The DC power supply unit provides reliable DC power supply for the control circuit, signal circuit, accident lighting circuit, relay protection device, automatic device, remote terminal (RTU) and inverter power supply, plays a important role for ensuring all primary and secondary equipment in the substation. The battery pack plays an important role as an important pillar in the DC power supply device. When a large accident occurs in the power grid, the AC power supply of the rectification power supply device is often lost, so that the battery is composed of the only DC power supply provider, and becomes the last one to ensure the DC stop.
The State Grid Corporation's "DC Power System Technical Standards", "DC Power System Operation Specifications" and "DC Power System Maintenance Specifications" were formulated in 2005 and officially implemented in 2006. Prior to this, because the standards were not clear and not uniform, the maintenance work of the battery packs of various power supply companies was extremely uneven.
Generally, 220kV substations are basically equipped with 200~300Ah two sets of batteries; 1lOkV substation is basically equipped with a set of batteries of 200Ah or below. At present, most units lack the necessary professional instruments to fully test the battery parameters. In particular, the battery capacity test mostly follows the traditional method of large resistance discharge manual recording. With the acceleration of the construction of the power grid, the maintenance personnel have not increased, and the regular detection methods have not been innovated. The traditional battery cells of the battery pack are still measured every week. There is no direct relationship between the voltage and capacity of the battery pack terminal. The overall capacity of the battery pack cannot be accurately determined from the voltage measurement.
According to the analysis of numerous data and field experience, most of the causes of possible failures and failures are caused by the lack of normal maintenance. The reasons for analyzing battery failure mainly include the following situations:
Acidification. When the battery is undercharged for a long time, the float voltage is low, and the battery cannot be replenished in time after the discharge. When the battery is left unused for a long time, the negative electrode will form a coarse and hard lead sulfate, which will hardly dissolve. If the battery loses water seriously, the concentration of sulfuric acid is too high, which will promote the rapid formation of lead sulfate. The direct consequence of salinization is the lack of battery capacity and even the battery open circuit.
Lost water. Water loss is a common failure that causes battery failure. Low gas compounding efficiency, water oozing from the battery casing, grid corrosion and self-discharge can cause the battery to lose water. The reason for the current decline in the capacity of most valve-regulated sealed lead-acid battery packs is caused by the loss of water from the battery. It is generally believed that when the water loss exceeds 15%, the battery fails.
Corrosion and deformation of the grid. Grid corrosion is an important factor in limiting battery life. In a lead-acid battery, the positive grid is thicker than the negative grid. One of the reasons is that when the battery is being charged, especially under overcharge conditions, the positive grid is corroded and gradually oxidized to lose the grid. The increasing content and volume can cause severe bending of the plates.
The active substance softens. As the number of battery cycles increases, the crystal form is O. Type to B type conversion. Type B grains are relatively small and have poor bonding force, which causes the lattice structure of the active material to be weakened, and finally the active material softens a