Eskom Transmission recently awarded a contract to ACTOM High Voltage Equipment (HVE) to supply, install and test 550kV circuit breakers to replace 420kV units at Duvha power station in Emalahleni, Mpumalanga.
Partnering with Grid Solutions, a business unit of GE Renewable Energy, HVE tendered for the contract and was awarded it last year.
The contract stipulated the provision of five of GE Grid’s GL 317X 550kV 4000A 63kA SF6-insulated circuit breakers – one for each of the power station’s five operating generator units.
Eskom Transmission’s decision to have the original circuit breakers replaced by the higher-rated units is based on studies showing that the currently installed circuit breakers are underrated for future increase of continuous nominal current above 3150A and an increase in Dielectric withstand requirements close to the Generators. Eskom specification therefore requires for Transmission circuit breakers on 400kV generator unit bays to be rated one voltage level higher for increased insulation withstand to overcome potential transient and overvoltage issues.
The new GL 317X circuit breakers, the first 550kV units sold into the local market, were supplied from GE Grid’s factory in India and delivered to Eskom Transmission at the beginning of 2021. The first unit was installed at Duvha power station by HVE’s Field Services team in August this year.
“In accordance with the Eskom specification to meet the new nominal current requirement, the new high voltage circuit breakers will mitigate electrical failures from overvoltage that could occur when the Generator is being synchronised to the HV Transmission busbar, stressing the insulation of the open position HV Transmission generator unit breaker that connects the generator via the Generator transformers,” said Craig Aaron, HVE’s Senior Product Support Manager
