How to select DC voltage level for Substations
How to select DC voltage level for Substations
(OP)
Can u pls explain the basics for selection of DC voltage for substation used for control and protection applications, i came across 30V, 110V, 125V and 220 volts level, breaker manufacturer will supply closing and tripping coils according to our request, and most of the numerical protection relays are also capable of operating from 48-220 V ac or Dc.






RE: How to select DC voltage level for Substations
RE: How to select DC voltage level for Substations
Is your breaker solenoid operated or is it mechanical energy storage? If it is solenoid operated, I would suggest 125 VDC to reduce the operating current. If it is mechanical energy (ie. spring charged) it really would make no difference.
If I were you, I'd specify 125VDC if for no other reason than it's the most common and easiest to find replacment parts.
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If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: How to select DC voltage level for Substations
Agree 110V DC or 125V DC is common. A nominal 110V battery (55x 2V cells) floats at 124V DC; beware when specc'ing equipment.
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If we learn from our mistakes I'm getting a great education!
RE: How to select DC voltage level for Substations
Many countries: 110/125V DC is common.
Biggest companies with air breakears/first GIS for the HV is 220V DC ( reason voltage drop and peak of current).
Today for my pinion, preferable 110/125 V DC, if possible of course 48V DC, for medium voltage level 48DC.
Best Regards.
Slava
RE: How to select DC voltage level for Substations
Some of my industrial clients used 48 VDC on older equipment but all the newer stuff was going in at 125 volts.
Much of the newer equipment doesn't have the current requirements of the older equipment and voltage drop is less of a problem.
old field guy
RE: How to select DC voltage level for Substations
RE: How to select DC voltage level for Substations
If the station is a very small distribution sub, then 48v will work. other wise use 125vdc.
If you look on the SEL web site there is a paper on balanced ungrounded, vers unbalanced ungrounded battery systems. (By balanced and unbalanced I am meaning that the natural tend is for the capacatance to balance the voltage to neutral, where if a high impedance resistor is used to tie each rail to ground you can modify that balance).
RE: How to select DC voltage level for Substations