The electromechanical relay can be defined as an electrically operated switch that completes or interrupts a circuit by physical movement of electrical contacts into contact with each other. 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 bi-directional overcurrent protection could produce unnecessary disconnection of circuits. In Hybrid relay, SSR & EMR are used in parallel.A relay control circuit is used for switching the SSR first. will depend on the type of relay that is being used. Numeric relays are the evolved form of a static and electromagnetic relay. An external fault is illustrated. It is of two types: instantaneous over current (IOC) relay and definite time overcurrent (DTOC) relay. These electronic static relays were the initial ones to be known in the classification of static relays. Where this is so, a current magnitude device can be used, such as a fuse or an instantaneous relay or trip device and selectivity can be obtained by grading current. The overcurrent detection circuit will operate as soon as overcurrent is detected and the (X) relay will operate less than 0.5 s later. So it eliminates the arching problem. Where, I is the relay current, t is the time of operation and n is the characteristic index of relay and K is constant. It is extensively used transmission lines, transformers, generators, or motors. These devices typically consist of a manual circuit breaker or contactor and a current sensing relay which interlocks with it. Can you guide me on how to calculate min & max fault current. The operating characteristics of the more commonly used protective relays are described in this section. Figure 5 - Differential Circuit Using a Simple Overcurrent Relay It has a limitation that it can be applied only to simple and non costly equipments. Relay. There exist different types of static relays. Overcurrent relay. Overcurrent Relay is a type of the protection relay, which operates when the current increases Overcurrent Relay MY CHANNEL brclip. If electromechanical relays are more used that solid state relays depends on your field of expertise. Overcurrent Relay in ETAP Software - Part 1. A Relay is an electromechanical device that can be used to make or break an electrical connection. The Solid Static relays use analogue electronic devices instead of magnetic coils and mechanical components to create the relay characteristics. Learn more about Chapter 7: Directional Overcurrent Relays on GlobalSpec. The overcurrent pro-tection may also be used in single-phase or two-phase applications, in which case inputs not to be used are left unconnected. 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. I’m working on Overcurrent relay setting of Primary Transformer Protection (2000KVA with 6% impedance) with 200/5 CT ratio. What is Relay? Types of Relays There are different types of relays including electromagnetic relays, latching relays, electronic relays, non-latching relays, multi-dimensional relays and thermal relays which are classified based on the function, application type, configuration or structural features, etc. Static Relay Presentation 1. For example, a relay including function 51 would be a timed overcurrent protective relay. Static relay can think , programmable operation is possible with static relay Effect of vibration is nil, hence can be used in earthquake-prone areas ... overcurrent relay. Static relays are contrasted with electromechanical relays, which use moving parts to create a switching action.Both types of relay control electrical circuits through a switch that is open or closed depending upon an electrical input. This relay does not need auxiliary power supply since it … An overcurrent relay is the simplest form of protective relay which operates when the current in any circuit exceeds a certain predetermined value, i.e. They are basically a device used for measuring electric parameters in an electrical network and convert them into numerical data which undergoes mathematical and logical analysis to decide on tripping an electrical network. Relay which means the Solid Static relays can perform tasks that the Electromechanical Relay can perform. Bernard Farrugia says: December 2, 2014 at 10:37 am. Reply. STANDARD IDMT OVERCURRENT PROTECTION RELAYS. numerical relay for overcurrent protection is shown in Figure 5 [8], [9]. Explain the construction, working principle and characteristics of reactance relay type distance relay. • Static distance relay are used extremely for protection of medium and long transmission lines, parallel feeders and unit back up protections as well as interconnected lines. A typical case where current grading can be used is shown in fig. Switchgear and Protection MCQ Objective questions & answers are available for a Electrical Engineering students to clear various technical interview, competitive examination, and another entrance exam. In single-phase applications, however, wiring the phase current through two current inputs in series may in-crease the operating speed of the relay, particu- POLYTECHNIC MAYURBHANJ, TIKARPADA 2. Overcurrent Directional overcurrent Distance Pilot Line Current Differential 5. The current/time-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 network0.10 For these needs, IEC 60255 determined … The operating time of overcurrent relays are constant irrespective of the level of the fault current.In this case, an intentional time delay is introduced through a timing circuit. Over-current relays can be used to protect practically any power system elements, i.e. To accommodate these requirements, a voltage-restrained or voltage-controlled overcurrent relay (Device 51V) is used. A solid state or static time-overcurrent relay typically comprises a signal sensing mechanism by which a d.c. input voltage proportional to the circuit quantity being monitored is derived, and a non-linear function generator which produces an output voltage related to this input voltage by a non-linear function which will determine the particular operating characteristic of the relay. In the simulation model shown here, the input currents of sine waveform with frequency of 50Hz can be generated. This same Motor Protective Relay can be used at 50 or 60 Hz and therefore Vde never really drops all the way to zero even in normal operation. 