Gas insulated metal enclosed switchgear (GIS) has become the preferred equipment for power grid construction due to its small footprint and high operational reliability. However, the on-site impact withstand voltage test before GIS equipment is put into operation is a difficult problem that troubles power grid operation and maintenance units.

After the overall assembly of GIS equipment is completed, only AC voltage withstand test is conducted on site, and a comprehensive final inspection before the equipment is put into operation cannot be provided. The lightning impulse withstand voltage test is an effective means of detecting fixed insulation defects inside GIS equipment and is an effective supplement to the AC withstand voltage test. The impulse voltage test is very effective in detecting abnormal electric field structures such as dirt and conductive burrs on the surface of insulators. However, the on-site lightning impulse withstand voltage test is limited by equipment volume and circuit inductance, making it difficult to apply in GIS substations, especially in ultra-high voltage GIS substations.

The UHV series lightning impulse voltage generator test device of Wuhan UHV Power Technology Co., Ltd. is designed to solve the pain points of GIS on-site impulse testing.

Low inductance design: solving the problem of waveform distortion under GIS large capacitive loads

GIS equipment is a typical capacitive load, and its tank structure and long busbar bring significant ground capacitance. Traditional impulse voltage generators often experience waveform distortion when driving large capacitive loads - longer wavefront time and intensified oscillation, which cannot meet standard requirements.

The Wuhan UHV series lightning impulse voltage generator adopts a multi-stage Marx circuit design, with small circuit inductance and the use of band stop filtering measures. Even when facing large capacitance loads, it can stably output standard impulse waves and has strong load capacity. In terms of specific parameters, the equipment voltage utilization coefficient is high, with lightning waves and operating waves not less than 85% and 80%, respectively. When the load capacitance is below 2000PF, the voltage utilization coefficient of standard lightning waves is ≥ 90%; When the load capacitance is below 4000PF, the voltage utilization coefficient of standard lightning waves is ≥ 85%.

This means that whether facing GIS tanks or long-distance cable sections, the equipment can output 1.2/50 μ s lightning full waves that comply with IEC and national standards, ensuring the accuracy and effectiveness of test results.

Modular design: making the impact generator "accessible and portable"

The GIS substation has a compact space, and equipment transportation and on-site deployment are the first hurdle. Traditional impulse voltage generators are bulky, difficult to transport, and even require disassembly, transportation, and on-site assembly, which is time-consuming and costly.

The Wuhan UHV series lightning impulse voltage generator adopts a 4-stage tower modular design, supporting single-stage low-voltage testing and multi-stage parallel expansion. The whole machine is mostly mobile. Modular design reduces the size of equipment by 40% compared to traditional devices. This design allows devices to easily enter GIS substations with limited space, and also means that transportation from one site to another is more convenient and efficient.

Wide temperature range and anti-interference: precise and reliable at the substation site

The complex electromagnetic environment of GIS substation site - high voltage bus, switch operation, adjacent live equipment - all pose challenges to the measurement accuracy of impulse voltage generators. Meanwhile, the equipment may be deployed in outdoor environments with extreme cold in the north or extreme heat in the south.

The Wuhan UHV series equipment adopts intelligent closed-loop control technology, which can achieve microsecond level fault location. The voltage fluctuation rate of the equipment is less than 0.1%. The device supports wide temperature operation from -30 ℃ to 50 ℃, overcoming extreme working conditions such as high altitude and strong electromagnetic interference.

In actual GIS field impact withstand voltage tests, isolation switches can be used to divide GIS into several sections during on-site operation to reduce load capacitance. The low inductance design and anti-interference ability of the device itself provide a basic guarantee for measurement accuracy.

For power grid operation and maintenance units, the procurement of lightning impulse voltage generators not only depends on how high voltage it can output, but also on whether it can stably output standard waveforms at the GIS substation site. The impulse voltage test is very effective in detecting abnormal electric field structures such as dirt and conductive burrs on the surface of insulators, and a set of on-site testing equipment that can be accessed, measured accurately, and trusted is a key link in ensuring the safe operation of GIS equipment. The Wuhan ultra-high voltage UHV series solves the problem of waveform distortion with low inductance design, solves on-site deployment problems with modular design, and ensures reliability in extreme environments with wide temperature range and anti-interference technology - three dimensions, one solution, making GIS on-site impact testing no longer limited by equipment.