Yearly maintenance is the deepest, most instrumented level in the PSI maintenance hierarchy — moving from visual checks to laboratory-grade tests (dissolved gas analysis, capacitance/tan delta, precision resistance measurement).
General — Real, Specific Tasks
Memory Aid — The Insect-Proofing Detail
A genuinely memorable, real instruction: open all trench covers, clean culverts, remove cobwebs, and specifically check the possibility of LIZARDS or other insects gaining entry into enclosed control equipment — making them insect-proof. This isn't a generic 'keep clean' instruction; it names a specific real-world failure mode (small animals entering control cabinets) that's easy to overlook.
- Inspect the fence all-round the sub-station, and between metal fencing panels and earth. Oil the hinges of all doors.
- Thermography of ALL equipment along with busbars to detect hot spots, if any — a full annual thermal-imaging sweep, connecting to the Thermo Vision Camera chapter covered earlier for OHE.
Lightning Arresters
- Check earthing terminals/strips condition and connection to the line.
- Where discharge counters are fitted, record the counter reading — tracking how many times the arrester has actually operated.
- Check the LA for THRC (Thermal Runaway Characteristic) testing.
Bonding & Earthing — Annual Depth
Exam Focus — Testing Each Earth Electrode Group SEPARATELY
The real technique: check and record the resistance of EACH GROUP of earth electrodes AFTER DISCONNECTING IT from the common earth system — not measuring the whole combined system at once. This isolates any one weak electrode group that a combined-system reading would otherwise mask.
- Check physical soundness of bonding/earthing connections to EVERY electrical equipment, steel structure, lightning arrester, AND inter-panel connections.
- Record earth resistance to the body of electrical equipment AND to all parts of the fencing and structural steel work.
- Check that overhead shield-wire terminations covering the whole sub-station are in good physical condition and properly bonded electrically to structures.
- Check condition of connections to the buried rails.
Traction Transformers — Annual Lab-Grade Tests
- Send oil samples to an APPROVED LABORATORY for all tests listed at Annexure 3.03B (IS 1866) — INCLUDING Dissolved Gas Analysis (DGA), the same technique covered in the earlier Transformer Condition Monitoring content.
- Move the tap-setting switch up and down the FULL RANGE a few times — this self-wiping action ensures good contact. Finally set the tap at the correct position, confirming tap-indication matches the actual main-contact position.
- Check capacitance and tan delta of bushings — a real, specific insulation-health test beyond simple resistance measurement.
- Check and record IR (insulation resistance) values of winding.
Isolators — Annual Precision Work
- Smoothen burrs on blade tips/fixed contact fingers with FINE EMERY PAPER, then smear Vaseline.
- Measure/record blade clearance in open position, adjust the crank mechanism if necessary.
- Check adjustable stop set-screws for condition and correct positioning.
- For motor-operated isolators: measure/record insulation resistance of motor windings and contactor coils using a 500V MEGGER.
- Check interlocking of isolators for normal working.
Exam Focus — The Ductor Test for Busbars
Busbar/connector contact resistance is measured using a 'Ductor' or other LOW-RESISTANCE measuring instrument — a genuinely different tool category from the monthly feel-by-hand check or the 500V/2500V Meggers used for insulation resistance elsewhere. This is precision contact-resistance measurement, not insulation testing.