Batteries for switch gear

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jimbo123

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Can someone explain to me why there are batteries used for switch gear? ICAN make a guess but are not sure why.
 
Basicly DC Systems are used in switchgear applications for breaker control in the event of a power failure ,charging both trip and closing springs,DC is used almost exclusively for tripping while some closing springs are AC as well.DC is used for montoring,system interface,UPS back up.

I was once told by an old timer that a DC closure of a motor breaker or large starters was faster and more positive than AC.it slams it home, thus less arcing.

dick
 
jimbo123 said:
Can someone explain to me why there are batteries used for switch gear? ICAN make a guess but are not sure why.
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DC low voltage supplies are required to provide power for the operating mechanisms of circuit breakers, for operating alarm, protection and control systems, and for emergency back up lighting. Typical DC voltage levels used at substations are 48, 110, 220 volts. The battery and the associated charger capacities are determined from the average load in association with the peak demand. Duplicate DC systems are sometimes installed at the larger substations to ensure high reliability.
 
dicklaxt said:
Basicly DC Systems are used in switchgear applications for breaker control in the event of a power failure
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Not just after a power failure, the batteries are the sole source of trip and closing power for the breakers.

dicklaxt said:
,charging both trip and closing springs,
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A motor or solenoid charges the closing springs, the act of closing the breaker charges the trip springs.

dicklaxt said:
I was once told by an old timer that a DC closure of a motor breaker or large starters was faster and more positive than AC.it slams it home, thus less arcing.
dick
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The closing spring pressure will determine contact speed. Contact closing speed should be measured via time travel analysis and contact pressures adjusted accordingly. Weather the closing coils ae AC or DC has nothing to do with it.
 
jimbo123 said:
Can someone explain to me why there are batteries used for switch gear? ICAN make a guess but are not sure why.
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It provides closing and tripping power to the coils. Not a backup to anything, the batteries are the control power and the most important piece of equipment in your power system. When a fault occurs the relays see the fault, actuate, close a set of contacts to allow power from the batteries to energize the trip coil of the breaker. Without those batteries nothing will be protected.
 
dicklaxt said:
Basicly DC Systems are used in switchgear applications for breaker control in the event of a power failure ,charging both trip and closing springs,DC is used almost exclusively for tripping while some closing springs are AC as well.DC is used for montoring,system interface,UPS back up.

I was once told by an old timer that a DC closure of a motor breaker or large starters was faster and more positive than AC.it slams it home, thus less arcing.

dick
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Zog in my defense I guess I could add in the commas as required yes it reads totally different,,,,,,,,,applications, for breaker control, in the event of a power failure ,,,,,,,,, and isn't the solenoid and/or motor on a DC circuit?,,,,,,,,,,I stand corrected on the DC slamming force,just passing on a statement

dick
 
DC control power from a battery rack is as uninterruptable as you can get. For switchgear that is what you want, as all protection is dependent on it. AC is on & off & on every time the wind blows hard.
 
SG-1 said:
DC control power from a battery rack is as uninterruptable as you can get.
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Until someone 'turns off' the battery charger. I am always amazed by the number of facilities I visit that do not monitor and alarm their DC bus voltage.
 
jim dungar said:
Until someone 'turns off' the battery charger. I am always amazed by the number of facilities I visit that do not monitor and alarm their DC bus voltage.
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Me too, that blows my mind. Whenever I find that situation I always ask about it, they usually think it is a back up supply too and seldom understand thier importance.
 
Just as a bit of opposing view, there are times where breaker control power can be derived from the line voltage of the gear, depending on the sequences (or lack thereof) that are expected when the power is out.
Some basic gear can be supported with CPT's and never need the additional functionality of a stored DC source.
 
ron said:
Just as a bit of opposing view, there are times where breaker control power can be derived from the line voltage of the gear, depending on the sequences (or lack thereof) that are expected when the power is out.
Some basic gear can be supported with CPT's and never need the additional functionality of a stored DC source.
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Well sure, but then you wouldn't have a battery system now would you? The OP was asking about the battery system.

Even if you have AC control power you will still have a cap trip device (stored DC source) for your trip coils. No one would want AC from the CPT's to be trip power. Disaster waiting to happen.
 
Great information ...
Our batterries are along side the switchgear , there are 24 in the rack [48vdc] that need maintenance [water added when low ] it has a battery charger connected to them with a status meter.

From the post that have been made that is the only power used to open or close,trip a breaker in the switchgear ? Also It would have alot to do with the clearing time with the switchgear and hrc should the batterries be in poor or fair condition ?
Would the breakers be able to trip with low dc power?
We will have to have some one monitor the status meter or maybe install a remote meter.
Thanks again for all the tips with this.
 
jimbo123 said:
Great information ...
Our batterries are along side the switchgear , there are 24 in the rack [48vdc] that need maintenance [water added when low ] it has a battery charger connected to them with a status meter.

From the post that have been made that is the only power used to open or close,trip a breaker in the switchgear ?
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Usually, yes.

jimbo123 said:
Also It would have alot to do with the clearing time with the switchgear and hrc should the batterries be in poor or fair condition ?
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Not really, the clearing times are determined by the relay setings and the breaker speed. Only if the batteries were off line or too low a voltage so the breakers won;t trip would it be an issue.
jimbo123 said:
Would the breakers be able to trip with low dc power?
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To a point yes, for example a 125VDC trip coil is required to be abe to trip the breaker at 90VDC. That is something we test on all our breakers, not many people do for some reason.
jimbo123 said:
We will have to have some one monitor the status meter or maybe install a remote meter.
Thanks again for all the tips with this.
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Alarm systems are very common for this. Always ensure the charger is set at the proper float voltage and maintain your batteries per IEEE Std 450
 
ron said:
Just as a bit of opposing view, there are times where breaker control power can be derived from the line voltage of the gear, depending on the sequences (or lack thereof) that are expected when the power is out.
Some basic gear can be supported with CPT's and never need the additional functionality of a stored DC source.
Click to expand...


Zog, I have seen one customer of late doing this very thing. A rectifier had to be placed in the circuit right before the trip coil, because they are all DC in this product line.

Maybe he is using a UPS ?

I agree, he will rue the day he did this thing.

Even the Capacitor Trip Devices have to be replaced every few years because the internal capacitors degrade.
 
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