This paper deals with a review of the state-of-the-art performance investigations of green gas for grid (g3) gas, which is an emerging eco-friendly alternative insulation gas for sulfur hexafluoride (SF6) that will be used in gas-insulated power facilities for reducing environmental concerns. The required physical and chemical properties of insulation gas for high-voltage applications are discussed, including dielectric strength, arc-quenching capability, heat dissipation, boiling point, vapor pressure, compatibility, and environmental and safety requirements. Current studies and results on AC, DC, and lightning impulse breakdown voltage, as well as the partial discharge of g3 gas, are provided, which indicate an equivalent dielectric strength of g3 gas with SF6 after a proper design change or an increase in gas pressure. The switching bus-transfer current test, temperature rise test, and liquefaction temperature calculation also verify the possibility of replacing SF6 with g3 gas. In addition, the use of g3 gas significantly reduces theabovementioned environmental concerns in terms of global warming potential and atmosphere lifetime. In recent years, g3 gas-insulated power facilities, including switchgear, transmission line, circuit breaker, and transformer, have been commercially available in the electric power industry.

This paper dealt with characteristics of partial discharge (PD) initiated by metallic particles under DC voltage in green gas for grid (g3), which is an emerging and promising eco-friendly alternative insulation gas to SF6. Experimental setup was configured to simulate PD under DC in gas-insulated power facilities. Two types of particle, namely rectangle particle and sphere particle were used. The results indicated that the discharge inception voltages in g3 gas were 90.1-92.5% of that in SF6. In two particles, PD occurred with higher average apparent charge and discharge repetition rate in g3 compared with those in SF6 gas. The time-resolved partial discharge presented similar characteristics in g3 and SF6 gas. The time interval between two successive discharge pulses were 0.1 ms-10 ms and 5 ms-15 ms in the rectangle particle and sphere particle, respectively. Results from this paper are expected to provide fundamental material for the development of SF6 -free gas-insulated power apparatus.

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Compared with conventional methods for insulation performance evaluation of power cables, the oscillating wave test system used in partial discharge measurement for power cables has advantages of high integrity, easy operation, low power consumption, and compact size in addition, partial discharge, defect localization, and dielectric loss can be measured simultaneously without any damage to cable insulation. Therefore, the oscillating wave test system has been widely applied for insulation performance evaluation of newly installed as well as fault power cables. However, there is no study so far on the verification method of oscillating wave test system. This paper dealt with the application and verification for cable partial discharge measurement devices based on oscillating wave voltage, which is aimed to verify performances of oscillating wave voltage generator, partial discharge measurement, and partial discharge localization. The proposed verification system is expected to be applied in the admittance testing and regular verification of oscillating wave test system, for the purpose of improving the its accuracy and standardization in partial discharge measurement of power cable.