Application of intelligent flexible technology in neutral point protection of 110kV and 220kV transformers

Abstract

In this paper, the intelligent flexible technology was applied to the neutral point protection of 110kV and 220kV transformers, and a new protection measure for transformer neutral point was proposed. This measure was used by parallel connection of controllable gap and arrester. Under lightning over-voltage, the arrester acts, and under the power frequency over-voltage, the gap breaks down to protect the transformer neutral point insulation and arrester. It can effectively solve the problem that the arrester is easy to explode under power frequency over-voltage, the gap can’t extinguish arc under lightning and power frequency over-voltage impulse, and the insulation coordination between gap and arrester in parallel protection is difficult. 110kV and 220kV SF6 gas insulated metal enclosed transformer neutral point intelligent protection equipment was researched. The equipment from top to bottom are bushing, grounding switch, operating mechanism, current transformer, controllable gap, arrester, spring mechanism. The secondary control cabinet and the product share the under frame, which is convenient for operation and maintenance. The reliability of the intelligent protection equipment was verified by the design and calculation of controllable gap, shell design and internal arc fault calculation.