In industrial, mining, metallurgy, steel, and power sectors, there is a very popular power test instrument called the DC high voltage generator. Its function is very powerful, capable of performing DC high voltage tests on high-voltage electrical equipment such as zinc oxide arresters, power cables, transformers, and generators.
The polarity reversal of a DC high voltage generator involves a series of processes such as generator voltage reduction, grounding, silicon stack polarity switching, grounding, and voltage boosting. Each step in the polarity reversal process requires a significant amount of time. To shorten the polarity switching time of the DC high voltage generator and achieve fast polarity switching, it is necessary to reduce the time of each process.
Several ways for the DC high voltage generator to achieve fast polarity reversal:
1. During the voltage reduction process, accelerating the voltage reduction speed is one aspect of shortening polarity switching. This is mainly achieved by increasing the discharge resistance to speed up voltage reduction. Increasing the discharge resistance does not increase the total resistance of the discharge resistor, but rather increases the number of resistors with the same resistance value connected in parallel with the voltage divider. The more columns, the lower the total resistance, and the faster the voltage reduction. At the same time, the lower limit of the discharge resistance should be considered, because an excessively small discharge resistance will inevitably lead to an increase in leakage current during normal operation of the device.
2. During the grounding process, it takes a long time for the test voltage to be grounded to zero or a zero value. When the voltage of the DC high voltage generator drops from the test value to a certain level, directly grounding with a fast grounding switch can greatly shorten the grounding process. However, a fast grounding switch that meets high voltage requirements must withstand all high voltages and large currents, which is extremely demanding for a fast grounding switch.
3. Simply put, the silicon stack needs to achieve fast polarity reversal to realize the reversal of the polarity of internal single tubes. To achieve this goal, we must first consider the driving mechanism. Currently, there are three simple driving methods: electric, pneumatic, and hydraulic. According to the structural characteristics of the DC high voltage generator, it is impossible to achieve electric power supply under high voltage. Pneumatic devices have the compression ratio of the air source used by the cylinder.
If all silicon reactors are connected in series through air pipes, when the humidity in the gas is high, the entire device will discharge from the air pipes, causing equipment damage, etc. The hydraulic method uses vacuum-treated alkylbenzene insulating oil, which will not cause discharge. Secondly, the compression ratio of oil is much smaller than that of gas, which can achieve smooth polarity reversal of silicon reactors, avoiding the problems of the other two methods. By comparison, it can be seen that the hydraulic selection method is reasonable.
