Abstract: A transformer fault analyzer provides on site fault analysis of electrical distribution transformers, relying on patterns of parameter variation in transformer winding ratios, winding resistance and magnetizing impedance, and comparison of these parameters to predetermined values. In a preferred embodiment the analysis considers transformer ratio balance and magnetizing impedance balance. The transformer analyzer may be used with the transformer under load or no load conditions, and thus can be used to test transformers in the field as well as surplus or refurbished transformers.

Abstract: A protective device for use with a surge arrester to prevent fracturing of the porcelain body of a failed arrester includes a fast-operating switch which shunts a current-limiting fuse. The switch is operated by ignition of a chemical propellant charge, thereby rapidly diverting fault current to the fuse and additionally isolating the arrester from ground. The switch has a moving contact in the form of a gas-driven piston which strikes a separable terminal connected to a ground lead.