The modern power system is like a intricately woven giant grid, and any node failure can trigger a chain reaction. To ensure the safe and stable operation of this network, it cannot be separated from the "pulse diagnosis" of professional testing instruments.
At key nodes of substations, power plants, and transmission lines, lightning impulse high-voltage generators, transformer comprehensive testers, power frequency withstand voltage test devices, dielectric loss testers, and transformer ratio group testers constitute the first line of defense for power grid safety. These devices are like precision medical instruments, constantly monitoring the health status of electrical equipment.
1、 Thunder impact high-voltage generator: the "lightning protection armor" of the power grid
Ellightning impulse high-voltage generator is a core device that simulates natural lightning environments, mainly used to evaluate the ability of high-voltage equipment to withstand transient overvoltages. It simulates the impact effect of real lightning strikes on power equipment by generating standard lightning waves (1.2/50 μ s waveform).
Influencing factors and key points:
Waveform accuracy: The wavefront time of standard lightning waves is 1.2 μ s ± 30%, and the half peak time is 50 μ s ± 20%, which directly affects the accuracy of the test
Voltage level: It needs to match the rated voltage of the tested equipment (such as 10kV, 220kV, etc.)
Environmental interference: Electromagnetic interference can affect the measurement accuracy of impulse voltage
Application Scenario:
Verification of insulation strength of high-voltage switchgear
Lightning arrester protection performance test
Evaluation of Insulation Tolerance of Transformer Winding
How can we do better? According to the IEC 60060-1 and GB/T 16927.1 standards, Wuhan Ultra High Voltage Power Technology Co., Ltd.'s solution adopts multiple shielding technology and a digital waveform calibration system to ensure accurate lightning impulse waveforms can still be output in complex electromagnetic environments, providing the equipment with a real "lightning test room".
2、 Transformer comprehensive tester: the "general practitioner" of electric heart
As a key equipment for transformer factory inspection and regular assessment, the transformer comprehensive tester can complete the testing of multiple key parameters such as DC resistance, transformation ratio, wiring group, and no-load loss in one go.
Core components:
Power supply unit: Provide the AC/DC power required for testing
High precision measurement circuit: collecting various parameters of transformers
Intelligent analysis system: built-in diagnostic algorithm automatically determines device status
Technological breakthrough points:
Color display and fully Chinese operation interface enhance user experience
Magnetic combination frame design for easy disassembly and maintenance
Linkage function of relay protection testing system to achieve closed-loop testing
How can we do better? Modern equipment such as the system provided by Wuhan Ultra High Voltage Power Technology Co., Ltd. adopts multi task parallel testing technology, which shortens the traditional testing that takes several hours to be completed within 30 minutes, and automatically generates formatted reports that comply with power testing regulations, greatly improving operation and maintenance efficiency.
3、 Power frequency withstand voltage test device: the ultimate examiner of insulation performance
Elpower frequency withstand voltage test device continuously tests the withstand voltage strength of insulation materials by applying a power frequency AC voltage (50/60Hz) much higher than the operating voltage of the equipment. According to the structure, it can be divided into integrated (below 30kV) and split type devices.
Three elements of the experiment:
Voltage value: usually 2-3 times the rated voltage of the equipment
Frequency: Strictly match the power grid frequency (50Hz or 60Hz)
Time: The standard test lasts for 1 minute to fully expose the insulation defects
Typical application scenarios:
Regular insulation assessment of power transformers
Acceptance after installation of power cables
Annual preventive testing of capacitive equipment
How can we do better? The new generation of intelligent devices adopts step boosting technology and real-time leakage current monitoring, automatically drawing voltage current curves during the testing process. Once the precursor of insulation breakdown (such as a sudden increase in current) is detected, immediately activate the protection to cut off the high voltage and avoid damage to the test sample. The power frequency withstand voltage equipment of Wuhan Ultra High Voltage Power Technology Co., Ltd. integrates these safety features, transforming destructive testing into a controllable evaluation process.
4、 Dielectric loss tester: an "early warning system" for insulation aging
Eldielectric loss tester evaluates the performance of insulation materials by measuring the dielectric loss factor (tg δ), based on the classical Xilin bridge measurement method. The smaller the TG δ value, the lower the energy loss of the insulation material and the better its quality.
