As maintenance periodicity extends from monthly to quarterly to half-yearly, the checks become progressively deeper and more instrumented — moving from visual/hand checks to precision measurement with proper test equipment.
Quarterly Maintenance
Batteries — Full Individual Cell Check
- Unlike the fortnightly check (pilot cell only), quarterly maintenance requires taking specific gravity AND cell voltage of EVERY INDIVIDUAL CELL, entered in the register.
- If the battery isn't fully charged, boost charging and increased trickle rate should be applied — but ONLY by a supervisory official, and only AFTER investigating the cause of excessive discharge, not as a routine top-up.
PTs, CTs & Auxiliary Transformers
- PTs and CTs follow lines similar to traction transformer maintenance, except items that don't apply. For PTs specifically, also check the fuse holders on the LV side.
- Auxiliary transformers: measure winding insulation resistance with recorded temperature; test an oil sample for BDV.
Exam Focus — The Spring-Latch Fuse Test
A real, specific check for auxiliary transformers: confirm the 25kV fuse-holder drops out FREELY on raising the spring latch, check rod gap setting, and measure earth resistance of the neutral conductor — three genuinely distinct checks bundled into one quarterly item, not a single generic 'check the fuse' task.
Annual maintenance and periodical overhaul for these items follow generally the same lines as for the traction transformers themselves.
Half-Yearly Maintenance
SSE(PSI) should personally visit the grid sub-station to ascertain whether any significant change has occurred (or is expected shortly) in the EHV grid network — directly connecting to the earlier PSI Fundamentals chapter's point about needing fresh voltage readings and possible tap re-adjustment whenever grid inter-connections change.
Traction Transformers — Half-Yearly Depth
- Test an oil sample from the TANK BOTTOM specifically for crackle test, acidity, and BDV. If BDV is below the prescribed value, the oil must be dried out.
- Check rod-gap settings on bushings against the Maker's drawings.
- Measure and record insulation resistance of ALL windings to earth and to each other, using a 2500V MEGGER, along with winding temperature and ambient temperature.
- Check all alarm and trip devices for proper functioning.
Isolators — Half-Yearly Depth
- Observe for overheating signs, check contact-blade wipe. Clean blade tips and fixed-contact fingers, lightly apply Vaseline to contact-making surfaces — the same Vaseline principle used elsewhere for connector maintenance.
- Clean all articulated joints, sliding and bearing surfaces thoroughly. Check split pins, lock nuts, check nuts for proper condition.
- Check correct setting/alignment of arcing horns.
- Operate the isolator SLOWLY, checking simultaneous blade operation across poles and correct blade-tip alignment in the fixed contact jaws — adjust to ensure blades are FULLY HOME between contacts when the handle is closed.
- Check locking arrangements.