Grounding of DC for Substation Trip Unit

[hanksmith]

This is a question about how to ground a DC system.

Currently I am looking at two options and I don't know which is the right way (is one right and the other wrong?).

First where the -ve of the DC is tied to the AC ground system.

The second is where the DC system ground is isolated from the AC system ground.

If people could provide me with some pros and cons of each. According to the Canadian electrical code if I isolate the DC ground I have to have a ground detector.

Thanks

 

[rcw retired EE]

Operate ungrounded and use a battery charger with a ground detector option. It can be wired out to SCADA or a local alarm panel. That is the lowest cost, most effective design.

When a ground occurs, the charger will alarm but very little current will flow.

There are several good threads on DC system grounding pro's and con's on this site. Try a search.

 

[dpc]

It may depend a little on the type of dc system. For dc control power, such as in a substation or switchgear assembly, the dc system is almost always floated to increase reliability, at least in the US and Canada.

Yes, some type of ground detection is needed, but that is relatively simple to provide.