An Accident Analysis of Longitudinal Differential Protection Fiber Channel Interruption Because of a Substation Short-line

This article analyzes the reason why 8 fiber channels of two 220 kV lines interrupted at the same time because of a single phase-to-earth fault near the substation. For this improving the secondary grounding grid in communication room is mentioned.Then in following emergency control and restoration all ground points were made into an equal potential bonding and grounded at one point.The power grid operation reliability is improved.