single phase 3 wire transformer primary fault

[mvsubstation]

If one has an open conductor fault on a medium voltage single phase overhead circuit (phase to neutral), then have a question;

Is the fault current or voltage level different between the two scenarios below where the circuit above feeds a single phase transformer with a 120/240 volt 3 wire secondary?

1) Case 1; the center tapped secondary winding is connected to earth at the transformer pole

2) Case 2; the center tapped secondary winding is NOT connected to earth at the transformer pole​

 

[Mbrooke]

It depends on a lot of conditions. It depends if an MGN exist or the customer has metal water mains. Connecting the MV MGN to the customers neutral may increase fault current if metal water mains exist in the home since it will provide another path back to the substation.

If the center tap is earthed and not connected to the utilities neutral fault current will not cross over unless the MV phase drops into the LV 120/240 supply.


But a lot more detail is needed, in addition to the goals or concerns.

Hope this helps

 

[waross]

What do you mean by an open conductor fault? When a conductor fails open, the current can be expected to drop to zero.

Bill
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