Question

A blocked electric current of 4000 A is passing through the primary side of a converter having 400/5 A current. The plug setting of the electric current relay is set at 50% at the secondary of the electric current converter. What will be the plug setting multiplier?
1. 20
2. 30
3. 10
4. 40

Answer 1

Correct Answer - Option 1 : 20

Concept:

Plug setting multiplier is the ratio of fault current and the product of plug setting and CT ratio.

Plug setting multiplier \(= \frac{{fault\;current}}{{plug\;setting \times CT\;ratio}}\)

Calculation:

Given: Fault current is 4000 A, CT ratio is  400/5 A, Relay setting is 50%.

Plug setting = relay setting × secondary CT current

= 0.5 × 5 = 2.5

CT ratio \(= \frac{{400}}{5} = 80\)

Plug setting multiplier \(= \frac{{4000}}{{2.5 \times 80}} = 20\)