The DC power supply system of a substation provides DC power for operating substation equipment, meeting the DC power demands of relay protection, telecommunication and remote control, central signaling, emergency lighting, and control operations. Its reliability is crucial to the power supply safety and stability of the entire power grid system. As the core equipment of the DC power supply system, the storage battery bank is like the heart of the DC power supply system and serves as the last line of defense for ensuring the normal operation of power equipment. In recent years, incidents of DC system undervoltage caused by battery bank problems, which lead to the failure of protection and control systems and even major accidents, have occurred from time to time, bringing heavy losses to the power system. This article focuses on the problems of DC bus power loss and undetected hidden faults in the DC power supply system and provides a brief introduction.

Common Solutions

1. Disconnect the AC input switch of the chargerThis method carries high risks. If there is a problem with the battery bank circuit or the batteries themselves, it will directly cause DC bus power loss.
2. Temporarily lower the output voltage of the chargerThe theoretical risk is relatively low, but the operation is complex. Inconsistencies in equipment manufacturers, operation passwords and steps may lead to a series of problems such as failure to reset the voltage to the original value and incorrect settings, which may bring more hidden dangers.

Existing Drawbacks

1. On-site operation is a mustSome municipal power supply bureaus are in charge of nearly 200 substations with fewer than 5 DC maintenance personnel. The shortage of staff against a large number of substations may result in the failure to detect hidden dangers in a timely manner.
2. Inability to verify the accident tripping capacityIt is impossible to ensure that the battery bank can meet the demand of impulse loads such as tripping while bearing conventional loads. Hidden dangers such as increased battery internal resistance, reduced capacity, and internal damage and virtual connection of fuses cannot be detected.

△ MDC-110 Battery Bank Open-Circuit Monitoring Device

In response to the above problems, Wuhan Haomai has developed and produced the MDC-110 Battery Bank Open-Circuit Monitoring Device, which conducts real-time monitoring of the charge-discharge current and voltage status of each segment of the battery bank. Once an open-circuit sign appears, it performs real-time analysis and verification to determine whether an open circuit has occurred, realizing on-line, automatic, regular and all-round monitoring of the status of the circuit from the battery bank to the busbar. The device can detect whether the battery bank can bear conventional loads and meet the impulse capacity requirements such as tripping, and issue early warnings for hidden dangers such as increased internal resistance, reduced capacity, internal damage of fuses and virtual connection of the battery bank.

△ Technical Schematic Diagram

Realization Method

On the premise of ensuring busbar power supply, without disconnecting the charger or changing battery parameters, the device conducts real-time open-circuit monitoring by measuring the voltage and current of the two half-segments of the battery bank. Combined with historical data, it accurately and quickly judges battery open circuits and issues alarms through trend analysis and verification analysis. Based on parameters such as the drop rate of busbar voltage and load current, it intelligently completes the validity detection of batteries and the tolerance test of battery banks against impulse loads, providing important technical support for improving the safety of DC power supply.

Functions and Features

Routine On-load Monitoring

1. Effectively monitor the battery bank failure caused by the outage or fault of all circuit equipment from the battery bank to the busbar, such as battery open circuit, battery switch fault or disconnection, battery fuse melting, connecting wire corrosion, fatigue-induced virtual connection and falling off, interlayer wire breakage, screw loosening, and fuse internal damage.
2. Timely detect the disconnection of the battery bank from the busbar, verify whether the system can bear normal loads and issue alarms in a timely manner, ensuring the effective backup power supply capacity of the DC power supply.
3. Dynamically monitor busbar voltage fluctuations and voltage drops to ensure the ability to meet the demand of tripping impulse loads while bearing conventional loads.
4. Test the internal resistance of the entire backup circuit, which can effectively detect changes in the entire circuit's internal resistance caused by problems such as battery bank sulfation and connecting wire corrosion. It issues early warnings in a timely manner when the backup capacity deteriorates, providing sufficient preparation and maintenance time for operation and maintenance personnel and effectively avoiding accidents.

Battery Sulfation Inhibition

Solve the sulfation problem that is prone to occur in battery banks with long-term floating charge and no discharge, and realize regular shallow discharge to effectively inhibit sulfation.