Connecting Two power system platforms with different grounding systems

[mj1980]

What are the problems with connecting two different power systems utilizing different grounding systems.
for example, one platform is delta/delta ungrounded and the second platform is delta/ wye with high resistance grounding. What would happen if a fault occurs?
What would happen if a fault occurs on the MCCs/switchgear?
What is the worst case scenario? Could it be done?
Any information would be of great help, thank you.

 

[jghrist]

If the primary of the delta-delta and the delta-wye transformers are the same system, then the secondaries will be out of phase and cannot be connected.

 

[slavag]

if, if!!!, you can connect two different system ( see again post of jghrist)and fault level is less than maximum for busbars, it will be no problem, but:
Need a very good protection scheme evaluation, maube with two sets of settings, etc...

 

[Bramb]

Hi,
as Slavag is saying:
- protection systems for grounded star point networks can be based on zero sequence current measurements
- in case of ungrounded star point networks, protection systems will be probably based on zero sequence voltage measurements (it depends by the lines type and length)

It means that probably the protection system you have on your first (delta/delta) system is not suitable to clear earth faults when fed by your second system (delta/wye high R earthed) and viceversa.

Ciao
Erminio

The difference between overload and short circuit lies in the nature of the fault, not in the value of the current.