Troubleshooting Single Pole Operated EHV Circuit Breaker Not Closing Problem: Practical Step by Step Action to be taken.

In the Substation, when we take an Outage on a EHV Feeder, the work is completed and the Feeder is ready to be charged. All the necessary permission is taken and all the Operations are performed, only now Breaker remains to be closed.

Now, we try to Close the Breaker, and the Breaker won’t Close. In EHV Power System, its very important to take the Line in Service as early as possible.

Now we are in big trouble, but don’t  worry, I will help you out.

Just follow the steps given below and I promise the problem will be solved in the least possible time.

 Lets say a 220 kV SPO Breaker is not Closing. 

Step 1) We re-check, if the Breaker LR Switch is on the ‘Remote’ and all the Trip Relays are Reset.

Step 2) If step 1 is Ok, we will try to Close the Breaker Locally.

Lets say the Breaker refuses to Close Locally also.

Step 3) Check the Operation of the PDR Relay

Now, there will be two cases here:
Case 1) Breaker Closes but Trips immediately on PDR Relay.

Case 2) Breaker does not Closes or we can say No Operation of PDR Relay.

Let’s say Case 2 happens i.e. Breaker does not closes i.e. No PDR Operation.

Step 4) Check the DC Supply to the Breaker i.e check the Voltage between K1 & K2.

Step 5) If step 4 is Ok, Check if the Spring is Charged in the Spring-Spring Type Breaker or Check Air pressure, if its a Spring-Pneumatic type Breaker.
And Check if the CB SF6 Pressure is ok.

Step 6) If everything mentioned in Step 5 is OK. We need to check the thoroughness of the Closing Circuit.
For this we will hold the TNC Switch on C position, one end of the probe on K2 (Negative) and with another probe, we will check for Positive Voltage. The element which is blocking the Positive Voltage is faulty and needs to be replaced.

Now, let’s consider Case 1 from Step 3. In this case we can skip Step 4, 5 & 6 and directly go to step 7.

In this case, Breaker Closes and immediately Trips on PDR.
The PDR Operates if one of the CB Poles does not Close or Trips.

Now, we will try to identify the Faulty CB Pole, by bypassing the PDR Relay, because PDR Relay trips all the CB Poles, and we cannot find out which CB Pole is Faulty.

Step 7) Bypass the PDR Relay and give the Closing command to the Breaker.

PDR Relay can be bypassed by removing +ve or -ve wire on the PDR Relay.
After bypassing the PDR, when we Close the Breaker, one Pole will not close or Trip.

Now that we have identified the Faulty Pole, we need to troubleshoot it.

Now, there may be two cases:

Case 1) CB Pole is having Mechanical Problem

Case 2) CB Pole is having an Electrical Problem.

Step 8) Check if the Closing Coil of the Faulty Pole is Operating when Closing Command is extended to the Breaker.

If the Closing Coil is Operating it means that there may be a Mechanical problem with that Pole.

Step 9) Switch Off the Main DC MCB and Close the CB Pole Mechanically.

If the Pole Closes, that means that the CB Pole Operating Mechanism is ok.

If it is not Closing Mechanically or if it is Tripping immediately on Closing, that means, there is a problem with the Operating Mechanism of that Pole. In this case we can do some adjustments in the Operating Mechanism or else we will have to call the experts.

Now, let’s say Operating Mechanism is OK, which means that there is some Electrical problem with the Breaker Pole. 

If there is an Emergency to take the Feeder in Service, we can Close the Faulty Pole Mechanically and the other two poles Electrically, of course with the PDR bypassed and attend the Faulty Pole Electrical problem in the next Outage.

Step 10) Let’s say we decide to attend the Faulty Pole Electrical Problem.

There are two possible cases here:
Case 1) Breaker Pole is Not Closing
Case 2) Breaker Pole is Tripping immediately when Closed.

Let’s consider Case 1 first i.e CB Pole is not Closing.

Step 11) Check if the Resistance of the Closing Coil is OK.

Step 12) If the Resistance is ok, we need to check the thoroughness of the Closing Circuit.

We can check this either by extending Positive through TNC Switch and checking the element which is blocking the Positive or else we can check the Element which is blocking the Negative coming from the Closing Coil.

Now, let’s consider Cse 2 from Step 2 i.e. The Breaker Pole is Tripping immediately on Closing.

Step 13) Check if there is Positive being extended to Trip Circuit 1  or Trip Circuit 2 and eliminate the same.

Thank you so much. Please let me know if this helped you.