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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
  • The answer is that both are done, but in different circumstances. Also I'm far from expert on this, so wait for other to chip in. There are some questions that will help clarify the situation.


    1) Is this in the UK? - if not the answer may change - here there are special rules about multiply earthed neutrals and other countries may do different things with HV side earths and fault detection.


    2) How is the HV earthing to be sorted ?

    If the site is "cold" (DNO may be needed to advise on characteristics of the HV side to determine this) then the HV earth -i.e. the transformer core and tank, and the LV earth i.e. the star point of the transformer and your PEN, may share earthing arrangements, and indeed if it is possible, then  it  is preferable if they do.

    If the site is "hot" - that is to say a credible HV fault current could provide enough current to raise the HV earth to a dangerous voltage, then the HV and LV earths must be separated systems, and must not be co-located,

    If the LV earth needs to be remote from the HV one where is it best physically?


    How far apart are the TX and the building with the breakers an so on?


    Mike.


    Mike.

Reply
  • The answer is that both are done, but in different circumstances. Also I'm far from expert on this, so wait for other to chip in. There are some questions that will help clarify the situation.


    1) Is this in the UK? - if not the answer may change - here there are special rules about multiply earthed neutrals and other countries may do different things with HV side earths and fault detection.


    2) How is the HV earthing to be sorted ?

    If the site is "cold" (DNO may be needed to advise on characteristics of the HV side to determine this) then the HV earth -i.e. the transformer core and tank, and the LV earth i.e. the star point of the transformer and your PEN, may share earthing arrangements, and indeed if it is possible, then  it  is preferable if they do.

    If the site is "hot" - that is to say a credible HV fault current could provide enough current to raise the HV earth to a dangerous voltage, then the HV and LV earths must be separated systems, and must not be co-located,

    If the LV earth needs to be remote from the HV one where is it best physically?


    How far apart are the TX and the building with the breakers an so on?


    Mike.


    Mike.

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