The general principle of the DC high voltage generator: the test voltage field strength applied to the test piece must simulate the working conditions of high voltage electrical appliances. The DC high voltage generator has high precision and accurate measurement. Both the voltmeter and the ammeter display digitally, with a voltage resolution of 0.1kV and a current resolution of 0.1uA. The voltmeter on the control box directly displays the voltage value added to the load test sample. It can be easily wired without the need for an external voltage divider. The instrument has high and low voltage terminals to measure leakage current, and the high voltage terminal is displayed by a circular shielded digital meter. It is not afraid of discharge shock, has good anti-interference performance, and is suitable for on-site use. A high voltage test pass or fail conclusion is meant to indicate whether a weakness in the high voltage appliance is detrimental to future operation. This means that the failure mechanism in the test should have the same physical process as the mechanism in the device operation.
The withstand voltage test of the DC cable of the DC high voltage generator is mainly manifested in the following aspects: 1. Under the DC voltage, the electric field distribution of the cable insulation layer depends on the volume of the material. The resistivity, as well as the electric field distribution at AC voltage, depends on the permittivity of each medium, especially the strength of the DC electric field in cable terminals, junction boxes, etc. The distribution and the distribution intensity of the alternating electric field are completely different, and the aging mechanism of insulation under DC voltage is different from that under AC voltage. Therefore, the DC withstand voltage test cannot simulate the cable 2, the cable will be under the DC voltage; memory; the effect is that the storage will accumulate a unipolar residual charge. Once caused by the DC withstand voltage test; memory; it takes a long time to release this DC bias. If put into service before the DC residual charge is fully discharged, the DC bias will be superimposed on the peaks of the power frequency voltage, causing the voltage on the cable to far exceed its rated voltage, which may cause damage to the cable. Insulation breakdown. 3. In the DC withstand voltage test, electrons are injected into the polymer medium to form a space charge, which reduces the electric field strength at that location, making it difficult to break down. Semiconductor Semiconductors and contamination sites are prone to space charge. However, if the surface of the cable lug flickers or the cable accessories are damaged during the test, fluctuations will occur on the cable core. Where space charge accumulates, the polarity of the oscillating voltage rapidly changes to the opposite polarity.
At this point, the electric field strength increases significantly, which can damage the insulation and cause multiple clicks. 4. One of the fatal weaknesses of the cable is that it is easy to produce water branches in the insulation. Once the water branch is generated, it will be rapidly converted into an electrical branch at a DC voltage and a discharge will be formed, which will accelerate the insulation degradation, so that it will operate at the power frequency voltage after operation. form a failure. And the pure water branch is communicating it can maintain a decent withstand voltage at the working voltage, and can maintain it for a period of time. 5. Practice has also shown that the DC withstand voltage test of the DC high voltage generator cannot effectively find some defects under the action of AC voltage, such as whether there is mechanical damage or stress cone dislocation in the cable accessories. A location where breakdown of insulation at AC voltage is likely to occur, and is generally not possible at DC voltage. Insulation breakdown at DC voltage often occurs, where the insulation does not break down under AC operating conditions.
In the early maintenance and post maintenance of electrical equipment, it refers to the maintenance after the electrical equipment fails. This maintenance method is extremely unscientific. The DC high-voltage generator adopts a new generation of PWM high-frequency pulse width modulation technology, adopts IF voltage doubler circuit, high-performance closed-loop regulation, and high-voltage large feedback function. Greatly improved voltage stability. With the development of electrical equipment overhaul technology, preventive maintenance is gradually replaced (using one substance to replace another substance (usually replacing the state of weak substance with a strong substance)) for post-event maintenance, mainly regular tests and regular maintenance, in During the overhaul process, the operation must be carried out in strict accordance with the "Temporary Test Regulations for Electrical Equipment" and other relevant regulations, and the test cycle and items should be formulated according to different electrical equipment. Preventive maintenance plays an active role in preventing and reducing equipment accidents. However, this type of maintenance has some shortcomings, mainly in the following three aspects: (1) The timeliness and initiative of traditional electrical equipment maintenance are poor.
Due to regular preventive maintenance, many maintenance personnel have formed a step-by-step work philosophy, focusing only on the regular maintenance work of electrical equipment, while ignoring the daily monitoring of the operation of electrical equipment. In this case, the initiative of maintenance personnel to overhaul electrical equipment is greatly reduced. If defects and hidden dangers of electrical equipment develop rapidly, regular maintenance methods may make it difficult to avoid equipment accidents. (2) The maintenance efficiency of traditional electrical equipment is low. The preventive maintenance of electrical equipment involves a wide range of areas and lacks specificity. Regular maintenance often requires a lot of manpower, material and financial resources, resulting in low maintenance work efficiency.
At the same time, in the process of preventive maintenance, the main points of electrical equipment maintenance are often unclear, resulting in insufficient attention to equipment in question, while equipment that is operating well wastes maintenance resources, resulting in problems during inspections. work and deal with problems. Low ability. (3) Too many maintenance restrictions on traditional electrical equipment When electrical and electronic equipment is regularly inspected, maintenance is often required after a power outage, which not only increases the maintenance cost of electrical equipment, but also affects the maintenance of the equipment. normal operation of the power system. At the same time, since the temperature and the used test voltage of the equipment in the power-off state are very different from those in the working state, the experimental accuracy of the electrical equipment is greatly reduced.
