CN101403775B - Short-distance test method for grounding impedance of large grounding network - Google Patents
Short-distance test method for grounding impedance of large grounding network Download PDFInfo
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Abstract
The invention provides a method used for testing the grounding resistance of a large grounding network, with short distance, belonging to the power technique field; the testing method is used for solving the testing problem of the grounding resistance. The technical proposal is that a current electrode is arranged at a position of the maximum diagonal length of the grounding network which is 1.2-1.5 times away from the grounding network to be tested; furthermore, current is injected between the current electrode and the upper lead of the grounding network; subsequently, a curve showing the change of the electric potential with the change of the relative distance is obtained by testing the grounding surface electric potential and the relative distance of multi-points between the test current electrode and the upper lead of the grounding network; and finally, the ratio between the electric potential of the point of the curve with the minimum curvature and the injection current is calculated to obtain the grounding resistance value of the grounding network. The method not only greatly improves the testing work efficiency, but also reduces the labor intensity of the testing personnel.
Description
Technical field
The present invention relates to a kind of method that is used to test the large-scale grounding network impedance ground of transformer station, generating plant, belong to the power technology field.
Background technology
Grounded screen plays crucial effect in the safe operation of transformer station, generating plant, in order to ensure the grounded screen operate as normal, in time find grounded screen fault, is necessary regularly its impedance ground to be tested.Increase along with voltage class of electric power system and power system capacity, the grounded screen yardstick of high pressure, ultra-high voltage transformer station is increasing, traditional grounded screen earth loop impedance test method, as three electrode method, the distance that goes up lead-in wire G that requires measuring electric current utmost point C and voltage pole P distance to be arranged at tested grounded screen edge is D
GC=(4～5) D and D
GP=(0.5～0.6) D
GC, wherein, D is the maximum diagonal length of tested grounded screen, when with classic method the impedance ground of large scale grounded screen being tested, because the distance of lead-in wire G is very big on electric current utmost point C and the voltage pole P distance, thereby the test job amount is very big.
In addition, two kinds of short distance measuring methods have been proposed recent years, a kind of is prerequisite with measured soil resistivity, obtaining on soil model and the grounded screen model based to draw zero-potential point on the face of land by computed in software, this method will be tested the workload of impedance ground and transferred in the measurement of soil resistivity, fundamentally not reduce working strength.Another kind then is to utilize earthing potential cubic spline functions test impedance ground, though this method does not need the remote arrange current utmost point when measuring the earth mat impedance ground, but require grounded screen that leakage current must be arranged, just can test, therefore this method mainly is applicable to the mine power supply system that electric leakage is bigger.
Therefore, it is very necessary seeking a kind of simple, fast short-distance test method for grounding impedance of large grounding network.
Summary of the invention
The present invention be used to overcome prior art defective, provide a kind of and can not only guarantee accuracy of measurement, and easy and simple to handle, short-distance test method for grounding impedance of large grounding network efficiently.
The alleged problem of the present invention realizes with following technical proposals:
A kind of short-distance test method for grounding impedance of large grounding network, it is at a distance of 1.2～1.5 times of grounded screen maximum diagonal length places the electric current utmost point to be set with tested grounded screen, and on the electric current utmost point and the grounded screen lead-in wire between injection current, the surface potential and the relative distance of multiple spot between passing through then to go between on the measuring current utmost point and the grounded screen, obtain current potential with the curve that relative distance changes, calculate the current potential of point of this curvature of curve minimum and the ratio of injection current at last and obtain grounded screen impedance ground value.
Above-mentioned short-distance test method for grounding impedance of large grounding network, it may further comprise the steps:
A, draw the testing current line from the lead-in wire of tested grounded screen to any grounded screen radiation direction in grounded screen outer, at testing current line end the electric current utmost point is set, the distance that makes the electric current utmost point and last lead-in wire is L=1.2～1.5D, and D is a grounded screen maximum diagonal length;
B, evenly choosing 10～12 surface potential test points between lead-in wire G point 0.3～0.8L on the distance on the testing current line, measure the relative distance that goes between on each face of land potential test point and the grounded screen;
The injection current of the electric current utmost point is flow through in c, measurement;
D, measure the current potential of each face of land potential test point respectively;
The relative distance of e, each face of land potential test point that will record and potential value are used least square method and are carried out data fitting, select the point of curvature minimum in the matched curve, calculate the ratio of this current potential and electric current utmost point injection current, obtain grounded screen impedance ground value.
Above-mentioned short-distance test method for grounding impedance of large grounding network, the injection current on the described electric current utmost point and the grounded screen between the lead-in wire is not less than 3A.
