During thunderstorms we experience trips of our GE Alstom LM1600 Gas Turbines. We have embarked on extensive earthing and lightning protection without remarkable improvements. Any suggestions or similar experiences?

 

I think that we need a little more information. What is the nature of the trip? Are protective relays in the electrical distribution system tripping the unit? Is there a first out alarm on the turbine that shows the nature of the trip? Is it the same thing that trips all, or most of, the time?

 

Earthing won't stop voltage surges nor will lightning protection, although both can limit the damage lightning might do.

You might want to tell us a little more, like just what trips do you get? Are they trips you can afford to put short time delays on?

 

This looks like an earthing issue too me. I note that you have done extensive earthing work.

Question 1: is any of this related to control systems?

Question 2: Has your control system cable shielding been checked?

If your control cable shielding is faulty it is very easy to induce reasonably high ground loop voltages giving false signals.

regards

 

Any idea why the trips are occuring? i.e. generator protection, bus over/undervolt/etc.?

 

Effect is primarily on the control system. What we have is a failure of about a dozen SPDs (sometimes)right after the lightning strike. This causes the transmitter signals to change state, due to the barriers failure, and various alarms come up on the panel. Trip occurs almost immediately.
Control cable shielding appears okay.
If there are overvoltages or voltage surges, i expect earthing and lightning protection to handle that or could there still be more to it?

 

What are the turbine trips or alarms?
What type of surge protection have you applied?
Where is the surge protection?
Are the generators in a building or not?
Since your in a area which is subject to higher than normal lightning strikes, electrical discharges and such, you may have to consider other forms of protection. In some cases you may not be able to do much.

Case, in point: Castle Pines, CO. - one well field area is on a large iron deposit, the wells are several thousands of feet deep, every year they lose at least one well pumping system due to a lightning strike, there is just nothing they can do about it. This area has one of the highest lightning strike occurances in the US.


I would be consulting with the turbine system manufatures for their input on ride through protection and other considerations. They have the required technical expertise to really help you.

Anyone here is going to be able to give you only rough, general ideas and guidelines, you require very specific technical support and expertise, which can best be provided by the manufacture, consultantion with an engineering group or firm that specilizes in this field.

MJH