question

tien avatar image
tien asked

Ground Relay Safety

We use a MultiPlus Compact 12/1600/70 in our development vehicles to supply our measurement equipment with 230V AC. Now we have the question how the saftey of the Neutral-to-PE(Ground) relay is ensured.
- Does the MultiPlus test the functionality of the relais contacts?
- If yes, is there a documentation about this available?
- What is the reaction if the test fails?

Thank you for a helpful answer.

Best regards Timo

Groundingmultipussafety
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2 Answers
shaneyake avatar image
shaneyake answered ·

https://www.victronenergy.com/live/ve.bus:ve.bus_error_codes
Have a look at Error 8.

"During inverter operation, disconnected from mains, the ground relay is continuously tested to be closed. While switching over to mains it is tested to open. The ground relay tests are always performed: in systems with a grid code configured as well as system without a grid code configured. The only exception is systems where the relay is disabled in VEConfigure. See product manual for more information regarding the ground relay."

The ground relay is tested on startup and then disconnecting from grid or connecting to grid.
The inverter is always monitoring the connection between Ground and Neutral if lost not then the inverter will shutdown with Error 8.

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tien avatar image tien commented ·
Thanks for this helpful link!
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Trevor Bird avatar image
Trevor Bird answered ·

I haven’t heard of the periodic testing as a function of the multiplus but I can speculate on the scenario of the ground neutral relay not engaging.

If the ground relay engages and a leakage to ground was detected, the RCD on the output of the multiplus would trip. This would stop the leakage to ground.


If the ground to neutral relay did not engage, the ground reference to the neutral or active output of the multiplus would be lost so no ground leakage would occur. In other words, without the ground neutral relay, the output of the multiplus would be like that of an isolation transformer, not having a ground reference. In other words, leakage current would not pass through a person who was grounded because that ground reference would not have been established. It may be safer without the ground relay than with it.



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tien avatar image tien commented ·

Hi @Trevor Bird ,

thanks for your answer. For only one device you have right. In the case, that the ground relay don't connect neutral and ground it is the same as a IT (=isolated terre) network.

But for more than one devices but with only one RCD we get a big problem if one device has a shortcut e.g. from L to ground and on an other device the N can be touched by an defekt of isolation. In this case the RCD see no difference but the guy who touch the isolation defekt get a problem.
The problem is, that you can not recognize the first fault. But the second can be deadly.

Thats why regulations in germany requires one separate RCD for each device if a IT net is using. Or a Isolation Observing Device is needed for IT. Both is not cheap.

The solution is to build up a TN network. But this requires a safe ground connection.

My hope was, that the MultiPlus is checking the functionality of the ground relay.


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marekp avatar image marekp tien commented ·

@Tien

My hope was, that the MultiPlus is checking the functionality of the ground relay.

It does, and when test of ground relay fails, error #8 turns the AC-out off.

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Trevor Bird avatar image Trevor Bird tien commented ·
Hello @Tien , yes, many thanks for that good explanation.
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