With the continuous expansion of the power system scale and the continuous improvement of voltage levels, the preventive testing and handover acceptance of high-voltage equipment in substations are becoming increasingly heavy. How to scientifically and reasonably select high-voltage testing equipment to ensure the accuracy of test results and the safety of equipment operation has become a focus of attention for practitioners in the power industry. Recently, the reporter visited Wuhan UHV Power Technology Co., Ltd. located in China Optics Valley, Wuhan. Based on the company's professional experience in the field of high-voltage electrical measurement for nearly 22 years, a set of selection guidelines for high-voltage testing equipment in substations has been compiled.

1、 Series resonance test device: the preferred choice for high-capacity capacitive test samples

In the AC withstand voltage test of substations, the variable frequency series resonance test device is one of the most widely used equipment. This device utilizes a resonant reactor and the tested capacitor to generate resonance, producing high voltage and high current at lower input voltages. The required power supply capacity is only 1/Q of the test capacity, greatly reducing the requirements for on-site power supply. Its weight and volume are generally 1/10 to 1/30 of ordinary testing devices, making on-site testing more convenient and flexible.

When selecting, the primary consideration is the voltage level coverage range. Industry experts point out that for the voltage withstand test of 10kV substation equipment, a set of 44-88kVA level devices can meet the requirements; The 35kV substation requires a rating of 108-135kVA; A 110kV substation requires a higher specification configuration. In addition, specific plans need to be determined based on the type of equipment being tested - different equipment such as power cables, transformers, GIS, etc. have different requirements for test voltage and frequency. The series resonance test device of Wuhan ultra-high voltage adopts advanced DSP platform technology, which has multiple protection functions such as overvoltage, overcurrent, zero start, and system detuning, effectively ensuring the safety of equipment and operators.

2、 DC high voltage generator: voltage level matching is the core

DC high-voltage generators are mainly used for conducting DC withstand voltage tests or DC leakage current tests on high-voltage electrical equipment such as zinc oxide lightning arresters, power cables, transformers, circuit breakers, and generators. This device adopts high-frequency voltage doubling circuit and PWM high-frequency pulse width modulation technology, which has the characteristics of high output power and small size.

The core basis for selection is the voltage level of the tested equipment. According to the selection reference provided by Wuhan UHV, the maximum test voltage for 10kV substations is generally 47kV, and ZGF-60/2 model can be selected; The maximum test voltage of the 35kV substation is 105kV, corresponding to the ZGF-120/2 model; The maximum test voltage for a 110kV substation is 192kV, and the ZGF-200/2 model can be used; The maximum test voltage for a 220kV substation is 305kV, and the ZGF-400/3 model is a suitable choice; Due to the maximum test voltage exceeding 400kV, the ZGF-800/10 model needs to be selected for the 330kV substation. For the testing of zinc oxide lightning arresters, the corresponding model is generally selected based on the rated voltage of the lightning arrester - the 10kV lightning arrester has a DC reference voltage of about 28kV, and ZGF-60/2 can be selected; The DC reference voltage of the 110kV lightning arrester reaches 168kV, and the ZGF-200/2 model needs to be selected.

3、 Relay protection tester: The number of channels determines the scope of application

The relay protection tester is the core equipment for debugging and verifying the relay protection devices in substations. It integrates AC/DC output and various protection testing functions, and can complete the whole set testing, individual verification, and fault simulation testing of various relay protection devices.

When selecting, the number of channels is the primary consideration factor. The four phase output for conventional line protection and capacitor protection can basically meet the requirements; The differential protection and busbar protection of the main transformer require six phase current and six phase voltage output, and six phase or above models should be selected. For substations of 110kV and above, it is recommended to directly choose six phase equipment. Although the price is higher than three-phase models, it can significantly save subsequent labor and time costs, and is compatible with all functions of three-phase equipment. The microcomputer relay protection tester for Wuhan ultra-high voltage adopts Android operating system and 10.5-inch touch screen, equipped with dual core DSP processor, with smooth output waveform and low distortion.

4、 Other key testing equipment

In addition to the three major types of equipment mentioned above, substation testing also requires the following equipment:

Transformer comprehensive testing bench: used for no-load and load characteristic tests and power frequency withstand voltage tests of distribution transformers. The measurement part is controlled by a microcontroller, which can avoid the errors of traditional manual readings.

Circuit breaker mechanical characteristic tester: used to measure the mechanical dynamic characteristic parameters of various voltage levels of circuit breakers, including closing time, opening time, bounce characteristics, and contact resistance. The internal anti-interference circuit can meet the reliable use in 500kV substations.

Non partial discharge power frequency withstand voltage testing system: used to test the insulation level of power transformers, transformers, high-voltage switches, and zinc oxide lightning arresters. The system's partial discharge can be controlled within the range of 5pC.

5、 Comprehensive selection suggestions

Overall, the selection of high-voltage testing equipment for substations should follow the following principles:

One is to clarify the experimental subjects. The requirements for test voltage, current, and frequency vary among different devices, and the equipment specifications need to be determined based on the type and parameters of the tested equipment.

The second is to match the voltage level. The equipment range must cover the maximum test voltage of the tested equipment and reserve appropriate margin.

Thirdly, pay attention to the on-site conditions. The electromagnetic interference at the substation site is high, and models with strong anti-interference ability and good data repeatability should be preferred. Equipment portability is also an important consideration, and lightweight design can greatly improve on-site work efficiency.

Fourthly, we attach great importance to security protection. Equipment with multiple protection functions such as overvoltage, overcurrent, and zero start can effectively ensure the safety of personnel and equipment.

Fifth, refer to standard regulations. DL/T596 "Preventive Testing Regulations for Power Equipment" has clear regulations on the testing items and methods for different equipment, and the selection and testing operations should be strictly compared and executed.

With the continuous improvement of the intelligence level of the power grid, high-voltage testing equipment is rapidly developing towards intelligence, digitization, and lightweighting. Scientific and reasonable selection can not only ensure the quality of testing, but also provide solid technical support for the safe and stable operation of substations.