In modern power system, cable, as an important transmission medium, carries a large amount of electric energy. In order to ensure the safe operation of the cable, regular partial discharge test is essential. Partial Discharge (PD) refers to the phenomenon of electrical discharge in a local area of the cable insulation material due to insulation defects or aging. The oscillating wave partial discharge test of cable is an effective detection method, which can find the potential problems of cable insulation in time and avoid power accidents caused by insulation failure.

Test preparation
1. Equipment preparation: Before performing the oscillating wave partial discharge test, prepare the corresponding test equipment, including the oscillating wave generator, partial discharge detector, and oscilloscope. These devices are capable of generating oscillating waves of a specific frequency and monitoring partial discharge signals.
2. Cable selection: Select the cable to be tested, usually the cable that is in operation or just stopped. The type, rated voltage, length and other parameters of the test cable should be recorded for subsequent analysis. 3. Environmental conditions: The test should be carried out under appropriate environmental conditions to avoid humidity, dust and other factors that affect the test results. At the same time, ensure the safety of the test area to prevent accidents.

Test steps
1. Connect the device: Connect the oscillating wave generator to the cable to be measured. Generally, the output end of the oscillating wave generator is connected to the high voltage end of the cable, and the partial discharge detector is connected to the grounding end of the cable.
2. Set parameters: According to the rated voltage of the cable and test requirements, set the frequency and amplitude of the oscillation wave. In general, the frequency of the oscillating wave should be selected near the resonant frequency of the cable insulation material to improve the detection sensitivity of partial discharge.
3. Apply oscillating wave: Start the oscillating wave generator and apply oscillating wave to the cable. At this time, the phenomenon of partial discharge in the cable will be excited to produce a specific electrical signal.
4. Monitoring signal: Use the partial discharge detector to monitor the partial discharge signal generated in the cable. The detector can record the amplitude, frequency and duration of partial discharge in real time, and transmit the data to the computer for analysis.
5. Data analysis: Analyze the monitored partial discharge signal by oscilloscope or special software. Generally, the larger the amplitude of the partial discharge signal, the more serious the insulation defect. During the analysis process, it should be compared with historical data to determine the change of cable insulation status.

Evaluation of test results
After the test, the insulation state of the cable is evaluated according to the detected partial discharge signal. In general, the evaluation criteria for partial discharge include:
1. Local discharge: The size of the local discharge directly reflects the health of the cable insulation. A higher discharge usually means there is a defect in the insulation.
2. Discharge frequency: The change in discharge frequency can also help judge the degree of aging of insulation. An increase in frequency may indicate deterioration of the insulating material.
3. Discharge mode: By analyzing the waveform of the discharge signal, the characteristics and source of the discharge can be judged to help locate the location of the insulation defect.

Precautions
When conducting the cable oscillating wave partial discharge test, the following points should be noted:
1. Safety: Safety operation procedures should be strictly followed during the test to ensure the safety of the operator.
2. Regular maintenance: The test equipment should be verified and maintained regularly to ensure its normal operation and avoid test errors caused by equipment failures.
3. Data recording: After each test, the test parameters and results should be recorded in detail for long-term tracking and analysis.
4. Environmental impact: When conducting the test, the impact of external electromagnetic interference on the test results should be avoided as far as possible, and shielding measures can be taken if necessary.

The oscillating wave partial discharge test is an efficient and reliable method to detect the insulation status of cable. By conducting this test regularly, the insulation defects of the cable can be effectively identified, thereby reducing the safety risk of the power system. With the development of the power industry, partial discharge detection technology is also improving, and there will be more innovative detection methods in the future to provide a more powerful guarantee for the safe operation of the power system.