CN105375127A - Method for reducing grounding resistance in manner of digging grounding deep well in transformer station - Google Patents

Abstract

The invention discloses a method for reducing grounding resistance in manner of digging a grounding deep well in a transformer station, comprising steps of calculating a station address soil layered model, calculating target parameters like a power frequency grounding resistance safety value of a horizontal grounding grid and safety values of a contact potential difference and a step potential difference, obtaining a power frequency grounding resistance calculation value of a horizontal grounding grid and calculation values of the contact potential difference and the step potential difference, determining the amount, the positions, the well depth, the perpendicular grounding electrode materials and equivalent radiuses of the grounding deep wells, regulating the parameters of the grounding deep well, providing a horizontal grounding grid material table, a perpendicular grounding body material table, rise of earth potential, the power frequency grounding resistance, the calculation values and the safety values of the contact potential difference and the step potential difference of the grounding grid of the station. The invention can dramatically reduce the grounding resistance of the transformer station, enables the contact potential difference and the step potential difference to be reduced to below the safety value, and enables the design of the high soil resistivity and transformer station grounding system having the ground water layer to be simple, accurate and effective.

Description

The reduction earth resistance method of ground connection deep-well mode is beaten in a kind of transformer station

Technical field:

The present invention relates to System in Substation technical field, be specifically related to a kind of reduction earth resistance method of beating ground connection deep-well.

Background technology:

Good grounding system is the basic guarantee of substation safety, reliable, stable operation, but current domestic substation location is selected to dodge the soils such as good farmland, residential block, economic development zone due to needs and can be used costly area, position, site is usually positioned at the region that soil resistivity is high, geologic condition is poor, this just brings great challenge to System in Substation design, therefore needs the grounding system of reliable a, function admirable.

At present, domestic design of ground system generally adopts following steps to carry out: according to soil resistivity measured value, earth current maximum value, transformer station's areal calculation obtains grounding resistance, contact potential difference and step potential difference minimum value in standing, pass judgment on ground network effect with this and adopt successively and fall resistance measure, method for designing like this is higher to designer's skill requirement, especially in the face of complex geological condition time (as high soil resistivity, there is water table), accurately cannot adopt the ground network model after falling resistance measure, subregion assessment ground network resistance reducing effect is not known where to begin especially, therefore for the purpose of conservative, often intrepidly increase horizontal grounding net materials and the material usage falling resistance measure, cause the waste of financial resource and material resource.

Summary of the invention:

The object of this invention is to provide in a kind of transformer station the reduction earth resistance method of beating ground connection deep-well mode, make high soil resistivity, exist the System in Substation of water table design easy, accurate and effective.

In order to solve problem existing in background technology, the inventive method step is as follows:

(1) obtain site soil resistivity measured value and the water table degree of depth, adopt steepest descent method to calculate site soil layering model;

(2) this project earth current maximum is calculated by transformer station's calculation of short-circuit current result, the target components such as the safety value of calculated level ground network power frequency earthing resistance safety value, contact potential difference and step potential difference;

(3) according to transformer station's area, the material of initialization horizontal grounding net, equivalent redius and mesh size, obtain horizontal grounding net power frequency earthing resistance calculated value, contact potential difference and step potential difference calculated value;

(4) according to substation location soil layering model, and step (2), the middle calculated value of step (3) and safety value depart from quantity, determine ground connection deep-well quantity, position, well depth, vertical grounding electrode material and equivalent redius;

(5) the earth potential liter beating ground network after ground connection deep-well is calculated, whether power frequency earthing resistance calculated value, contact potential difference and step potential difference calculated value meet safety value in step (2), if do not meet, return step (4), adjustment ground connection deep-well parameter, until meet safety value requirement;

(6) calculated value and the safety value of the horizontal grounding net material list of this station ground network, Grounding Grids material list, earth potential liter, power frequency earthing resistance, contact potential difference and step potential difference is provided.

The present invention can significantly reduce substation grounding resistance, and makes contact potential difference and step potential difference be reduced to below safety value, make high soil resistivity, exist the System in Substation of water table design easy, accurate and effective.

Accompanying drawing illustrates:

Fig. 1 is the FB(flow block) of the inventive method;

Fig. 2 is that this method adopts and beats ground connection deep-well mode and reduce earth resistance schematic diagram.

