CN102508006A - Step voltage multipoint fitting test method - Google Patents

Abstract

The invention discloses the technical field of power system earthing, in particular relates to a step voltage multipoint fitting test method. The method comprises the following steps of: uniformly distributing surface potential test points with an appointed amount in a form of a grid shaped like a Chinese character tian by taking a step voltage test point as a center; then, measuring potential differences between each surface potential test point and the step voltage test point; and finally, fitting the measured relative distances and the potential differences between each surface potential test point and the step voltage test point to calculate the maximum potential difference as a step voltage value of the step voltage test point. The step voltage multipoint fitting test method can be used for ensuring the measuring accuracy and is simple, convenient and rapid in operation.

Description

A kind of step voltage multi-point fitting method of testing

Technical field

The invention belongs to electric system grounding technology field, relate in particular to a kind of step voltage multi-point fitting method of testing.

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, confirms the security of grounded screen, is necessary regularly its step voltage to be tested.But present method of testing generally is the center of circle with the test point, and the steplength of standard-required is a radius, adopts and thinks that seeking the potential difference (PD) maximal value obtains step voltage.The inevitable great errors of this method.Therefore, seek a kind of easy, the step voltage method of testing is very necessary accurately.

Summary of the invention

To mention in the above-mentioned background technology existing step voltage method test error big, can not accurately obtain deficiency such as step voltage numerical value, the present invention proposes a kind of step voltage multi-point fitting method of testing.

Technical scheme of the present invention is that a kind of step voltage multi-point fitting method of testing is characterized in that this method may further comprise the steps:

Step 1: with the step voltage test point is the center, evenly arranges specified quantity surface potential test point by the matrix pattern grid;

Step 2: measure the potential difference (PD) between surface potential test point and the step voltage test point;

Step 3: relative distance between surface potential test point that records and the step voltage test point and potential difference (PD) are carried out data fitting, obtain maximum potential difference (PD), be the step voltage value of step voltage test point.

Said surface potential test point is inserted underground 0.1 meter.

The computing formula of the potential difference (PD) between said surface potential test point and the step voltage test point is:

Wherein:

is the potential difference (PD) between i surface potential test point and the step voltage test point;

c _kBe 10 coefficients to be asked, k=0 ..., 9;

x _iIt is the horizontal ordinate of i surface potential test point;

y _iIt is the ordinate of i surface potential test point.

Said potential difference (PD) records through the alternating voltage test instrumentation.

The precision of said alternating voltage test instrumentation is not less than 0.1 millivolt.

The present invention tests the surface potential difference and the relative distance of multiple spot near the step voltage test point, utilize numerical fitting to obtain potential difference (PD) with the curve that relative distance changes, and calculates the step voltage value that potential difference (PD) maximal value on this curve promptly obtains this point at last.The present invention can not only guarantee accuracy of measurement, and is simultaneously easy and simple to handle, quick, compares with existing method of testing, utilizes the multi-point sampler result to carry out match, and the test result accuracy is significantly improved.

Description of drawings

Each measurement point arrangenent diagram when Fig. 1 is test;

Fig. 2 is test result matched curve figure.

Embodiment

Below in conjunction with accompanying drawing, preferred embodiment is elaborated.Should be emphasized that following explanation only is exemplary, rather than in order to limit scope of the present invention and application thereof.

The alleged problem of the present invention realizes with following technical proposals:

A kind of multi-point fitting method of testing of step voltage; It is the surface potential and the relative distance of near test multiple spot test point; Utilize numerical fitting to obtain potential difference (PD), calculate the step voltage value that potential difference (PD) maximal value on this curved surface promptly obtains this point at last with the curved surface that relative distance changes.

Referring to Fig. 1, when the step voltage of step voltage test point P0, need survey sheet mid point P respectively ₁-P ₁₆With a P ₀Surface potential poor, with P ₀Point is true origin, and all the other 16 point coordinate are respectively P ₁(0.5,0.5), P ₂(0,0.5), P ₃(0.5,0.5), P ₄(0.5,0), P ₅(0.5,0), P ₆(0.5 ,-0.5), P ₇(0 ,-0.5), P ₈(0.5 ,-0.5), P ₉(1,1), P ₁₀(0,1), P ₁₁(1,1), P ₁₂(1,0), P ₁₃(1,0), P ₁₄(1 ,-1), P ₁₅(0 ,-1), P ₁₆(1 ,-1), below note is made (x _i, y _i) (1≤i≤16).Point P ₁-P ₁₆Each point and P ₀The potential difference (PD) of point is designated as

(following unified note is done

1≤i≤16).

