With the continuous improvement of voltage levels in the power system and the large-scale operation of high-voltage equipment such as cross-linked cables, GIS composite appliances, and transformers, the demand for on-site AC withstand voltage testing is increasing. The variable frequency series resonance test device has become the mainstream choice for on-site high-voltage withstand voltage testing due to its advantages of lightweight equipment, small required power capacity, and good output waveform. However, facing the wide variety of products in the market, how to scientifically and reasonably choose a suitable AC resonance testing system for their own needs is a practical problem faced by many power construction and maintenance units.

The primary consideration for selection: matching voltage level and capacity

Voltage level is the first threshold for selection. The range of series resonance is selected based on the highest voltage level of the equipment under the jurisdiction of our unit. The specifications required for 10kV distribution networks and 110kV substations are completely different. The Wuhan UHV series variable frequency series resonant device can adapt to voltage levels ranging 10kV to 750kV, covering the AC withstand voltage test requirements of various capacitive test samples such as cross-linked cables, transformers, busbars, GIS, etc.

In terms of capacity, the required reactor capacity should be determined based on the capacitance range of the test sample. The larger the capacitance, the greater the required reactor capacity. For example, for a 10kV, 300mm ² cable, a device equipped with one 22kV reactor can be selected for a 1km length; If the length increases to 3km, a larger capacity model needs to be selected accordingly. For the voltage withstand test of the generator, the device model should be determined based on the capacity and voltage level of the generator.

Select device configuration based on the type of test sample

Different subjects have different requirements for the experimental apparatus. When conducting voltage withstand tests on power cables, it is necessary to comprehensively consider the voltage level, length, and cross-sectional area of the cable; When conducting AC withstand voltage tests on GIS and SF6 switches, such as 110kV GIS, a device equipped with multiple reactor combinations can be selected.

For scenarios with strict requirements for partial discharge indicators, such as GIS, precision transformers, etc., a series resonant device without partial discharge should be selected. The Wuhan UHV series resonant device without partial discharge can control the partial discharge within 5pC, which is better than the industry standard of 10pC. It adopts multi-layer shielded cables, spherical pressure equalization structure, and low partial discharge special insulation materials, effectively weakening external electromagnetic interference.

Pay attention to technical parameters and performance indicators

When selecting, it is important to focus on key technical parameters such as resonant voltage waveform, output frequency range, and quality factors. The device should be able to output stable sine wave voltage with a waveform distortion rate of less than 1.0%. The output frequency range of the variable frequency series resonant device is usually 20-500Hz, with a frequency resolution of 0.01Hz and voltage stability controlled within ± 0.5%.

The level of intelligence is also an important consideration. Modern series resonant devices often use DSP digital signal processing platforms, supporting multiple working modes such as fully automatic, manual, automatic tuning, and manual boost. They can automatically search for and track resonant points, and the built-in parameter calculator can generate key parameters such as resonant frequency and current with one click. After the experiment is completed, a standardized report will be automatically generated.

Consider the on-site environment and usage scenarios

The on-site testing environment is complex and varied, and the selection of equipment should be based on the environmental conditions of the testing site to meet the requirements of pressure resistance and protection level. If the frequency of outdoor use is high, it is recommended to choose a model with a dust-proof and waterproof shell; For scenarios with poor detection environmental conditions such as wind turbine tower foundations and box transformers, it is necessary to select models with higher protection levels. At the same time, the volume, weight, and ease of handling of the equipment also need to be taken into consideration. The weight of a single piece of equipment for the Wuhan UHV series resonance device is controlled within 50kg. The modular design facilitates on-site handling and rapid assembly, and is suitable for complex working conditions such as outdoor and high-altitude environments.

Security protection and after-sales service cannot be ignored

A comprehensive security protection function is a basic requirement for selection. The device should have multiple protection functions such as overvoltage protection, overcurrent protection, short circuit protection, overheating, detuning, and flashover. When the test sample breaks down, it can automatically detune and record data. The voltage divider is connected in parallel to the test object, which is used to measure the resonant voltage and also serves as an overvoltage protection signal.

In addition, the manufacturer's after-sales service and technical support capabilities are equally important. Wuhan UHV, as an enterprise deeply engaged in the field of high-voltage electrical testing for nearly 22 years, has a product line covering more than 200 equipment in 14 categories including series resonance, partial discharge testing, high-voltage insulation and withstand voltage, etc., which can meet customers' one-stop procurement needs.

Price range and budget reference

The price of series resonant devices varies greatly due to differences in brand, range, and accuracy. Economical type suitable for daily 10kV distribution equipment testing, with relatively low prices; The standard type covers voltage levels 35kV to 110kV, with data storage and communication functions, and is the most commonly purchased specification by power supply companies; The high-precision type is used for metrological verification and precision measurement, and the price is usually more than twice that of the standard type.

In short, selecting an AC resonance testing system requires comprehensive consideration of various factors such as voltage level, capacity requirements, type of test object, technical parameters, environmental requirements, safety protection, and after-sales service. Only based on practical needs and scientific comparison can the most suitable experimental equipment be selected to safeguard the safe and stable operation of the power system.