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 Post subject: Does anyone out there have experience with Virtual Mains?
PostPosted: Mon Oct 11, 2021 3:11 pm 

Joined: Tue Aug 18, 2020 3:14 pm
Posts: 7
Hello Everyone,

I came across a very interesting document recently from Schneider electric regarding virtual mains. It seems it's used as an AF mitigation technique in some cases.

I read there are two implementations.

The first is for systems where the HV of an XFMR has protection but the LV side does not.
Here a new set of CTs and a relay is added to the secondary. This new relay has the inst. curve enabled and is only in action if enabled through a maintenance switch when work is done below the XFMR secondary.

The document below then also says the following "The second form utilizes zone-selective interlocking with downstream branch circuit breakers in the switchgear, which eliminates the need for the maintenance selector switch."

Can anyone shed some light on how this second version works?

Does this mean the additional relay on the XFMR secondary somehow communicates with the low voltage breakers downstream? I have only heard of this technology through LVCBs with Zone selective interlocking technology built-in. So im having trouble picturing this applied through a combination of relays and LVCBs.

Any help is greatly appreciated, thanks!

https://download.schneider-electric.com ... 1910BR1302


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 Post subject: Re: Does anyone out there have experience with Virtual Mains
PostPosted: Mon Oct 11, 2021 6:37 pm 
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Joined: Mon Jan 18, 2010 11:35 am
Posts: 547
Location: Wisconsin
wfg42438 wrote:
The document below then also says the following "The second form utilizes zone-selective interlocking with downstream branch circuit breakers in the switchgear, which eliminates the need for the maintenance selector switch."

Can anyone shed some light on how this second version works?

Does this mean the additional relay on the XFMR secondary somehow communicates with the low voltage breakers downstream? I have only heard of this technology through LVCBs with Zone selective interlocking technology built-in. So im having trouble picturing this applied through a combination of relays and LVCBs.


Yes, Zone Selective Interlocking can be applied to combinations of both relays and breakers. Sometimes you will need to add some external power supply and interposing relays (don't forget to include any introduced time delays), especially between products from different families or manufacturers.


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