X, y coordinate and corresponding ground difference with these 16 points are set up the two dimension three rank polynomial expressions suc as formula (1).

Wherein:

is the potential difference (PD) between i surface potential test point and the step voltage test point;

c _kBe 10 coefficients to be asked, k=0 ..., 9;

x _iIt is the horizontal ordinate of i surface potential test point;

y _iIt is the ordinate of i surface potential test point.

Set up matrix form based on formula (1) suc as formula (2)-Shi (4).

$B=\left[\begin{array}{cccccccccc}1& x_1& y_1& x_1{y}_1& {x_1}^2& {y_1}^2& {x_1}^2{y}_1& x_1{y_1}^2& {x_1}^3& {y_1}^3\\ 1& x_2& y_2& x_2{y}_2& {x_2}^2& {y_2}^2& {x_2}^2{y}_1& x_2{y_2}^2& {x_2}^3& {y_2}^3\\ \·& \·& \·& \·& \·& \·& \·& \·& \·& \·\\ \·& \·& \·& \·& \·& \·& \·& \·& \·& \·\\ \·& \·& \·& \·& \·& \·& \·& \·& \·& \·\\ 1& x_{16}& y_{16}& x_{16}{y}_{16}& {x_{16}}^2& {y_{16}}^2& {x_{16}}^2{y}_{16}& x_{16}{y_{16}}^2& {x_{16}}^3& {y_{16}}^3\end{array}\right]---\left(2\right)$

C＝[c ₀?c ₁?c ₂?c ₃?c ₄?c ₅?c ₆?c ₇?c ₈?c ₉] ^T (3)

Wherein:

B is a matrix of coefficients;

C is matrix of coefficients to be asked;

Φ is the potential difference (PD) matrix.

With formula (2)-Shi (4) is that the Error Calculation formula of formula (5) form and the mean square deviation calculating formula of the each point result of calculation shown in the formula (6) are set up in the basis.

E＝Φ-BC (5)

$\mathrm{MSE}=\frac{1}{9}{\mathrm{EE}}^T---\left(6\right)$

Wherein:

E is the error between test result and numerical result;

MSE is a mean square deviation.

Treating in the formula (6) asked matrix of coefficients C computing differential, and make that derivative is zero to find the solution, can obtain the result of calculation of formula (7).

C＝[B ^TB] ^-1[B ^TΦ] (7)

Can wait to ask the value of matrix of coefficients C thus.Therefore the relation of surface potential and its coordinate is that formula (1) just can obtain.

Utilize x=rcos θ; Y=rsin θ is with coordinate x; Y converts polar form into; Step voltage test radius r=0.8 that the substitution national standard requires meter can obtain the relation of potential difference (PD)

and angle θ, and shape is suc as formula shown in (8).

Calculate potential difference (PD) Maximal value, i.e. step voltage test point P ₀Maximum step voltage.

Concrete measuring method is following:

The step voltage test point P that surveys ₀The surface potential of near zone multiple spot and relative distance are carried out the data fitting analysis, obtain the maximal value of potential difference (PD), and this value is step voltage test point P ₀The step voltage of point.

Its concrete testing procedure is following:

(1) at needs test step voltage point P ₀Around choose 16 surface potential test points according to Fig. 1, each point inserts the ground connection drill rod into 0.1 meter of the ground degree of depth respectively;

(2) utilize precision to reach to be not less than 0.1 millivolt alternating voltage test instrumentation test point P respectively ₀With the potential difference (PD) of 16 points on every side;

(3) the each point potential difference (PD) that relative distance that step 1 is obtained and step 2 obtain is carried out data fitting, calculates the maximal value of matched curve, is the step voltage of this point.

Utilize the method for the invention that one actual grounded screen is tested.At step voltage test point P ₀Near the P that selects ₁, P ₂..., P ₁₆Amount to 16 points, record step voltage test point P respectively ₀With P ₁, P ₂..., P ₁₆The potential difference (PD) of each point, test result is recorded in the table 1.

