Very Low Frequency Withstand Voltage Test (Very Low Frequency, VLF Withstand Voltage Test
Usually refers to 0.1Hz sine wave or cosine square wave test) is an advanced testing technology specifically designed for evaluating the insulation strength of high-voltage cables (especially long-distance cross-linked polyethylene XLPE cables). It was developed to solve the problem that traditional power frequency (50/60Hz) AC withstand voltage test equipment is too bulky and cannot be used for on-site testing of long cables. In the power operation and maintenance system of 2026, VLF has become the preferred standard method for medium and high voltage cable acceptance tests and preventive tests. 1. Core Principle: Why Choose 0.1Hz? Capacitive current is proportional to frequency: A cable is essentially a huge cylindrical capacitor. Its charging current (capacitive current) formula is:
