Energising without a structured review raises the risk of equipment damage, long production outages and danger to personnel. This checklist summarises typical commissioning stages for medium- and high-voltage substations. The final list for each project should follow the client's standards, manufacturers' instructions and the operator's regulations.
1. Documents and drawings
- Match the as-built drawings with the actual installation, including single-line, control and terminal drawings
- Review the short-circuit and protection coordination studies and obtain the approved relay settings
- Review factory acceptance test (FAT) reports and type-test certificates
- Complete installation records: bolt torque, alignment and clearances
2. Visual and mechanical inspection
- Equipment condition, cleanliness and absence of transport damage
- Torque check of busbar and cable connections
- SF6 gas pressure in GIS and gas breakers, oil levels in transformers and bushings
- Labelling, circuit identification and safety signs
3. Earthing system
- Measure the substation earth resistance and check step and touch voltages
- Verify continuity of equipment, panel and structure bonding to the earth grid
4. Equipment tests
- Cables: megger test and, where required, VLF, partial discharge and sheath tests
- Busbars and switchgear: insulation test and contact-resistance (micro-ohm) test
- Transformers: turns ratio, winding resistance, megger, tan delta, oil tests, polarity and vector group
- CTs and VTs: ratio, polarity, excitation curve, burden
- Breakers and disconnectors: open/close times, pole synchronism, contact resistance, motor and spring operation
- Surge arresters and lightning-protection equipment
5. Relays, protection and control circuits
- Secondary injection of all enabled functions and comparison with approved settings
- Trip circuit tests, trip circuit supervision (TCS), breaker failure and trip matrix
- Signals, alarms, and control and mechanical interlocks
- Primary injection to verify CTs and directionality, where required
6. Auxiliary systems
- Battery bank and DC charger: capacity, charge voltage, discharge test and alarms
- AC auxiliary supply, emergency generator and automatic transfer switch (ATS)
- Emergency lighting, ventilation, fire suppression and detection
- Communications: network, fibre, telecom and time synchronisation
7. SCADA integration tests
- Point-to-point test of signals, measurements and commands from relay to control centre
- Sequence-of-events recording and time synchronisation tests
8. Functional and safety checks before energising
- Check interlocks and mechanical locks in all positions
- Work permit, tag removal and removal of temporary connections and temporary earths
- Clean the substation and remove tools and unrelated personnel
- Coordinate with dispatching and the operator and agree a staged energisation plan
9. Energisation and on-load verification
- Staged energisation: busbars first, then the transformer on no load, then gradual loading.
- Phasing test: confirm phase sequence and phase coincidence at synchronising points.
- Vector check: once on load, verify current and voltage direction and angle in relays (especially differential and directional) with real measurements.
- Monitor temperature (thermography), noise and vibration during the first hours.
- Record measured values and review alarms.
10. Handover documentation
- Signed test reports, final settings and configuration files
- As-built drawings and the operating manual
- Spare-parts list and maintenance recommendations
- Provisional handover minutes with a punch list and a plan to close it
Note: every stage must be signed off by the responsible person, and no step should start before the previous one is complete.