Part 2: Equipment-level inspection and operation and maintenance SOP of the high-voltage transformation, distribution and boost system on the energy storage side of the photovoltaic power station
This article corresponds to the panoramic topology diagram of the energy storage power station [Module 2: High-voltage transformation, distribution and boost system], covering 10kV/35kV high-voltage switch cabinet, step-up box-type transformer (box-type transformer), high-voltage busbar/cable head and station main grounding grid.
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 and protecting the AC high-voltage main circuit of the entire station.
(1) SF6 air pressure and vacuum circuit breaker inspection
SF6 gas pressure gauge: Check the switchgear gas pressure gauge. 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), forced opening and closing operations are strictly prohibited!
Vacuum circuit breaker and spring energy storage: Check that the opening/closing position indicator light and mechanical indicator plate are correct; confirm that the spring energy storage status displays "Stored".
Contact synchronicity: During a power outage for maintenance, use a switching characteristic tester to measure the three-phase closing non-synchrony of the vacuum circuit breaker, which must be < 1.0 ms.
(2) Handcart position, mechanical five-proof locking and live display
Handcart position: Confirm that the circuit breaker handcart is in the "working position" or "test position" and the secondary overload 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 the cabinet door are mechanically locked and cannot be forcibly opened.
Charged indicator: The L1, L2, and L3 indicators of the high-voltage charged indicator light up normally and there is no missing phase.
2. Maintenance SOP for step-up box-type transformer (box-type transformer)
The box-type transformer steps up the low-voltage AC power (such as 690V) output by the PCS to 10kV or 35kV and integrates it into the grid. Divided into oil-immersed transformers and dry-type transformers.
(1) Inspection specifications for oil-immersed box-type transformers
Oil level gauge and oil color inspection: 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 has been carbonized, and a sample must be taken for oil dissolved gas analysis (DGA).
Respirator (moisture absorber) silica gel inspection: Check that there is oil in the sealing 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; 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 ℃; when the temperature ≥ 100 ℃, the forced air cooling fan starts automatically; when the temperature ≥ 130 ℃, an over-temperature alarm is triggered; when it reaches 150 ℃, a trip is triggered.
3. Maintenance of 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 temperature of bushings and terminal blocks must be < 70 ℃, 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. If the discharge pulse frequency is detected and increases significantly (partial discharge value > 20 pC) or obvious corona discharge sound is heard, it indicates that there is a defect in the internal insulation, and a power outage withstand voltage test needs to be arranged.
(2) Inspection of zinc oxide high-voltage arrester (SPD): Check that the porcelain sleeve/composite insulation sleeve of the arrester is not damaged and flashover: record the readings of the arrester leakage current meter and lightning action counter. Continuous leakage current values should be within the normal range (typically < 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 bonding test
Ground grid resistance test (annual):
Testing tool: Large ground resistance tester (different frequency method).
Standard: The power frequency grounding resistance of the main grounding network of the power station must be < 0.5 Ω. In areas with high soil resistivity (such as Gobi and mountainous areas), the maximum value shall not exceed 5.0 Ω, and an equipotential bonding network must be equipped.
Grounding overlap and corrosion inspection: Check the overlap of the flat steel (or copper cable) between the booster transformer casing, the base of the high-voltage cabinet, the arrester grounding terminal and the main grounding grid. 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 specification must be repaired (double-sided welding, the welding length must be ≥ 2 times the width of the flat steel).
Photovoltaic power station energy storage side high-voltage transformation and distribution system on-site inspection sign-in form
Power station name: _______________________________ Inspection date: ____ month ____ day, 2026
Inspection area: high-voltage switch room and booster box area Inspection person in charge: ____________________
1. On-site equipment inspection and testing actual data records:
2. 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