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. A type of relay in which the time of relaying varies directly as the distance of the fault from the station . 4: Network map with non-directional, maximum-overcurrent time protection relay. Note: Enabled only for overcurrent operation. 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 Lecture -18 Directional Overcurrent Relaying If the fault current is larger than the overcurrent setting, the relay will trip. If we clear the concept for these relays first then understanding the Numerical Relay settings becomes easy. For example, the relay can be set for 175 percent of generator rated current with rated voltage applied. 13 An IDMT type over current relay is used to protect a feeder through 500/1A CT. Fuse - Relay coordination requires a minimum 0.3 second time margin between the curves. We refer the pre-set value of current in the relay coil as pickup setting current. It shows both the minimum fault current and the maximum load current. Example1: Determine the PSM (plug setting multiplier) of a 5A, 2.2 sec over current relay having a plug setting P s =200%. A relay that operates or picks up when its current exceeds a predetermined value (setting value) is called Over-current Relay. To understand this concept easily, it is better to know about settings of the Electromechanical Relays. The overcurrent relay REJ 513 is a secondary relay which is connected to the current transformers of the object to be protected. This relay is referred as instantaneous over current relay, as ideally, the relay operates as soon as the current in the coil gets higher than pick upsetting current.There is no intentional time delay applied. We need to setting the value of overload relay properly depend on our application and motor full load ampere.If we setting low from FLA,it can cause motor trip c0ntinues and process […] Overcurrent Coordination Page 3 Qual-Tech Engineers, Inc. 8. 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. 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. The REJ 523 is based on a microprocessor environment. 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. The Directional Overcurrent element needs a polarizing signal to operate reliably; otherwise anything could happen depending of the sophistication of the relay. A definite time over-current (DTOC) relay is a relay that operates after a definite period of time once the current exceeds the pickup value. In this way, establishing an optimal coordination strategy is recognized as the first prerequisite in assuring a safe protection scheme. Current setting is the setting of current(pick-up current) in a relay at which we want to operate that relay. These spreadsheets below will make your endless calculations much easier! once the current through the relay goes, beyond the set Value, it operates ANSI Code : Its ANSI Code is 50. RE: Overcurrent Relays - Tap Setting vs. The basic element in overcurent protection is the overcurrent relays. Consequently, additional protective measures are needed here. More recently, dual-setting over-current relays are evolved as competent countermeasures for such cases. 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. 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. This indicates for any fault causes over current in the earth element of the relay that exceeds the setting value. Model overcurrent overcurrent or earthfault boards size † inst † inst † inst MCGG 22 14 MCGG 42 26 MCGG 52 38 MCGG 53 28 MCGG 62 36 MCGG 63 16 MCGG 82 48 Application The relay can be used in applications where time graded overcurrent and earth fault protection is required. 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 relay operates for the defined direction when the fault current is in the same direction and exceeds the over current setting value. The characteristic angle is the phase angle by which reference or polarising voltage is adjusted such that the directional relay operates with maximum sensitivity. Overcurrent relay. Tap Range dpc (Electrical) 13 Aug 12 18:36 In general, the tap range is fixed based on the relay model, not a setting you can change. Hence, this relay has current setting range as well as time setting range. 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. In this case, the relay is sensing Z A between the relay and the fault. Introduction 3.1. This should be 0.50 - 15.00 for U.S. curves and 0.05 - 1.00 for IEC curves. The MTA setting is commonly thought of in terms of the forward-looking line impedance angle. At 25 percent voltage the relay picks up at 25 percent of the relay setting (1.75 0.25 = 0.44 times rated). The supply CT is rated 400:5A and the fault current is 12000A. is 400/5, then the plug setting multiplier should … Over Current Protection: It finds its application from the fact that in the event of fault the current will increase to a value several times greater than maximum load current.