It is the core equipment for AC withstand voltage testing of high-voltage electrical equipment in modern power systems.
It cleverly utilizes the physical principle of LC series resonance, solving the problems of large size, heavy weight, and high power supply capacity requirements of traditional power frequency withstand voltage test equipment, and is particularly suitable for withstand voltage testing of large capacitive test objects such as long cables, GIS (Gas Insulated Switchgear), and large transformers.
The following is a detailed technical analysis of the device:
1. Core Working Principle
The device works based on the LC series resonance principle. When the inductive reactance in the circuit
are equal, the circuit resonates.
Resonance condition: adjust the output frequency of the variable frequency power supply
Where, $ L $ is the inductance of the reactor in the device, and $ C $ is the equivalent capacitance of the test object (such as a cable).
Voltage amplification effect:
In the resonant state, the loop impedance is minimal
1This means that the device only needs to input a low voltage ( $ U_{in} $ ) to generate the required high test voltage ( $ U_C $ ) on the test object.
Energy saving principle:
During resonance, energy is exchanged between the inductor and the capacitor, and the power supply only needs to
provide the active power consumed by the loop resistance, without providing a large amount of reactive power. Therefore, the required power supply capacity is only 1/Q of the test capacity (usually 1/10 ~ 1/50), greatly reducing the requirements for on-site power supply.
2. Main Components
A complete set of equipment usually consists of the following four parts:
Table
Component Name Core Function Key Technical Points
Variable Frequency Control Power Supply The "heart" of the system Converts power frequency (50Hz) power into a sine wave with adjustable frequency (usually 30-300Hz) and adjustable voltage, used to find the resonance point.
Excitation Transformer Voltage matching and isolation Steps up the voltage output by the variable frequency power supply to a level suitable for exciting the reactor, and achieves high and low voltage electrical isolation.
High Voltage Reactor Core resonant component Provides adjustable inductance
