Under Voltage release / relay for the final distribution board 1

[NickParker]

Do under voltage release / relays are required for the final distribution board installed at the absolute bottom of the power stream? Any disadvantages by not providing it?

 

[davidbeach]

Back when I was doing that type of work, I never saw any use of undervoltage releases in general application. They might be used for specialized uses like computer rooms, but that was about it. But the voltages you list suggest that you are working somewhere other than the US and local practices vary all over the world.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[dpc]

As David said, UV release is rare in the US. More common elsewhere in the world it seems. For a system in the US, I would never even consider put in UV release in this location.

 

[che12345]

Dear Mr. NickParker (Electrical)(OP)31 Jan 22 13:15
"... Do under voltage release / relays are required for the final distribution board installed at the absolute bottom of the power stream? Any disadvantages by not providing it? ..."
1. Based on the 690/400, 400/230V ; it is an installation based on IEC standards. Where IEC 61439 applies. As per the standards, there is No mandate that the incomer CB must be provided with a UV or shunt.
2. If you are facing with frequent under-voltage for prolong time which are causing damages to your loads, yes; install a separate UV relay set to trip <85% with time delay. Attention: A CB with UV will NOT trip at <85% voltage. It may go ss low as <45% to trip out !
3. A motorized CB can be switched I/O remotely (usually) without any increase in size. The motor unit is NOT costly, compared to the price of the DB.
4. Do NOT consider using a contactor, as it has very low short-circuit kA rating; unless fused; which lowered the security.
5. You may consider a motorized CB installed with Shunt release instead of UV; if prolong under-voltage is not your concern to the loads. Note: A CB installed with a shunt release doe NOT open at all, when the incoming voltage dropped to zero. Attention: A CB may install with either a UV or a shunt, but NOT both. They are not costly.
Che Kuan Yau (Singapore)

 

[RRaghunath]

Undervoltage release is a requirement at incomer level if the board is provided with an alternate incomer such as DG set (to provide supply in case of failure of normal supply).
In all other switchboards, UV release has no relevance.

 

[Padlock01]

My take is that yes the final DB to the consumer should have UV and OV protection,
A recent case at our complex where robbers stole the 400V neutral cable which blow up most of the
residents appliances.

 

[FreddyNurk]

What RRaghunath said.

We used them all the time for the applications that I was dealing with, but all of them were either multiple generator, or generator and mains with closed transition.

The only reason I can think of to use them for general distribution is that the operator of the site wants to be able to manually or progressively return equipment to service.
Bear in mind that pretty much all of us have assumed that you're using a nominal voltage UV release coil direct fitted to the breaker, as there are obviously other possibilities (UV coil at control voltage, not nominal, and perhaps driven by a phase fail relay) that don't behave the same way.

EDMS Australia