Buchholz Relay alarm Part 1

Once upon time the Main Transformer (Generator Transformer) 22.8 kV / 525 kV shown Buchhozl relay alarm, and then check actual at location that accumulation gas appear on sight glass of buchholz relay.



The accumulation gasses on the transformer means the oil as cooling, isolation and dielectric has degradation of oil quality. The accumulation gasses as H2, CH4, C2H2, C2H4, C2H6, CO and CO2 so long so high and the Unit load got alarm level light when the accumulation gasses reach 350 cm3 as picture below this ( Unit trip at heavy categorize on gasses level > 550cm3 ).

Operator try to make the Unit electric produce more longer by vent that gasses but combustible gasses accumulation so long reach the danger level, so that we reduce the Unit load until operator can control that accumulation gasses, but it was useless.

The Unit must shutdown, but after Unit de-synchronized, the gasses on transformer buchholz relay still appear, so we had to de-energize the transformer and do insulation test and internal inspection.


Power Main Transformer Specification.
Back-feed power source of supply at the plant starting up.
Step up of generated voltage to 525kV from generator output voltage 22.8kV.





Rated Power : 786 MVA at 65oC Winding Temperature

Unit Net Output at Turbine Maximum Continuous Rate = 671.6MW
Power Factor = 0.9
Transformer Capacity = (671.6MW / 0.9) = 746.2MVA

Generator Voltage variation 95% to 105%
Transformer shall be capable of operating at 746.2MVA under 95% of the generator voltage.

Hence Transformer Capacity = (746.2MVA / 95%) = 786MVA

to be continue to other specification of Power Main Transformer on Buchholz Realy Part 2.