Intelligent Cable Partial Discharge Oscillatory Wave Tester

principle
By adjusting the frequency through a variable frequency source and isolating the boost excitation through an excitation transformer, the resonant reactor resonates with the distributed capacitance of the tested cable. Under resonance conditions, a test voltage Q times the excitation voltage can be obtained on the tested power cable. During the process of maintaining the test voltage on the cable, the output terminal of the short-circuit excitation transformer causes the resonant reactor and the tested cable to form a gradually decaying damping oscillation. The measurement and feedback control are carried out through a voltage divider, and the partial discharge signals that occur in the weak insulation links of the tested cable and its joints can be displayed regularly using software. By analyzing waveform data, the discharge capacity of partial discharge can be measured and the accurate location of the partial discharge point can be determined. And through software, the damping oscillation waveform can be controlled to repeat multiple times, which can more reliably verify the insulation defects of the tested cable.

Performance and characteristics of the system

1) The method of using AC series resonant boost and oscillation wave to test partial discharge is combined with the equipment, and one set of equipment can complete both partial discharge test and AC withstand voltage test, making it a dual-use device. The AC withstand voltage test complies with existing regulations

2) Suitable for handover testing of new cables (before commissioning) and preventive testing of old cables (after power outage).

3) Follow the IEC60270 standard to measure the local discharge of cables.

4) Measure the distance of cable discharge points.

5) Measure the position and total distance of cable joints.

6) The variable frequency host can automatically boost the voltage according to the relevant regulations of State Grid, and the laptop system can automatically collect data, which is simple and convenient.

7) The combination of hardware and software anti-interference technology can effectively remove external interference.

8) The software expert system displays parameters such as partial discharge waveform, discharge amount, and test voltage, and has functions such as real-time saving of test data, generation of test reports, and printing.

summary:

At present, the management of power cable maintenance is mainly based on the items and testing cycles specified in the "Regulations for Handover and Preventive Testing of Power Equipment", and insulation performance tests are conducted regularly under power outage conditions. The frequency conversion series resonance test has become the most widely used test method in China due to its test conditions being close to the operating conditions of the cable.

However, extensive experiments and experience have shown that the series resonance withstand voltage test cannot quantitatively evaluate the overall insulation state of the cable, and some high-voltage cables that have passed the series resonance withstand voltage test still experience discharge breakdown in the short term. After long-term research, experimentation, and practice on high-voltage cables, it is believed that partial discharge is a precursor to cable insulation faults, and effective detection of partial discharge is an important way to improve the level of cable condition maintenance.

The oscillation wave cable partial discharge diagnosis and positioning system (OWTS system for short) is a new method of "state maintenance" for power cables. This method first applies a DC voltage to the XLPE cable and uses the damping oscillation wave conditions formed to diagnose and locate the partial discharge. It can reliably detect weak insulation defects in cables and cable joints, and accurately locate them.

The integrated 10kV cable DC oscillation wave partial discharge testing device is an integrated testing equipment that is compact and easy to carry. The on-site connection is very simple, and it has a wide range of adaptability to the length of cable specimens. It can quickly and accurately diagnose and locate partial discharge in cables.

Intelligent Cable Partial Discharge Oscillatory Wave Tester

Main technical parameters

1. Maximum output voltage: 3-30kV

2. Sample capacitance: ≤ 5 μ F

3. Damping oscillation wave frequency range: 30-1000Hz

4. Partial discharge testing range: 5pC~100nC

5、 局放定位精度：0.1米

6. Communication protocol: USB 2.0 and serial port

Components of the equipment

1. High voltage cable partial discharge testing system software (laptop)

2. Integrated oscillating wave partial discharge testing host

1) High voltage generating device

2) Input power supply: AC220V ± 10%

3) Resonant reactor

4) Coil inductance: 0.8H

5) Specialized partial discharge data filtering and acquisition device

6) Sampling frequency: 125MHz 8-bit

7) Software: Expert Diagnostic System

3. Partial discharge calibrator (50pC, 100pC, 200pC, 500pC, 1nC, 2nC, 5nC, 10nC, 20nC)