way to increase reliability through redundancy is to
use multiple protection methods on the same line such as phase
comparison and permissive over-reaching transfer trip, using
different communications channels. This method protects against
individual element failure of both relays and communications
channels. More importantly, it protects against the failure of one
of the protection methods. For example, a VT circuit fuse failure
blocks a distance relay from operating, while a line differential
system or phase comparison system will continue to operate. For
this reason, often at least one current-only scheme, such as phase
comparison or line differential, and then one pilot protection
scheme based on distance relays are employed.
A second advantage of using multiple protection methods to
protect one line is the ability to increase the security of the line.
It is possible to implement a “voting” scheme, where at least 2
protection methods must operate before the line can be actually
tripped. Such a voting scheme may be applied permanently on lines
where security is an issue, such as major inter-tie lines. A voting
scheme may also be applied only when the system is at risk, such
as during wide-area disturbances, either automatically based on
system conditions, or by command from system operators.
GE Multilin simplifies solutions when multiple protection schemes
are used by providing both protective relays that only use current
and protective relays that use both current and voltage. The L60
Line Phase Comparison Relay and the L90 Line Differential Relay
are both current-only protection relays with different operating
principles. The D90Plus, D60 and D30 Line distance protection
systems are full-featured distance relays. These relays are on a
common hardware and software platform, simplifying engineering,
design, installation, and operations issues. All of these relays
support multiple communications options, including power line
carrier, microwave, and fiber optic communications. The relays
are also designed to communicate with each other, to implement
voting schemes, reclosing control, and other applications.
4. Typical Applications
This section highlights some typical application of GE Multilin line
protection relays. This section is not intended as a comprehensive
list of possible applications. For questions about the correct relay
for a specific application, visit www.GEMultilin.com to review the
brochure for a specific relay model, or contact GE Multilin.
Transmission Line Protection Principles
7. Directional Overcurrent
Typical Functions
3Y
52
3Y
or
2D
Additional Functions
67P
67N
25
79
V, S
Phase directional overcurrent
Neutral directional
overcurrent
Synchrocheck
Reclosing
Voltage and Power metering
Functions
Typical Product Order Code
Typical Functions
F60-N00-HCH-F8L-H6P-MXX-PXX-UXX-WXX
Alternative
67P 67N 25
V
D30-N00-HCH-F8L-H6P-MXX-PXX-UXX-WXX
+ Additional functions
Included in typical
Included in typical
Included in typical
Alternative
Alternative
79
S
Directional Overcurrent – Dual Breaker
1
Typical Functions
3Y
Additional Functions
67P
67N
25
79
V, S
Phase directional overcurrent
Neutral directional
overcurrent
Synchrocheck
Reclosing
Voltage and Power metering
52
Functions
Typical Product Order Code
Typical Functions
3Y
or
2D
52
67P 67N 25
3Y
V
D60-N02-HCH-F8L-H6P-M8L-PXX-UXX-WXX
+ Additional functions
Included in typical
External electrical sum of
breaker currents (traditional
method)
Only 1 synchrocheck function in
F60 and D30
F60-N00-HCH-F8L-H6P-M8L-PXX-UXX-WXX
D30-N00-HCH-F8L-H6P-MXX-PXX-UXX-WXX
