Fusing of breaker DC tip/close ccts

[marks1080]

I'm talking about DC trip/close coils in primary switch gear typically found in a HV switchyard.

Do you folks typically fuse your DC circuits inside the relay building or at the breaker mech box? For example, we typically supply these ccts from a DC panel, the cct is fused inside the relay building, then sent to the breaker. We throw slugs in the mech box.

I'm just curious if anyone in the HV world is fusing at the mech box.

thanks!

 

[dpc]

We fused at the breaker. Seems less prone to error and gives the tech a more positive indication that the control power is off. But I can't say I've ever really considered remote fusing. We have a dc panelboard with breakers to protect the circuit out the breaker.

 

[DTR2011]

Our local transco and disco both slug at the mech. It's either a fused switch or breaker at the DC Panel. Some form of fuse / DC undervoltage monitoring via SCADA is used. Typically the Fuse Monitor sensing is wired downstream of the Fuse (Slug) isolation switch in the breker mech.

 

[bacon4life]

We typically leave the fuses in the mech box, even though the trip/close circuit is supplied from a DC breaker panel. No idea which device would operate first as they are often the same ampere rating. Note that some HV PCB suppliers use breakers and some use fuses.

In small distribution substations, the circuit will go DC+ to PCB to control house relay panel to PCB to DC-, which enables wire crews to isolate the PCB mech box by pulling the local fuses.

In larger substations, the voltage drop associated with the extra runs out & back is too high, so the +DC supply from the trip contacts comes directly from the relay panel an cannot be isolated by a switching device inside PCB mech box.

 

[Sn00ze]

Definitely at the breaker cabinet. Otherwise you'd have to run a higher AWG cable to the breaker control module.