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High voltage test for current limiting resistor

time:2020/11/30   source:华天电力  reading:806 time

The purpose of the DC high voltage generator test is mainly to check whether the leakage current obtained from the withstand voltage test of the cables, zinc oxide arresters, transformers, switch cabinets, etc., meets the national standard. But sometimes when the leakage current is too large and exceeds the maximum flow range of the host and the high-voltage cylinder, it will cause irreparable damage to the instrument. At this time, we need to connect a high-current resistor on the top of the high-voltage cylinder, and then install a microampere. table;

Technical principle of field test of DC high voltage generator:

The power of the micro-inverter ranges from 200W to 500W and is mainly used on curtain walls, window sills and small roofs. For micro-inverters, the capacitor C1 functions as a step-down and current-limiting function: as everyone knows, the characteristics of the capacitor are AC and DC blocking. When the capacitor is connected to an AC circuit, the capacitive reactance calculation formula is: XC=1/2πfC Where XC represents the capacitive reactance of the capacitor, f represents the frequency of the input AC power supply, and C represents the capacity of the step-down capacitor.

DC Hipot Tester.png

The formula for calculating the current flowing through the capacitor step-down circuit is: I=U/XC where I represents the current flowing through the capacitor, U represents the power supply voltage, XC represents the capacitive reactance of the capacitor in a 220V, 50Hz AC circuit, when the load voltage is far When it is much less than 220V, the relationship between current and capacitance is: I=69C, where the unit of capacitance is uF and the unit of current is mA

On-site personnel often use a clamp-on ammeter to clamp the iron core grounding wire to monitor the performance of the current DC high-voltage generator. However, due to the interference of the transformer's strong magnetic field, the DC high-voltage generator may even have several different measured values at the same measuring point. The reference value of this measurement is doubtful; however, the automatic monitoring device developed by some domestic units can detect multiple grounding points in time. Failure, but lack of real-time monitoring function after failure. For this reason, a line monitoring device based on GSM communication is designed, which better solves the problem of on-line monitoring of transformer core ground current. In order to solve the problem that the ground current is very small under normal conditions, but it is more severely interfered by the scene.

The change in the core current of a large power transformer can directly reflect the fault state of the transformer—whether there are multiple grounding of the core. In the past, the monitoring method used hand-held instruments to conduct regular inspections and records by substation staff on duty. There are serious hidden dangers that further expand the accident. With the improvement of power automation level and the increase of unmanned substations, there is an urgent need for a stable, reliable, high-precision, and powerful online monitoring device for the core current of large power transformers. The device described in this article is designed for this with extremely high application value.

The technical principle of the DC high voltage generator meets the electrical power requirements of the equipment under the maximum load. The efficiency of the DC high voltage generator is improved. The rated output power represents the ability of the photovoltaic inverter to supply power to the load. The photovoltaic inverter with high rated output power can carry more electric loads. When choosing a photovoltaic inverter, you should first consider having sufficient rated power. And the expansion of the system and the access of some temporary loads.

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