GB 50150-2016 stipulates that handover tests for 35kV and below cross-linked polyethylene cables may adopt 0.1Hz very low frequency withstand voltage, with a test voltage of 3U₀. Procurement personnel often encounter several common questions during model selection, which are explained one by one below.
The test voltage is calculated based on the cable rated voltage U₀, and the handover test adopts 3U₀. For example, for 8.7/10kV cables, U₀ is 8.7kV, and the test voltage is 26.1kV; for 26/35kV cables, U₀ is 26kV, and the test voltage is 78kV. The output voltage range of the device should cover the corresponding voltage level and leave a certain margin.
Common output frequencies include 0.1Hz, 0.05Hz, and 0.02Hz. 0.1Hz is suitable for most 35kV and below cables and offers higher efficiency; 0.05Hz and 0.02Hz are suitable for longer cables or test specimens with larger capacity, which can reduce the capacity requirement of the device. During model selection, confirm that the device supports multiple adjustable ranges for flexible on-site use.
Distribution cable trenches and tunnels have narrow spaces, so the device needs to be easy to carry. The controller weighs about 4kg, and the voltage booster weighs 25~50kg; the split design allows one person to carry it. The power supply only requires AC 220V civil mains electricity, with no need for industrial power, making it suitable for field work and scenarios without a power source. During procurement, check the weight and power supply requirements to determine whether on-site conditions are met.
The device should have overvoltage, overcurrent, and zero-position protection, with an action time of ≤20ms. The voltage waveform distortion rate should be <5%, and the peak instability should be ≤1%. These indicators directly affect test safety and data validity, and suppliers should be required to clearly mark them during inquiry.
If there is no destructive discharge throughout the withstand voltage process, it is judged as qualified, and no upper limit for leakage current is specified. Before and after the test, a 5000V megohmmeter is required to measure and compare the insulation resistance. The device should be equipped with a touch screen, automatic storage, and printing functions for easy archiving and traceability.
The KD-150 very low frequency withstand voltage test device supports 0.1Hz, 0.05Hz, and 0.02Hz output, and its output voltage meets the 3U₀ test requirements for 35kV and below cables. It is suitable for cable handover and preventive tests, generator stator winding insulation assessment, and power capacitor insulation assessment.
