Trip/Close Coil Monitor and Voltage drop across coil

[Uquresh1]

For Trip Coil monitor and Close coil monitor we use a Protection relay Input (high Impedance) wired in parallel to the Tripping relay output contacts, and in series with the Trip/close coil and the 52a/b status.
Has anyone ever had issues where the relay input (125VDC control voltage) would not pickup due to the voltage drop across the Trip/Close Coil? A vendor brought that up that they would like to set the relay Input to pickup for almost half of the full VDC, so around 65VDC, since they expect voltage to possibly drop to that value across the TCM/CCM Input.
I have never heard of a Trip or close coil creating such a big voltage drop that the Input only sees 50-60% of the full DC. Any help is appreciated.

 

[cranky108]

Not unless there is a PC board in the breaker that monitors the trip coil health. Then the input on terminal 9 is also a high impedance.

 

[stevenal]

Yes. We tried that type of circuit on a recloser equipped with magnetic actuation, and the voltage drop was too much. No problem using it with conventional coils.

 

[davidbeach]

Those breakers typically have a Breaker Ready (or Breaker Not Ready) contact. Monitor that.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[cranky108]

But the trip coil monitor from a relay, as it is called, also monitors the cable between the switchboard and the breaker. As I have pointed out to several younger engineers here, the coil monitor is only part of what the monitor does. By placing a monitor board in the breaker, you are not solving a monitor problem, you are creating a cable monitor problem.

 

[davidbeach]

Flux shift type breakers, 15kV class. The trip signal goes to a control board in the breaker, not to an actual trip coil. Unfortunately not much for a conventional trip circuit monitor to do. Haven't seen them at higher voltages and so those mostly do have trip circuit monitors. With the flux shift breakers you have to monitor the breaker ready status anyway, at least if you do high-speed reclosing, because sending a close signal too soon, even 1/4 cycle too soon, and the breaker will ignore it.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[Uquresh1]

Thank you to all who replied.
Turns out the reason the vendor was mentioning voltage drop up to half of nominal DC voltage was due to the fact that in Europe for some projects they use a different Trip coil monitor where one relay input is wired as shown in my figure above, and then an additional input is wired as per figure below. In my project we weren't wiring it this way so this issue should not have been brought up, but it still was since vendor didn't understand that our TCM is different than what they are used to seeing.