When the threshold is exceeded, the oc comparator forces the output and. Overcurrent earth fault protection principle equation. Figure shows the block diagram of the microprocessorbased relay. Introduction the bureau of reclamation operates and maintains 58 hydroelectric powerplants. Cost comparison of numerical relay with electromechanical and static relay 3. Unit i introduction of relays a relay comprises of an. Over current relay, microcomputer module, pickup current. As shown, the power source is given to the electromagnet through a control switch and through contacts to the load. Figure 2 shows cost comparison of numerical relay with electromechanical and static relay 1. The current derived from the ct is fed to the input transformer which gives a proportional output voltage. While early comparators used discrete transistor circuits, modern designs use operational amplifiers. Overcurrent relay characteristics and implementation an overcurrent relay ansi device number is 50 for an instantaneous overcurrent ioc, 51 for.
This relay, for example, can be used as an earthfault, shown in figs. A big difference between conventional electromechanical and static relays is how the relays are wired. Static relay circuit using analog and digital ics for over current. In this article, an overcurrent relay is designed based on fuzzy logic control to improve the overall. The diagram shows an inner section diagram of a relay.
Using digital signal processing in power system overcurrent. The solid static relays was first introduced in 1960s. The simplified block diagram of a numerical protective relay including an. Jun 30, 2017 numerical relay is the relay in which the measured ac quantities are sequentially sampled and converted into numerical data that is mathematically andor logically processed to make trip decisions. The instantaneous overcurrent relay is designed to operate with no intentional time delay when the current exceeds the relay setting. Each relay is energized by current from its respective phase and voltage. Staticrelays components of static relays block diagram of static. Slc 51e static overcurrent relay ge grid solutions online store. The current circuits are connected to the relay via a 12point terminal block on. For example, an overcurrent protective relay may have an ac to dc power supply for the input circuit, a level detector circuit and an rc time delay circuit. Design and implementation of oc relay using microprocessor. When a relay contact is open, the relay is not energized. A new chapter on microprocessor applications to protection has been added. Nonetheless, the operating time of this type of relay can vary significantly.
Overcurrent relay my channel channelucczvfc7ry59vekcqflqvpyg. In such type of relays, the output is obtained by the static components like. There is only one current operated element in the relay, no voltage coil. Static relays are contrasted with electromechanical relays, which use moving parts to create a switching action. Wib1 ct powered time overcurrent and earth current relay. Jun 01, 2019 a simple currentgraded scheme applied to the system of the form shown in fig.
Overcurrent relay protection is given at b, c, d and e, that is, at the infeed position of each part of the electrical power system. A big difference between conventional electromechanical and static relays is. The type nlr relay, for example, is being increasingly. A digital protective relay may also be called a numeric protective relay. Overcurrent relay protection abdullah alnujaimi 1, abdulaziz almuhanna 1. Relays switches are used to open and close circuits electromechanically or electronically. Numerical relays are based on the use of microprocessors. One should study the diagram to develop an understanding. In digital relays also called numeric or microprocessor based relays the input voltages and currents are converted. Both types of relay control electrical circuits through a switch that is open or closed depending upon an electrical input. The static relay only gives the response to the electrical signal. Overcurrent and overload protection using protective. Raig is available in several versions, with and without timelag relay and with different duty on trip outputs.
Over current relay working principle types electrical4u. The sfc151da and the sfc153da static timeovercurrent relays are shown in block diagram form in figure 2. The term static implies that the relay has no moving mechanical parts in it. The operating characteristic of this relay is illustrated by the. In a protection relay, the term static refers to the absence of moving parts to create the relay characteristic. Static over current relays the output of this summation c. Definitetime overcurrent relays and inversetime overcurrent relays, which will be discussed in this paper. Dsp based numerical relay for overcurrent protection. The offered overcurrent relay is based on a reed switch 1, with a highvoltage thyristor as an electronic amplifier, fig. Compared to the electromechanical relay, the solid static relay has longer lifespan, decreased noise when operates and faster respond speed. Type co circuit opening overcurrent relay instruction leaflet.
Operation and maintenance of protective relays and associated circuits. The electromechanical relay operates when operating torquefence exceeds the restraining torqueforce. A recommended minimum of relays for different types and sizes of generators is given under section protective relay schemes. Digital relay bulletin 3030im9301r398 contents june 1998 116 1998 square d all rights reserved 9. The starting element is usually an overcurrent relay. Electromechanical and static relays have fixed wiring and the setting is. Numerical relays protection and control products for power. Overcurrent earth fault protection can be provided with only one overcurrent relay connected in the residual circuit or across the zero phase sequence filter. An4999 overcurrent internal block diagram 23 1 overcurrent internal block diagram an internal block diagram of overcurrent protection is depicted in figure 1. Static relays phase, amplitude comparators synthesis of various relays using static comparators block diagram of numerical relays overcurrent. The output of the ct line is given to the input receiver block where the signal is processed. These contacts are able to transfer the heavy current due to a short circuit and permit this current to. The relay which does not contain any moving parts is known as the static relay. There is only one current operated element in the relay, no voltage coil etc.
Two phase plus earth fault with instantaneous elements. Introduction of static relays began in the early 1960s. In such an application, the current inputs to a particular sbc relay must be from the cts that measure the current in. Overcurrent protection of feeders nondirectional time.
