Dedicated ground fault protection for all feeders on a LV solidy ground system

[majesus]

We are designing a 480V solidly grounded system for an industrial mine located in the Southern USA, where the climate is mild and the area will be designed with a solid industrial ground grid with multiple ground rods. Customer has requested that all 480V branch circuit feeder (15A CB and higher) come with dedicated ground fault protection as they have had issues with intermittent ground fault. One example given was lighting transformer failure which caused a fire that could of been prevented by using dedicated ground fault protection.

I haven't seen any 480V solidly grounded system with ground fault detection unless the feeder was for mobile equipment or another application I've experience was way up north where throughout the year, the ground was frozen Tundra and with permafrost and frequent ice accumulation throughout site, grounding was difficult. We provided ground fault protection on all feeders for that site.


However, for this current mine application, the climate is mild and as mentioned, it is a solid grounded system in an industrial site that shall a robust heavy ground grid installation. My experience is that individual feeder ground protection is typically not done on LV solidly grounded system.

We shall implement ground protection for all the LV feeders as per the client's request, however I'm curious on feedback from other member's experience.

Regards,
Majesus

 

[7anoter4]

In my opinion, it is a problem of temperature limitation in classified zone.

http://www.cablejoints.co.uk/upload/Hazardous-Area-T-Class-and-Technical-Guide---Redapt.pdf

The nature of material extracted from the mine imposes temperature limitation in short-circuit situation. Usually a cable insulated XLPE or EPR withstand up to 250 oC.
If the class temperature is T5 or T6 no temperature rise above the rated [90oC] is allowable so the short-circuit clearance duration has to be very short.