While shutting down a gas turbine there are different ways of opening the GCB. Using reverse power relay or low forward relay are some examples. Are there any other methods like giving a control signal through Mark V at a particular MW value?? If it is there, can anybody describe / send me the mark V rung of that logic please!!

Thanks,
Wasantha K

 

Hi Wasantha,

I am not experienced enough to give you any examples, but just wish share some opinion.

First question is why do you want to trip the GCB at any predetermined MW other than that sensible by reverse power or low forward relay? Contact opening at large current could jeopardize your CB contact life.

Of course you could make use of the input from MW transducer, and use a CMP block in the BBL to drive a DO to a auxiliary relay in your switchgear to trip the GCB. But I think this is unnecessary.

Do you have any reason why would you want to do this?

Please advice. Thanks

Kevin
ITS-Industrial Turbine Services GmbH
*P/s - we have Windows based I-DOS replacement solution.

 

Thanks Kevin.

well, its a matter of KVA demand while shutting down the GT. We used to consume the MW from the off taker while shutting down and it incurred a big cost called maximum demand charge. As we have not configured any low forward relay on it and reverse power relay gives some contribution for the KVA, we want to change the scheme which will open the GCB on positive MW.

 

Hi Wasantha K,

We have 6 GE 7EA's with MARK V's, 2001 vintage. On a normal shutdown our breakers open via a signal from the MARK V when the unit is at or below -1.5MW's for 3 seconds.

Hope this helps,
RichT88

 

Check you logic for LK32DWLP which is the min load setpoint which is selected when L94X normal shutdown is active.

If the CSP contains this control constant: the MKV will open the breaker during normal shutdown on the LK32DWLP constant which is usually a positive value. The LK32DWRP constant is for reverse power.

Older CSP logic uses LK32DWRP exclusively. Rather than modify that constant. I would add the logic to select between the two constants.

Let me know if your logic does not have these control constants.

 

Dear Wasantha,

CuriousOne is right. The older MkV CSP should contain a BBL where LK32DWRP and L32DW reside.

Out of the BBL, L32DW should energize 1 or 2 relay coils, namely L52GT to trip the GCB.

Default Lk32DWRP value should be 0.0 MW.

I always thought the action was done by a reverse power relay, and it can sense zero crossing current so as to reduce the damage to the contact of CB.

Regards,
Kevin