Students’ name: 1) Date: 2) EXERCISE 05 - 172 Consider the two-source network as Figure These sources have wye connection with solid grounding Figure 1: Two-source network Question: Prove that OCRs can not selectively protect two-source network _ _ _ _ Consider the loop network as Figure 02 Question: Prove that OCRs can not selectively protect two-source network Figure 2: Loop network _ _ _ _ What is directional overcurrent relay-operating principle ? _ _ Consider two-source network as Figure 1/4 Students’ name: 1) Date: 2) Figure 3: Two-source network Question: Prove that directional OCRs can selectively protect two-source network _ _ _ Consider the loop network as Figure Figure 4: The loop network Question: Prove that directional OCRs can selectively protect two-source network _ _ _ _ Consider two-source network as Figure These sources have wye connection with solid grounding Question: a Determine max currents through these relays R1, R2, R3, and R4 Relay R1 R3 R2 R4 2/4 Students’ name: 1) Date: 2) Max current (A) b Set up tripping angles of these relays Relay R1 R3 R2 R4 Tripping angle θ (0) c Set up pick-up current of these directional OCRs R1, R2, R3, and R4 where safety factor of 1.2, start-up factor of 1.5, return factor of 1.0, CT ratio of 400:1, and CT connection diagram factor of 1.0 Relay R1 R3 R2 R4 Pri Pick-up current (A) Sec Pick-up current (A) d Set up tripping time of these directional OCRs R1, R2, R3, and R4 We use definite time Relay R1 R3 R2 R4 Tripping time (s) Consider the loop network as Figure The source have wye connection with solid grounding Question: a Calculate max currents through these relays R1, R2, R3, R4, R5,and R6 Relay R1 R3 R5 R2 Max current (A) b Chỉnh định hướng công suất cho rơ le R1, R2, R3 R4 R4 R6 Relay R1 R3 R5 R2 R4 R6 Tripping time θ ( ) c Set up pick-up currents of these relays R1, R2, R3, R4, R5,and R6 where safety factor of 1.2, start-up factors of 1.3, return factor of 1.0, CT ratio of 800:5, and CT connection diagram of 1.0 Relay Pri Pick-up current (A) Sec Pick-up R1 R3 R5 R2 R4 R6 3/4 Students’ name: 1) Date: 2) current (A) d Set up tripping time of these directional OCRs R1, R2, R3, R4, R5,and R6 We use definite time Relay Tripping time (s) R1 R3 R5 R2 R4 R6 4/4