The power grid system is equipped with a large number of lead-acid battery packs as emergency backup power sources after a power outage. After a period of use, lead-acid batteries are often prone to a gradual decrease in capacity due to the detachment of effective active substances, decreased battery performance, corrosion of positive electrode grids, and sulfurization. In order to evaluate the time during which the battery pack can still supply power after a power outage or to confirm whether the performance of all individual cells is within the normal range, it is necessary to regularly check the capacity (i.e. discharge) of the battery. Nuclear capacity discharge is currently the most scientific and accurate way to evaluate the performance of lead-acid batteries. According to the maintenance standards for lead-acid batteries, the minimum requirement is to perform nuclear capacity discharge on the battery pack every year. However, traditional nuclear capacity discharge equipment can only achieve semi-automatic nuclear capacity discharge and cannot achieve fully automatic nuclear capacity discharge. It requires a large number of maintenance personnel to manually measure the unit voltage, group terminal voltage, nuclear capacity discharge current, and other series of work, which is very labor-intensive; In addition, the discharge of nuclear capacity requires a 10 hour rate, which means that maintenance personnel must be on duty for a long time, which is boring and exhausting. It is obvious that traditional battery capacity discharge work consumes a lot of manpower and time, and users of lead-acid batteries find it difficult to meet the annual inspection capacity discharge requirements. When the battery is not properly discharged and maintained, its lifespan will be greatly shortened, and quality problems in the battery pack cannot be detected in a timely manner, which cannot avoid safety hazards caused by battery pack open circuit or short circuit failure.

To solve the above problems, a remote battery capacity system can be introduced, and this article briefly introduces some basic system functions.

Keywords: lead-acid battery; Nuclear capacitive discharge; 10 hour rate; Remote nuclear capacity

1 System composition

Figure 1 Schematic diagram of system composition

Remote maintenance control terminal: composed of terminal server and related control software.

Information transmission channel: An information transmission channel provided by a communication network.

61850 protocol converter: Convert the collected parameters according to the 61850 protocol.

Remote nuclear capacity device: connected in series with the battery pack circuit, changes the battery pack voltage, and achieves discharge function.

Battery pack data acquisition module: collects the total voltage, cell voltage, cell internal resistance, and cell temperature of the battery pack.

Charger parameter acquisition module: collects AC and DC parameters of the charger (rectifier).

2. The system should have functions

2.1 Online monitoring function

The main station software can display various forms such as data, charts, curves, etc., showing the working status of the battery, the terminal voltage of the battery pack, the voltage of each individual cell, the temperature of each cell, the internal resistance of each cell, the charging/discharging current of the battery pack, the ambient temperature of the battery pack, and other parameters.

2.2 Silent remote online nuclear capacity discharge testing function

The main station software can perform remote online capacity testing on the site battery, that is, by issuing instructions through the main station software, the battery can be discharged online according to the actual load of the power supply, with multiple discharge parameters as conditions, and any parameter reaching the threshold will automatically stop discharging; The system accurately records the discharge duration, discharge capacity, cell voltage, and cell temperature changes, and automatically generates a discharge report. Through the above functions, it should be possible to conduct battery discharge capacity testing without the need for maintenance personnel to be on duty at the site.

2.3 Automatic generation function of discharge test report

The main station software has the function of automatically generating and exporting nuclear capacity discharge test reports, which can summarize and generate battery charge and discharge test reports in various forms such as bar charts, change curves, and numerical analysis tables based on the monitoring data of battery discharge process, and export them in EXCEL format.

2.4 Operation monitoring function

The main station software displays and views real-time and historical operating information of equipment and battery packs at each station through various forms such as curves, bar charts, and tables, and the query content can support report export function.

2.5 Traceable visualization display function for the performance of the entire battery group and individual cells

The main station software can fully record the voltage change trend of each individual battery after installing system equipment, thereby eliminating blind spots in the interval between two nuclear capacity tests and achieving fine management of the battery's entire life cycle.

2.6 User Management Function

The main station software provides role group management policies, and different users need to have different operating permissions. Legitimate users can log in to the local system to perform corresponding operations with the appropriate permissions. When remote control or remote adjustment of the host requires facial recognition, the operator must authenticate the face and perform a legitimate security authentication check on the host. Only after passing all authentication verifications can the operator access the parameters of the communication battery remote capacity system host.

3 System operation process

This system is mainly operated by maintenance personnel who log in to the remote maintenance control terminal in the monitoring center. The remote maintenance control terminal simultaneously controls multiple remote nuclear capacity devices at different sites. The system operation process is mainly as follows:

Open maintenance software system ->Enter password (or facial recognition) ->Enter maintenance software system ->Select site ->Select remote nuclear capacity function option ->Set condition parameters (discharge current, discharge termination time, discharge termination total voltage, discharge termination capacity, discharge termination cell voltage, etc.) ->Start discharge program.

During the discharge process, when any condition for discharge termination is reached, the system automatically terminates the discharge.

4 Conclusion

This system utilizes the existing communication network resources of each site and monitoring center to upgrade and transform the existing communication power supply system of each site, with low investment and significant improvement in discharge efficiency.

This system utilizes the load provided by the site communication power supply to consume the electrical energy released by the battery. By isolating the boost circuit, it automatically adjusts the output voltage of the battery pack. When the load current is greater than the current set for nuclear capacity discharge, it strictly follows a 10 hour rate for fully automated constant current discharge. During the discharge process, diodes are used in parallel with normally closed switches to ensure that the battery pack can seamlessly switch to the DC system load power supply in the event of bus voltage loss in the communication power supply, regardless of whether it is in a nuclear capacity discharge state. This can solve the long-standing problem of a single battery pack being unable to discharge nuclear capacity without a backup power source. By implementing automatic current limiting charging through program control, it is possible to avoid damage to the battery pack caused by instantaneous high current charging due to excessive voltage difference between the battery pack terminal voltage and the bus voltage after long-term discharge of the battery.