Key influencing factors:
Temperature: For every 10 ℃ increase, the TG δ value may increase by 1.5-2 times
Humidity: Moisture in insulation materials causes a significant increase in TG δ
Test voltage: Suitable test points should be selected within the rated voltage range
Technological evolution:
Anti interference technology: Eliminating electromagnetic interference through phase conversion and forward/reverse measurement
CVT specific mode: a special measurement algorithm for capacitive voltage transformers
Variable frequency measurement: using off frequency testing to avoid power frequency interference
How can we do better? Professional equipment such as the dielectric loss tester from Wuhan Ultra High Voltage Power Technology Co., Ltd. integrates an automatic temperature and humidity compensation system and three-dimensional anti-interference technology, which can accurately capture 0.01% level TG δ changes even in strong electromagnetic field environments. A certain substation used this technology to promptly detect the deterioration of the insulation of the bushing, avoiding the tripping accident of the 220kV main transformer.
5、 Variable ratio group tester: "gene detector" for transformer windings
Elratio group tester has completely revolutionized the traditional ratio bridge measurement method, achieving fully automatic and wide range transformer ratio and wiring group testing.
Technical advantages:
Measurement range: covering a range of 0.8-10000 aspect ratios
Test speed: Single measurement time ≤ 3 seconds
Intelligent judgment: automatically identify 12 wiring groups including Yyn0, Dd11, etc
Application value:
Transformer factory calibration: Ensure that the winding turns ratio meets the design requirements
Fault diagnosis: Determine winding short circuit or open circuit through abnormal transformation ratio
Energy Efficiency Assessment: Discovering Energy Loss Caused by Ratio Deviation
How can we do better? Modern instruments adopt three-phase simultaneous measurement technology and dynamic impedance matching algorithm, which can obtain stable readings even under residual magnetic interference of transformers. A certain power supply company used this technology to conduct a survey of old substations and found that three transformers that have been in operation for more than 20 years have a phenomenon of variable ratio drift. After timely adjustment of the tap changer, the annual energy loss was reduced by about 120000 kilowatt hours.
Practical case inspiration: After a provincial power grid company introduced a complete set of professional testing platforms, the average time for equipment failure warning was advanced by 6 months. The hidden danger of loose windings in the main transformer discovered through the transformer comprehensive tester was resolved in just 3 days during the annual maintenance, avoiding potential power outage losses that could last for a week.
Instrument synergy effect: When the dielectric loss tester detects an abnormal increase in the bushing's TG δ value, it immediately links with the power frequency withstand voltage test device for verification. After confirming the defect, the internal winding status is evaluated using a variable ratio group tester, and finally the repair effect is verified through a lightning impulse high-voltage generator - this systematic detection process improves the accuracy of fault diagnosis to 98%.
Professional testing equipment is evolving from a single function to system integration. Wuhan Ultra High Voltage Power Technology Co., Ltd.'s innovative platform has achieved data interoperability and joint analysis of five types of instruments, promoting the operation and maintenance of the power grid into a new era of intelligent diagnosis.
frequently asked questions
1.Why does the power frequency withstand voltage test usually last for 1 minute?
This is the best balance point specified by international standards: it can fully expose insulation defects while avoiding cumulative damage to intact insulation due to prolonged exposure. In special circumstances, it can be extended to 5-10 minutes.
2.Why use multiple frequencies for dielectric loss testing?
Off frequency measurement (such as 40Hz/60Hz) can effectively avoid 50Hz power frequency interference and improve on-site testing accuracy. Frequency conversion technology can also analyze the characteristics of dielectric loss changing with frequency.
3.What does the 1.2/50 μ s waveform represent in lightning strike testing?
This value defines the standard lightning pulse characteristics: wavefront time of 1.2 μ s (time for voltage to rise from 0 to peak), and half peak time of 50 μ s (time for voltage to decay from peak to 50%).
4.Why do transformer ratio tests need to measure groups simultaneously?
The wiring group directly affects the phase relationship of transformer parallel operation. Incorrect grouping can lead to short circuit accidents, so it must be verified synchronously with the transformation ratio.
5. How to choose the voltage value for power frequency withstand voltage test?
Determine based on equipment type and voltage level. For example, the AC withstand voltage value of a 10kV switchgear is 42kV, calculated based on 3.5 times the maximum voltage of the equipment (Um=12kV).
