Question

if the fault current is 2000 a, the relay setting is 50% and ct ratio is 400/5, the plug setting multiplier wil be

Answer 1

The plug setting multiplier is calculated by dividing the relay setting by the CT ratio. In this case, the plug setting multiplier is 0.0125.

Step-by-step explanation:

The plug setting multiplier is the ratio between the current that flows through the relay and the current that the relay is set to detect. In this case, the fault current is 2000 A and the relay setting is 50%, which means the relay is set to detect 50% of the fault current. The CT ratio is given as 400/5, which means that for every 400 A of current flowing through the primary winding of the CT, 5 A of current is induced in the secondary winding.

To calculate the plug setting multiplier, we need to divide the relay setting by the CT ratio. In this case, the relay setting is 50% or 0.5, and the CT ratio is 400/5. Dividing 0.5 by (400/5) gives us a plug setting multiplier of 0.0125.

Therefore, the plug setting multiplier is 0.0125.

The plug setting multiplier (PSM) in a protective relay is calculated using the following formula:

�

�

�

=

Relay Setting

CT Ratio

×

Fault Current

PSM=

CT Ratio×Fault Current

Relay Setting

​

In this case, you have:

Fault Current = 2000 A

Relay Setting = 50%

CT Ratio = 400/5

Plug Setting Multiplier (PSM)

=

50

%

400

5

×

2000

=

5

400

​

×2000

50%

​

First, simplify the CT Ratio:

400

5

=

80

5

400

​

=80

Now, plug in the values:

�

�

�

=

50

%

80

×

2000

PSM=

80×2000

50%

​

Calculate the denominator:

�

�

�

=

50

%

160000

PSM=

160000

50%

​

Convert the percentage to a decimal:

�

�

�

=

0.5

160000

PSM=

160000

0.5

​

Now, divide to find the PSM:

�

�

�

=

3.125

×

1

0

−

6

PSM=3.125×10

−6

So, the plug setting multiplier is

3.125

×

1

0

−

6

3.125×10

−6

Answer 2

The Plug Setting Multiplier (PSM) is calculated as 10 using the fault current of 2000 A, a relay setting of 50%, and a CT ratio of 400/5.

Step-by-step explanation:

To calculate the Plug Setting Multiplier (PSM), which is used in the setting of electrical protection relays, we can use the following formula:

PSM = Fault Current / (CT Ratio x Relay Setting)

In the given question, we have a fault current of 2000 A, a relay setting of 50%, and a current transformer (CT) ratio of 400/5. Let's perform the calculation step by step:

1. First, convert the relay setting percentage into a decimal: 50% = 0.50.
2. Next, compute the secondary current corresponding to the fault current using the CT ratio:
   Secondary Current = Fault Current / (CT Primary / CT Secondary) = 2000 A / (400/5) = 25 A.
3. Finally, calculate the PSM: PSM = Fault Current on Secondary / (Relay Setting x CT Secondary) = 25 A / (0.50 x 5) = 10.

Therefore, the Plug Setting Multiplier will be 10.

The complete question is:if the fault current is 2000 a, the relay setting is 50% and ct ratio is 400/5, the plug setting multiplier wil be