Solution: I p 12000A I s 150A 400 5 12000 u On PS of 200%: The relay current 10A 100 200 5u Hence PSM 15 10 150 The over current relay can be used as overload (thermal) protection when protects the resistive loads, etc., however, for motor loads, the over current relay cannot serve as overload protection Overload relays usually have a longer time setting than the over current relays. Breaker Failure If after a programmable time delay, the circuit breaker has not opened, breaker failure protection issues a trip signal to isolate the failure breaker by tripping other surrounding backup circuit breaker. Introduction 3.1. Most electro-mechanical relays, and GE relays like the one from The Relay Testing Handbook example, use the phase-phase voltage from the two un-faulted phases as a polarizing signal. Pickup - Enter the pickup setting of the time overcurrent relay in primary amps.. Time Dial - Enter the Time Dial setting of the time overcurrent relay. If the fault current is 2000 amps, the relay setting is 50% and the C.T. Note: Enabled only for overcurrent operation. Overload relay is the one of important device for motor control.It can prevent our motor from overheat or winding burning due overload of ampere. In this way, establishing an optimal coordination strategy is recognized as the first prerequisite in assuring a safe protection scheme. The supply CT is rated 400:5A and the fault current is 12000A. We refer the pre-set value of current in the relay coil as pickup setting current. Directional overcurrent protection schemes were replaced with line impedance relays (21) to prevent a situation like this from occurring. Consequently, additional protective measures are needed here. Low Voltage Breaker - Fuse coordination requires a minimum 0.1 second time margin between the … Current setting is the setting of current(pick-up current) in a relay at which we want to operate that relay. The fault analysis that will be study only for over current, short circuit and earth fault, 1.5 Expected results . The Reyrolle 7SR10 Argus overcurrent and earth fault relay is developed using the latest generation of hardware technology and is available in multiple variants depending on the power supply, binary input/binary output configuration and data communication facility. The tappings are connected to plug setting bridge.With the help of this bridge, the number of turns of the primary winding can be adjusted.Thus the desired current setting for the Non-Indirectional Induction Overcurrent Relay can be obtained.There are usually seven sections of tappings to have the overcurrent range from 50% to 200% in steps of 25%. Fault Current - Enter the Fault Current for which the operate time should be calculated. Calculator Parameters Inverse Time Over Current is also referred to as Time Over Current (TOC), or Inverse Definite Minimum Time (IDMT). Lecture -18 Directional Overcurrent Relaying The varying pick-up level makes it more difficult to co-ordinate the relay with other fixed pick-up overcurrent … Overcurrent relay. The Inverse Time Over Current (TOC/IDMT) relay trip time calculator calculates the protection trip time according to IEC 60255 and IEEE C37.112-1996 protection curves. A relay that operates or picks up when its current exceeds a predetermined value (setting value) is called Over-current Relay. Successful in coordinating and implementing the IDMT MK2000 relay in … On the 50/51 overcurrent relay, the time-overcurrent-element (device 51) setting is made by means of a plug or screw inserted into the proper hole in a receptacle with a number of holes marked in CT secondary amperes, by an adjustable calibrated lever or by some similar method. The MTA setting is commonly thought of in terms of the forward-looking line impedance angle. The disadvantage here is that a fault in the vicinity of the feed point, where the tripping time t > is longest, results in the highest current. A type of relay in which the time of relaying varies directly as the distance of the fault from the station . relay settings, over current relay settings, idmt relay setting, earth fault relay setting, instantaneous relay setting, how to set relays, relay setting calculation, relay characteristics, calculation to set relays, IDMT relay setting calculation At 25 percent voltage the relay picks up at 25 percent of the relay setting (1.75 0.25 = 0.44 times rated). However, when quadrature The relay operates for the defined direction when the fault current is in the same direction and exceeds the over current setting value. If we clear the concept for these relays first then understanding the Numerical Relay settings becomes easy. In this case, the relay is sensing Z A between the relay and the fault. Fig. The basic element in overcurent protection is the overcurrent relays. Module-4 Overcurrent Protection. 9. Now ideally, one can set the pick up current of the overcurrent relay anywhere within the maximum feeder load current (column 2) and minimum fault should not allow PSM to be below 1.5. Use of the relay The overcurrent relay REJ 523 is intended for selective short-circuit protection in medium voltage distribution networks but can also be used for protection of generators, motors and transformers. Overcurrent Coordination Page 3 Qual-Tech Engineers, Inc. 8. Lecture -14 Fuse Protection; Lecture -15 Fundamentals of Overcurrent Protection; Lecture -16 PSM Setting and Phase Relay Coordination (Tutorial) Lecture -17 Earth Fault Protection using Overcurrent Relays; Module-5 Directional Overcurrent Protection. Table 2 details the calculations associated with setting of overcurrent relays. 13 An IDMT type over current relay is used to protect a feeder through 500/1A CT. 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