What is the technical principle of the series resonance withstand voltage testing system in power cable withstand voltage testing?

The series resonance withstand voltage testing system has important application value in the withstand voltage testing of power cables. The technical principles mainly involve the following aspects:

1. Basic concepts and principles

The series resonance withstand voltage testing system is a device that uses the principle of series resonance to perform withstand voltage testing on power cables. Series resonance refers to the resonance phenomenon that occurs in a circuit containing inductance and capacitance when the frequency of the power supply is equal to the natural frequency of the circuit. In a series resonant circuit, the voltages of the inductor and capacitor cancel each other out, causing the current in the circuit to reach its maximum value.

2. System components

① Excitation power supply: Usually using direct digital frequency synthesis technology (DDS), it can generate continuous high-resolution frequency sine signals. After power amplification, it is used as a resonant excitation power supply.

② Inductance and capacitance: form a resonant circuit, and together with the tested power cable, form a series resonant circuit.

③ Control section: used to adjust the output frequency of the signal to meet the resonance requirements of the series system.

3. Working process

① Frequency regulation: By continuously adjusting the output frequency of the excitation power supply, find a point equal to the natural frequency of the circuit to cause resonance in the circuit.

② Resonant state: In the resonant state, the current in the circuit reaches its maximum value, and the voltage on the power cable also increases accordingly.

③ Voltage withstand test: Apply the increased voltage to the power cable for voltage withstand testing. If the cable can withstand the voltage without breakdown or other faults, it indicates that the insulation performance of the cable meets the requirements.

4. Technical advantages

① Efficiency: Compared with traditional testing transformers, the series resonant withstand voltage testing system can greatly reduce the requirements for power capacity. For example, in the 220kV cable withstand voltage test, the use of variable frequency series resonance technology successfully completed the test, greatly reducing the capacity of power testing equipment and improving testing efficiency.

② Accuracy: By precisely adjusting the frequency, the system can accurately reach resonance state, thereby improving the accuracy of testing. Some studies have shown that in the withstand voltage testing of long-distance high-voltage power cables, the optimized multi resonant system connection method can control the absolute error between the calculated and measured resonant frequency values within a small range.

③ Flexibility: The equipment composition is relatively flexible and can be adjusted according to different cable parameters and testing requirements. For example, in the withstand voltage testing of submarine cables in wind farms, a combined optimization method including series resonance and parallel compensation is proposed, which can effectively reduce the number and power of testing equipment.

5. Application Cases

① 10kV power cable testing: Voltage withstand testing was conducted on power cables with a length of 1km and a rated voltage of 10kV. It was found that the DDS based series resonant high voltage testing system design meets the requirements of regulatory testing and has broad application prospects in this field.

② 220kV cable testing: The use of variable frequency series resonance technology in 220kV cable withstand voltage testing has demonstrated the feasibility and effectiveness of this technology in long-distance high-voltage XLPE cable AC withstand voltage testing.

③ Fault location of high-voltage power cables: A fault location method for high-voltage power cables is proposed by combining the principle of traveling wave location with wavelet analysis. By designing a corresponding series resonant withstand voltage test power supply, cable faults can be clicked through, combined with electric field coupled non-contact sensors to collect traveling wave signals, and using wavelet mother functions to analyze fault information, effective fault location of high-voltage and ultra high voltage cables can be achieved.

In summary, the series resonance withstand voltage testing system has technical advantages such as high efficiency, accuracy, and flexibility in power cable withstand voltage testing. By utilizing the principle of series resonance, effective withstand voltage testing and fault location can be carried out on power cables of different voltage levels.

The ZCVF-A series variable frequency series resonant withstand voltage test device adopts the method of adjusting the power supply frequency to achieve resonance between the reactor and the tested capacitor, thereby obtaining high voltage and high current on the tested object. Due to its low required power supply, light weight and small size, it has been widely praised and applied at home and abroad, and is a new method and trend of high voltage testing. This device is mainly designed for AC withstand voltage testing of cross-linked cables, hydroelectric generators, main transformers, busbars, GIS, etc. It has a wide range of applications and is an ideal withstand voltage equipment for high-voltage testing departments and power installation and maintenance engineering units at the local, municipal, and county levels. The equipment mainly consists of a variable frequency control power supply, an excitation transformer, a reactor, a capacitive voltage divider, and a compensation capacitor (optional).

Kvtester Electronics Technology Co.,Ltd. is a high-tech enterprise specializing in power testing, testing, research and development, production, and sales of testing equipment. It has been engaged in the electrical testing industry for many years, and its products are of high quality. We welcome customers to come and purchase. Service hotline: 0086-27-81778799, to learn more, visit the official website: www.kvtester.com