POWER SYSTEMPROTECTION &SWITCHGEARLAB ASSIGNMENT - 02SURABHI RAMAN17BEE0029
MICRO-CONTROLLER BASED OVER/UNDER VOLTAGE RELAY IDMT/DMT RELAYEx.No : 02AIMi.To study the Micro Controller based over voltage relay.ii. To study the Micro Controller based Under Voltage relay.EQUIPMENT REQUIRED1)VPL – 05 Module 2)1 φ Auto transformer 3)Connecting wiresFormulae Used:1.Calculate Relay tripping time for over voltage IDMT Relayt=TMS[K[VVS]α−1]+C2.Calculate Relay tripping time for Under voltage IDMT Relayt=TMS[K[VSV]α−1]+Cα=0.02,K=0.14,C=0TheoryIn a power system consisting of generators, transformers, transmission anddistribution circuits, it is inevitable that some failure will occur somewhere in thesystem. When a failure occurs on any part of the system, it must be quickly detectedand disconnected from the system. There are two principle reasons for it. Firstly, ifthe fault is not cleared quickly, it may cause unnecessary interruption of service tothe customers. Secondly, rapid disconnection of faulted apparatus limits the amount
of damage to it and prevents the effects of fault from spreading into the system.The detection of a fault and disconnection of a faulty section or apparatus canbe achieved by using fuses or relays in conjunction with circuit breakers. A fuseperforms both detection and interruption functions automatically but its use is limitedfor the protection of low-voltage circuits only. For high voltage circuits, relays andcircuit breakers are employed to serve the desired function of automatic protectivegear. The relays detect the fault and supply information to the circuit breaker whichperforms the function of circuit interruption.A Protective relay is a device that detects the fault and initiates the operationof the circuit breaker to isolate the defective element from the reset system. Therelays detect the abnormal conditions in the electrical circuits by constantlymeasuring the electrical quantities which are different under normal and faultconditions. The electrical quantities which my change under fault conditions arevoltage, current, frequency and phase angle.