DC or AC Spring Charging Motor 1

[AussiePower]

Hi Friends,
Can anyone tell me what are the pros and cons of DC and AC spring charging motors for an 11kV circuit breaker?

 

[oldfieldguy]

I am a fan of DC, using the house battery supply for a source. In a "black startup" situation, you'll have your batteries to charge and close breakers.

old field guy

 

[dpc]

I think it is mainly a function of available control power sources. If there is a station battery, I would use that. If not, then an ac motor is used.



David Castor

http://www.cvoes.com

 

[potteryshard]

Many manufacturers make use of universal series motors which will run on AC or DC. This works out well as the same motor can be fed from either the batter or line power, often through a throwover switch.

 

[cranky108]

With a DC charging motor, you need to be sure the battery set is sized for it's capacity.
With an AC charging motor, you can't charge the breaker when station power is not available. However, if station power is not available, it's either during construction, a failure in the substation, or because of a larger outage.

A DC charging motor seems more convient, but most people don't take the time to understand the additional cost. The additional cost is in the form of possible larger battery needed, possible larger battery charger, effects of added noise on the DC bus.

A AC system may require you to evaluate the AC power for the substation, and maybe add additional backup sources for certion outage contengecies.

Either way some thinking should be involved.

 

[rasevskii]

It should be perfectly obvious that the DC motor option is the best, as long as there is a 125V or 250V battery available. The motor only runs for at the most about 20 seconds and draws a few amps hardly affecting the battery capacity or charging system.

Murphys Law applies: Everything goes wrong at once or cascades during an AC blackout. Not being able to reclose breakers as the springs are not tensioned can be disasterous. Especially in remote controlled unmanned stations where no one is available on site to recharge the springs by hand.

Exception: When only a weak 24 or 48 volt battery is available, it might be a concern.

rasevskii

 

[rcw retired EE]

What type of breaker? Is it in draw-out switchgear, an outdodor substation breaker or is it a high current generator breaker direct connected to isophase bus? The first two have relatively small charging motors. Some generator breakers only come with AC charging motors that are rated about 15 HP at 480 Vac 3 phase.

DC is probably best, but you have to consider all situations and impacts as others have stated.

 

[sonic02]

I would go with a DC system for charging the breaker spring operating mechanism. A battery bank (eg 125Vdc, 60 cells) may be used to feed a DC panelboard which is being utilized to provide a DC supply for motor spring charging.

sonic02

 

[AussiePower]

It is a 630A, 11kV, VCB. (VD4 ABB)

 

[rcw retired EE]

That's a small load. If you have a battery in the area use it.

 

[slavag]

Possible use UPS ( from station battery), for small substation.

 

[AussiePower]

To be more precise the load is 7x630A, 11kV, VD4 ABB circuit breaker. Each spring charging motor is 200W for 15 Sec. What size would you recommend for DC charger considering diversity factor?

 

[veritas]

The charger size does not only depend on charging the spring rewind motors, substation standing as well as dynamic load (operation of the largest number of circuit breakers with a system disturbance)and battery size needs to be considered.

With regards to diversity it needs to be considered if all the breakers could operate at the same time such as for a buszone fault.

I have seen AC spring charge motors used with a mechanical cranking handle as backup should there be a loss of AC supply.

Regards.

 

[rasevskii]

for AussiePower:

You do not mention the battery voltage available, or whether this is a manned or unmanned installation. The DC choice is obviously the best one, in principle. If all the breakers were to trip simeltaneously (as said in a bus zone fault) they would not be ever reclosed simeltaneously. The spring charging occurs when the breaker is closed giving energy storage for one more trip, reclose and trip sequence. If at that time the spring is not recharged the breaker cannot be reclosed. This is for truck-typr gear in my experience, other types may differ.

Therefore the situation of all the charging motors running at the same time is unlikely, unless someone has switched off the DC supply and put it back on, has happened.

rasevskii

 

[Zogzog]

A "compressed air battery" is another option, I don't have any personal experience with these but it is a different concept.

http://www.pnu-power.com/

 

[electricnewbie]

For those in favor of DC motors, would you still use this philosophy on >230kV, independent pole breakers?

 

[slavag]

For the HV, we use only DC motors ( for breakers, disconnectors, earthing switches).
For GIS, I would like separate it in the wiring from trip and control, separated cable from distribution board is used too..

For DC consumption, always calcualted worst case, 87B/BBP operated on all zones, and trip coil 1 and trip coil 2 on the same battarey and all charging motors start in the same time.
wort case is worst case .

 

[bacon4life]

It is a bit different at transmission voltages. All of our transmission breakers are fed AC for the charging motors. If they have stored energy capacity for >3 operations, they should have at least one operation left for a black start situation. If they are spring mechanisms that don't have multiple stored operations, we specify a backup DC charging option via a universal motor.

Hand charging a medium voltage breaker takes a fair amount of cranking, but hand cranking three 230 kV mechanisms will take quite a long time.

In sizing the battery and cabling voltage drops, I would start by assuming that they would all operate at the same time unless you have lockouts or other interlocks to prevent it. It may not happen often, but we have had a few different odd circumstances that had several or all the MV breakers in a lineup close at approximately the same time. When looking at voltage drop, remember that all the trip coils could be trying to operate while there are motors charging.

The battery charger would be sized to recharge the battery in a reasonable period, with the momentary peak load being supplied by the battery.

 

[dpc]

For HV Transmission Substations - dual battery systems and dual trip coils. And dc closing.

David Castor

http://www.cvoes.com