Ghost Tripping 4160V Switchgear

[poseidonsampmeter]

Hello All,

There recently has been an interesting development happening at the power plant I'm currently working at. It started with 1 pulverizer two nights ago, and now another pulverizer and a boiler circ pump.

We currently are experiencing "ghost" tripping of some of our 4160V switchgear, one of which wasn't even running. We are currently using the Series 81000 Type 97H35 Vacuum AC Contactor, 4800V w/ 6R fuses.

I can come up with a couple of reasons, but was looking for some help and to hear out other possible theories. The main culprit of this is likely that is has been very cold here (avg. of about 2 degrees Fahrenheit), and it also quite chilly in our MV room where this equipment is located. I pulled some data from all 3 relays this morning (Siemens Siprotec), and found an interesting trend. All of these trips are associated with a flexible function labeled "flx01" showing that it has tripped, and an LED light showing on the relay indicating that a fuse has blown.

When I look at the drawings, there is a "BFS actuator" that is in series with a binary input that is the same as "flx01" (I can provide pictures/drawings when I get back to work tomorrow). This is essentially showing us that there is perhaps some sort of linkage problem between the support tray (trip bar) of the fuses and the pushrod that connects to the safety switch. There is a possibility that some movement had triggered the trip bar just slightly enough to trigger the safety switch to send a command to trip the breaker.

The more interesting thing is, is that the two breakers that tripped last night occurred at the exact same time, and one was positioned on top of the other (one was running, and the other was not).

Let me know if any of you guys have seen something like this before, or have any idea of how to mitigate this without opening every cabinet and trying to repair the linkages (almost 0% chance at this current moment).

 

[Elect117]

Any chance you can post the logic with flag flx01 when you get back to work. Is flx01 the flag for a pickup current or voltage event?

I found some stuff when googling but I have only really used Doble and SEL.

 

[poseidonsampmeter]

Elect117,

No, it has nothing to do with pickup current or voltage event. It is simply a binary input on the multifunction relay.

 

[Elect117]

"If, for example, voltage VA drops to such degree that voltages VAB and VA exceed their threshold values, the device indicates pickups “Flx01 Pickup A” and “Flx01 Pickup C”, because the undershooting was detected in the first and third measured-value channel."

I found a manual and searched the "flx01" and it looked like a trigger or flag to trip. The binary input would be internal to the device based on the threshold VT or CT value. Something like 10% of V + nominal would have a "High V flag" with and the logic level is in the device. Or sometimes the VTs and CTS are not in the device. Since the VTs and CTs follow the circuit I am assuming the logic is in the relay device and the siemens product is not just a display for controls like a SCADA screen. Same for phase differentials and such. The flagged term is usually in some kind of logic in the relay. I just might not be knowledgeable enough with the product class or application. Sorry friend.

This level of knowledge might require a ticket with siemens and having them go through the devices, settings, "AS BUILTs" and temperatures experienced in the room to get to a conclusion.

My short answer is the temperature is unlikely so long as the material used is not outside of it's normal operating temperature. You would more likely be seeing other issues if the cold temperature was effecting things in the morning.