DC power system accident and fault handling plan

　　1. Battery failure and accident handling plan

　　(I) Acid-proof battery failure and treatment

　　1. If the internal plates of the acid-proof battery are short-circuited or open-circuited, the battery should be replaced.

　　2. For acid-proof batteries that are in floating charge mode for a long time, white lead sulfate crystals will gradually appear on the surface of the plates, which is usually called "sulfurization". Treatment method: withdraw the battery pack from operation, first use I10 current for constant current charging, when the single cell voltage rises to 2.5V, stop charging for 0.5h, then use 0.5 I10 current to charge until strong bubbles appear, then stop charging for 0.5h and continue charging until the electrolyte "boils"; when the single cell voltage rises to 2.7~2.8V, stop charging for 1~2h, then use I10 current for constant current discharge, when any single cell voltage drops to 1.8V, stop discharging, let it stand for 1~2h, then use the above charging procedure for charging and discharging, repeat several times, the lead sulfate crystals on the plates will disappear, and the battery capacity will be restored.

　　3. If there is too much sediment at the bottom of the acid-proof battery, use a straw to remove the sediment and add the configured standard electrolyte.

　　4. If the acid-proof battery plates are bent, cracked, or deformed, and if the charge and discharge capacity still does not reach more than 80% after verification, the battery should be replaced.

　　5. The insulation of the acid-proof battery is reduced. When the insulation resistance value is lower than the on-site requirement, a grounding signal will be issued, and when the voltage can be measured both positively and negatively to the ground, the battery casing and insulating bracket should be wiped with alcohol, the ventilation conditions in the battery room should be improved, the humidity should be reduced, and the insulation will be improved.

　　(II) Failure and treatment of valve-regulated sealed lead-acid batteries

　　1. The shell of the valve-regulated sealed lead-acid battery is deformed. The general reasons are that the charging current is too large, the charging voltage exceeds 2.4V×N, there is an internal short circuit or partial discharge, the temperature rise exceeds the standard, the safety valve fails to work, etc., which causes the internal pressure to rise. The solution is to reduce the charging current, lower the charging voltage, and check whether the safety valve is blocked.

　　2. The floating charge voltage is normal during operation, but once discharged, the voltage quickly drops to the termination voltage value. The general reason is that the battery loses water and dries up, and the electrolyte deteriorates. The solution is to replace the battery.

　　(III) Cadmium nickel battery failure and treatment

　　The capacity of nickel-cadmium batteries decreases and the discharge voltage is low. The solution is to replace the electrolyte, replace the irreparable battery, charge with I5 current for 5 hours, reduce the charging current to 0.5 I5 current, continue charging for (3-4) hours, stop charging for (1-2) hours, discharge with I5 to the termination voltage, and then charge and discharge with the above method, repeat (3-5) times, and the capacity will be restored. If the capacity still cannot be restored, the battery should be replaced.

　　2. The fault and accident handling of the charging device and insulation monitoring device should be carried out in accordance with the manufacturer's regulations, and the specific handling methods should be clearly stated in the on-site operating procedures.

　　Three DC system fault and accident handling plans

　　(i) When the absolute value difference between the voltages at both poles of a 220V DC system and the ground exceeds 40V or the insulation is reduced to below 25KΩ, or when there is a significant change in the voltage at either pole of a 48V DC system and the ground, the DC system should be considered to be grounded.

　　(ii) After the DC system is grounded, the cause should be immediately identified and the grounding fault point should be found out and eliminated as soon as possible based on the indication of the grounding line selection device or the working conditions, weather and insulation conditions of the DC system on that day.

　　(III) When using the Lalu method to find DC grounding, at least two people should be involved and the DC disconnection time should not exceed 3S.

　　(IV) The push-pull inspection should first push and pull the circuit that is easy to ground, followed by the emergency lighting, anti-mislocking device circuit, outdoor closing circuit, indoor closing circuit, 6-10kV control circuit, other control circuits, main control room signal circuit, main control room control circuit, rectifier and battery circuit.

　　(V) When the battery pack fuse blows, it should be checked and handled immediately, and appropriate measures should be taken to prevent the DC bus from losing power.

　　(VI) When the capacitor of the DC energy storage device breaks down or has insufficient capacity, it must be replaced in a timely manner.

　　(VII) When a DC charging device trips due to an internal fault, the backup charging device should be started in time to replace the faulty charging device, and the operating parameters should be adjusted in time.

　　(VIII) When a short circuit or AC or DC voltage loss occurs in the DC power supply system equipment, the cause should be quickly identified, the fault eliminated, and spare equipment put into use or other measures should be taken to restore the normal operation of the DC system as soon as possible.

　　(IX) When a battery pack explodes or opens, the main fuse or air circuit breaker of the battery should be disconnected immediately, and the backup equipment should be put into use or other measures should be taken to eliminate the fault in time and restore the normal operation mode. If there is no backup battery pack, the DC system load can only be operated by the charging device during the accident handling period, and if the charging device does not meet the closing capacity requirements of the circuit breaker, the closing circuit power supply should be temporarily disconnected and resumed in time after the accident is handled.

　　Safety requirements for maintenance and fault and accident handling of DC power supply systems

　　(i) Before entering the battery room, ventilation must be turned on.

　　(2) All operations related to DC power supply equipment and circuits must comply with the relevant provisions of the "Electric Power Safety Work Regulations".

　　(III) When a rectifier fails, the operation should be carried out strictly in accordance with the manufacturer's requirements to prevent damage to the equipment.

　　(IV) When searching and handling DC grounding, workers should wear wire gloves and long-sleeved work clothes. A high internal resistance voltmeter with an internal resistance greater than 2000Ω/V should be used, and the tools should be well insulated. Prevent new grounding from occurring during the search and handling process.

　　(V) When checking and replacing batteries, be sure to check the polarity to prevent DC voltage loss, short circuit, or grounding. Workers should wear acid-resistant and alkali-resistant gloves and necessary protective clothing when working.