A transmission utility's experience to date with feeder unit protection systems

This paper investigates a number of design, operation and lifetime management experiences of feeder unit protection systems installed on National Grid Electricity Transmission (NGET) UK networks. The paper will consider the policy, application design and operational experiences under the following categories in particular since the move to numeric protection: Policy and application design SDH communication networks Operational experience to date Maintenance and post commissioning support Application of future current differential protection Future IEC61850 application GPS synchronised feeder current differential protection has been installed on NGET UK networks since early 2000. This paper highlights a number of problems and solutions of this type of protection, particularly NGET's experiences in the performance of GPS receivers. Finally NGET's application policy for future installation of feeder unit protection is also discussed.