A radial 11 kV feeder connects three substations: A, B and C. Substation A Substation B Substation C Fault Level 240 MVA

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A Radial 11 Kv Feeder Connects Three Substations A B And C Substation A Substation B Substation C Fault Level 240 Mva 1 (93.75 KiB) Viewed 29 times

A radial 11 kV feeder connects three substations: A, B and C. Substation A Substation B Substation C Fault Level 240 MVA 180 MVA 95 MVA Relay Rating 5 A 5 A 5 A CT ratio 600/5 300/5 200/5 At A, B and C, standard overcurrent protection relays with a rating of 5 A are used. At C, the relay has been configured to have a plug setting of 125% and a TMS of 0.097. Load current at C need not be considered as it will not exceed the operating level of the relay at C. Determine the plug setting and time multiplier settings for the relays at B, and C, assuming a time margin for discrimination of 0.15 s. No plug setting multiplier should exceed 20. The available plug settings are between 50% and 200% in 25% steps, and the time multiplier can vary between 0.001 to 1.0, in steps of 0.001. (0) What is relay C's operating time for a fault at C? Tc= ) s (ii) What settings should be chosen for Relay A and B? Relay B: PSB =( ) % TMSB =( Relay A: PSA =( ) % TMSA =( (iii) Is it suitable to apply instantaneous overcurrent protection at location A and B? If so, what would a suitable setting be, expressed in primary amps (per phase)? Relay B: Relay A: