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Earthing of Neutral in Substation or MCB at LV Panel ? or both ?

Former Community Member
Former Community Member
Hello everyone! 


Im having some doubts regarding where I should ground the Neutral and why ?


This is a new installation which is in an industry that will have its own substation 15/0.4Kv with a transformer of 1250KVA 15/0.4KV DY.


This substation will only feed the MainCircuitBreaker of the plant which is located 80meters away from the substation, there will be no other consumers from this substation/transformer.


The cables are already buried. They will be 6 cables per phase alluminum 240mm2 and 4 other cables 240mm2 alluminum also that could be used for neutral or PE or PEN depending... 


Should I ground the neutral the the transformer ? at the income of the LV MCB ? at both sides ? run only a PEN from substation or run Neutral and PE separate ?


These are the possible options i was considering.. and was hoping some of you guys give your opinions. 


Remember the distance between the TX and LV main panel is 80m
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In the picture the PEN in option 1 and earth in option 2 is grounded at both sides (transofmer and LV mainboard) 


The other options would be as 1) and 2) but grounding only at one of those sides... (those would be pure TNS or TNCS)


Whats your opinions ?!


Thanks in advance!!


Parents
  • 0
    The contractor suggested me to ground the neutral only at the main circuit breaker, and not at both sides

    I think it's usual to earth the N at just one point - as that tends to produce better EMI results as there's less current flowing unbalances around random metalwork or soil. In the UK it also avoid legal complications of a "consumer" having a combined neutral and earth conductor in their installation.


    Whether N is earthed at the transformer or switchboard end tends to vary depending on the circumstances. With one one consumer DNOs tend to favour earthing the N at the consumer's end (PNB) as that reduces the potential difference between N and PE for the consumer. Clearly where the HV and LV earths have to be kept separate it's likely to be convenient to earth the LV N away from the transformer, if they're combined it might well be easier to earth everything together at the transformer.


      - Andy.
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  • 0
    The contractor suggested me to ground the neutral only at the main circuit breaker, and not at both sides

    I think it's usual to earth the N at just one point - as that tends to produce better EMI results as there's less current flowing unbalances around random metalwork or soil. In the UK it also avoid legal complications of a "consumer" having a combined neutral and earth conductor in their installation.


    Whether N is earthed at the transformer or switchboard end tends to vary depending on the circumstances. With one one consumer DNOs tend to favour earthing the N at the consumer's end (PNB) as that reduces the potential difference between N and PE for the consumer. Clearly where the HV and LV earths have to be kept separate it's likely to be convenient to earth the LV N away from the transformer, if they're combined it might well be easier to earth everything together at the transformer.


      - Andy.
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