A kind of using electricity system that is applied to big-and-middle-sized thermal power plant high pressure factory
Technical field
The utility model relates to the mode of connection of electrical system, relates in particular to a kind of using electricity system that is applied to big-and-middle-sized thermal power plant high pressure factory.
Background technology
Thermal power plant HV Auxiliary Transformer adopts angle scheme high-voltage Auxiliary section, and transformer neutral point cannot ground connection.And big-and-middle-sized thermal power plant high-voltage Auxiliary section single-phase-to-ground current generally all exceedes 10A, in the time there is single phase ground fault, will produce higher arcing ground over-voltage, and easily develop into heterogeneous short circuit.Many power plants for many years that moved are at initial operating stage, and single-line ground electric current does not exceed 10A, but along with the increase of loading in high-voltage Auxiliary section, high-tension cable is more and more, and single-phase-to-ground current increases gradually, and to equipment, operation has produced hidden danger.At present, newly-designed power plant, in order to save first investment, often utilizes the angle scheme transformer of old factory as start and stop power supply, and makes the newly-designed station service transformer cannot wiring.
Utility model content
The purpose of this utility model is to provide a kind of using electricity system that is applied to big-and-middle-sized thermal power plant high pressure factory, divide bus section, busbar section that Z-shaped grounding transformer is set in high-voltage Auxiliary section, solve thermal power plant HV Auxiliary Transformer and adopt angle scheme high-voltage Auxiliary section, the problem that transformer neutral point cannot ground connection.
For achieving the above object, the utility model adopts following technical scheme:
A kind of using electricity system that is applied to big-and-middle-sized thermal power plant high pressure factory, thermal power plant HV Auxiliary Transformer adopts angle scheme high-voltage Auxiliary section, divide on bus section, busbar section Z-shaped grounding transformer is set in high-voltage Auxiliary section, Z-shaped grounding transformer neutral point passes through grounding through resistance.
The described each transformer being connected with high-voltage Auxiliary section connects respectively 2 sections of points of bus section, busbar sections, and high-voltage Auxiliary divides bus section, busbar section subsection setup, nothing electrical connection between each point of bus section, busbar section.
Described each section point bus section, busbar section is by high-tension fuse, vacuum contactor loop and protection measure and control device access Z-type grounding transformer.
Described Z-shaped grounding transformer adopts dry-type transformer, and Z-shaped grounding transformer neutral point is by metallic resistance ground connection.
Described Z-shaped grounding transformer is three-phase six winding constructions.
The utility model divides and on bus section, busbar section, accesses respectively a Z-shaped contact transformer at station-service high pressure; a neutral point of artificial increase; then ground connection after connecting resistance; adopt Z-type grounding transformer; in the time of high-voltage Auxiliary system single-phase earthing; limited internal overvoltage, and the zero sequence overcurrent protection becoming for factory provides reliable operating current.Solve thermal power plant HV Auxiliary Transformer and adopted angle scheme high-voltage Auxiliary section, the problem that transformer neutral point cannot ground connection.
Further, Z-type grounding transformer is three-phase six winding constructions, and it has higher positive and negative order impedance.When system is normally moved, ground connection impedance is very high, and winding only flows through very little exciting current, and in the time of system generation earth fault, winding will flow through larger zero-sequence current.
Brief description of the drawings
Fig. 1 is electrical principle wiring schematic diagram of the present utility model.
Embodiment
Below in conjunction with accompanying drawing, the utility model is described in further detail:
Kind of the present utility model is applied to the using electricity system of big-and-middle-sized thermal power plant high pressure factory; thermal power plant HV Auxiliary Transformer adopts angle scheme high-voltage Auxiliary section; divide on bus section, busbar section by high-tension fuse, vacuum contactor loop and protection measure and control device access Z-type grounding transformer in high-voltage Auxiliary section; Z-shaped grounding transformer neutral point is by metallic resistance ground connection; it is three-phase six winding constructions that described Z-shaped grounding transformer adopts dry-type transformer, and Z-shaped grounding transformer neutral point passes through ground connection.
As shown in Figure 1, each transformer that high-voltage Auxiliary section connects connects respectively 2 sections of points of bus section, busbar sections, and high-voltage Auxiliary divides bus section, busbar section subsection setup, nothing electrical connection between each point of bus section, busbar section.Power plant high-voltage Auxiliary section, connects 6kV and divides bus section, busbar section A, B, C, D section, and then each section point bus section, busbar section accesses a Z-type grounding transformer by cable by high-tension fuse, vacuum contactor loop and an integrated protection and monitoring device.
The capacity of Z-type contact transformer can be according to formula S
n=(1.732*U
n* I
10S/ 3)/k calculates, wherein:
1) U
nsystem rated voltage (kV)
2) I
10Sallow in short-term phase current
3) K is the grounding transformer 60s through-flow time in short-term
Neutral resistance value can be according to R
n=Ue/1.732*IR calculates, wherein:
1) Ue system rated voltage (kV)
2) I
rthe earth resistance electric current (A) allowing
Divide and on bus section, busbar section, access respectively a Z-shaped contact transformer at station-service high pressure; a neutral point of artificial increase; Z-shaped grounding transformer neutral point passes through grounding through resistance; solve thermal power plant HV Auxiliary Transformer and adopt angle scheme high-voltage Auxiliary section; transformer neutral point cannot ground connection problem; while exceeding for power plant high-voltage Auxiliary section capacitance current the 10A that code specifies, and station service transformer neutral point adopts the zero-sequenceprotection in the big-and-middle-sized thermal power plant of angle scheme that solution is provided.
Above content is in conjunction with concrete preferred implementation further detailed description of the utility model; can not assert that embodiment of the present utility model only limits to this; for the utility model person of an ordinary skill in the technical field; without departing from the concept of the premise utility; can also make some simple deduction or replace, all should be considered as belonging to the utility model and determine scope of patent protection by submitted to claims.