The overcurrent relay is defined as the relay, which operates only when the value of the current is greater than the relay setting time. Figure 10 shows the overall printed circuit card internal connections. Automatic reclosing of distribution and transmission line. Sep 01, 2018 in an over current relay or oc relay the actuating quantity is only current. New developments in commercial relay manufacture are also included. Disadvantages block diagrams for over current rel ay definite, inverse and. The current from the line ct is reduced to 1th by an auxiliary ct, the auxiliary ct has taps on the primary for selecting the desired pickup and current range and its rectified output is supplied to level detector i overload level detector and an rc timing. All versions are equipped with test switch, rtxp 18, for simple secondary testing, and most of them with output relay with red trip flag indicator. The sbc static breaker backup relays are applied on a per breaker basis that is, one sbc relay for each breaker in any given bus arrangement. The proposed system block diagram is shown in figure 6 7, 8. Basically, in the phph fault, relative to phground fault, note that both v. Definitetime characteristic for the directional groundfault relay a. Relay switch pin diagram how to identify a relay switch. The relay must work efficiently to trip the circuit breakers if there are faults present.
It protects the equipment of the power system from the fault current. The input a is proportional to the system current supplied to a directional unit through auxiliary. Overcurrent protection fundamentals r ced engineering. Signal processing includes overvoltage protector, rectifier, smoothing filters, auxiliary ct, etc. Basler electric be127 solid state protective relay, overunder voltage history of relay the static relay is the next generation relay after electromechanical type. The only difference is that the negative feedback network is external, so it can be varied fig. Static distance protection relay are characterized by having two input quantities respectively proportional to the voltage and current at a particular point in the power system, referred to as the relaying point.
The shorting switches shown on the relay diagram are fitted internally across the relevant case terminals and close when the module is withdrawn. Wear cotton or cottonblend materials as much as possible because these do not store static. The value of i o, should not be too small or large so that the relay is either too sensitive or slow in responding. In a static relay, the measurement is performed by static councils. Directional over current relay linkedin slideshare. The solid state relay static relay overview on photo. One of the methods of such connections is 30o connection and other is 90o connection. Unit ii relay circuit static relay circuit using analog and digital ics for over current. Inverse definite minimum time idmt overcurrent relay 24. Each relay protection device comprises a definitetime delay overcurrent protection relay in which the trip of the current sensitive element starts the time delay device. It incorporates the latest developments in semiconductor technology and its applications to power system protection. Circuit details for each function are shown in figures 3 through 9.
Protection and switchgear miet engineering college. Block diagram for the overcurrent relay module spcj 3c3. In static relays it is advantageous to choose a circuit accommodating a wide range of alternative inverse time characteristics, precise minimum operating levels, definite minimum times and additional high set features, if necessary. Directional static overcurrent relay, electrical engineering. The overcurrent protections raig are built up based upon the overcurrent relay rxig 2. Numerical relay is the relay in which the measured ac quantities are sequentially sampled and converted into numerical data that is mathematically andor logically processed to make trip decisions. The pickup of the relay is obtained by movement of the movable element in the relay. Working of relayshow relay works,basics,design,construction. The other physical quantities like heat temperature etc. In such an application, the current inputs to a particular sbc relay must be from the cts that measure the current in the protected breaker. The type slc51e relay is a rack mounted solid state overcurrent relay fo. In an over current relay or oc relay the actuating quantity is only current. The book is a thoroughly revised and updated second edition of a successful text. Overcurrent relay design in 1985, digital relays dominated electrometrical relays.
The overcurrent relay will trip after the intended operation time which is calculated from the protection algorithm 9. The block schematic diagram of the static instantaneous overcurrent relay is shown in the figure. The static relay gives the quick response, long life, high reliability and accuracy and it is shockproof. Static distance relays and its characteristics electrical. When a relay contact is closed, there is a closed contact when the relay is not energized. Here we look at relay switch pin diagram and the different kinds of relay switches. A current will flow through the relay winding only when a fault involving earth occurs. If the test block type mmlg is provided, the connections. Abb network partner ab generator protection 1mrk 502 003aen page 7 4 protective relays for generators and generatortransformer units fig. The relay modelled in matlabsimulink can be directly downloaded into target support package. The relay function can be better understood by explaining the following diagram given below. In electrical systems, a static relay is a type of relay, an electrically operated switch, that has no moving parts.
The block diagram of a static overcurrent time relay is shown in fig. This directly affects the possible sensitivity of the relay. Avoid the buildup of static electricity on your body by not wearing clothing made of synthetic materials. Co circuit opening overcurrent relay the overcurrent unit contacts are in the contactor switch coil circuit and when they close, the solenoid plunger moves upward to open the deion contacts which normally short circuit the trip coil. Working principle of over current relayin an over current relay, there would be essentially a. Switchgear and protective devices 2015 12 p a g e relay, mathematically this can be defined as the ratio between the short circuit fault current i s and the relay operating current i o. Operation and maintenance of protective relays and. Numerical relays protection and control products for. The measuring unit is a static overcurrent relay of type rxig 2 107. A practical static distance protection scheme includes a starting, measuring and timing elements made up of solid state devices.
There are, however, many exceptions to this general rule. Their design is based on the use of analogue electronic devices instead of coils and magnets to create the relay characteristic. Phase comparators are employed in the measuring devices. It is essential that such switches are fitted across all ct circuits. Basic circuit diagram of a simple very high speed overcurrent relay on reed switch the basic sensitive element in this device is the reed switch, which begins to vibrate at a pickup with frequency of 100 hz. Jul 14, 2016 each relay is energized by current from its respective phase and voltage.