With the acceleration of the construction of new power systems, the voltage level of substations continues to increase, and the operating environment of equipment is becoming increasingly complex. The scientific selection of electrical testing equipment has become a key link in ensuring the safe operation of the power grid. Faced with a wide variety of testing instruments in the market, how to choose the right equipment and use it well is a challenge that every power operation and maintenance personnel must face.
Standard procedures come first, selection is based on evidence
Equipment selection is not an imagination, it must strictly follow the technical standards issued by the country and industry. The "DL/T 596-2021 Preventive Testing Regulations for Power Equipment" provides a detailed list of testing items, cycles, and qualification criteria for equipment such as transformers, circuit breakers, cables, and lightning arresters. It is the fundamental guiding document for all selection work. The GB 50150-2016 Electrical Equipment Handover Test Standard for Electrical Equipment Installation Engineering specifies the test methods and requirements before the equipment is put into operation, and the standards are usually more stringent.
In addition, large operators such as State Grid and Southern Power Grid will develop more specific enterprise standards based on their own management needs. If the equipment mainly serves the power grid system, they must prioritize following their enterprise standards. The first step in selection is to clarify which regulations need to be followed and which specific equipment should be subjected to which prescribed test items.
Match according to voltage level, accurately adapt to requirements
The technical parameter requirements for testing equipment vary significantly among substations of different voltage levels. 10kV systems usually choose test transformers and insulation testing equipment with a range of 0-15kV; The 35kV system requires equipment with a range of 0-50kV. For the first level testing units of 330kV-500kV, the equipment configuration is more complex and needs to include high-voltage generating equipment such as DC high-voltage generators, frequency conversion series resonance test sets, partial discharge test sets, as well as electrical measuring instruments such as dielectric loss testers, circuit resistance testers, and transformer volt ampere characteristic testers.
Taking the series resonance test device as an example, Wuhan UHV Power Technology Co., Ltd. provides differentiated solutions for different application scenarios: for switch and bus testing with voltage levels of 10kV and below, the UHV-50/50 model is the ideal choice; For the withstand voltage test of 35kV cables, the UHV-108/108 model is more suitable and can meet the testing requirements of 1km of 35kV (300mm ²) cables. Before selecting, it is necessary to provide the voltage level, length, cross-sectional area, or nameplate parameters of the test sample, and have technicians accurately calculate the required resonant frequency and reactor configuration.
Core functional coverage, balancing current and future needs
Substation electrical testing involves multiple dimensions such as insulation characteristics, withstand voltage tests, and characteristic parameters. Equipment selection must ensure full coverage of core functions.
In terms of insulation testing, the output voltage range of the digital insulation resistance tester must include 2500V and 5000V, the range should be wide enough, the short-circuit current should be greater than 3mA to ensure testing stability, and it should have automatic calculation functions for absorption ratio and polarization index. The dielectric loss tester should focus on its anti-interference ability and choose a model with "frequency conversion" or "off frequency" anti-interference technology to cope with the complex electromagnetic environment on site.
In the field of withstand voltage testing, the series resonant AC withstand voltage testing device is the preferred choice for capacitive equipment such as cables and GIS for AC withstand voltage. The rated output voltage should not be less than 35kV (as the test voltage for 10kV equipment is usually 28kV or 42kV), and the frequency adjustment range should be between 30-300Hz. At the same time, the portability of the equipment and whether the reactor adopts a separate lightweight design should be considered. The DC high-voltage generator is used for cable DC withstand voltage and leakage current testing. The rated voltage should not be less than 60kV, and the ripple factor is usually required to be no more than 3%.
In terms of characteristic parameter testing, the output current of the circuit resistance tester must be 100A DC, which is a clear requirement of the regulations; The transformer DC resistance tester should use a model that adopts "fast voltage stabilization" technology, which can measure the winding resistance value within tens of seconds and greatly improve efficiency.
On site adaptability: a neglected yet crucial dimension
The electromagnetic environment at the substation site is complex, the space is limited, and the operational level of the operation and maintenance personnel varies greatly. The on-site adaptability of the instruments directly affects the detection efficiency and data stability. Prioritizing the selection of devices with strong anti-interference ability, portability, ease of operation, and high level of intelligence can significantly improve on-site detection efficiency and data stability.
The selection of relay protection comprehensive testing equipment should pay special attention to the power supply mode. For substations without AC power supply, models that support DC power supply or have built-in batteries should be selected. The volume and weight should also match the usage scenario, and lightweight and sturdy models should be preferred for on-site use.
In the field of cable fault testing, the UHV-500 model of Wuhan UHV can accurately test high resistance flashover faults, high and low resistance grounding, short circuits, and cable disconnections. Outdoor testing instruments must also have a protection level of IP54 or above to cope with various harsh weather conditions.
Balancing Compliance and Economy
Scientific equipment configuration must strictly follow the three core principles of compliance, practicality, and economy. All testing instruments must be calibrated and qualified by legal metrological verification institutions, used within the validity period of verification, with testing accuracy and technical parameters meeting the requirements of power testing standards, traceable testing data, and reliable reports. At the same time, the instrument parameters need to be accurately adapted to the voltage level, equipment type, and detection items of this station, without the need to excessively purchase high-end equipment that exceeds specifications and has high redundancy.
Wuhan UHV Power Technology Co., Ltd. has been deeply involved in the field of high-voltage power testing for 22 years, and has formed a product system consisting of more than 100 products in 15 categories, including series resonance testing devices, partial discharge testing systems, high-voltage insulation and withstand voltage equipment, transformer testing equipment, circuit breaker testing equipment, and relay protection testing equipment.
Industry experts point out that the selection of electrical testing equipment for substations should adhere to the principle of "on-demand selection and moderate advance", which not only meets current testing needs, but also reserves interfaces for future intelligent substation construction and digital transformation. With the deepening application in smart substations, equipment with digital interfaces and automated testing capabilities will gradually become the mainstream choice.
