Trip circuit Monitor on a circuit with a lighted nameplate lockout

[cranky108]

Has anyone sucessfully been able to apply a trip circuit monitor on a circuit with a lighted nameplate lockout?
The problem dosen't seem to be in the reset state of the lockout, but in the tripped state there is an interaction between the lighted nameplate and the trip circuit monitor.

The issue is that someone had this wonderful idea to place the lockout in a 35 kV switchgear, but the transformer differential relay was placed in the control building. The lighted nameplate trip coil monitor monitors the trip coil, but leaves much of the circuit without monitor. The trip circuit monitor monitors a greater part of the circuit. During testing it was found that the two monitors interact while the lockout is triped. This interaction was on the order of several thousand outputs of the trip circuit monitor a miniute.

I have contacted both venders, and nether were helpful in providing a solution. The lockout out vender has really made my list, because i had contacted then prior to the instalation, and they did not have time to discuss it with me. And after the instalation they have provided very little (OK they had a huracane, but they appear to have a sustanability problem also).

Any ideas to a solution?

This is a utility application, and the schematics are very utility common.

 

[dpc]

Can you just disconnect the backlight in the LOR? I assume this is the Electroswitch LOR? I've used a separately mounted pilot light to monitor the trip coil in conjunction with the relay trip coil monitor in the past without any issues (that I am aware of), but never a light built into the LOR. You could maybe try putting a diode in the trip coil monitor input to the relay.

 

[cranky108]

This is an electroswitch, and trying to use an SEL relay input as a a trip circuit monitor. SEL did give me some information, but no solution. Electroswitch has given me the typical, we haven't seen this before, so give us time to study it.

I was looking at using a latch function to fix the output during these osolations, but I am still troubled with the unlatch part.

If there is a moral to this, put the relay with the lockout.

 

[mgtrp]

Depending on the model of SEL relay, you may be able to adjust the pickup/dropout voltage of the input to prevent the chattering. If you're just trying to prevent chattering of the output then a timer with perhaps 120 cycles pickup/drop out would probably be more effective, although I'm not sure that the large number of writes of the internal memory are going to be terribly healthy for the relay.

 

[dpc]

Normally, when using a separate pilot light, the light is OFF when the relay is tripped, since the trip coil circuit is opened by LOR "b" contacts that open when the relay is tripped. Is the backlight lamp in the LOR even in the circuit when the relay is tripped?

 

[amurray]

Could you provide a sketch? I am not seeing how the LOR coil is in the CB trip circuit.. I have seen LOR circuits with a light in series with the LOR coil to monitor the LOR coil & I have seen LOR contacts in a CB trip coil, but am not familiar with the two being tied together. If you are using the same contacts to both trip the CB and operate the LOR then I could see how when the LOR is operated you are providing a sneak circuit for the CB's trip coil monitor circuit.

Andy

 

[cranky108]

The LOR has an LED to indicate a trip signel is on the lockout prior to resetting it. It's that 4 or 5 mA LED that is causing the problem.

The 387 relay has a fixed input pickup voltage, which is being picked up by the trip signel indacator LED.

No one said, but I expect that as the SEL input voltage goes up and down, so does the voltage on the trip indicator LED.

The engineer that decided to make this sepration of the lockout and relay has retired, and good ridence.