High Voltage DC GFCI

[masa6614]

Hi,
I'm wondering on how I can make or buy a Direct Current GFCI for +/- 300Vdc. Attached is a picture of my power source, the 'ground' is tied to chassis and any loads are connected between the +/- 300V lines so will see 600Vdc.

I'm wondering if for a GFCI, would i be monitoring for any current on the ground, and if any amount is detected, to open some contactors or shut off the source. Or should I clamp one of those round DC current transducers (

http://www.a-a-c.com/2dccurrentxducr/2 DC Current Xducr.htm

)on both the + and - 300V lines, and I'm thinking it should output 0, because both lines current readings are cancelling out each other, and if it was to detect a difference, that is a ground fault? I've looked for some DC GFCIs and came up with nothing, saw some at BENDER but they werent high enough voltage rated.

And also if someone can help direct me to a GFCI spec or requirement for that DC voltage, like it should trip if 5mA difference is detected for a certain amount of time?
Thanks alot.

 

[Skogsgurra]

Yes. This is a problem. Hall effect transducers have too high offset and temperature dependence to work properly. I have been looking at GMRs and Flux Gates to detect difference in forward and return current. It is not difficult to have a working prototype up and running, but it has to be 'productified' also. And I do not do that.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Skogsgurra]

I had a look at the DC transducers in your link. They seem to be able to do the job. Two wires through the hole should work very well.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ScottyUK]

A rotor earth fault relay as normally used to protect the field of a synchronous generator would be an option. These can normally survive on 1000V or more.

Alternatively, Areva's MR627 earth fault relay can operate on up to 1500V DC - search Areva T&D's website.


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If we learn from our mistakes I'm getting a great education!

 

[masa6614]

Thanks,
Now I'm sort of having trouble finding out what is the standard tripping current and time for this sort of GFCI. Since this is for a vehicle, reading from SAE J2344 - Guidelines for EV safety, in section 3.7 it says the resistance between the battery high voltage and the vehicle conductive structure should be greater or equal to 500 ohms/V, which is defined as "isolated". So would that sort of be saying any more than 2mA flowing through the chassis be cause for a trip? And how long?