According to the requirements for 0.1 Hz very low frequency withstand voltage testing in DL/T 596—2021 Preventive Test Code for Electric Power Equipment, a 0.1 Hz test voltage can effectively detect insulation defects in XLPE cables, and the required capacity is approximately 1/500 of that for power-frequency testing. The following key points can serve as a checklist during design and selection.
The output capability of a very low frequency withstand voltage test depends on the specimen capacitance and the test voltage. Taking XHVLF-65/0.5 as an example, it has a peak output voltage of 65 kV and a frequency of 0.1 Hz, and can cover common 10 kV~35 kV XLPE cables as well as generator and motor stator windings. During selection, typical specimen parameters such as cable cross-sectional area, length, and single-core or three-core construction should be provided to the supplier, who will calculate whether the load capacitance and voltage rise time meet the on-site schedule, avoiding slow voltage rise or waveform distortion caused by insufficient capacity.
The frequency deviation and waveform distortion of the 0.1 Hz sine wave directly affect leakage current readings. The device adopts digital waveform synthesis and closed-loop feedback, with frequency deviation controlled within ±0.1% and low output waveform distortion, making it easy to read the current variation trend during the withstand voltage test in accordance with the code. On site, it should be confirmed that the equipment has overcurrent, overvoltage, and discharge protection, and the grounding method and discharge rod configuration should be checked.
Working space in substations and cable trenches is limited, so the overall weight and volume of the device must match the handling method; usually two people can complete the setup. Power can be supplied by AC 220 V or an built-in power source, adapting to conditions where on-site power access is inconvenient.
Before procurement, it is recommended to check typical specimen parameters, the required maximum test voltage, and on-site power supply conditions, and to determine the model configuration only after the supplier issues a matching calculation statement.
