Why system neutral should be grounded at the power source only?
Why system neutral should be grounded at the power source only?
(OP)
Hi,
I don't see what will happen if a system neutral is grounded at 2 or more points and what's the danger. Can you explain me that? In many reference it is written that you should not do that, but why? If you have any good reference about this it'll be very appreciated.
Thanks
I don't see what will happen if a system neutral is grounded at 2 or more points and what's the danger. Can you explain me that? In many reference it is written that you should not do that, but why? If you have any good reference about this it'll be very appreciated.
Thanks






RE: Why system neutral should be grounded at the power source only?
In a uni-ground system the ground is intended to be a non-current carrying conductor and the neutral is intended to carry all normal imbalance current. Multiple connections between ground and neutral puts neutral currents onto the ground. Ground fault detection that assumes all ground fault current on the ground and none on the neutral will not function properly if there are multiple connections.
RE: Why system neutral should be grounded at the power source only?
RE: Why system neutral should be grounded at the power source only?
RE: Why system neutral should be grounded at the power source only?
When you put a current probe over conduit and see load current flowing on it, you better appreciate what tying neutral to ground in more than one place can do..
Removed the second tie of neutral to ground and problem resolved.
RE: Why system neutral should be grounded at the power source only?
I will admit that at 600v and less it is not very likely, but that is some of the concern in the NEC rules.
Haveing said that, in large spread systems it becomes difficult to ensure, and maintain single point grounding.
I've seen 480v systems extending a quarter mile in each direction from the source.
RE: Why system neutral should be grounded at the power source only?
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PME does not allow the use of a fast acting earth fault protection scheme using residual connected CTs or a core balance CT. On the other hand, any phase-earth fault implicitly becomes a phase-neutral fault with a resultant healthy fault level which results in rapid clearance. Use of PME in the UK is limited to the distribution companies: larger industrial consumers with a dedicated transformer will have a TN-S supply which does allow use a fast acting earth fault protection.
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RE: Why system neutral should be grounded at the power source only?
At the 120v level there has been an improvment with ground fault indicating(GFI) breakers and outlets. But such systems require an isolated neutral for that circuit. This may also apply to 240v as I don't keep up with all the new products.
The arc fault indicating(AFI) breakers may also save some lives, but I haven't studied these to know the requirments of the neutrals.
There are new relays that are made to detect arcing faults, but these are used mainly in power systems. Besides I have heard reports that these are less than 50% effective.