Why is the leakage current test conducted for a DC high-voltage generator? When conducting a DC withstand voltage test, is it sufficient to simply reach the specified voltage level? Actually, it is not. For the insulation inspection of electrical equipment, the leakage current is one of the important reference data for judging the insulation condition. During the application of the specified DC voltage by the DC high-voltage generator, it can measure the leakage current generated by the tested item. Through the magnitude and trend of the current, it can assist in determining whether there are moisture, aging, pollution or other abnormal conditions in the insulation.
The leakage current refers to the small current that passes through the insulation medium and the insulation surface after applying DC voltage to the insulation material. An ideal insulator does not have an infinitely large resistance, so even when electrical equipment is under pressure, there will be a certain degree of leakage current. Under normal circumstances, the better the insulation performance, the smaller the leakage current usually is; if the insulation condition changes, the leakage current may increase accordingly.
The role of the DC high-voltage generator in the leakage current test is to provide stable and adjustable DC high voltage, and at the same time, it can observe the leakage current changes of the tested item under different voltages through the current measurement circuit. During the test, the operator can gradually increase the voltage and record the corresponding current data, and then combine the equipment technical requirements and test standards for analysis.
Why can’t we just look at the insulation resistance? This is because although both insulation resistance testing and leakage current testing are related to insulation performance, the focus of attention is not exactly the same. Insulation resistance is usually used to evaluate the overall resistance level of the insulation system, while the leakage current test focuses more on the actual current changes of the equipment under the specified DC voltage. Especially at higher test voltages, some insulation defects may be more easily manifested.
In actual tests, the value of leakage current is of course important, but the trend of change is also worth paying attention to. For example, as the test voltage gradually increases, the leakage current remains steadily increasing, which usually indicates that the insulation condition of the tested item is relatively stable. If the voltage increases little but the leakage current suddenly increases significantly, or the current continues to rise over time, it is necessary to further judge based on the condition of the test item.
For damp insulation materials, the leakage current may increase significantly. If the equipment is exposed to a humid environment for a long time, with dust, salt, or other contaminants adhering to the insulation surface, a more obvious surface leakage channel may form. In this case, even if the equipment does not show obvious breakdown, the leakage current may indicate changes in the insulation performance in advance.
The leakage current can also help detect problems that are not easily found through visual inspection in the insulation system. For example, insulation aging inside the equipment, local damage, surface contamination, and uneven insulation structure may all cause abnormal leakage current. Therefore, the leakage current test conducted by the DC high-voltage generator is not just for obtaining a current value, but to obtain more test information that can be used to judge the insulation condition.
During the leakage current test, the test wiring also affects the results. The tested item must be correctly wired according to the test requirements, the equipment grounding should be reliable, and the layout of the high-voltage line and grounding line should comply with the on-site safety requirements. If the wiring is incorrect, the contact is poor, or the test site is subject to obvious electromagnetic interference, it may lead to abnormal measurement results.
The test environment cannot be ignored either. Temperature, humidity, and the cleanliness of the surface of the tested item can all affect the leakage current. Therefore, when analyzing the test results, one cannot simply compare a single measurement value with a fixed number, but should also make a comprehensive judgment by combining the test conditions, historical data, and relevant test standards.
For larger tested items, there may be a relatively obvious charging current at the beginning of the voltage rise. The current change measured at this time may not necessarily indicate insulation abnormalities. It is necessary to wait for the charging process to gradually stabilize before analyzing the changes in leakage current in combination with the trend. Especially in the tests of samples with large capacitance such as cables, it is necessary to distinguish between the charging current and the leakage current under the stable state.
When conducting the leakage current test using a DC high-voltage generator, attention should also be paid to the voltage rise process. Generally, the voltage should be gradually increased according to the test requirements, and it is not advisable to quickly rise to a high voltage at once. During the voltage rise process, observe the changes in current, which can help detect abnormalities in time. If the leakage current suddenly increases rapidly within a certain voltage range, or even shows a significant jump, the test should be immediately stopped and the insulation condition of the sample and the test wiring should be checked.
The leakage current test also has practical significance, as it can complement the DC withstand voltage test. The DC withstand voltage test mainly examines whether the insulation system can withstand a certain amount of electrical stress for a specified period of time, while the leakage current test provides more detailed information on current changes. When combined, these tests can allow the test personnel to have a more comprehensive understanding of the insulation condition of the sample.
The LDZGF DC high-voltage generator produced by Wuhan Guodian Xigao Electric Co., Ltd. can be used for DC withstand voltage tests and leakage current tests. When conducting tests using the LDZGF DC high-voltage generator, the output voltage can be set according to the test requirements of the sample, and the leakage current changes can be observed through gradual voltage rise. The test results can be judged in combination with the test procedures.
When applying the LDZGF DC high-voltage generator to power equipment tests, it is necessary to select appropriate test voltages and testing methods based on different samples. For cables, lightning arresters, transformers, and other insulating equipment, the wiring method and test parameters should be determined based on specific test items. The insulation structure of different equipment varies, and the normal range of leakage current also differs. Therefore, the same value cannot be simply used as the judgment standard for all equipment.
It should be emphasized that the leakage current test is not just about “whether the current is large or small”. What is more important is to combine the test voltage, current changes, test time, and historical test data for analysis. If the trend of leakage current changes in the same equipment over previous tests is relatively stable, but there is a significant deviation in this test, further investigation of the insulation condition is necessary.
During on-site operations, after completing the DC high-voltage test, it is necessary to follow the regulations to reduce the voltage, discharge, and ground. Especially for samples with large capacitance such as cables, there may still be residual charges after the output is stopped. Only after confirming that the sample has been fully discharged and is in a safe state can the wiring be disconnected and subsequent processing be carried out.
Overall, the reason for conducting the leakage current test with the DC high-voltage generator is that insulation performance cannot be judged solely by appearance and a single parameter. By measuring the leakage current under the specified DC voltage and observing its size and trend, it can provide important evidence for judging the insulation condition of the equipment.
Post time: Sep-28-2026