Periodic inspection items and cycle for neutral section insulators

Neutral section insulators operate at phase boundaries, so both insulation and mechanical condition must be verified:

• Check the level and the sliding surface; the pantograph must pass without impact or arc.
• Measure insulation resistance of each insulation slide and compare with the record.
• Inspect arc horns for erosion and replace when the wear limit is reached.
• Verify the clearances to the phase boundary and to adjacent live parts.
• Inspect the fittings and connections for looseness caused by vibration.

Recommended cycle: monthly visual inspection during the initial period of a new line, then quarterly; insulation test annually and after any flashover event.