Test GIS Circuit Breakers Without Lifting a Ground
Timing and contact resistance measurement with both sides grounded, using the DV Power CAT500 and GIS Test Module.
The problem with conventional GIS breaker testing
In a gas-insulated substation, the breaker's main circuit terminals sit inside a grounded metal enclosure filled with SF6. You cannot clamp onto them the way you would on an air-insulated breaker.
The conventional workaround is to disconnect the ground on one side of the breaker before testing. That removes the parallel path through the enclosure and grounding system that would otherwise distort the measurement. It also removes a safety ground from an energized substation environment, adds setup and teardown time, and makes GIS maintenance slower and more complicated than it needs to be.
The Both Sides Grounded (BSG) method
DV Power developed the BSG method for GIS to eliminate that step. Both grounds stay connected for the entire test.
The method injects high DC current through the parallel connection of the main circuit and the grounding path. The GIS Test Module carries three battery-based current sources, each capable of 400 A DC, connected to the breaker's test terminals at the enclosure.
DC current probes on the GIS test terminals for per-phase contact resistance measurement.
For timing, AC current probes record the response signal on the current transformer secondary during breaker operation (applicable for CT taps with turns ratio up to 1000, with the measuring core preferred). Where the CT secondary is not usable, the response is recorded through the primary circuit at the test terminals instead.
For contact resistance, the instrument uses the Kelvin four-point method with an automatic two-step sequence: it measures the grounding path resistance with the breaker open, measures the parallel resistance with the breaker closed, and calculates the true main circuit resistance from the two. On three-pole controlled breakers, DC current probes at the test terminals give you each phase separately.
No ground removal. No setup modifications. Results you can trend against your existing records.
What you need
The BSG feature for GIS runs on the DV Power CAT500 circuit breaker analyzer working together with the GIS Test Module. If you already own a CAT500, adding GIS capability is a module, not a new instrument.
Who this is for
Utilities, NETA testing firms, and industrial plants that maintain GIS assets. If your crews are removing grounds to get timing or micro-ohm readings on GIS breakers, this method takes that step off the procedure and gives the time back to the outage window.
Get the full application note
DV Power's application note covers cable and probe connections, CT secondary versus primary measurement, per-phase resistance on three-pole breakers, and the CAT500 setup screens step by step.
Talk to ProgUSA
ProgUSA has supplied test equipment to utilities and NETA firms for more than 20 years, and we have supported DV Power instruments in the field across the U.S. If you want to see the BSG method on your GIS gear, or you want a CAT500 and GIS Test Module configuration matched to your fleet, contact us. We will walk you through the setup, the training, and the quote.
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