Trip and close coil for power breakers 5

[kookypedia]

Hey guys,
Do all power breakers have separate trip and close coils? and is there any difference between main breaker and feeder breaker in this regard?
Any link would be appreciated!

 

[davidbeach]

You may want to define your usage; what kind of breaker are you talking about? If it didn't have both trip and close coils what use would it be? Somehow I'm guessing you're thinking low voltage but that would be something useful to state.

 

[kookypedia]

@davidbeach: Thanks for your response,
I thought all MV's have trip and close coils and I was wondering about LV breakers.
I am working on a Battery sizing for a petrochem and previous engineers have accounted for trip coils which made me to wonder why close is missing?

 

[davidbeach]

The plant isn't likely to be doing auto reclosing so never more than one close at a time, but you might have to clear a bus and need to trip multiple breakers simultaneously.

 

[kookypedia]

Thanks David, I also think low voltage breakers don't need charging spring (close coil) so they will only have trip coil, am I right?

 

[bacon4life]

Some MV breakers use AC and some use DC for close coils. Also some MV and HV breakers use AC for charging up the spring/hydraulic mechanism. An incoming breaker should not be designed to need AC for closing.

At a recent substation I worked on, the worst case DC voltage was for a bus trip following a breaker closing. In this case, the DC motor would be still be charging the closing spring when the bus lockout activated all of the trip coils.

 

[kookypedia]

@bacon4life:
1- Do you mean close or trip in this sentence?

Some MV breakers use AC and some use DC for close coils. Also some MV and HV breakers use AC for charging up the spring/hydraulic mechanism.

2- "An incoming breaker should not be designed to need AC for closing" is there any reason for this?

 

[davidbeach]

I'm sure he means close. We have lots of older DC trip, AC close breakers with the stored energy mechanism (often compressed air) charging on AC. Close charges the tripping springs, so loss of AC won't prevent a trip, but it can certainly prevent a close. If the only way to get AC station service is to close the incoming breaker and the only way to close the incoming breaker is to have AC station service you're going to have a wee bit of a problem.

 

[kookypedia]

@David:
These are for MV and HV breakers and in LV we don't need close coil (spring charging coil) right?

 

[FreddyNurk]

When involved in remote area LV power projects, one company I worked for always used AC coils fed from the generator side for breaker closing, it was a neat way of preventing automated closing onto a stopped generator.

Otherwise the summary from davidbeach is quite accurate.

If there's no requirement for any automated breaker closing (OH&S / arc flash / safety requirements notwithstanding) then trip coils can be provided so that remote means of tripping the breaker can be used, but manual intervention is required to reclose the breaker.

 

[davidbeach]

Closing the breaker must provide the stored energy necessary to trip/open the breaker. If your LV breaker can be closed manually and provide that energy, and you have no particular need for remote closing then a close coil may well not be necessary. But even at LV there comes a point at which it much easier to not to rely on human energy to get the breaker close.

 

[DTR2011]

Many contactors, used for motor control, have an AC close solenoid, which is continuously held in. Removal of the AC causes the contactor to open.
I would imagine a petrochem would have lots of these. I haven't seen DC solenoids for this application, but I imagine they exist.

 

[Zogzog]

LV breakers can be manual or electrically operated and may or may not have trip/close coils and charging motors. Typically the mains and ties would be electric and feeders manual but can be any combo.

 

[waross]

I have worked on several low voltage power breakers (480 V) that were manual. A charging handle was pumped to charge the spring.
Once charged the spring would close the breaker and then open the breaker. One basic breaker had a close button and a mechanical current trip. No remote control at all.
Closing coils, tripping coils, and charging motors were options that most other plants included.
I haven't seen a power circuit breaker that could be closed unless there was enough stored energy to trip it open.
I seem to remember one breaker with remote close and trip. Once closed the spring could be recharged manually (No motor charging option installed). It then had enough stored energy for a remote trip, a remote close and another remote trip.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

Every power breaker I've seen that could use trip and close coils also required spring charging, via a manual lever or motor. Low or medium voltage made no difference. With MV breakers, I've found I generally just specify the close coil, trip coil and charging motor voltages meaning they come standard in the breaker. With the LV breakers, the close coil, trip coil and charge motors have always been options and you order any combination you wanted from none to all of them.

AC close can be used for a mains if you have a MCC with a drawout or line connected CPT.