SF6 Circuit Breaker Maintenance Schedule — Traction Distribution Notes

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SF6 circuit breakers get their OWN dedicated, genuinely granular maintenance schedule — 6 distinct periodicities (fortnightly, quarterly, annually, 3-yearly, 8-yearly, 10-yearly), far more layered than the general equipment schedule covered in earlier chapters. Before any switchgear maintenance begins, the manufacturer's instruction manual must be fully studied — proceeding without this knowledge risks both equipment performance and personnel safety.

Fortnightly Schedule

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Exam Focus — The Real 5.5 kg/cm² Minimum

Gas pressure must be measured and recorded, and should NOT be less than 5.5 kg/cm² — a real, specific minimum threshold worth memorizing precisely.

Drain water from the reservoir, and drain air from the air reservoir separately.
Measure and record gas pressure, air pressure, and temperature.
Check indicator position correctness, and foundation bolt looseness.

Quarterly Schedule — Real Numbered Checklist

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Exam Focus — Torque Wrench Is Mandatory, Not Optional

Both terminal connector fasteners AND pole fasteners must be tightened to specified torque using a TORQUE WRENCH ONLY — an ordinary spanner isn't an acceptable substitute, since over/under-tightening either connection has real consequences for contact integrity.

Check/clean porcelain insulator surfaces. Check earth connection for the supporting structure and operating mechanism.
Remove dust, clean internal wiring/components. Check functioning of: Local/Remote switch, ON/OFF switch, Anti-Pumping Device (for CB only), Interlock, and gas-pressure-switch settings per the individual switchgear make's graph.
Check the Operation Counter and note the number of operations — a real quarterly tracking figure feeding into the longer-term overhaul thresholds below.
Ensure proper functioning of: ON/OFF indicator, spring charging indicator, limit switch of spring charging motor, auxiliary switch.
Check space heater connection/operation, all LT wiring tightness, trip circuit healthiness, and control/motor circuit terminal voltage — if voltage isn't within permissible variation, check the battery and battery charger for health.
Pneumatic/spring mechanism items: pressure switch settings, normal/max/minimum/trip/lockout pressures, valve operation, air-reservoir drain valve operation, air leakage checks, compressor crankcase oil level, and compressor suction filter cleaning.

Annual Schedule

Check water seepage from pole joints of housing and the top cover of the operating mechanism.
Check door gasket intactness.
Check trip and closing coil resistance, comparing values against the manufacturer's DESIGN VALUES in the manual — not just checking for continuity.

Overhauling of Switchgear — The Real 4-Condition Trigger

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Exam Focus — ANY ONE Condition Triggers Overhaul

Overhauling is triggered when ANY ONE of these 4 conditions is met — not all four together: (a) circuit breaker has completed 10 years of service, (b) electrical switching operations exceed 3000, (c) mechanical operations exceed 6000, (d) the breaker has completed 20 full short-circuit tripping operations. Note mechanical operations (6000) are DOUBLE the electrical operations threshold (3000) — a real, specific ratio worth remembering rather than two arbitrary numbers.

Overhauling must be carried out by trained persons as per the manufacturer's instruction manual — not generic maintenance staff.

Pre-Monsoon Checks

Before monsoon onset, confirm NO scheduled maintenance is overdue for any equipment. In the inspection immediately preceding monsoon, pay special attention to points vulnerable to moisture ingress — since moisture reduces dielectric strength and causes rusting — and ensure heaters are working.

Overhaul Schedule — Real Equipment-Specific Periods

Equipment	Overhaul Trigger
Transformers	In case of internal fault, OR once in 7-10 years
Circuit Breaker/Interrupter Operating Mechanism	Once in 10 years, OR whenever a major part (e.g. springs) needs replacement, OR mechanism becomes sluggish and needs shop attention