The present invention is being provided with electric current utmost point C with tested grounded screen at a distance of 1.2～1.5 times of grounded screen maximum diagonal length places, by the surface potential and the relative distance of the multiple spot between the G of going between on measuring current utmost point C and the grounded screen, tries to achieve grounded screen impedance ground value.Simultaneous interpretation unified test method for testing is compared, and the distance of lead-in wire between the G shortens greatly on electric current utmost point C and surface potential test point and the tested grounded screen, makes easy and simple to handlely, quick, has reduced the test job amount.The present invention has not only improved test job efficient greatly, and has reduced tester's labour intensity.
Description of drawings
The invention will be further described below in conjunction with accompanying drawing.
Surface potential distribution schematic diagram when Fig. 1 is test;
The synoptic diagram of each measurement point when Fig. 2 tests for the present invention;
Fig. 3 is test result matched curve figure.
Each label is among the figure: the point of K, curvature minimum, and D, grounded screen maximum diagonal length, C, the electric current utmost point go between P on G, the grounded screen
1～P
n, the surface potential test point, U, surface potential liter, the point on S, the face of land line and the relative distance of last lead-in wire, U
P, the surface potential test point current potential, S
GP, surface potential test point and last lead-in wire relative distance.
Embodiment
The present invention is directed to existing actual earth loop impedance test problem, proposed a kind of new short-distance test method that is different from traditional grounded screen earth loop impedance test method.
Referring to Fig. 1, when carrying out earth loop impedance test, forming current return between the lead-in wire and the current reflux utmost point on the grounded screen, on 2 face of land line, current potential is attenuation distribution from high to low.Near Potential distribution curvature of curve minimum zero-potential point.Therefore search out the curvature smallest point, determined the potential difference (PD) between online lead-in wire in ground and this point, also just obtained the current potential of grounded screen.Choose n difference test surface potential when supposing test, the online lead pitch in each point and ground is from being respectively S
1, S
2..., S
n, the potential difference (PD) that can record between the online lead-in wire in each point current potential and ground is respectively P
1, P
2..., P
nSet up the polynomial of degree n that surface potential changes with distance S, suc as formula (1).
With S
1, S
2..., S
n, and P
1, P
2..., P
nSubstitution formula (1) utilizes least square method that test result is carried out match, can obtain the undetermined coefficient α in the polynomial expression
iCurve is carried out differentiate, and its derivative expression formula is suc as formula (2) form.
Find the solution and make P ' get the S value of minimum value, be designated as S
MinWith S
MinSubstitution formula (1) can obtain the potential difference (PD) between online lead-in wire in ground and this point, has therefore obtained the current potential of grounded screen.The ratio of this result and earth current is the impedance ground of grounded screen.
Concrete measuring method is as follows:
To draw length outside the G be that the current measurement line of L is to electric current utmost point C to lead-in wire on grounded screen to be measured, measuring current by the lead-in wire and the electric current utmost point on the grounded screen is I, the surface potential and the relative distance of multiple spot between the lead-in wire G on measuring current utmost point C and the grounded screen, utilize least square method to carry out the data fitting analysis, seek the point of surface potential with the curvature minimum of relative distance change curve, the ratio of this current potential and injection current is grounded screen impedance ground value.Its concrete testing procedure is as follows:
(1) select near the few zone of the stone grounded screen, outside the grounded screen lead-in wire G of needs test, draw the testing current line to electric current utmost point C, on the go between distance of G and electric current utmost point C between 1.2～1.5D, choose;
(2) be evenly to choose 10～12 surface potential test points between 0.3～0.8L at lead-in wire G point on the distance, utilize the GPS orientator to measure the relative distance that lead-in wire G is ordered on surface potential test point and the grounded screen respectively;
(3) utilize the earth loop impedance test instrument, the electric current I of the electric current utmost point is flow through in test;
(4) utilize the earth loop impedance test instrument, test the current potential of surface potential test point respectively;
(5) the test point current potential that obtains of relative distance that step 2 is obtained and step 4 and relative distance are used least square method and are carried out data fitting, select the point of curvature minimum in the matched curve, the ratio of the electric current that the fitting result of this current potential and step 3 obtain is grounded screen impedance ground value.
Referring to Fig. 2, utilize the method for the invention that one actual grounded screen is tested, long 410 meters of grounded screen maximum diagonal D, outside grounded screen lead-in wire G point, draw the testing current line to putting C, point G and apart 600 meters of some C are about 1.46D, current return injection current I=3.5A.Determine P1, P2 ..., P10 amounts to 10 points as the potential measurement point, table 1 has provided each test point with the distance of some G and in each point potential measurement value.
