I. Test Items and Requirements
1. Insulation Resistance Test
Core Instrument Equipment: 2500V Megohmmeter, 1000V Megohmmeter
Standard and Procedure Requirements:
For the capacitor pair and shell: Use 2500V Megohmmeter to test, with the insulation resistance value not less than 500MΩ.
For the small bushing to ground: Use 1000V Megohmmeter to test, with the insulation resistance value not less than 500MΩ.
Notes: Do not conduct the insulation resistance test between the plates, to avoid damaging the instrument.
2. Capacitance Value Measurement
Core Instrument Equipment: Capacitance Bridge, Capacitance Meter
Standard and Procedure Requirements:
Measure the capacitance values of each phase, each arm, and the overall.
The ratio of the maximum value to the minimum value of the capacitance of each phase of the capacitor bank should not exceed 1.02.
The deviation of the capacitance value of a single capacitor should be controlled within the range of -5% to +5% of the rated value.
3. AC Withstand Voltage Test
Core Instrument Equipment: Power Frequency Withstand Voltage Test Device
Standard and Procedure Requirements:
The test voltage shall be executed at 75% of the factory test voltage, and it shall last for 10 seconds without breakdown.
The factory test voltage for 10kV capacitors is approximately 30-42kV, and the交接 test voltage is approximately 22.5-31.5kV.
Notes： The test shall be conducted between the electrodes and the housing (ground) externally， and the plates should be short-circuited.
4. Impact Closing Test
Core Instrument Equipment： Circuit Breaker Operating Device， Ammeter
Standard and Procedure Requirements：
Complete 3 impact closing operations on the capacitor bank under the rated voltage of the power grid.
During the closing process， the protection fuse should not melt， and the deviation of all currents should not exceed 5%.
II. Main Referenced Standards
GB 50150-2016 “Electrical Installation Engineering – Electrical Equipment Commissioning Test Standard”
GB/T 11024.1 “Capacitors for AC Power Systems – Nominal Voltage Above 1000V – Part 1： General”
III. On-site Test Operation Methods
(1) Insulation Resistance Test
Preparations
Power off， test for electricity， and hang grounding wires for the capacitor bank. Fully discharge for no less than 5 minutes； remove the external connection lines of the capacitor bank to ensure complete isolation of the tested equipment from the system.
Test Connections
Capacitor pair and shell test： Connect the “L” terminal of the 2500V Megohmmeter to the short-circuited three-phase plates of the capacitor， and the “E” terminal to the grounding end of the capacitor shell.
Small bushing to ground test： Connect the “L” terminal of the 1000V Megohmmeter to the small bushing (discharge coil or CT secondary side)， and the “E” terminal to ground. Operation steps
Hand-cranked megohmmeter should be rotated at a speed of approximately 120 r/min at a constant rate. After the pointer stabilizes, read the value; for electronic megohmmeter, press the test button and record the reading when it stabilizes. After the test is completed, disconnect the “L” lead first, then stop the operation or turn off the instrument.
Discharge operation
After the test is completed, use a discharge rod to fully discharge the capacitor plates and the small bushing to prevent residual charges from causing personal injury.
(II) Capacitance measurement
Preparations
Confirm that the capacitor bank has completed power-off, discharge, and grounding operations, remove the connection lines, and expose the connection terminals of a single capacitor or the entire capacitor bank.
Connection and measurement
Capacitance bridge method: Connect according to the instrument manual, connect the capacitor to the test end, select an appropriate range, balance the instrument, and read the capacitance value.
Capacitance meter method: Place the test clamp directly on the capacitor plates, read the value when it stabilizes, and record the value.
Measure the total capacitance value of each phase of the three-phase capacitor bank separately, and measure the single-phase capacitance value of the capacitors with a serial-parallel structure on a per-unit basis.
Recording and calculation
Record the measured capacitance values of each phase and individual capacitors, calculate the ratio of the largest minimum value of the three-phase capacitance values and the deviation percentage of the single-phase capacitance value relative to the rated value.
(III) AC withstand voltage test
Preparations
Use short-circuit wires to short-circuit all the plates of the capacitor bank, reliably ground the shell, and connect the high-voltage output end of the test transformer to the short-circuited plates.
Test steps
Close the test power supply, slowly increase the voltage to the specified test voltage (75% of the factory test voltage), maintain the voltage for 10 seconds, observe for any discharge, flashover, or breakdown phenomena. After the test is completed, slowly reduce the voltage to zero, and cut off the power supply.
Discharge operation
Use a discharge rod to fully discharge the plates, connect a series-limiting resistor during the discharge, first discharge through the resistor, then directly ground for discharge.
(IV) Impulse closing test
Preparations
Confirm that the connection lines of the capacitor bank have been restored, the protection device has been put into operation, an ammeter has been installed on the inlet side (or the current can be read through the protection device), and check that the circuit breaker operating mechanism and closing circuit are normal. Operation steps
Under the rated voltage of the power grid, complete the secondary closing operation through the circuit breaker, observe for any abnormal sounds, protection actions, or fuse blowouts, and record the three-phase current values. Disconnect the circuit breaker, wait for 5-10 minutes, and then complete the second and third closing operations one after another, for a total of 3 times.
Result determination
During the three closing operations, the fuses did not blow out. The difference between the maximum and minimum values of the three-phase current after closing did not exceed 5% of the average value.
Post time: Mar-31-2026