Contact Erosion at High Currents in High-Voltage Gas Circuit Breakers—Part II: Assessment of Energy Balance of Arc-Electrode

In high-voltage gas circuit breakers, arc-electrode interaction plays an important role during current interruption. The energy exchanges of arc-electrode not only influence the arc energy balance but also induce irreversible electrode erosion. To estimate the non-negligible amount of energy provided by the arc column through radiation, parameters related to the arc erosion should be fully used, including the area of molten pool, the thickness of molten layer, the effective voltage drop, etc. Under the free-burning conditions with a peak current of 40 kA and an arcing duration of 10 ms, the energy radiated from the CO₂ arc to the electrode surface accounts for 42.5% to 50.5% of the total energy absorbed by the contact material, which is higher than that of SF₆ (34.5%–44.3%). The equivalent voltage drop is defined for the energy transferred from arc column to electrode surface through radiation. It has been found that the equivalent voltage drop of the anode by arc radiation is from 7.7 V to 10.6 V in CO₂, and the range is 5.4–8.1 V in SF₆. These parameters can be utilized to accurately predict the mass loss of Cu-W contacts in gas circuit breakers following high-current interruption tests.