Grounding Method of Impedance Type Neutral Point for Huge Hydrogenerator Set

Abstract

The invention discloses an impedance-type neutral point grounding method for a giant hydroelectric generating set, and relates to a method for arranging the grounding side of a generator neutral point grounding method group. It includes determining the neutral point grounding scheme and equipment parameters, and the equipment layout of the hydro-generator set on the generator floor of the plant; judging whether the generator needs to be grounded, and judging whether instantaneous shutdown is required according to the relevant guidelines of the power industry; Intrinsic capacitive current I c , comparing the intrinsic capacitive current I c and short-circuit current I safe The limit value, according to the resistance R and the reactance X L The formula for determining the parameter configuration interval of the parameter, determine the resistance R and reactance X L parameter configuration interval, determine the final resistance R and reactance X L Grounding parameter configuration mode; output the final grounding scheme configuration parameters, and according to the final resistance R and reactance X L Grounding parameters Install the neutral point grounding device of the combined cabinet type impedance type generator. The invention can transform or replace the equipment in a single equipment cabinet, and the transformation is more flexible and easier.

Description

technical field [0001] The invention relates to a method for arranging the grounding side of a generating set, in particular to an impedance-type neutral point grounding method for a giant hydroelectric generating set. Background technique [0002] A total of 12 vertical shaft Francis turbine generators with a unit capacity of 850MW are installed in Wudongde Hydropower Station (6 units on the left bank and 6 units on the right bank), with a total installed capacity of 10200MW. Baihetan Hydropower Station is equipped with 16 sets (8 sets each on the left bank and 8 sets on the right bank) vertical axis Francis turbine generating units with a single unit capacity of 1000MW, with a total installed capacity of 16000MW. The generators in Wudongde and Baihetan have a capacity of 850MW and above, and the traditional grounding method of the neutral point of the generators is generally difficult to keep the ground fault current within the allowable range. [0003] Traditional genera...

AI Technical Summary

Problems solved by technology

[0007] For giant units above 600MW, foreign reactance grounding methods can meet the requirements, but because of the need for overload protection devices, the cost is high; in giant units above 600MW, since the current of the 600MW unit can easily reach 30A, it will burn out battery cells, resulting in a waste of resources. Therefore, at present, in the existing technology, domestic giant units above 600MW are divided into several large units or small and medium-sized units connected together, so that the capacity of a single unit will not exceed 600MW. So as to meet the common domestic unit construction method in my country

[0008] Aiming at the problem that the unit current of domestic generator sets is easy to be too large, the Chinese invention patent "A Generator Neutral Point High Inductive Reactance Grounding Device" (patent number: ZL201510310760.7) discloses a generator neutral point high inductive reactance Grounding device, which can make the short-circuit current limit below 15A, which is suitable for small and medium-sized generator sets below 200MW, and the single-phase ground capacitance is 2.068μF

For giant hydroelectric generators with a capacity of 600MW and above, the above-mentioned generator neutral point high inductive reactance grounding device cannot meet the requirements. The specific reasons are as follows: if the structure described in this patent is adopted, the neutral point grounding device All electrical equipment is placed in the unit casing, so the neutral point grounding device will not only be bulky (if the height is too high, it will be inconvenient to install), but also inconvenient to repair (since all units are placed in the same device, Therefore, it is inconvenient to modify)

[0009] At the same time, in view of the problem that the unit current of domestic generator sets is easy to be too large, the Chinese invention patent "New Neutral Point Grounding Resistor" (Patent No.: ZL200920096920.2") discloses a new type of neutral point grounding resistor. It is an improvement based on the high-impedance grounding method of the distribution transformer, but it is still difficult to solve the problem caused by the large capacitance of the stator winding of the giant hydro-generator to the ground

At the same time, since the device only changes the resistance value, when the ground fault capacitor current exceeds 18A, it will be difficult to limit the ground fault current to below 25A

[0010] The neutral point grounding method and parameters of units with a capacity of 850MW and above must break through the traditional method. At present, there is no research or engineering experience in this area at home and abroad to learn from

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