CN104267263A - Method and device for measuring resistance of branches of ground wire network - Google Patents

Abstract

The invention provides a method and device for measuring the resistance of branches of a ground wire network. The method comprises the steps that an overall test is carried out on direct current resistance properties of the ground wire network, the direct current resistance properties of the whole ground wire network are completely represented in a matrix form, measurement of the matrix parameters of the direct current resistance properties of the ground wire network is achieved, then the resistance values of all the branches of the ground wire network are obtained, and therefore reliable data support is provided for detection of the laying quality of the ground wire network and the design simulation of the ground wire network. The device comprises a standard direct current source, a digital nV gauge, a current selector switch matrix, a voltage selector switch matrix and a control computer. The ground wire network is an n-node ground wire network which comprises one reference node and n independent nodes. The current selector switch matrix is provided with one input end and n output ends. The voltage selector switch matrix is provided with n input ends and one output end.

Description

A kind of earth cord network branch resistance measuring method and device

Technical field

The present invention relates to space flight, aviation, metering field and metal construction ground networks, particularly relate to a kind of earth cord network branch resistance measuring method and device.

Background technology

Earth cord network is the important ingredient of Large-Scale Equipment, is the critical facility of Support Equipment safe and stable operation.Earth cord network is generally made up of structure, bus, Copper Foil, connector, ground stud etc., for each load provides current return, realize electric energy supply, for measuring equipment provides unified reference ground, for between load, Signal transmissions provides loop, for equipment Electro-static Driven Comb provides passage, exist power supply ground, signal ground, with reference to ground, shielding etc. loop.According to load and signal characteristic, most of earth cord network adopts low frequency single-point grounding and the hybrid grounding scheme such as high frequency multipoint earthing and " flexible ground ", it is a complicated cubic network, its direct current resistance characteristic is the important indicator of earth cord network, direct working condition and the performance affecting Large-Scale Equipment, affects the serviceability of each load of Large-Scale Equipment.Such as, the laying defect etc. of the cable model used mistake of the ground wire due to certain position or plug connector loose contact or ground wire Copper Foil, causes the line resistance at this position to increase, and due to the parallel connection of other branch road, simple test is difficult to find; Larger current will change normal flow direction, or local damage ground configurations, cause and will increase other branch current load, damage the pernicious chain reaction of other branch road; In addition, when power supply ground, signal ground and shielding etc. heterogeneous networks should not the local short circuit of short circuit, also will have a strong impact on the performance measured and control.These are all the key factors that serious threat Large-Scale Equipment normally works.

In the design of earth cord network, performance calibration and quality evaluation thereof, not only need spider lines system dc resistance characteristic matrix definitely, also need the direct current resistance determining each branch road of ground net system, generally adopt following proposal before:

One, independent measurement scheme

After laying earth cord network, randomly draw several nodes, after disconnecting relevant connection at the scene, carry out independent measurement to every root wire, measurement result and design load compare difficulty action accomplishment and assess.The advantage of the program is that the feature measurement of earthed system is more accurate because the accuracy of measurement of independent measurement conductor resistance is higher.But there is following shortcoming in this technical scheme: a. can not expose the laying quality of ground wire; B. the contact resistance connecting and bring can not be exposed; C. the contact performance of plug connector can not be reflected; D. workload is large, and efficiency is low; Etc..

Two, hybrid measurement scheme is carried out at the scene with m Ω table

After laying earth cord network, show the resistance value measured between all nodes at the scene with m Ω, calibrate the DC characteristic of earthed system with this.The advantage of the program contains part laying quality factor, as contact resistance.But there is following shortcoming in this technical scheme: a., due to the topological structure of earth system complexity, can not reflect parallel connection fault paths among the nodes; B. can not the misuse problem of exposed to wire material; C. workload is large, and n node needs to measure

Summary of the invention

According to the defect that prior art exists, the invention provides a kind of earth cord network branch resistance measuring method and device, integrated testability is carried out to the direct current resistance characteristic of earth cord network, obtains the direct current resistance feature matrix of entirely spider lines, by calculating the resistance value of each branch road of earth cord network; For checking the laying quality of earth cord network, provide reliable Data support for giving the design and simulation of earth cord network.

Technical scheme of the present invention is as follows:

A kind of earth cord network branch resistance measuring method, is characterized in that, comprising:

1) entirely as a multiterminal pure resistance passive linear network, a reference mode P will be comprised by spider lines ₀and n isolated node, be called n node earth cord network;

2) with P ₀point is reference, applies electric current, then form unique group node voltage at n isolated node at n isolated node:

$\left(\begin{array}{c}{U}_1\\ U_2\\ .\\ .\\ U_n\end{array}\right)=\left(\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& .& .& .& r_{\mathrm{nn}}\end{array}\right)\left(\begin{array}{c}{I}_1\\ I_2\\ .\\ .\\ I_n\end{array}\right)---\left(1\right)$

Matrix [R]:

$\left[R\right]=\left[\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& r_{n2}& .& .& r_{\mathrm{nn}}\end{array}\right]---\left(2\right)$

Characterize the impedance operator of n node earth cord network, be called direct current resistance feature matrix, reflect the relation between earth cord network node Injection Current and each node voltage;

4) by being injected into the DC current of each node of earth cord network, the node voltage produced on each node is measured, by calculating the measurement realized described direct current resistance feature matrix [R] parameter;

5) by Gauss-about when elimination method tries to achieve the inverse matrix [G] of [R], i.e. conductance matrix [G];

6) by conductance matrix [G], the resistance value of each branch road of earth cord network is asked for.