Embodiment:

Below in conjunction with embodiment, the invention will be further described:

Embodiment 1, with reference to Fig. 1-2, embodiment 1 is for Anqing 110kV transformer station:

(1) System in Substation initial condition

1) soil resistivity measured value and geological conditions,

This transformer station is positioned at Anqing Area, and district of standing is of a size of 48m × 81.5m, and present position soil resistivity measured value is higher, as table 1, according to exploration specialty " exploration of geotechnical engineering report ", our station ground ground 0.5m ~ 4.2m is silty clay, and first meeting bury of groundwater is at 3.5 ~ 4.5m.

Table 1

2) horizontal grounding net initial parameter, as table 2, calculating earth current maximum is 3.43kA.

Table 2

The material of horizontal grounding net	Cross section (mm*mm)	Mesh size (mm*mm)	The depth of burying
				Zinc-coated flat steel sheet	-50*6	6*6	-0.8m

3) steepest descent method is adopted to calculate site soil layering model as table 3:

Table 3

The number of plies	Soil resistivity (ohm-m)	Layer depth (m)
			1	153.67	0.2
2	172.79	1.44
			3	117.94	1.87
4	20	1
			5	117.94	+∞

(2) calculated value of horizontal grounding net power frequency earthing resistance, contact potential difference and step potential difference, safety value is calculated as table 4:

Table 4

Note: when power frequency earthing resistance does not meet safety value requirement, if earth potential liter is less than 4000V and contact potential difference and step potential difference meet safety value requirement, then also thinks that ground network meets safety value requirement.

(3) according to substation location soil layering model, quantity is departed from calculated value and safety value in horizontal grounding net power frequency earthing resistance, contact potential difference and step potential difference, determine ground connection deep-well quantity, position, well depth, vertical grounding electrode material and equivalent redius, because our station power frequency earthing resistance and contact potential difference cannot meet safety value requirement, according to water table distribution situation, adopt and beat ground connection deep-well method reduction earth resistance.

(4) parameters such as ground connection deep-well quantity, position, well depth, vertical grounding electrode material and equivalent redius are determined, as table 5:

Table 5

(5) ground network assessment, is confirmed whether to meet safety value requirement, refers to table 6:

Table 6

Contact potential difference can be made to reach safety value requirement by making a call to 4 mouthfuls 50 meters dark ground connection deep-wells in transformer station four corners, and make earth potential be elevated to below 4000V, meet the safety value requirement of note in table 4, now think that this ground network meets safety value requirement, this design is safe, reliable, economical.

(6) provide the horizontal grounding net material list of this station ground network as table 2, Grounding Grids material list table 5, the calculated value of earth potential liter, power frequency earthing resistance, contact potential difference and step potential difference and safety value are as table 6.

These are only preferred embodiment of the present invention; but protection scope of the present invention is not limited thereto; anyly be familiar with those skilled in the art in the technical scope that the present invention discloses, the change that can expect easily or replacement, all should be encompassed in protection scope of the present invention.

Claims (1)

1. beat a reduction earth resistance method for ground connection deep-well mode in transformer station, step is as follows:

(1) obtain site soil resistivity measured value and the water table degree of depth, adopt steepest descent method to calculate site soil layering model;

(2) this project earth current maximum is calculated by transformer station's calculation of short-circuit current result, the target components such as the safety value of calculated level ground network power frequency earthing resistance safety value, contact potential difference and step potential difference;

(3) according to transformer station's area, the material of initialization horizontal grounding net, equivalent redius and mesh size, obtain horizontal grounding net power frequency earthing resistance calculated value, contact potential difference and step potential difference calculated value;

(4) according to substation location soil layering model, and step (2), the middle calculated value of step (3) and safety value depart from quantity, determine ground connection deep-well quantity, position, well depth, vertical grounding electrode material and equivalent redius;

(5) the earth potential liter beating ground network after ground connection deep-well is calculated, whether power frequency earthing resistance calculated value, contact potential difference and step potential difference calculated value meet safety value in step (2), if do not meet, return step (4), adjustment ground connection deep-well parameter, until meet safety value requirement;

(6) calculated value and the safety value of the horizontal grounding net material list of this station ground network, Grounding Grids material list, earth potential liter, power frequency earthing resistance, contact potential difference and step potential difference is provided.