Grounding system and method for high-voltage and high-capacity flexible DC engineering

Abstract

The invention relates to a grounding system and method for high-voltage and high-capacity flexible DC engineering. The grounding system is characterized by comprising a three-winding transformer and agrounding device, wherein the three-winding transformer includes a transformer grid-side winding, a transformer valve-side winding and a transformer third winding, the grounding device includes a grounding resistor, a current measuring device, a lightning arrester and a bypass circuit breaker; the neutral point of the transformer grid-side winding is directly grounded; the neutral point of the transformer valve-side winding is connected to the grounding device; the grounding resistor is used for weakening the fault current of the flexible DC engineering after the occurrence of key faults; thecurrent measuring device is used for measuring the current flowing through the grounding resistor after the occurrence of the key faults; the lightning arrester is used for providing overvoltage protection for the transformer valve-side neutral point after the occurrence of the key faults; and the bypass circuit breaker is used for preventing the fault range extension caused by the inability of outputting the protection after the failure of an AC incoming line circuit breaker of the flexible DC engineering. The grounding system can be widely applied to the high-voltage and high-capacity flexible DC engineering adopting symmetrical unipolar connection.

Description

technical field [0001] The invention relates to a grounding system and method for a high-voltage and large-capacity flexible DC project, belonging to the field of flexible DC. Background technique [0002] Commonly used grounding systems for flexible DC projects using symmetrical unipolar wiring include the DC pole line through a large resistance grounding system, the transformer valve side grounding reactor forming a neutral point through a large resistance grounding system, and the transformer valve side winding neutral point through a large resistance grounding system , respectively as figure 1 , figure 2 with image 3 shown. [0003] In the high-voltage large-capacity flexible DC project using symmetrical unipolar wiring, if the DC pole line is grounded through a large resistance system, since the resistance is a long-term high-energy load during normal operation, it is easy to cause damage to the resistance due to overheating; if the transformer valve is used The s...

AI Technical Summary

Problems solved by technology

[0003] In the high-voltage large-capacity flexible DC project using symmetrical unipolar wiring, if the DC pole line is grounded through a large resistance system, since the resistance is a long-term high-energy load during normal operation, it is easy to cause damage to the resistance due to overheating; if the transformer valve is used The side grounding reactor forms a neutral point through a large resistance grounding system. Due to the large reactive power absorbed by the high-voltage level grounding reactor, the reactive power supply capability of the flexible DC project will be greatly affected; due to the high-voltage and large-capacity flexible DC The AC system connected to the project usually adopts the neutral point direct grounding method. If the neutral point of the transformer valve side winding is grounded through a large resistance system, the transformer grid side is required to be connected in an angled shape, which will lead to a drastic increase in the insulation level of the transformer grid side equipment.

Therefore, there is a need for a grounding system for high-voltage and large-capacity flexible DC projects, which can solve the problems of easy overload, high reactive power consumption, and increased grid-side insulation level caused by common grounding methods

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