UHV-75kVA/75kV AC Resonant Test System

Présentation du produit

The UHV-75kVA/75kV Series Resonant System is suitable for the handover and preventive testing of large-capacity, high-voltage capacitive test objects. The device features multiple protection functions such as overvoltage, overcurrent, zero-start, and system detuning (flashover). With its lightweight and portable design, it is highly convenient for on-site application, and incorporates DSP platform technology for enhanced control and performance.

Main technical parameters and functions

Rated capacity: 75kVA

Rated voltage: 25k；75kV

Rated current: 3A；1A

Measurement accuracy: System RMS level 1.5

Operating frequency: 30-300Hz

Device output waveform: Sinusoidal wave

Quality factor: Device Q≥30(f=45Hz)

Waveform distortion rate: Output voltage waveform distortion ≤1%

Input power supply: Single-phase 220 or three-phase 380V voltage, frequency 50Hz

Working hours: Allow continuous 60min under rated load; Overpressure 1.1 times 1 minute

Temperature rise: Temperature rise ≤65K after continuous operation under rated load for 60 minutes

Protection function: Overvoltage, overcurrent, zero start, system mismatch (flashover) and other protection functions

Ambient temperature: －20℃-55℃

Relative humidity: ≤90%RH

Altitude: ≤3000m

Comparison between series resonance and traditional power frequency

 test  transformers

1. Power supply capacity requirement (the biggest difference):

The series resonant device exploits resonance, so its required power supply capacity is only

 1/Q of the output capacity (Q is typically ≥30). For testing a long cable, a series resonant

 set may need only a few tens of kVA, whereas a direct power‑frequency transformer would

 require thousands of kVA – often impossible to source or transport on site.

2. Size and weight:
A series resonant device weighs only 1/5 to 1/10 of a power‑frequency transformer of the same voltage class, making it highly suitable for field outdoor handling. In contrast, the power‑frequency transformer is as bulky as a steel tower and is usually fixed in a laboratory.

3. Safety behaviour upon test object breakdown:
This is the “trump card” of series resonance. When the test object (e.g., a cable) breaks down under high voltage, the resonant circuit immediately detunes, the current drops sharply, and the arc extinguishes almost instantly – without producing destructive overvoltages. A power‑frequency transformer, however, is a “stiff” source: once breakdown occurs, the short‑circuit current is huge, which can easily burn the weak point of the test object and cause “secondary aggravated damage”.

4. Application scenarios:
Series resonance is specialised for large‑capacity, high‑voltage test objects (long cables, GIS, generators). Power‑frequency transformers are suitable for small‑capacity, low‑voltage items, or for specific old‑style equipment that strictly requires a 50 Hz frequency.

Application of Series Resonance in High Voltage Electrical Equipment Testing

AC voltage withstand test: Using series resonance to generate high power frequency voltage, conduct AC voltage withstand test on capacitive specimens with large capacity and high voltage. This method can effectively detect hazardous concentrated defects in equipment and is the most effective and direct way to test the insulation strength of electrical equipment.

Handover and preventive testing of equipment such as transformers, cables, and motors: Through series resonance testing, the electrical performance of the equipment can be comprehensively evaluated to ensure its safe operation.

Advantages of Series Resonant Devices

1. High efficiency: In the series resonant state, the circuit impedance is ideally small, and the ratio of current to voltage reaches its maximum, thereby improving the overall efficiency of the circuit.

2. Low losses: Because the circuit impedance is small and the current-to-voltage ratio is large in the series resonant state, the losses within the circuit are also relatively low.

3. Stability: The series resonant device can effectively suppress noise interference in the circuit, ensuring circuit stability.

Common problems with series resonance

Q1: What is "resonance"? Why can it generate high voltage? A1: Resonance refers to the periodic exchange of energy in a circuit composed of an inductor (L) and a capacitor (C) when the frequency of an external power source is equal to the natural resonant frequency of the circuit, resulting in a voltage and current far greater than the power source voltage in the circuit.

Q2: What are the risks encountered during resonance withstand voltage testing? A2: The main risks include overvoltage breakdown, overcurrent damage to equipment, and electric shock accidents caused by improper operation. Therefore, it is necessary to ensure that the device has complete protection functions and is operated by professionals.

Q3: Is the variable frequency series resonant device suitable for all voltage levels of equipment? A3: Variable frequency series resonance technology is suitable for various types of power equipment with voltage levels of 35kV and above, but the specific model selection needs to be determined based on the capacitance and test voltage requirements of the tested equipment.

Q4: How to ensure the accuracy of the results when conducting frequency conversion series resonance tests? A4: Ensuring good grounding of the equipment before the test, selecting appropriate test voltage and frequency, accurately measuring capacitance, and paying attention to the influence of environmental factors, in conjunction with the use of qualified measuring instruments, is the key to ensuring the accuracy of the results.

Q5: What should be paid attention to in the daily maintenance of the variable frequency series resonant device? A5: Regularly check the appearance of the equipment, whether the connecting wires are intact, clean the surface of the equipment, check the working status of the components in the control box, and ensure the normal operation and long life of the equipment.