Method for preventing neutral line current of built low-voltage water-turbine generator set from being too large

Abstract

The invention discloses a method for preventing the current of a neutral line of a built low-voltage water-turbine generator set from being too large, relates to the technical field of hydropower station power generation, and well solves the problems that the current of the neutral line of the low-voltage water-turbine generator set is large and heating is serious by installing an electric reactoron the neutral line. In addition, the built low-voltage water turbine generator set is still kept to be a neutral point direct grounding system, and the problem that the voltage deviation is not larger than 10% due to the fact that the voltage of the generator outlet end rises after the neutral point is displaced under the unfavorable operation working condition is solved. According to the specific scheme, the method comprises the following steps that an electric reactor is connected between a built neutral line leading-out wire of the low-voltage water turbine generator set and a 0.4 kV sideneutral line leading-out wire sleeve of a boosting transformer in series; and the built low-voltage water-turbine generator set is still a neutral point direct grounding system, so that the generatorcan be reliably disconnected to implement protection when a single-phase grounding fault occurs.

Description

technical field [0001] The invention relates to the technical field of hydroelectric power generation, and more specifically relates to a method for preventing the neutral line current of the built low-pressure hydroelectric generating set from being too large. Background technique [0002] Due to the simple structure and relatively low cost of the low-pressure hydroelectric generator set, it is widely used in small hydropower stations in rural areas. [0003] However, in the existing equipment, it often occurs that the three-phase symmetry of the generator is not good, which is reflected in the neutral point potential U of the generator. N It is not zero, but after connecting the neutral point of the generator to the neutral point of the low-voltage side of the step-up transformer through the cable line, since the distance between the neutral point of the generator and the neutral point of the transformer is very short (about ten meters), the connection of the neutral point...

AI Technical Summary

Problems solved by technology

After the neutral connection is cancelled, the low-voltage units stipulated by the national regulations should adopt the neutral point direct grounding system, which becomes the neutral point ungrounded system. The voltage increases by √3 times and becomes the line voltage, causing large-scale overvoltage damage to all household appliances in the same 0.4 / 0.23KV power supply area, causing electric shock accidents for humans and animals

See Figure 5 ; If the user-end load is asymmetrically operated, the three-phase current cannot be balanced through the neutral line, and the neutral point potential displacement of the generator will occur, causing the three-phase voltage to be unbalanced, and some phase voltages will drop very low, causing the user-end electrical equipment to Seriously insufficient output; some phase voltages rise much higher than the rated voltage, which may cause dangerous overvoltage damage to users, see Figure 4 ; It may also cause a single-phase ground fault in the system, the ground current cannot form a loop through the neutral line, the current protection will refuse to operate, and the generator set cannot be effectively protected

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