①Daily operation and maintenance
1. DC lightning protection combiner box
The DC lightning protection combiner box shall be inspected regularly, and a safe distance from the live equipment shall be maintained during the inspection. Operation and maintenance personnel must bring a patrol inspection record manual and follow the on-site inspection route to prevent missing equipment. During the equipment patrol inspection, work methods such as watching, listening, sniffing, and touching should be carefully implemented to prevent missed inspections. The detected equipment defects and abnormalities should be recorded on the spot and carefully analyzed. Its daily maintenance work includes:
(1) Whether the signal indication is normal and whether the switch position is normal.
(2) Check the electrical components of the system for abnormalities such as overheating, peculiar smell, and disconnection.
(3) Clean the DC lightning protection combiner box regularly.
(4) Check the insulation of the equipment regularly. The insulation resistance of the positive pole to ground and the negative pole to ground of the DC output bus should be greater than 2MΩ.
(5) Analyze the health of the equipment regularly.
(6) The defects found in the operation of the equipment should be handled by maintenance personnel as soon as possible to prevent the expansion of the scope of the fault.
(7) Maintenance and debugging of automation components.
(8) The DC combiner box must not be deformed, rusted, leaked, or accumulated dust, and has a safety warning on the outer surface of the box.
2. AC combiner box
The daily maintenance of the AC combiner box mainly includes the following:
(1) Check whether the circuit breaker in the AC combiner box is operating normally and whether there is a flashover phenomenon to prevent the failure of the circuit breaker from affecting the AC input of the string inverter.
2) Check whether the wiring of the AC combiner box is firm and whether the bolts are loose.
3) Check whether the anti-arms protection in the AC combiner box is invalid, especially after lightning, check whether the lightning protection module is invalid in time.
(4) When replacing the components in the AC river box, first disconnect the branch pedal breaker in the box substation to which the AC river box belongs, and then disconnect the output circuit breaker and the equipped string inverter in the AC combiner box. The AC/DC conversion switch can be replaced only after the instrument detects that there is no voltage at the input and output terminals of all circuit breakers in the AC combiner box.
(5) When testing or maintaining the AC combiner box, note that the input and output may be live to prevent electric shock or damage to other equipment.
3. Combiner box inspection cycle
Periodic and meticulous point inspection and regular repair is one of the important measures to ensure the safe and stable operation of the combiner box. The length of the inspection period is directly related to the installed capacity of photovoltaic power plants and the number of equipment. Generally speaking, large-capacity power stations can be arranged for inspection in phases once a year. Power stations with a capacity of 50MW and below can be relatively flexible, generally once a quarter. The specific inspection items and cycles are shown in Table 1.
| Serial number | Check item | cycle |
| 1 | Cleaning and inspection of combiner box and its components | Once every quarter |
| 2 | Inspection, testing and operation simulation of signal same path and device | Once every quarter |
| 3 | Inspection of the mechanism and operation of various switch appliances | Once every quarter |
| 4 | Operating circuit check | Once every quarter |
| 5 | Cable appearance and connection inspection | Once every quarter |
②Operation specifications and precautions
1. DC combiner box
(1) Power transmission process.
1) The first step: Check and close the positive and negative DC fuses (see Figure 1).
A. Check the combiner box number, whether it is an operation number combiner box, and check whether the branch of the combiner box is open;
B. According to the system diagram in the DC combiner box, check whether the components and connection methods in the combiner box are correct;
C. Measure the voltage of all branches, and close the positive and negative fuses in turn if there is no grounding or abnormal conditions;
D. Check whether the voltage is normal and the communication is normal after all closed.
2) Step 2: Close the DC circuit breaker (see Figure 2)
A. Check whether the cable is reliably connected before closing;
B. Whether the DC circuit breaker is in good condition;
C. After closing, observe whether the combiner box is abnormal;
D. After closing, measure the DC current with a clamp ammeter, and observe whether the current display of the communication module is consistent with the measurement.
(2) Power failure process.
The power outage process of the combiner box is opposite to that of power transmission. First, disconnect the DC circuit breaker, and then disconnect the positive and negative fuses of the combiner box in turn. Before disconnecting, check whether the circuit breaker has any abnormal phenomena such as leakage, and check whether the combiner box has abnormal noise and odor; check the name of the device to avoid accidentally disconnecting the DC circuit breaker.
(3) Precautions for the stop and power transmission of the combiner box.
1) Protective equipment must be worn.
2) Prevent touching the DC busbar.
3) Pay attention to protect the fuse base to avoid damage to the base caused by excessive force.
4) Prevent touching the DC busbar; when disconnecting, pay attention to protect the fuse base to avoid damage to the base caused by excessive force.
2. AC combiner box
(1) Power transmission process (see Figure 3).
A. Check the number of the combiner box correctly;
B. Check whether the appearance of the AC combiner box is deformed, whether it is firmly fixed, whether there is abnormal noise, etc.;
C. Check whether the lead wire sag of the circuit breaker in the AC combiner box is moderate, whether the contact is good, and whether the phase sequence is correct;
D. Protective equipment must be worn during operation;
E. Check whether the opening and closing position indications of the circuit breaker in the AC river box are correct, close the main AC circuit breaker of the river box, and then turn on the branch circuit breakers in turn.
(2) Power failure process (see Figure 4 and Figure 5).
A. Check the number of the combiner box correctly;
B. Confirm that the inverters belonging to the branch of the combiner box have been shut down;
C. Turn off the AC input switches of each branch in turn.
A. Check that the AC output switch is intact before opening, and there is no discharge or abnormal conditions;
B. After disconnection, measure that the AC busbar is indeed without voltage, and disconnect the lightning protection module circuit breaker;
C. The cable at the lower end of the AC output switch is still live, so keep a safe distance from the live equipment;
D. After the operation is completed, lock the cabinet door.
