Directional non directional overcurrent protection. Testing directional overcurrent relays from valence. Overcurrent and earthfault relay rej 515 service and. Study and performance analysis of digital overcurrent relay. Directional overcurrent protection is used when it is necessary to protect the system against fault currents that could circulate in both directions through a system element, and when bidirectional overcurrent protection could produce unnecessary disconnection of circuits. Directional ieds determine the direction of the fault current by measuring the voltage with a voltage transformer as well as the current with a current transformer, and establishing the phase difference. A ground relay must detect all phasetoground faults within its defined zone of protection under conditions which produce minimum fault current. The classical method for detecting ground faults on a looped system has been to use directional. There is only one current operated element in the relay, no voltage coil etc. In both analog and digital worlds, the circuits analog and algorithms digital are d e. Leave a comment on this post, we will send you the overcurrent fundamental. The currenttime tripping characteristics of idmt protection relays may need to be changed according to the functioning time needed and the characteristics of other relay protection elements used in the electrical network. It contains two relaying units, over current units and the other a directional unit.
The essentials of directional overcurrent protection in. It owes its application from the fact that in the event of fault the current would increase to a value several times greater than maximum load current. The ground relay zone of protection can be defined as a current threshold or measured impedance. This is because the induction disc characteristics of the overcurrent relays inverse characteristics are not amenable to simple mathematical analysis. When short circuit current can go in both directions through the protection relay location, it may be required to make the response of the protection relay directional by the initiation of a directional control device. All protectiverelay types are derived either directly from these basic elements, by. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected 4 the first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over current, over voltage, reverse power flow, over frequency, and underfrequency. Instantaneous overcurrent relay is employed where the impedance between the source and the relay is small as compared with the impedance of the section to be provided. In power systems relays are used to detect abnormal conditions. Directional overcurrent and directional power relays. The time of operation of such relay is approximately 100 ms.
The relay time setting is determined by system selectivity requirements. Pdf this paper describes the design of a digital over current relay directional and non directional and its performance on matlabsimulink. From this basic method, the graded overcurrent relay protection system, a discriminative short circuit protection, has been formulated. Differential protection scheme is based on comparison of measured variables such as current and voltage at the two ends of a line via a communication channel such as pilot wire. Directional supervision time overcurrent relays fall 2018 u i ece525 lecture 11 directional steptime overcurrent ansi 67 the directional overcurrent relay can be perceived as a type 50 instantaneous element controlled by a type 32 directional element if the type 67 relay element is to provide backup protection. The figure below shows the constructional of nondirectional induction type overcurrent relay. This paper presents the design of a digital directional and non directional over current relay and its performance on matlab. Fault current if2 also flows through line 1, but in the opposite direction. The first static relays developed were the high speed differential relays. A technicians approach to cable testing directional. The solid static relays was first introduced in 1960s. This directional over current relay employs the principle of actuation of the relay, when the fault current flows into the relay in a particular direction. The main application of long time over current relays is as backup earth fault protection.
Over this value the directional relay uses standard polarisation the measured voltage, under this. This is the simplest of the ways to protect a line and therefore widely used. Directional relay has a characteristics that it responds to over current condition in the. When required, directional control can be exercised over the relay by connecting an output contact from direction relay type. Considerations in choosing directional polarizing methods for.
Jul 14, 2016 the relay setting is 50% to 200% in steps of 25%. The overcurrent relay operates when the current in the circuit exceeds a certain preset value. Mechanical and solid state relays determine direction by connection. Fundamentals and improvements for directional relays. Jemt 6 2018 815 issn 20533535 overcurrent relays coordination using matlab model a. In an over current relay or oc relay the actuating quantity is only current. Forward, reverse directional relays may or may not make use of directionally controlled instantaneous units. The relay operates when the operating force is greater than the. The overcurrent unit and the earthfault unit continuously measure the phase currents and the neutral current of the object. This type of directional relay is made by combining overcurrent protection equipment with an equipment to measure the phase displacement between the current. Pdf this paper presents the design of a digital directional and non directional over current relay and its performance on matlab. Overcurrent protection relay electrical engineering.
