Hi,

I am new to this field, so my explanation may not sound right, so here it goes.

Once I put one generator online (Gen 1) and try to sync the other one (Gen 2) with the help of a synchroscope, it stays on for 8 secs and then trips. No other fault indications. There is a synchronizing relay if that might be a cause.

Things to note:
Before CTs directions change
1. If I sync Gen 1 to Gen 3 or vice versa, Gen 3 KVAR and Ampere meters go really high.

After CTs directions reversal
2. Reversed all 3 CTs on both Gen, now the breaker trips as mentioned earlier. The KVAR meter don't show any reading now and the ampere meter shows around 150 amps on no load.

How do I identify if the CTs are in the right direction with the arrow mark on it?

 

So, the sequence of events is this:

--The units were all working fine

--The direction of one (set of) CT(s) was changed, and then the problem started

--The direction of several CTs on multiple units changed and the problem still exists.

<b>What prompted the change of CT wiring in the first place?

Why wasn't the original CT change(s) reverted back to initial position?</b>

Devices in CT circuits are sensitive to the polarity of the connections of the CT wiring. It is VERY customary for CT circuits to be re-tested <b>any time</b> they are disturbed. CT circuits <b>MUST</b> be connected correctly for the protection provided by the devices in the circuits (reverse power; over current; negative phase sequence; differential current protection; etc.) to work propery and protect generators and transformers, and ultimately people.

CT (and PT) circuits are both critical to protection of electrical systems and components, and ultimately the people working in close proximity to them. This not something to be just trying to change a couple of wires because someone thinks that's the problem or that might solve the problem.

Please, please have someone knowledgeable come to site with the appropriate test equipment, knowledge and experience to help sort the CT circuits out, and then to help with the problem--whatever is causing it.

A synchronizing relay is not typically a protective relay. It's a device for ensuring (based on tested and verified inputs!) that the generator breaker is not closed when the phases of the generator and running systems are not in phase. They don't typically provide any tripping/protective functions after the breaker is closed.

Please, get someone to site to help with your issue, and get the CT circuits tested and verified and then to help troubleshoot the problem.

Please.

 

I agree, never change something that was working. Make the ccurrent transformers match the other units would be a start. Get someone on site to help you that has experience.

Are you tying on a grid in Droop or are you the grid with one unit in asynchronous?