17 Aug-2026

In August 2026, Wuhan Kedia Zhongwei Electric Co., Ltd. (hereinafter referred to as “Kedia Zhongwei”) issued a technical analysis on variable‑frequency series resonance withstand voltage testing, systematically presenting its application value and core advantages in the insulation testing of power equipment.

As voltage levels in power systems continue to rise and high‑voltage cable routes grow longer, traditional power‑frequency withstand voltage test equipment—bulky and demanding in power supply capacity—increasingly falls short of the flexibility and safety requirements for field testing. At the same time, commissioning and preventive tests for large‑capacitance capacitive specimens, such as power cables, GIS switchgear, and main transformers, are becoming more frequent and demanding. Test engineers urgently need a solution that reduces on‑site operational challenges while ensuring accurate assessment of equipment insulation strength.

To address this industry need, Kedia Zhongwei independently developed the KDXZ series variable‑frequency series resonance withstand voltage test device. The device operates on the LC series resonance principle: when the output frequency of the variable‑frequency power supply matches the natural frequency of the circuit formed by the reactor inductance (L) and the test object capacitance (C), resonance occurs. The voltage across the test object can then reach Q times the input voltage (where Q is the quality factor, typically ranging from several tens to over a hundred), and the resonant frequency is given by f₀ = 1/(2π√LC). The complete system comprises five core modules: a variable‑frequency power supply, an excitation transformer, reactors, a capacitive voltage divider, and an optional compensation capacitor. The KDXZ series incorporates an imported SPWM digital waveform generation chip with 16‑bit frequency resolution, achieving a frequency fineness of 0.1 Hz within the 20‑300 Hz range. The reactors feature a dry‑type epoxy resin cast structure, each designed as an independent unit, and can be flexibly connected in series or parallel to suit different voltage classes. Under resonance, the power supply only needs to cover the system’s active losses, reducing the required supply capacity by more than 95%. The overall weight and volume are about one‑third to one‑fifth of those of conventional test equipment. In addition, the resonant filtering circuitry effectively suppresses output waveform distortion, delivering a clean sinusoidal waveform and preventing harmonic peaks from causing false breakdown of the test object.

Leveraging these technical strengths, the KDXZ series has been successfully deployed in substations, power plants, renewable energy stations, and many other scenarios. In practice, it reliably performs AC withstand voltage tests on cross‑linked polyethylene cables, hydro generators, main transformers, busbars, GIS, and various other equipment. Customer feedback consistently highlights its ease of on‑site operation, accurate and repeatable test data, and marked improvements in both efficiency and safety during high‑voltage testing.

Wuhan Kedia Zhongwei Electric Co., Ltd. (referred to as “Kedia Zhongwei”) was established in 2012 and is a high‑tech enterprise integrating R&D, production, and sales of power testing equipment, instrumentation, and online power monitoring systems. The company has obtained certifications including the “High‑Tech Enterprise Certificate” and “ISO9001:2000 Quality Management System Certification.” Its product portfolio encompasses more than 300 models across 15 major categories, such as series resonance test systems, high‑voltage test equipment, transformer testing instruments, high‑voltage switch testers, relay protection testers, and cable fault detectors. These products are widely applied in power, water conservancy, petroleum, railway, mining, chemical, and other industries. The company boasts a team of professionals—including doctors, masters, and professor‑level senior engineers—specialising in high voltage, computer science, and electronics, all dedicated to providing high‑quality products and services that support the development of China’s power industry and the safe operation of power systems.