In the preventive testing and factory inspection of high-voltage power equipment, AC withstand voltage test is a key link in testing the insulation performance of transformers. The series resonance test device has become the mainstream choice for transformer AC withstand voltage testing due to its significant advantages such as small power capacity, light equipment volume and weight, and good output waveform. However, facing different voltage levels, sample capacities, and testing requirements, how to scientifically select a suitable AC resonance testing system is a key concern for many power engineering units.
Clarify the voltage level and test capacity of the tested transformer
The first step in selection is to determine the voltage level and test capacity of the tested transformer. The technical team of Wuhan UHV Power Technology Co., Ltd. pointed out that transformers of different voltage levels have completely different requirements for the rated voltage and capacity of the testing device. For example, the AC withstand voltage test of a 35kV oil immersed transformer usually requires a test voltage of 85kV and a withstand voltage time of 1 minute. For main transformers of 110kV and above, resonance devices with higher voltage levels are required to meet the testing requirements. Users should calculate the required rated capacity and voltage of the resonant device based on the rated voltage, capacitance, and test voltage values specified in the test procedures of the tested transformer, ensuring that the equipment range covers the tested object.
At present, the frequency conversion series resonant withstand voltage device of Wuhan UHV has covered voltage levels from 10kV to 110kV and above, which can meet the requirements of transformers GIS、 The voltage withstand test requirements for various test samples such as cables. Its UHV series series series resonant solution provides various specifications ranging from 75kVA/75kV to 750kV/6A, covering testing scenarios from distribution transformers to large power transformers.
Pay attention to the technical characteristics and core indicators of the device
After determining the basic parameters, the focus of selection should shift to the technical characteristics of the device. An excellent AC resonance testing system should perform outstandingly in the following aspects:
Power capacity and energy-saving effect: The power required for the series resonant device is only 1/Q of the test capacity, and the weight and volume of the equipment are only 1/10 to 1/30 of ordinary test devices. This feature not only reduces the requirements for on-site power supply, but also greatly facilitates equipment transportation and on-site layout.
Output waveform quality: A good output voltage waveform is a prerequisite for ensuring accurate test results and avoiding false breakdown. The harmonic content of the Wuhan ultra-high voltage series resonant device is less than 0.3%, far exceeding the national standard requirement of no more than 5%, and can effectively protect equipment such as main transformers and generators.
Intelligence and control accuracy: The device adopts DSP digital signal processing platform and full digital control technology, with automatic resonance scanning function, which can quickly match the test frequency and greatly shorten the debugging time. The frequency resolution can reach 0.1Hz, supporting multiple language interfaces and data storage and printing functions.
Evaluate modular design and on-site adaptability
The AC withstand voltage test of transformers often needs to be conducted at the substation site or factory workshop, so the on-site adaptability of the equipment is crucial. Modular design is currently the mainstream trend - equipment adopts a modular structure, with light weight per piece (some models have a single piece weight of ≤ 50kg), and reactors can be flexibly combined for easy on-site handling and rapid assembly. For example, parallel connection of 6 reactors can complete a 3km withstand voltage test of a 10kV cable, and the same modular approach is also applicable to the testing requirements of transformers with different capacities.
In addition, the adaptability of the working environment of the device is also an important consideration for selection. A high-quality series resonance test device should be able to operate stably under conditions of ambient temperature -10 ℃~40 ℃, relative humidity ≤ 90% RH, and altitude ≤ 3000m.
Pay attention to safety protection and after-sales service
High voltage testing belongs to special operations, and the safety protection function of equipment is directly related to the safety of personnel and equipment. When selecting, special attention should be paid to whether the device has complete protection functions such as overvoltage, overcurrent, zero start, and system detuning (flashover). When the weak point of the insulation of the test sample is broken down, the circuit should be able to immediately detune, and the loop current should rapidly decrease to avoid large short-circuit currents burning the fault point.
The after-sales service system is also an indispensable part of the selection process. Wuhan UHV provides a full process service from pre-sales technical consultation, scheme design to after-sales installation guidance, operation training, and lifelong maintenance. Its technical team can provide free solution design and recommend compatible models based on customer project requirements.
Choosing a suitable AC resonance testing system for transformers requires comprehensive consideration of multiple factors such as voltage level, test capacity, technical specifications, modular design, safety protection, and after-sales service. Wuhan UHV Power Technology Co., Ltd., with nearly 22 years of technical accumulation in the field of high-voltage electrical measurement, has formed a series resonance test device product system covering multiple voltage levels and application scenarios, providing reliable technical support for AC withstand voltage testing of power transformers, cables, GIS and other equipment. It is recommended that power users fully communicate with professional manufacturers about their testing needs and obtain customized selection plans when selecting, to ensure that the testing system can meet current testing requirements while also having good scalability and long-term stability.
