A combined neutral point grounding comprehensive control device

Abstract

A combined neutral point grounding integrated control device belongs to the field of power grid automatic control. The technical problem to be solved in the invention is to provide a combined neutral point grounding integrated control device which can improve the level of integrated control on power grid voltage greatly and improve the reliability of power grid operation. The technical scheme is as follows: a combined grounding control device is arranged at the neutral point of a transformer or generator, and the device comprises a protection branch (1), a protection branch (2), a protection branch (3) and an integrated control unit (7). The CPU master control program of the integrated control unit (7) controls the three protection branches. Overvoltage of a power grid is controlled in a cascaded manner according to the duration of overvoltage of a power supply network, wave steepness, energy magnitude, and voltage parameters. A protection scheme including the steps of voltage limiting, energy inhibition, low-voltage grounding and the like is adopted. Cascade control on the power grid voltage is realized through cascaded cooperation of all levels of protection according to the voltage parameters, time parameters and energy parameters.

Description

technical field [0001] The invention relates to a neutral point grounding device of a power grid, in particular to a 3-66kV medium-voltage power supply network, which can greatly improve the power supply reliability of the power grid and ensure the safety of electrical equipment. A combined neutral point comprehensive control device . Background technique [0002] Three voltage levels of 6kV, 10kV, and 35kV are commonly used in my country's 3-66kV medium-voltage power grid. In recent years, with the development of power supply networks, vacuum circuit breakers have been used in large quantities, and the number of users using cable lines is increasing. The use of power equipment such as inverters, high-voltage thyristors, etc. is also increasing day by day, resulting in frequent fluctuations in grid voltage, and more and more frequent system failures caused by voltage fluctuations in the power supply network, resulting in damage to power transmission and transformation equipme...

AI Technical Summary

Problems solved by technology

This kind of protection scheme has high accuracy and reliable protection. Its main disadvantages are: firstly, when a single-phase ground fault occurs, it is impossible to distinguish whether it is permanent or instantaneous, and it is also impossible to distinguish between metal grounding and intermittent arc grounding. Because of tripping, the number of tripping of the line is greatly increased, which seriously affects the normal power supply of users and reduces the reliability of power supply

This technology believes that the energy capacity of the high-energy zinc oxide nonlinear resistor is designed according to 300% of the system energy capacity, but it does not talk about the energy capacity of the system. As we all know, the energy of a power system is proportional to voltage, current, and time. The duration of the overvoltage is indeterminate. For example, intermittent arc grounding may be instantaneous, may last for a few minutes, or may exist for a long time. Due to the uncertainty of the duration of the overvoltage, the maximum energy of the overvoltage can be considered infinite. However, the energy of the non-linear resistance cannot be designed to be infinite, so the so-called 300% is meaningless. Once the energy of the overvoltage exceeds the designed energy of the high-energy zinc oxide non-linear resistance, it will lead to the breakdown of the zinc oxide resistance, and then Heat accumulation leads to thermal collapse. Although the patented technology of patent number ZL2010201575037 adds a fuse to protect the high-energy zinc oxide non-linear resistor, the withdrawal of the zinc oxide non-linear resistor will make the device unable to work normally.

[0008] To sum up, for the problem of system overvoltage, there are various problems in the previous three operation modes and known solutions, lack of comprehensive protection and unified consideration of the power grid system, and it is impossible to achieve protection Harmonious unity of comprehensiveness, reliability and system security

Images