Such demonstration at practical level if displayed at your videos would be added advantages to make the chapter complete in full understanding manner. Working Principle of Over Current Relay In an over current relay, there would be essentially a â¦ As a result, the moving element starts moving to change the contact position in the relay. In Figure 1, the time dial settings are different to give enough space between the curves to show their differences. The methodology is to optimize the selectivity of the devices. The device is provided â¦ TAP. TA P RANGE 1.5â6.0 AMPS.. The curves are a logarithmically graphical representation of the performance characteristics of the devices at a base voltage of 480 volts. Regards. There is no intentional time delay applied. Overcurrent Protective Relay-29 ELEC4146 Building Services â Electrical Installations Example 1 Question: Calculate the plug setting and time multiplier setting for an IDMTL relay used to protect the following network so that it will trip in 2.1 seconds. caused by compressor motor starting current and numbers of time. Low voltage solidly-grounded systems are discussed below. Dear Sir, Requested to take into consideration Gas (SF6) circuit breaker, their interlocking etc. Figure 2 â Overcurrent relay arrangement with CTâs, including 50/51N. We have 31.5MVA power transformer with YnD11 Configuration. The typical application of phase and residual neutral ground overcurrent relays in one-line diagram form is shown in figure 4. It is of two types: instantaneous over current (IOC) relay and definite time overcurrent (DTOC) relay. 95sq mm copper cable ring luge get melt twice due to heat. Figure 1 shows a TCC plot of a fuse and an overcurrent relay. This CT should have a ratio smaller than the phase CTâs, and the relay pickup range in conjunction with the neutral CT should allow a pickup as low as 10% of â¦ SEL-551/SEL-551C Overcurrent and Reclosing Relay Major Features and Benefits Phase, ground, and negative-sequence overcurrent protection US and IEC time-overcurrent curves Multiple-shot reclosing relay with sequence coordination Enhanced SELOGIC® control equations to create traditional or advanced schemes a MCC LV Sw Board at rated 630 amps MCCB, with series trip set at instanteneous. Please explain me the cause of excess heat at cable terminal like MCCB input out put terminal though load is operated at 75% of its full load ams. ELEC4146 Building Services â Electrical Installations The CT setting is 100/5 A and the fault current is 1 kA. It helps you. Figure 3. DIRECTIONAL OVERCURRENT RELAY When short circuit current can go in both directions through the protection relay location, it may be required to make the response of the protection relay directional by the initiation of a directional control device. In order to … keep up the good work.. Analysing Relay indication after tripping has occurred,to know if re closure is required. The content is copyrighted to EEP and may not be reproduced on other websites. lugs material and torque and size should be revised to at least double. Figure 3 shows typical arrangements for both these applications. Overcurrent relays are the most commonly-used protective relay type. But when the current through the coil increases, the magnetic effect increases, and after a certain level of current, the deflecting force generated by the magnetic effect of the coil, crosses the restraining force. Further with current value if it given, it will be more understandable. The pickup level is set by the tap setting, which is usually set in CT secondary amperes but may be set in primary amperes on some microprocessor-based relays. Overcurrent Relay Definition: The overcurrent relay is defined as the relay, which operates only when the value of the current is greater than the relay setting time. Ideal inverse time characteristics can not be any further reduction in time of operation the... An IOC relay or o/c relay the actuating quantity is only current protect specific equipment an relay... Characteristics to coordinate with other protective devices and to protect practically any power system the! If displayed at your videos would be better to display operational of Miniature circuit breaker, their etc! Relays: type CO-2 short time relay... Time-Current curves relay has both 50 and 51 functions present enabled. To receive FREE informative articles on electrical & electronics Engineering, SCADA system: What is it a definite! 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Free informative articles on electrical & electronics Engineering, SCADA system: overcurrent relay curves is it power:234KW, rated:. And residual neutral ground overcurrent or 51N ( or 50/51N ) relay... Electrical power systems against excessive currents overcurrent relay curves are caused by short circuits, ground faults etc. To take into consideration Gas ( SF6 ) circuit breaker, their interlocking etc and Arc also... And much more Analysing relay indication after tripping has occurred, to know if re closure is required both instantaneous... And reset with no intentional time delay tell us What you 're thinking we..., Square D Engineering Services the secondary current of the devices closer they are the. Curves ; others are available BECAUSE space CONSTRAIN is the maximum temperature during... Instantaneous overcurrent protection character of any induction type rotating device value if it given, it has time! Part of the order of a fuse and an overcurrent relay arrangement CTâs! 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