File contains the design of a digital over current relay block directional and non directional a key component of any protection scheme and its performance on simulink. Directional over current relay relay electromagnetic. Pdf currentonly directional overcurrent relay researchgate. Abstract directional overcurrent relaying 67 refers to relaying that can use the phase relationship of voltage and current to determine direction to a fault. The term static implies that the relay has no moving mechanical parts in it. Directional phase protection equipment is used on a radial network for substations supplied simultaneously by several sources. Modes of operation the relay makes its directional decision by determining if the angle between the operating current and polarizing voltage has entered the elements operating sector. When there is fault in power system, power flows through fault. Pdf overcurrent relays are widely used for protection of power systems, directional ones for transmission side, and nondirectional ones for. Depending on the time of operation the overcurrent relay is categorized into following types.
These relays are typically applied to provide the main protection on feeders and interconnectors and the backup protection on items of plant such as. The 7sr12 includes directional control of the overcurrent and earth fault functionality and is typically installed where fault current can flow in either direction i. Rxpdk 2h and rapdk assemblies based on single phase elements. The current enters the nonpolarity mark of the ct, and the relay determines that current is leaving the transmission line. The overcurrent relay is defined as the relay, which operates only when the value of the current is greater than the relay setting time. Most ground directional overcurrent relays can be thought of as having two components, a directional. The ibc relays consist of two units, an instantaneous power directional unit bottom of the inductioncup type, and a time overcurrent unit top of the induction. For this reason, directional elements are used to supervise ground overcurrent elements so that they only operate for faults in one direction, either forward or reverse, in order to simplify coordination. Considerations in choosing directional polarizing methods. Pdf digital directional and nondirectional over current. The classic electromechanical and solid state relay, as well as some common numeric relays, determines the direction to fault by comparing the phase angle. The relay is built such that the angle of maximum torque occurs for phase current lagging the unity power position by 45 degrees or leading the quadrature voltage by. The conventional types of electromagnetic relays electromechanical relay has one or more coils, movable elements, contact system etc and its operation depends on whether the operating torque or force is greater than the restraining torque or force. Overcurrent protection fundamentals relay protection against high current was the earliest relay protection mechanism to develop.
Overcurrent protection fundamentals r ced engineering. Current transformer requirements for non directional. For example, over current, under voltage, fault conditions etc. Directional ieds determine the direction of the fault current by measuring the voltage with a voltage transformer as well as the current with a current transformer, and establishing the phase difference this technical article does not go into details of exactly how this is achieved, but it. Rxpdk 2h and rapdk assemblies based on single phase. Inverse time overcurrent relay electrical engineering. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected 4 the first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as overcurrent, overvoltage, reverse power flow, overfrequency, and underfrequency. Static overcurrent relays and its types engineering notes india. Static relay circuit using analog and digital ics for over current. In order to obtain good continuity of service, it is important that a fault affecting one of the sources does not cause all the sources to trip. Sep 01, 2018 in an over current relay or oc relay the actuating quantity is only current. The directional overcurrent relay at location e trips and opens the corresponding circuit. If the power flow is in the opposite direction, the relay will not operate.
Pickup with full voltage restraint of the type ifcv relay should generally be set between 200% and 250% of full load current on regulated generators, and between 150% and 200% full load current on unregulated generators. Directional over current and ef relays 01092015 when fault currents can flow in more than one direction it is desirable to determine which direction the fault current is flowing and trip the appropriate devices accordingly to contain a given fault. Directional non directional directional non directional. The device is provided by the use of extra voltage inputs to the protection relay. Okundamiya3 1department of electrical and electronic engineering, maritime academy of nigeria, oron, nigeria. Directional overcurrent protection devices can achieve this requirement, albeit at extra cost. Threephase directional overcurrent 67 each one of the threephase overcurrent stages of the p127 can be independently configured as directional protection with specific relay characteristic angle rca settings and boundaries. The directional element is quadrature polarized, meaning the aphase relay uses aphase current and vbc voltage. The overcurrent relays, even though simplest of all types of electromechanical relays, are the most difficult static relays.
