F60 Form A Voltage monitoring Contact Voltage

[MeinKaun11]

I am struggling to understand zero voltage across terminals H1a and H1c of GE F60
UR relay. Contact status in the relays shows de-energized(open).

This contact is part of GR UR family Form A and has a current and voltage monitoring
circuit and for some reason there is no detail what is the internal of this circuit is.
Even GE support people don't know.

Substation battery voltage +ve to ground is 96 voltage and -ve to ground is
31 volts. Station has 125 V DC system.

When I put a multi-meter across Block switch BS-1 blade (1) to ground, I see a
voltage of 96 Volts but I am wondering why since contacts are open
as per relay but it should show zero voltage to ground if blocking switch is open

But when I take the main fuse of 20A, multimeter, then the H1a and H1c voltage reads 0 volts.

Can you please advise what I am missing here ?

I am wondering if this voltage monitoring circuit is messing something up.

 

[DTR2011]

I would expect 1/2 of battery voltage on each leg of the circuit with respect to ground, assuming the battery charger has some kind of DC ground detection circuit. The 96 & 31 volts suggests a ground fault. When measuring at either BS test switch do you have the breaker closed? Else, there may be other element (red light bulb), where a positive can bleed through. I would expect (-) 1/2 battery voltage.

From the location of the 43R switch, I hope this is a SCADA close / trip, rather than a protection trip.

It is not clear to me what the box with the "R" and what appears to be a resistor in series with the box is to the left of the H1C contacts. If this is the "red light" the positive will bleed through. Try removing the red light bulb.

Its been many years since I've worked with UR relays, but I recall there is some kind of application note related to the voltage/current monitoring contacts and testing the relay. I believe this may explain the inner workings of the contacts a bit better.

The 0 volts indicates a very low impedance (or a shorted contact). I believe these are actually transistors, rather than mechanical contacts.

I would start by locating the DC ground fault. This is a bad thing that needs to be resolved one way or the other.

 

[davidbeach]

If your BS-1 is open, it means the F60 contact H1A/H1C is closed. If BS-1 is closed, then you're just measuring the voltage on the trip coil side of the red light. It would probably be easier to figure out if you fix the ground fault and then make all your measurements using the negative bus as the reference. Voltages to ground are less useful than voltages to either bus.

 

[MeinKaun11]

Thanks DTR and David Beach.

The DC voltage distribution is laid out in a fashion where +ve to ground is 96 V and -ve to ground is 30 V, so I am sure it is not a ground fault.

Breaker is open at the moment and I want to make sure that is isolated either side disconnects open, it is an outdoor breaker and want to avoid a trip free operation.

What I don't get is that how come when Blocking switch BS-1 is open and breaker is open, H1a and H1c are supposed to be open but I see a short with a multimeter and BS-1(1) is 96 Volts but why ? UR ENervista shows contact status OPEN/De-Energized.

I think this voltage monitoring circuit is messing some thing up.

Any input.

 

[3I0]

The voltage monitoring circuit acts as a high impedance in parallel with the output contact, provided it is wired in-circuit (I believe there are options for 'Voltage Monitoring w/ Optional Current' and 'Current Monitoring w/ Optional Voltage' which require jumpers).

Testing them requires a bit more thought, as they don't appear as a standard "dry contact".

 

[jghrist]

Is it possible that H1C is polarity dependent? Some Schweitzer relay outputs are polarity dependent and if put in backwards allow a path through a supposedly open contact (found out embarrassingly during commissioning).