PSP EXERCISE 05 172 bài tap role PSP EXERCISE 05 172 bài tap role PSP EXERCISE 05 172 bài tap role PSP EXERCISE 05 172 bài tap role PSP EXERCISE 05 172 bài tap role PSP EXERCISE 05 172 bài tap role

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EXERCISE 05 - 172
1. Consider the two-source network as Figure 1. These sources have wye connection with solid
grounding.

Figure 1: Two-source network
Question: Prove that OCRs can not selectively protect two-source network.
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2. Consider the loop network as Figure
02.

Question: Prove that OCRs can not
selectively protect two-source network.

Figure 2: Loop network
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3. What is directional overcurrent relay-operating principle ?
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4. Consider two-source network as Figure 3.

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Figure 3: Two-source network
Question: Prove that directional OCRs can selectively protect two-source network.
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5. Consider the loop network as Figure 4.

Figure 4: The loop network
Question: Prove that directional OCRs can selectively protect two-source network.
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6. Consider two-source network as Figure 5. 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
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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)
7. Consider the loop network as Figure 6. 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 các rơ le R1, R2, R3 và R4

R4

R6

Relay
R1

R3
R5
R2
R4
R6
0
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

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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

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