4.1, where there is a high impedance unit such as a transformer which makes the fault much less for faults beyond the transformer. For digital and numerical relays, it is common to use starconnected line CTs on all windings of the transformer and compensate for the winding phase shift in software. Of course en home appliances, computer and IT industry solid state are more used. the pick -up value. 1-3, 4-6 and 7-9 are used. In electrical systems, a static relay is a type of relay, an electrically operated switch, that has no moving parts. Modern electrical protection relays are mainly micro processor based, but still electromagnetic relay holds its place. The overcurrent relay of IDMT type can be used for the same. The relay is an electromechanical switch used as a protecting device and also as a controlling device for various circuits, equipments, and electrical networks in a power system. The relay pickup setting should be low enough to trip in response to the minimum sustainable generator contribution (i.e., synchronous current E/Xd), but should not trip unnecessarily due to normal overloads. RACID Three- phase time overcurrent relay with phase-and earth fault overcurrent was introduced 1981 RACID Microprocessor time overcurrent relay RACIF- is a low-power version of RACID and it performs the same protection functions. Relay Search. In conventional electromagnetic relays, n may vary between 2 and 8. It consists of a flexible moving mechanical part which can be controlled electronically through an electromagnet, basically, a relay is just like a mechanical switch but you can control it with an electronic signal instead of manually turning it on or off. A few of those are: Electronic Static Relay. This is the simplest of the ways to protect a line and therefore widely used. There are, however, relays with other inverse time characteristics in use, and so it is important that the manufacturer’s commissioning and operating documentation is immediately available during any testing. STATIC RELAY NAME- ROHIT KUMAR MARNDI REGD NO- F15152002039 BRANCH- ELECTRICAL ENGINEERING YEAR:- 2015-18 GOVT. pdf. There are limitations to each of these protective schemes. For feeder protection, there would be more than one over-current relay to protect different sections of the feeder. Now we look at various types of relays which are more popularly used in many applications. 4. Static overcurrent relay is made in the form of a single unit in which diodes, transistors, resistors, capacitors etc. The SSR takes the load current. Leave a comment on this post, we will send you the Overcurrent Fundamental. The most commonly used type of relay is the inverse definite with minimum time lag relay (IDMT) in which inverse characteristic plus definite time characteristic are used. An overcurrent relay is an electrical protection device designed to cut off the power supply to a circuit, appliance, or machine in the event of an overload or failure. Overcurrent induction disc relays used offshore usually have a current/time operating characteristic in accordance with BS EN 60255-151 for an inverse definite minimum time relay. Relay protection for faults producing large magnitudes of phase current is generally a combination of overcurrent, differential and distance relaying. Then the control circuit energizes the EMR coil & its contact closes but there is no arching since the SSR is taking the load in parallel. the measurement is carried out by static circuits consisting of comparators, level 2.1 Overcurrent protection. The inputs are then quantized in … It will take much longer time to replace all electromagnetic relays by micro processor based static relays. The protective relay is the device that responds to signals from the transducers by quickly initiating or allowing a control action to be implemented in order to prevent damage to the faulted equipment and to restore service as soon as possible. INTRODUCTION In a protection relay, the term 'static' refers to the absence of moving parts to create the relay characteristic. Static Relays Kongunadunadu College of Engineering and Technology Depar tment of EEE 20. Filter by colors. Overcurrent Relay The differential circuit using a simple overcurrent relay is shown in Figure 5. In this relay, the operating time is approximately inversely proportional to the fault current near pickup value and … Electromagnetic Relay. Electromechanical and static relays use appropriate CT/ICT connections to ensure that the primary and secondary currents applied to the relay are in phase. An overcurrent relay is a type of protective relay which operates when the load current exceeds a pickup value. Electromagnetic relays are those relays which are operated by electromagnetic action. 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