Paralleling power tf

[mhalarjani]

Hi every body


Hope find aswers for my inquiries

I have 2 power transformers
Each one 20 mva
Each one in separate grid station
And distrbution feeders 13.8 kv connected together from both of substations
When I paralleled both feeders trips occurred
Both feeders have same voltage
And hz
But transformers different vector group
Can any expert explain that .

Thanks advanced

 

[waross]

There is a lot of "It depends" here, but the different vector groups may have caused the phasing to be rotated 120 degrees.
It could be the equivalent of a three phase fault on both transformers.
The paralleling switch should be checked with a "Phasing Stick" before being closed.
There should be close to zero volts across the open poles of the switch before it is safe to close.
There may be some voltage present but it should be much less than the impedance voltage of the transformers.
Line to line voltage across an open pole is a bad indication.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[stevenal]

What are the two vector groups?
faq238-1154