Table 1 potential test point position and potential measurement result
| Potential test point numbering | Potential test point and some G distance (rice) | Test point current potential (volt) |
| |
150 | 0.5525 |
| P2 | 175 | 0.5820 |
| |
200 | 0.6025 |
| P4 | 225 | 0.6245 |
| P5 | 250 | 0.648 |
| P6 | 275 | 0.666 |
| P7 | 300 | 0.6865 |
| P8 | 325 | 0.709 |
| P9 | 350 | 0.7555 |
| P10 | 375 | 0.7935 |
Fig. 3 is test result matched curve figure, and fitting result is asked for the each point derivative, obtains curvature smallest point K on the curve, and by fitting result as can be known, this current potential is 0.65811V, so the grounded screen impedance ground is 0.65811V ÷ 3.5A=0.188 Ω.
Use conventional test methodologies (three electrode method) simultaneously and test, test result is 0.191 Ω, and two kinds of method test result deviations are less, are no more than 2%.
Claims (2)
1. short-distance test method for grounding impedance of large grounding network, it is characterized in that, it is at a distance of 1.2～1.5 times of grounded screen maximum diagonal length places the electric current utmost point (C) to be set with tested grounded screen, and at the injection current between (G) that goes between on the electric current utmost point (C) and the grounded screen, surface potential and relative distance by the multiple spot between (G) of going between on the measuring current utmost point (C) and the grounded screen then, obtain current potential with the curve that relative distance changes, calculate the current potential of point of this curvature of curve minimum and the ratio of injection current at last and obtain grounded screen impedance ground value;
Specifically carry out according to the following steps:
A, draw the testing current line from the lead-in wire of tested grounded screen to any grounded screen radiation direction in grounded screen outer, at testing current line end the electric current utmost point is set, the distance that makes the electric current utmost point and last lead-in wire is L=1.2～1.5D, and D is a grounded screen maximum diagonal length;
B, (G) point that goes between on distance on the testing current line are evenly to choose 10～12 surface potential test points between 0.3～0.8L, measure the relative distance of lead-in wire (G) on each face of land potential test point and the grounded screen;
The injection current of the electric current utmost point is flow through in c, measurement;
D, measure the current potential of each face of land potential test point respectively;
The relative distance of e, each face of land potential test point that will record and potential value are used least square method and are carried out data fitting, select the point of curvature minimum in the matched curve, and it is straight with the ratio of electric current utmost point injection current to calculate this current potential, obtains grounded screen impedance ground value.
2. according to the described short-distance test method for grounding impedance of large grounding network of claim 1, it is characterized in that the injection current on the described electric current utmost point (C) and the grounded screen between the lead-in wire (G) is not less than 3A.
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| CN101825662B (en) * | 2010-05-28 | 2012-10-17 | 贵州南源电力科技开发有限公司 | Short-distance measurement method and structure of grounding resistance of grounding network |
| CN102508006A (en) * | 2011-11-21 | 2012-06-20 | 华北电力大学 | Step voltage multipoint fitting test method |
| CN103954842B (en) * | 2014-04-03 | 2017-01-18 | 贵州电力试验研究院 | Method for determining grounding resistance value of large-scale grounding system |
| CN105510721B (en) * | 2016-02-19 | 2019-02-15 | 云南电网有限责任公司电力科学研究院 | A kind of New Device for Grounding Resistance Measurement of Grounding Grids and its application method |
| CN110879312B (en) * | 2018-09-06 | 2021-08-24 | 余振邦 | Method and device for measuring grounding impedance |
| CN113219254A (en) * | 2020-01-21 | 2021-08-06 | 武汉市康达电气有限公司 | Method and device for measuring grounding impedance of grounding grid, electronic equipment and medium |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN2888458Y (en) * | 2005-10-27 | 2007-04-11 | 珠海泰坦科技股份有限公司 | Geodetic network grounding impedance tester |
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| CN2888458Y (en) * | 2005-10-27 | 2007-04-11 | 珠海泰坦科技股份有限公司 | Geodetic network grounding impedance tester |
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| JP特开2000-137047A 2000.05.16 |
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Effective date of registration: 20121008 Address after: 030012 No. 6, Qingnian Road, Shanxi, Taiyuan Patentee after: Electric Power Research Institute of Shanxi Electric Power Company Patentee after: State Grid Corporation of China Address before: 030012 No. 6, Qingnian Road, Shanxi, Taiyuan Patentee before: Electric Power Research Institute of Shanxi Electric Power Company |