A transmission utility's experience to date with transformer protection systems

This paper investigates a number of design, operation and lifetime management experiences of transformer protection systems installed on National Grid Electricity Transmission (NGET) networks. The paper will consider the policy, application design and operational experiences under the following categories particularly since the move to numeric protection: Policy and application design Operational experience to date A bespoke transformer protection scheme solution Maintenance and post commissioning support Examples of protection mal-operations during transformer energisation are discussed in the paper. A bespoke transformer overall protection scheme is presented for application of the scheme on a transformer banked with a long cable circuit (> 5km).