High-voltage side open circuit or connected to measuring voltage divider and partial discharge coupling capacitor

Wiring: Connect the output of the triple-frequency power supply to the low-voltage side of the transformer under test (e.g., 10kV side), with the high-voltage side open or connected to a measuring voltage divider and partial discharge coupling capacitor.

Calibration: Check the wiring, set the frequency (e.g., 150Hz), and perform a no-load verification.

Voltage increase:

Quickly raise to 40% of the test voltage.

Uniformly increase at a rate of 3% per second to 100% (or first raise to 1.5 times for partial discharge background measurement, then to 2 times for withstand voltage).

Timing: Start timing after reaching the target voltage (e.g., at 150Hz, it needs to be sustained for 40 seconds).

Voltage decrease: After the time is up, quickly and uniformly reduce the voltage to zero, and cut off the power supply.

Discharge: Fully discharge the test object.

6. Safety and Precautions

Core heating: Although triple frequency is used, prolonged high-voltage operation can still cause heating of the core and windings, so the test time must be strictly controlled.

Resonance risk: At certain specific frequencies, the transformer inductance may resonate with stray capacitance, causing abnormal voltage rise, so the voltage waveform must be closely monitored.

Neutral point insulation: For graded insulated transformers (e.g., 110kV and above), the neutral point insulation level is lower. During induced voltage withstand test, the neutral point must be grounded (or grounded through a protective gap), otherwise, the neutral point may break down due to excessive potential.

Partial discharge interference: If partial discharge testing is performed simultaneously, the noise of the triple-frequency power supply itself must be extremely low, and the on-site grounding system must be very well-established.

7. Selection Recommendations

If you need to purchase or rent an induced voltage withstand test device:

Capacity matching: Calculate the required power supply capacity (kVA) based on the capacity and no-load current of the transformer under test.

Frequency range: Choose a variable-frequency generator with frequency continuously adjustable from 100-300Hz to meet different standard requirements.

Integrated design: It is recommended to choose a portable device that integrates the "triple-frequency source + control box + measurement unit" for easy on-site movement.

Partial discharge support: If high-end testing is required, confirm whether the device has reserved low-noise partial discharge measurement interfaces and shielding measures.

Are you interested in learning how to calculate the required device capacity, or do you need a wiring scheme for a specific transformer (e.g., 110kV main transformer)?