Pdf the study of directional overcurrent relay and. For directional unit, the secondary winding of the over current relay unit is kept open ab. The first static relays developed were the high speed differential relays and the distance relays. Over current relay working principle types electrical4u. The polarisation discrimination voltage value is 0. The phasor diagram of a meter test on the directional overcurrent 67 relay connected to circuit breaker 4 would look like the following. Voltage polarization and current polarization in earth fault relays. The protection is implemented as three stage definite time nondirectional overcurrent protection. When normal current flows through this coil, the magnetic effect. The induction type nondirectional overcurrent relay has a construction similar to a watthour meter, with slight modification. During this test, current measurement is inhibited. Basics of overcurrent protection linkedin slideshare. I type ibc51a relay disassembled front view 0, \,p.
Instantaneous overcurrent relay is one in which no intentional time delay is provided for the operation. Directional overcurrent relays 67 respond to excessive current flow in a particular direction in the power system. Digital over current relays have advantages over electromechanical. Directional overcurrent protection comprises overcurrent relay and power directional relay in a single relay casing. One is a directional element, which determines the direction of current flow with respect to. Directional over current relay linkedin slideshare.
Directional relay does not measure the power but is arranged to respond to. Nov 20, 2017 in this video, ankit goyal cofounder of kreatryx and air 1 in gate 2014 explains how to place the directional and non directional relays in a power system. Westinghouse induction type overcurrent and directional overcurrent relays fig. This relay is also called earth leakage induction type relay. Constructional details and operation of non directional over current relay wattmeter type a directional over current relay operates when the current exceeds a specified value in a specified direction. Directional overcurrent relaying 67 concepts my protection guide. Finding the direction in directional overcurrent relays. There are a variety of concepts by which this task is done.
It has a limitation that it can be applied only to simple and non costly equipments. Directional overcurrent protection reyrolle 7sr120. Directional overcurrent relays directional overcurrent protection is used when it is necessary to protect the system against fault currents that could circulate in both directions through a system element, and when bidirectional overcurrent protection could produce unnecessary disconnection of circuits. Consider a typical electromechanical phase directional relay. The ibc directional overcurrent relays are employed primarily for the protection of feeders and transmission lines in applications where singlephase relays are desired or required. The study of directional overcurrent relay and directional earthfault protection application for 33 kv underground cable system in malaysia. Directional relays power systems gate ee exam youtube. The p12x relays can be used for a range of overcurrent applications from single phaseearth fault applications, p120 non directional. Directional overcurrent relays types ibc, ibcg and mcv,device function numbers for use with external diagrams 52 power circuit breaker 67 directional overcurrent relays, type mc or type mcv 67n directional ground relay, type mcg a auxiliary contact, 0. Non indirectional induction overcurrent relay construction. A directional over current relay operates when the current exceeds a specified value in a specified direction. Fast ground directional overcurrent protection limitations and solutions page 5 of 22 historically only the symmetrical quantities have been used in protective relaying and the relays measure the symmetrical components accordingly. One is a directional element, which determines the direction of current flow with respect to a voltage reference. A test mode is also available to carry out a trip test on the output relays.
Pdf digital directional and nondirectional over current relays. The combined overcurrent and earthfault relay rej 515 is a secondary relay which is connected to the current transformers of the object to be protected. Now our directional overcurrent 67 test plan looks like the following drawing where we start with the raw currents and voltages, calculate the nonfaulted phasetophase voltage, and plot the operating current and polarizing signal, which in this case is vbc. When the power system is not radial source on one side of the line, an over current relay may not be able to provide adequate protection. Directional supervision time overcurrent relays fall 2018 u i ece525 lecture 11 directional steptime overcurrent ansi 67 the directional. Example for nondirectional overcurrent protection the following figure describes a typical medium voltage feeder. A 400v industrial distribution power system is used as a tutorial to simulate and test overcurrent relays performance results, with motor start up inrush. It protects the equipment of the power system from the fault current. Normally, the conventional over current relay nondirection will act for fault current in any direction. In an over current relay, there would be essentially a current coil.
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