Electromechanical and static relays use appropriate CT/ICT connections to ensure that the primary and secondary currents applied to the relay are in phase. 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 … Overcurrent relay. What is Relay? numerical relay for overcurrent protection is shown in Figure 5 , . Overcurrent relays must be set above the normal load current and a differential relay cannot detect a turn-to-turn fault. STANDARD IDMT OVERCURRENT PROTECTION RELAYS. Electromagnetic Relay. the measurement is carried out by static circuits consisting of comparators, level 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. Overcurrent Relay in ETAP Software - Part 1. It has a limitation that it can be applied only to simple and non costly equipments. This is the simplest of the ways to protect a line and therefore widely used. There exist different types of static 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 bi-directional overcurrent protection could produce unnecessary disconnection of circuits. In conventional electromagnetic relays, n may vary between 2 and 8. Overcurrent Relay is a type of the protection relay, which operates when the current increases Overcurrent Relay MY CHANNEL brclip. Of course en home appliances, computer and IT industry solid state are more used. In the simulation model shown here, the input currents of sine waveform with frequency of 50Hz can be generated. 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. 4.1, where there is a high impedance unit such as a transformer which makes the fault much less for faults beyond the transformer. A typical case where current grading can be used is shown in fig. 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. POLYTECHNIC MAYURBHANJ, TIKARPADA 2. 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 overcurrent relay of IDMT type can be used for the same. 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. An overcurrent relay is a type of protective relay which operates when the load current exceeds a pickup value. pdf. Only the effect on bus differential relaying will be discussed in this paper. • 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. will depend on the type of relay that is being used. 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. Learn more about Chapter 7: Directional Overcurrent Relays on GlobalSpec. It will take much longer time to replace all electromagnetic relays by micro processor based static relays. 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. 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. Bernard Farrugia says: December 2, 2014 at 10:37 am. (4) When solid-state relay s are used, overtravel. 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. 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 is extensively 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 Hybrid relay, SSR & EMR are used in parallel.A relay control circuit is used for switching the SSR first. For feeder protection, there would be more than one over-current relay to protect different sections of the feeder. Relay protection for faults producing large magnitudes of phase current is generally a combination of overcurrent, differential and distance relaying. Now we look at various types of relays which are more popularly used in many applications. I’m working on Overcurrent relay setting of Primary Transformer Protection (2000KVA with 6% impedance) with 200/5 CT ratio. 1-3, 4-6 and 7-9 are used. The inputs are then quantized in … Modern electrical protection relays are mainly micro processor based, but still electromagnetic relay holds its place. Static Relays Kongunadunadu College of Engineering and Technology Depar tment of EEE 20. Numeric relays are the evolved form of a static and electromagnetic relay. It is of two types: instantaneous over current (IOC) relay and definite time overcurrent (DTOC) relay. Relay Search. 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. To accommodate these requirements, a voltage-restrained or voltage-controlled overcurrent relay (Device 51V) is used. Static Relay Presentation 1. Overcurrent Directional overcurrent Distance Pilot Line Current Differential 5. Can you guide me on how to calculate min & max fault current. Overcurrent Relay The differential circuit using a simple overcurrent relay is shown in Figure 5. An external fault is illustrated. the pick -up value. These electronic static relays were the initial ones to be known in the classification of static relays. So it eliminates the arching problem. 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 SSR takes the load current. STATIC RELAY NAME- ROHIT KUMAR MARNDI REGD NO- F15152002039 BRANCH- ELECTRICAL ENGINEERING YEAR:- 2015-18 GOVT. 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. Filter by colors. These devices typically consist of a manual circuit breaker or contactor and a current sensing relay which interlocks with it. Where, I is the relay current, t is the time of operation and n is the characteristic index of relay and K is constant. There are limitations to each of these protective schemes. A few of those are: Electronic Static Relay. 4. For example, a relay including function 51 would be a timed overcurrent protective 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. The Solid Static relays use analogue electronic devices instead of magnetic coils and mechanical components to create the relay characteristics. A scientist named Fitzgerald showed a carrier current test which conveys the … In electrical systems, a static relay is a type of relay, an electrically operated switch, that has no moving parts. 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. Leave a comment on this post, we will send you the Overcurrent Fundamental. 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- This relay does not need auxiliary power supply since it … INTRODUCTION In a protection relay, the term 'static' refers to the absence of moving parts to create the relay characteristic. Electromagnetic relays are those relays which are operated by electromagnetic action. If electromechanical relays are more used that solid state relays depends on your field of expertise. The overcurrent detection circuit will operate as soon as overcurrent is detected and the (X) relay will operate less than 0.5 s later. Reply. Relay which means the Solid Static relays can perform tasks that the Electromechanical Relay can perform. 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. Figure 5 - Differential Circuit Using a Simple Overcurrent Relay In this relay, the operating time is approximately inversely proportional to the fault current near pickup value and … 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. 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. 2.1 Overcurrent protection. 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. transmission lines, transformers, generators, or motors. Relay. Explain the construction, working principle and characteristics of reactance relay type distance relay. 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. A Relay is an electromechanical device that can be used to make or break an electrical connection. 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. Static overcurrent relay is made in the form of a single unit in which diodes, transistors, resistors, capacitors etc. 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. 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. The operating characteristics of the more commonly used protective relays are described in this section. Over-current relays can be used to protect practically any power system elements, i.e.