The DC system is an independent power supply that is not affected by generators, station service power, or system operation modes. When the external AC power is interrupted, the backup power supply—storage batteries—continues to provide DC power for signal equipment, protection and automatic devices, emergency lighting, emergency power supplies, and circuit breaker opening and closing operations. Therefore, the maintenance of storage batteries is crucial to the stability of the DC system. The maintenance work of storage batteries is mainly reflected in the discharge and capacity testing of battery banks.

A storage battery can convert electrical energy into chemical energy for storage, and also convert chemical energy back into electrical energy to supply the load. When a battery is connected to a load, it discharges; when the load is disconnected and the battery is connected to a DC power supply with a voltage higher than the battery's terminal voltage, the battery is charged.

Charging Modes of Storage Batteries

Normal Charging: The regular charging process of a storage battery, which transitions from equalizing charge to floating charge.

Equalizing Charging: A charging mode used to balance the capacity of individual battery cells, typically with a high charging voltage for rapid capacity recovery.

Floating Charging: A charging mode for maintaining battery capacity, used to offset capacity loss caused by battery self-discharge and also for partial capacity recovery.

Constant Voltage Equalizing Charging: Charging the battery at a fixed constant voltage.

Project Information

 

Project Name: Discharge Maintenance of a Storage Battery Bank in a Substation

Test Equipment: FDT-220/110 DC System Comprehensive Tester

Storage Batteries: 220V 600Ah battery bank

 

1. Precautions

1. It is recommended that the operator remain on-site throughout the discharge test.
2. The load tester generates significant heat during the test; the test device should be placed in a well-ventilated area.
3. Implement on-site safety measures, including issuing work tickets and appointing an on-site person in charge.
4. Perform load transfer before the test.

2. Test Wiring

1. Connect the bus tie switch to link the two busbar sections and ensure no load interruption, then disconnect the battery bank from the system and isolate it for discharge preparation.
2. Connect the two thick red and black current cables of the tester to the positive and negative terminals of the battery bank (red to red, black to black). The two thin red and black cables are the voltage collection lines for the battery bank terminals.

3. Connect the battery cell monitoring module to monitor the voltage of each individual battery cell.

Insert the red and black cables into the corresponding color jacks of the FDT-220/110 DC System Comprehensive Tester.

3. Parameter Setting

(Full capacity discharge is performed in this test)

Operation is available via panel buttons or an external mouse. The main parameters to be set include:

Substation name

Number of battery cells

Discharge current

Lower voltage limit of individual battery cells

Lower voltage limit of the battery bank

After completing the above parameter settings, press the ALT key or use the mouse to switch to the battery discharge page.

△ Software Operation Interface

Click Start Test to initiate discharge. During the discharge process, the required monitoring data can be selected from the menu bar on the right side of the interface.

△ Voltage of Each Individual Battery Cell

The battery voltage can be detected on this interface to check the health status of the batteries and identify and replace underperforming cells.

△ Bar Chart of Individual Battery Cells

A more intuitive comparison to identify underperforming battery cells.

△ Terminal Voltage Curve of the Battery Bank

The trend of the battery bank's terminal voltage can be observed from this curve, and the battery capacity can be judged in combination with the discharge time.

Discharge Termination Rules

The test stops automatically at the end of the preset discharge process, indicating a normal discharge.

The test will terminate automatically if the voltage of any individual cell or the entire battery bank drops below the set lower limit; specific measures shall be taken according to on-site conditions:

If an individual cell voltage is below the limit: internal damage of the cell is indicated, and the cell shall be replaced with one of the same specification and model.

If the battery bank terminal voltage is below the limit: check the charging voltage of the charger, identify and replace the underperforming battery cells.

4. Post-discharge Operations

The total discharge duration is 10 hours; strict adherence to safety protocols is required throughout the process.

Upon the completion of discharge, the test report is automatically saved in the device's folder, which can be copied for review and record-keeping.

Restore the on-site wiring and reconnect the battery bank to the DC system.

Maintenance Effect

This battery maintenance effectively prevents issues such as insufficient voltage caused by inadequate maintenance, and further improves the operational reliability of the DC system.