Table 1 potential test point position and potential measurement result

Potential test point numbering	With P 0Point potential difference (PD) (mV)	Potential test point numbering	With P 0Point potential difference (PD) (mV)
				P 1	-0.7	P 9	-7.3
P 2	1.7	P 10	0.2
				P 3	0.8	P 11	-3.3
P 4	-2.5	P 12	-7.6
				P 5	-1.0	P 13	-4.0
P 6	-7.3	P 14	-19.0
				P 7	-4.8	P 15	-10.9
P 8	-5.7	P 16	-15.0

The matrix B that obtains is:

$B=\left[\begin{array}{cccccccccc}1& -0.5& 0.5& -0.25& 0.25& 0.25& 0.125& -0.125& -0.125& 0.125\\ 1& 0& 0.5& 0& 0& 0.25& 0& 0& 0& 0.125\\ 1& 0.5& 0.5& 0.25& 0.25& 0.25& 0.125& 0.125& 0.125& 0.125\\ 1& -0.5& 0& 0& 0.25& 0& 0& 0& -0.125& 0\\ 1& 0.5& 0& 0& 0.25& 0& 0& 0& 0.125& 0\\ 1& -0.5& -0.5& 0.25& 0.25& 0.25& -0.125& -0.125& -0.125& -0.125\\ 1& 0& -0.5& 0& 0& 0.25& 0& 0& 0& -0.125\\ 1& 0.5& -0.5& -0.25& 0.25& 0.25& -0.125& 0.125& 0.125& -0.125\\ 1& -1& 1& -1& 1& 1& 1& -1& -1& 1\\ 1& 0& 1& 0& 0& 1& 0& 0& 0& 1\\ 1& 1& 1& 1& 1& 1& 1& 1& 1& 1\\ 1& -1& 0& 0& 1& 0& 0& 0& -1& 0\\ 1& 1& 0& 0& 1& 0& 0& 0& 1& 0\\ 1& -1& -1& 1& 1& 1& -1& -1& -1& -1\\ 1& 0& -1& 0& 0& 1& 0& 0& 0& -1\\ 1& 1& -1& -1& 1& 1& -1& 1& 1& -1\end{array}\right]$

The coefficient C that calculates is:

C＝[-0.3652?1.4000?6.7944?-0.0059?-5.6057?-5.1351?0.2985?0.2000?0.4000?-1.2434]

The potential difference (PD) that obtains thus

is as shown in Figure 2 with the relation of angle θ.Calculate potential difference (PD) Maximal value, i.e. step voltage test point P ₀Maximum step voltage be 8.7 millivolts.

The above; Be merely the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, any technician who is familiar with the present technique field is in the technical scope that the present invention discloses; The variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claim.

Claims (5)

1. step voltage multi-point fitting method of testing is characterized in that this method may further comprise the steps:

Step 1: with the step voltage test point is the center, evenly arranges specified quantity surface potential test point;

Step 2: measure the potential difference (PD) between surface potential test point and the step voltage test point;

Step 3: relative distance between surface potential test point that records and the step voltage test point and potential difference (PD) are carried out data fitting, obtain maximum potential difference (PD), be the step voltage value of step voltage test point.

2. a kind of step voltage multi-point fitting method of testing according to claim 1 is characterized in that said surface potential test point inserts underground 0.1 meter.

3. a kind of step voltage multi-point fitting method of testing according to claim 1 is characterized in that the computing formula of the potential difference (PD) between said surface potential test point and the step voltage test point is:

Wherein:

is the potential difference (PD) between i surface potential test point and the step voltage test point;

c _kBe 10 coefficients to be asked, k=0 ..., 9;

x _iIt is the horizontal ordinate of i surface potential test point;

y _iIt is the ordinate of i surface potential test point.

4. a kind of step voltage multi-point fitting method of testing according to claim 1 is characterized in that said potential difference (PD) records through the alternating voltage test instrumentation.

5. a kind of step voltage multi-point fitting method of testing according to claim 4 is characterized in that the precision of said alternating voltage test instrumentation is not less than 0.1 millivolt.