150 kV protection

[insinyur02]

can somebody explain function of 150 kV protection for generator.

situation: we have new steam turbine generator which is still under commissioning and it is parallel with other old turbines to 150 kV bus.

the problem: we can not go to 50 MW due to 150 kV protection failure and raised safety concern. what is the function of 150 kV? please describe in details.

Many thanks

 

[RRaghunath]

150kV is on secondary of the Generator step-up Trafo (GSUT).
The protection provided generally includes Overcurrent / earth fault protection for GSUT, 150kV Standby earth fault protection, Under impedance protection for uncleared grid faults.
The GSUT Differntial / REF protection, GSUT Buchholz and other trafo mounted protections are generally part of the Generator protection panel (not on 150kV protection panel).
In addition, breaker fail protection also is provided for 150kV CB.
None of the above protections on 150kV side can by themselves be restricting the loading of turbine. May be, the restriction is through operating instructions/practices.
Some times grid companies put restriction on the max load from the machine keeping in mind the impact that outage of such a source can have on the grid, if the 150kV grid in the area is weak (may be a temporarily) due to outage of some important feeders or other generators in the area.
If you let us know more about the protections provided on 150kV side for your plant and also the operating instructions / agreement details with grid company, we can have more fruitful discussion.