DC Ground Fault - Discret IO Card Suspected


Thread Starter



9E GE Gas Turbine with MK6e, For about 2 month we suffered with a ground fault. it's appears only after opening the generator breaker, taking about 3 to 6 minutes and disappears again.

3 or 4 times the alarm persists until we come. We suspected at first time 33CB-4. after we remove its cable the alarm disappeared, but it doesn't reappear when we return the cable to its place (that happened for 3 times about).

We changed its cable (33CB-4), but the problem is the same.
-Can the Discret IO Card be the original of this problem?

-Is there an explication for the phenomena of disappearing/Not reappearing of the alarm while decabling/cabling the suspected instrument?

Thanks for all your contributions


Was the Mark VIe supplied when the turbine was new, or was it supplied as an upgrade of an older Speedtronic turbine control system on an existing unit (in other words, a turbine control system upgrade or retrofit)?

What are the DC voltage readings (positive and negative), with respect to ground, when the '125 VDC Battery Ground' alarm is active?
Can you give us a reading for +125VDC and -125VDC to ground. You are maybe just on the borderline of tripping the alarm. Try it with and without the suspicious cable connected.
CSA & glenmorangie, thank you for replying me.

The Mark VIe was installed at the same time of the turbine, so there is no upgrade or retrofit.

Unfortunately I didn't remember the exact value for the P & N legs, but the G125VDCO reached about 100 before decabling the instrument (and about 0 after recabling it).

Next time I'll try to take the maximum of theses informations.