BPA Energizes Upgraded 500 kV Series Capacitor Banks and 1,300 MVA Transformer at Slatt Substation

The Bonneville Power Administration (BPA) has completed commissioning of modernized 500 kV series capacitor platforms and a 1,300 MVA 500/230 kV autotransfor...

BPA Energizes Upgraded 500 kV Series Capacitor Banks and 1,300 MVA Transformer at Slatt Substation

The Bonneville Power Administration (BPA) has completed commissioning of modernized 500 kV series capacitor platforms and a 1,300 MVA 500/230 kV autotransformer bank at Slatt Substation in Oregon, reinforcing the Pacific AC Intertie by 600 MW.

Mitigating Transient Reactance on Long 500 kV Corridors

Slatt Substation is a vital switching hub along the Pacific AC Intertie, routing bulk federal hydropower from Columbia River dams toward California and intermountain load centers. The newly energized series capacitor banks provide 45% inductive compensation, slashing electrical impedance across the 500 kV transmission lines.

The upgrade incorporates state-of-the-art metal-oxide varistors (MOV), triggered spark gaps, and optical bypass switches engineered to ride through extreme 63 kA short-circuit fault currents without platform flashover.

Boosting Regional Transmission Transfer Capability

In tandem with the series capacitors, BPA commissioned a replacement 1,300 MVA 500/230 kV autotransformer bank featuring low-loss step-lap cores and fiber-optic winding hot-spot sensors.

The completed project increases southern transmission capacity by 600 MW, preventing severe voltage sagging during high summer transfer periods across the Western Interconnection.