Question

(a) Draw the protective zones for the power system shown in Figure 10.45. Which circuit breakers should open for a fault at (a) ${\mathit{P}}_{\mathbf{1}}$, (b) ${\mathit{P}}_{\mathbf{2}}$, and (c) ${\mathit{P}}_{\mathbf{3}}$?

Short answer

Answer

(a) The breakers B12a and B21a operates for the fault $P_1$.

(b) The breaker should open when the fault occurred at $P_2$are B21a, B21b, B24a, B24b and B23.

(c) The breaker should open when the fault occurred at $P_2$are B21a, B21b, B24a, B24b, B32 and B23.

Step-by-step solution

Write the given data from the question.

Consider the system as,

Draw the protective zone of power system.

(a)

Consider the protective zone of the system as,

The breaker under the protection zone 3 are B12a and B21a.

When the fault occurred at $P_1$, it lies under the protection zone 3 Therefore, the breaker B12a and B21a should operate under the fault at $P_1$.

Hence breakers B12a and B21a operates for the fault $P_1$.

Determine the breaker that operate under fault at P2.

(b)

When fault occurred at $P_2$, it lies under the protective zone 7.

The breakers under the protection zone 7 are B21a, B21b, B24a, B24b and B23.

Therefore, the breaker should open when the fault occurred at $P_2$are B21a, B21b, B24a, B24b and B23.

Determine the breaker that operate under fault at P3.

(c)

When the fault occurred at $P_3$, it lies under the 2 two protective zones that are zone 6 and 7. The circuit breakers of zone 6 and 7 are highly sensitive against the fault under their zone.

The breakers under the protection zone 7 are B21a, B21b, B24a, B24b and B23.

The breakers under the protection zone 6 are B23 and B32.

Therefore, the breaker should open when the fault occurred at $P_2$are B21a, B21b, B24a, B24b, B32 and B23.