D60-N00-HCH-F8L-H6P-MXX-PXX-UXX-WXX
79
2
S
1
Stepped-Distance Protection
Additional Functions
21P
21G
3Y
Typical Functions
67P
67N
Phase distance
Ground distance
Synchrophasors
52
3Y
Phasor Measurement Unit
50BF
25
79
V, S
Phase directional overcurrent
Neutral directional
overcurrent
Breaker Failure
Synchrocheck
Reclosing
Voltage and Power metering
Functions
3
V
3
S
25
79
D30-N00-HCH-F8L-H6P-MXX-PXX-UXX-WXX
Alternative
21P 21G 67P 67N
Typical Product Order Code
Typical Functions
D60-N00-HCH-F8L-H6P-MXX-PXX-UXX-WXX
D90P-A-E-S-S-01-S-S-S-X-H-X-A-X-A-X-X-01-X
+ Additional functions
Included in typical
50BF
No 50BF in D30
+ Synchrophasors
Transmission Line Protection Principles
D60-N06-HCH-F8L-H6P-MXX-PXX-UXX-WXX
D90P-A-E-S-S-01-P-S-S-X-H-X-A-X-A-X-X-01-X
13
8. Stepped-Distance Protection – Dual Breaker
Additional Functions
21P
21G
1
Typical Functions
67P
67N
Phase distance
Ground distance
50BF
25
79
V, S
3Y
Phase directional overcurrent
Neutral directional
overcurrent
Breaker Failure
Synchrocheck
Reclosing
Voltage and Power metering
Synchrophasors
52
Phasor Measurement Unit
Functions
21P 21G 67P 67N
3
V
50BF
S
25
D60-N00-HCH-F8L-H6P- MXX-PXX-UXX-WXX
D30-N00-HCH-F8L-H6P-MXX-PXX-UXX-WXX
+ Synchrophasors
2
3
Included in typical
External electrical sum of
breaker currents (traditional
method)
Only 1 synchrocheck function
In D30
52
3Y
D90P-A-E-S-S-01-S-S-S-X-H-X-A-X-A-X-X-01-X
D60-N02-HCH-F8L-H6P-M8L-PXX-UXX-WXX
+ Additional functions
3Y
Typical Product Order Code
Typical Functions
D90P-A-E-S-S-01-P-S-S-X-H-X-A-X-A-X-X-01-X
D60-N08-HCH-F8L-H6P-M8L-PXX-UXX-WXX
79
2
1
Pilot Protection Schemes
Typical Functions
21P
21G
85
3Y
Additional Functions
Phase distance
Ground distance
Power line carrier /
microwave transmitter
receiver / fiber or digital
channel
67P
67N
50BF
25
79
V, S
52
3Y
85
Other Communications Options
85
85
Phase directional overcurrent
Neutral directional
overcurrent
Breaker Failure
Synchrocheck
Reclosing
Voltage and Power metering
Synchrophasors
Inter-Relay Communications
Sonet Multiplexer
Phasor Measurement Unit
3
V
50BF
3
S
25
79
85
Functions
Typical Product Order Code
Typical Functions
85 by others
D90P-A-E-S-S-01-S-S-S-X-H-X-A-X-A-X-X-01-X
D60-N00-HCH-F8L-H6P-MXX-PXX-UXX-WXX
+ Additional functions
Included in typical
+ Synchrophasors
21P 21G 67P 67N
D90P-A-E-S-S-01-P-S-S-X-H-X-A-X-A-X-X-01-X
D60-N06-HCH-F8L-H6P-MXX-PXX-UXX-WXX
Other Communications Options
Direct I/O, 1300nm Singlemode
Laser, 64km
RS422 interface
D60-N00-HCH-F8L-H6P-M8L-PXX-UXX-W7W
G.703
D60-N00-HCH-F8L-H6P-M8L-PXX-UXX-W7S
C37.94
D60-N00-HCH-F8L-H6P-M8L-PXX-UXX-W77
SONET Multiplexer
14
D60-N00-HCH-F8L-H6P-M8L-PXX-UXX-W7K
JungleMux with 86448 and 86441 units
Transmission Line Protection Principles
9. Pilot Protection Schemes – Dual Breaker
Typical Functions
21P
21G
85
1
Additional Functions
Phase distance
Ground distance
Power line carrier /
microwave transmitter
receiver
67P
67N
50BF
25
79
V, S
3Y
52
Other Communications Options
85
85
Phase directional overcurrent
Neutral directional
overcurrent
Breaker Failure
Synchrocheck
Reclosing
Voltage and Power metering
Synchrophasors
Inter-Relay Communications
Sonet Multiplexer
Phasor Measurement Unit
Functions
3Y
85
52
Typical Product Order Code
Typical Functions
85 by others
D90P-A-E-S-S-01-S-S-S-X-H-X-A-X-A-X-X-01-X
D60-N00-HCH-F8L-H6P-M8L-PXX-UXX-WXX
+ Additional functions
21P 21G 67P 67N
3Y
3
S
External electrical sum of
breaker currents (traditional
method)
2
25
D90P-A-E-S-S-01-P-S-S-X-H-X-A-X-A-X-X-01-X
D60-N06-HCH-F8L-H6P-M8L-PXX-UXX-WXX
D60-N00-HCH-F8L-H6P- MXX-PXX-UXX-WXX
