Part 5: Equipment-level inspection and operation and maintenance SOP of the high-voltage transformation, distribution and booster station system on the PV side of the photovoltaic power station
This article corresponds to the panoramic topology diagram of the photovoltaic power station [Module 5: High-voltage Transformer, Distribution and Booster Station System], which is the final channel for high-voltage boost and grid connection of the power station, covering 10kV/35kV high-voltage switch cabinet, local step-up box-type transformer (box transformer), high-voltage cable head infrared temperature measurement and partial discharge (PD) detection, zinc oxide high-voltage arrester (SPD) and maintenance of the main grounding network for the station.
1. 10kV / 35kV high-voltage switchgear maintenance and inspection SOP
The high-voltage switch cabinet (SF6 ring main unit or central vacuum switch cabinet) is responsible for controlling, protecting and isolating the 35kV / 10kV high-voltage AC main circuit of the entire station.
(1) SF6 gas pressure and air tightness inspection
SF6 gas pressure gauge inspection: Check the switch cabinet SF6 gas pressure gauge pointer. The air pressure must be in the green qualified area (usually 0.35 ~ 0.45 MPa). If the pointer drops to the red zone (low voltage lockout), it is strictly forbidden to force the opening and closing operations. Nitrogen/gas must be filled and the leakage point must be checked.
Air tightness check: Use a portable SF6 gas leak detector close to the welding seam of the switch cabinet gas chamber and the gas valve pipeline. The detection rate of air leakage must be < 1%/year.
(2) Vacuum circuit breaker, energy storage mechanism and three-phase asynchronous
Circuit breaker position and energy storage status: Confirm that the opening/closing position indicator light and mechanical mark are correct; check that the energy storage time of the electric energy storage mechanism is < 10s, and the sign shows "Storeed".
Three-phase closing asynchronous test: During power outage and overhaul, use a switching characteristic tester to measure the three-phase closing asynchronous test of the vacuum circuit breaker, which must be < 1.0 ms; the closing bounce time must be < 2.0 ms.
(3) Handcart position, mechanical five-proof locking and live display
Handcart position and heavy-duty plug: Check that the circuit breaker handcart is in the "working position" or "test position", the handcart locking pin is in place, and the secondary heavy-load plug is locked firmly.
Mechanical five-proof locking verification: Confirm that when the circuit breaker is in the closed state, the grounding knife switch and cabinet door are mechanically locked and cannot be forcibly opened.
High-voltage live indicator: The three-phase indicators L1, L2, and L3 of the high-voltage live indicator light up normally, and there is no missing phase on the high-voltage side.
2. Maintenance SOP for on-site step-up box-type transformer (box-type transformer)
The box-type transformer steps up the low-voltage AC power (such as 800V) output by the inverter to 10kV or 35kV and then sends it to the high-voltage switch station. Divided into oil-immersed transformers and dry-type transformers.
(1) Inspection specifications for oil-immersed box-type transformers
Oil level gauge and oil color check:
Observe the indication of the oil level gauge. The oil level must be between the scale lines corresponding to the ambient temperature (such as the 25°C scale line).
The transformer oil must be transparent and light yellow in color. If the oil is black, dark or turbid, it means that partial discharge has occurred internally or the insulating oil is carbonized, and a sample must be taken for oil dissolved gas analysis (DGA chromatography analysis).
Respirator (moisture absorber) silicone inspection:
Check that there is oil in the sealed oil cup at the bottom of the moisture absorber, and the discolored silica gel particles in the tank are dark blue. If > 2/3 of the silica gel turns pink or white, it means that the silica gel is saturated with moisture and must be replaced with dry silica gel immediately.
Casing and leakage inspection: Check that the high and low voltage porcelain casings have no cracks or traces of discharge; check that there is no oil leakage in the box radiator and high-pressure valves.
(2) Inspection specifications for dry box-type transformers
Winding temperature control: Check the three-phase winding temperature of the temperature controller. Under natural air cooling, the winding temperature must be < 90.0 ℃; when the temperature ≥ 100.0 ℃, the forced air cooling fan starts automatically; when the temperature ≥ 130.0 ℃, an over-temperature alarm is triggered; when it reaches 150.0 ℃, a trip is triggered.
3. Maintenance SOP for high-voltage busbars, cable heads and high-voltage lightning arresters (SPD)
(1) Infrared temperature measurement and partial discharge (PD) detection of high-voltage cable heads
Infrared thermal imaging temperature measurement: When the power station is running at full power, infrared temperature measurement is performed on the intermediate head and terminal head of the 35kV cable. The maximum temperature of the bushing and terminal block must be < 70.0 ℃, and the temperature difference between phases ΔT ≤ 5.0 ℃.
Ultrasonic partial discharge (PD) detection: Use a portable partial discharge tester close to the high-voltage cable head and switch cabinet busbar. The partial discharge pulse must be <20 pC, and there should be no obvious high-frequency corona discharge sound. If the partial discharge value is > 50 pC, a power outage withstand voltage test and a redo of the cable head must be arranged.
(2) Maintenance of zinc oxide high-voltage arrester (SPD)
Appearance and counter records: Check that the porcelain sleeve/composite insulation sleeve of the lightning arrester is free of damage and flashover; record the lightning strike action counter reading.
Continuous leakage current test: Use a leakage current tester to measure, the continuous leakage current of the arrester must be < 1.0 mA. If the leakage current exceeds the standard, it means that the valve plate is old and damp, and must be replaced after a power outage.
4. Station main grounding grid and equipotential grounding test SOP
Grounding network power frequency resistance test (annual):
Testing tools: Large-scale multi-frequency ground resistance tester.
Standard: The power frequency grounding resistance of the main grounding network of the power station must be < 4.0 Ω (large booster stations/high-salt areas must be < 1.0 Ω).
SOP for anti-corrosion repair welding of ground lap and flat steel:
Check that the flat steel (or copper cable) overlap between the booster transformer casing, high-voltage cabinet base, arrester grounding terminal and main grounding grid is not loose.
Check for corrosion 0.5 meters underground on the grounded flat steel. If the cross-section corrosion rate is >30%, galvanized flat steel of the same specifications must be repaired (the length of double-sided lap welding must be ≥ 2 times the width of the flat steel), and the welds must be repaired with anti-corrosion asphalt paint.
Equipment-level inspection and operation and maintenance sign-in form for the high-voltage transformation, distribution and booster station system on the PV side of the photovoltaic power station
Power station name: _______________________________ Inspection date: ____ month ____ day, 2026
Inspection area: high-voltage switch room and booster box area Inspection person in charge: ____________________
Field equipment inspection and test data recording
Inspection defect registration and defect elimination dispatch
3. Inspection sign-in and review signature
Inspection Engineer (Signature): _______________ Supervision Engineer (Signature): _______________
Review (signature) of the shift leader: _______________ Sign-in and filing time: ____ hour on ____ month ____ day 2026