Same 87T for 2 transformer not paralleled 1

[odlanor]

the transformer auxiliary service of a hydroelectric power plant 13.8/0.44kV-3.5MVA, Delta / star grounded was protected by a 87 as main protection. Later was added another transformer 13.8/13.8kV-6.5MVA, Delta / star grounded using the same 87.
13.8kV delta sides are connected at same source power.Star grounded sides are connected at separated loads. All CTs were appropriate ratio.
What would be the recommendations for 87 operate correctly?

 

[rasevskii]

There should be a separate 87T for each transformer, in principle, that trips the HV and LV breakers for its own transformer only and not the other one. This assumes that there is actually a breaker on the HV side of each transformer that can be tripped. If you have fuses only on he HV side or only one breaker for both transformers, then this will not work.

rasevskii

 

[odlanor]

I have breaker at each terminal of transformer.
I was worrying about inrush. I guess to energize transformers sequentially with a little delay. Will be this necessary?

 

[inpran]

odlanor,

If yours is a numerical relay, the second energisation, ergo the inrush current that follows the second energisation should be restrained by the internal algorithm of the differential function block in the relay. So, even if you energise the two transformers sequentially, it shouldn't be a problem.