50BF
3
V
Included in typical
+ Synchrophasors
79
85
2
Other Communications Options
Direct I/O, 1300nm Singlemode
Laser, 64km
D60-N00-HCH-F8L-H6P-M8L-PXX-UXX-W7W
G.703
D60-N00-HCH-F8L-H6P-M8L-PXX-UXX-W7S
C37.94
D60-N00-HCH-F8L-H6P-M8L-PXX-UXX-W77
SONET Multiplexer
Line Differential Protection
D60-N00-HCH-F8L-H6P-M8L-PXX-UXX-W7K
RS422 interface
1
JungleMux with 86448 and 86441 units
Typical Functions
Additional Functions
87L
85
21P
21G
67P
67N
Line differential
Sonet Multiplexer
1
3Y
50BF
25
79
V, S
52
3Y
85
Other Communications Options
85
87L
67P 67N
21P 21G 25
3
3
79
50BF
85
Identical relay
on other line
terminals
Synchrophasors
Inter-Relay Communications
Functions
Phase distance
Ground distance
Phase directional overcurrent
Neutral directional
overcurrent
Breaker Failure
Synchrocheck
Reclosing
Voltage and Power metering
Phasor Measurement Unit
Typical Product Order Code
Typical Functions
L90-N00-HCH-F8L-H6P-LXX-NXX-SXX-UXX-W7W
+ Additional functions
Included in typical
+ Synchrophasors
L90-N06-HCH-F8L-H6P-LXX-NXX-SXX-UXX-W7W
SONET Multiplexer
JungleMux with 86448 and 86443 units
Other Communications Options
D60-N08-HCH-F8L-H6P-M8L-PXX-UXX-WXX
Direct I/O, 1300nm Singlemode
Laser, 64km
Included in typical
+ Synchrophasors
L90-N00-HCH-F8L-H6P-LXX-NXX-SXX-UXX-W7K
G.703
L90-N00-HCH-F8L-H6P-LXX-NXX-SXX-UXX-W7S
C37.94
L90-N00-HCH-F8L-H6P-LXX-NXX-SXX-UXX-W77
Transmission Line Protection Principles
15
10. Line Differential Protection – Dual Breaker
Additional Functions
87L
85
1
Typical Functions
21P
21G
67P
67N
Line differential
Sonet Multiplexer
Phase distance
Ground distance
Phase directional overcurrent
Neutral directional
overcurrent
Breaker Failure
Synchrocheck
Reclosing
Voltage and Power metering
50BF
25
79
V, S
3Y
52
Other Communications Options
85
Synchrophasors
Phasor Measurement Unit
Inter-Relay Communications
Functions
Typical Product Order Code
85
L90-N02-HCH-F8L-H6P-L8L-NXX-SXX-UXX-W7W
+ Additional functions
3Y
Typical Functions
Included in typical
+ Synchrophasors
52
87L
3Y
67P 67N
3
3
79
L90-N00-HCH-F8L-H6P-LXX-NXX-SXX-UXX-W7W
SONET Multiplexer
50BF
2
21P 21G 25
L90-N08-HCH-F8L-H6P-LXX-NXX-SXX-UXX-W7W
Electrical sum of breaker
currents (traditional method)
JungleMux with 86448 and 86443 units
Other Communications Options
85
2
1
Phase Comparison Protection
Direct I/O, 1300nm Singlemode
Laser, 64km
L90-N02-HCH-F8L-H6P-L8L-NXX-SXX-UXX-W7K
G.703
L90-N02-HCH-F8L-H6P-L8L-NXX-SXX-UXX-W7S
C37.94
Identical relay
on other line
terminals
L90-N02-HCH-F8L-H6P-L8L-NXX-SXX-UXX-W77
Typical Functions
3Y
Additional Functions
87PC
85
1
21P
21G
67P
67N
Phase Comparison
Power Line Carrier /
Microwave
52
3Y
50BF
25
79
V, S
85
Phase distance
Ground distance
Phase directional overcurrent
Neutral directional
overcurrent
Breaker Failure
Synchrocheck
Reclosing
Voltage and Power metering
Functions
87
PC
67P 67N
21P 21G 25
3
50BF
79
Identical relay
on other line
terminals
85
Typical Product Order Code
Typical Functions
L60-N00-HCH-F8P-H6P-L8L-NXX-SXX-UXX-WXX
3
Phase Comparison Protection – Dual Breakers
3Y
Typical Functions
Additional Functions
87PC
85
1
21P
21G
67P
67N
Line differential
Power Line Carrier /
Microwave
50BF
25
79
V, S
52
Phase distance
Ground distance
Phase directional overcurrent
Neutral directional
overcurrent
Breaker Failure
Synchrocheck
Reclosing
Voltage and Power metering
Functions
3Y
85
Typical Product Order Code
Typical Functions
L60-N00-HCH-F8P-H6P-L8L-NXX-SXX-UXX-WXX
52
3Y
87
PC
67P 67N
50BF
2
21P 21G 25
3
79
85
Identical relay
on other line
terminals
3
0925-v5
16
Transmission Line Protection Principles