Task-2 A radial feeder is shown in Figure 1. -3-Phase Transmission Line Bus-A Bus-B Bus-C Bus-D CB, CT CB, CTB CB.CTC 个 G .... 30MVA RA Re 11 kV Load-A Load-B Load-C Load-D 3MVA 7.5MVA 5.5MVA 6MVA Figure 1 Radial Feeder Time graded overcurrent protection scheme is to be designed for this feeder using Inverse Definite Minimum Time (IDMT) relays at all busses. The maximum fault current of 10000 Ampere and a minimum fault current of 4000 Ampere is expected to flow for three-phase fault and single line to ground fault, respectively, between bus C and D. IDMT relays located at all buses can be assumed to be of 1 Ampere OR 5 Ampere rating with 100% plug setting. Circuit breakers at bus B and C take 0.6 S to operate. Relay located at bus A has an overshoot time of 0.08 S while relay at bus B has an overshoot time of 0.1 S. The Time Setting Multiplier (TSM) QEAD- Template A Rev: 04_ ver 02 Date: 014 October 2018 Page 2 of 6 F/QAP/021/001 for the fastest relay is to be set to 0.5. Neglect the voltage drop in the line sections for the calculations. ASsume the Overload capacity of this feeder in the range of 20-35%. (i) Design appropriate CT ratios for CTA, CTB, and CTc. [06] (ii) Estimate time of Operation for all three relays for maximum value of fault current to maintain the selectivity. [06] (ii) Determine TSM for relays at bus A and B for maximum fault current. (Use the standard formula for IDMT relays for these calculations.) [06]
Task-2 A radial feeder is shown in Figure 1. -3-Phase Transmission Line Bus-A Bus-B Bus-C Bus-D CB, CT CB, CTB CB.CTC 个 G .... 30MVA RA Re 11 kV Load-A Load-B Load-C Load-D 3MVA 7.5MVA 5.5MVA 6MVA Figure 1 Radial Feeder Time graded overcurrent protection scheme is to be designed for this feeder using Inverse Definite Minimum Time (IDMT) relays at all busses. The maximum fault current of 10000 Ampere and a minimum fault current of 4000 Ampere is expected to flow for three-phase fault and single line to ground fault, respectively, between bus C and D. IDMT relays located at all buses can be assumed to be of 1 Ampere OR 5 Ampere rating with 100% plug setting. Circuit breakers at bus B and C take 0.6 S to operate. Relay located at bus A has an overshoot time of 0.08 S while relay at bus B has an overshoot time of 0.1 S. The Time Setting Multiplier (TSM) QEAD- Template A Rev: 04_ ver 02 Date: 014 October 2018 Page 2 of 6 F/QAP/021/001 for the fastest relay is to be set to 0.5. Neglect the voltage drop in the line sections for the calculations. ASsume the Overload capacity of this feeder in the range of 20-35%. (i) Design appropriate CT ratios for CTA, CTB, and CTc. [06] (ii) Estimate time of Operation for all three relays for maximum value of fault current to maintain the selectivity. [06] (ii) Determine TSM for relays at bus A and B for maximum fault current. (Use the standard formula for IDMT relays for these calculations.) [06]
Power System Analysis and Design (MindTap Course List)
6th Edition
ISBN:9781305632134
Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Chapter5: Transmission Lines: Steady-state Operation
Section: Chapter Questions
Problem 5.30P
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