Described step 4) in, adopt the superposition principle of linear circuit, inspiring standard electric current is applied in turn to earth cord network, travels through each node, that is:

$\left[\begin{array}{c}{I}_{s1}\\ 0\\ .\\ .\\ 0\end{array}\right],\left[\begin{array}{c}0\\ I_{s2}\\ .\\ .\\ 0\end{array}\right],......\left[\begin{array}{c}0\\ 0\\ .\\ .\\ I_{\mathrm{sn}}\end{array}\right]$

Measure each node voltage respectively:

$\left[\begin{array}{c}{U}_{11}\\ U_{21}\\ .\\ .\\ U_{n1}\end{array}\right],\left[\begin{array}{c}{U}_{12}\\ U_{22}\\ .\\ .\\ U_{n2}\end{array}\right],......\left[\begin{array}{c}{U}_{1n}\\ U_{2n}\\ .\\ .\\ U_{\mathrm{nn}}\end{array}\right]$

Substitute into following formula respectively

$\left(\begin{array}{c}{U}_1\\ U_2\\ .\\ .\\ U_n\end{array}\right)=\left(\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& .& .& .& r_{\mathrm{nn}}\end{array}\right)\left(\begin{array}{c}{I}_1\\ I_2\\ .\\ .\\ I_n\end{array}\right)$

Obtain each parameter of [R] matrix:

$\left(\begin{array}{c}{r}_{11}\\ r_{21}\\ .\\ .\\ r_{n1}\end{array}\right)=\left(\begin{array}{c}\frac{U_{11}}{I_{S1}}\\ \frac{U_{21}}{I_{S1}}\\ .\\ .\\ \frac{U_{n1}}{I_{S1}}\end{array}\right),\left(\begin{array}{c}{r}_{12}\\ r_{22}\\ .\\ .\\ r_{n2}\end{array}\right)=\left(\begin{array}{c}\frac{U_{12}}{I_{S2}}\\ \frac{U_{22}}{I_{S2}}\\ .\\ .\\ \frac{U_{n2}}{I_{S2}}\end{array}\right).........\left(\begin{array}{c}{r}_{1n}\\ r_{2n}\\ .\\ .\\ r_{\mathrm{nn}}\end{array}\right)=\left(\begin{array}{c}\frac{U_{1n}}{I_{\mathrm{Sn}}}\\ \frac{U_{2n}}{I_{\mathrm{Sn}}}\\ .\\ .\\ \frac{U_{\mathrm{nn}}}{I_{\mathrm{Sn}}}\end{array}\right)$

Also namely:

$\left[R\right]=\left(\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& r_{n2}& .& .& r_{\mathrm{nn}}\end{array}\right)=\left(\begin{array}{ccccc}\frac{U_{11}}{I_{s1}}& \frac{U_{12}}{I_{s2}}& .& .& \frac{U_{1n}}{I_{\mathrm{sn}}}\\ \frac{U_{21}}{I_{s1}}& \frac{U_{22}}{I_{s2}}& .& .& \frac{U_{2n}}{I_{\mathrm{sn}}}\\ .& .& .& .& .\\ .& .& .& .& .\\ \frac{U_{n1}}{I_{s1}}& \frac{U_{n2}}{I_{s2}}& .& .& \frac{U_{\mathrm{nn}}}{I_{\mathrm{sn}}}\end{array}\right)$

Described step 5) in, the inverse matrix [G] using Gauss-about to try to achieve [R] when elimination method is

$\left[G\right]=\left[\begin{array}{ccccc}{G}_{11}& G_{12}& .& .& G_{1n}\\ G_{21}& G_{22}& .& .& G_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ G_{n1}& G_{n2}& .& .& G_{\mathrm{nn}}\end{array}\right]$

[G] is conductance matrix, and i capable j row parameter is G _ij.

Described step 6) in, for any one node P _i, node P _iwith reference mode P ₀between branch resistance be R _ii, node P _iwith node P ₁between branch resistance be R _i1, node P _iwith node P ₂between branch resistance be R _i2, node P _iwith node P _jbetween branch resistance be R _ij, node P _iwith node P _nbetween branch resistance be R _in; As i ≠ j,

$G_{\mathrm{ij}}=-\frac{1}{R_{\mathrm{ij}}}$

Obtain node P _iwith node P _jbetween branch resistance be:

$R_{\mathrm{ij}}=-\frac{1}{G_{\mathrm{ij}}}---\left(3\right)$

As i=j,

$R_{\mathrm{ii}}=-\frac{1}{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{G}_{\mathrm{ij}}}---\left(4\right)$

A kind of earth cord network branch resistance measurement mechanism, is characterized in that, comprise standard DC current source, digital nV table, current changeover switch matrix, voltage changeover switch matrix and computer for controlling; Described earth cord network also has n isolated node except a reference mode, is called n node earth cord network; Described current changeover switch matrix has 1 input end and n output terminal, and described voltage changeover switch matrix has n input end 1 output terminal; Described standard DC current source output is high-end to be connected with the input end of current changeover switch matrix, and n output terminal of current changeover switch matrix is connected with n node of tested earth cord network in order respectively; N input end of described voltage changeover switch matrix is connected with n node of tested earth cord network in order respectively, and the input that output terminal and the digital nV of voltage changeover switch matrix show is high-end to be connected; Standard DC current source exports low side and is connected with the reference mode of tested earth cord network with digital nV table input low side simultaneously; Described standard DC current source, digital nV table, current changeover switch matrix, voltage changeover switch matrix are all connected with computer for controlling by programmable interface; Described computer for controlling is for controlling the switch on and off of current changeover switch matrix, the switch on and off of control voltage change-over switch matrix, the output state of control criterion DC current source, arranges the output current amplitude of standard DC current source, obtains the measurement data that digital nV shows.

Described current changeover switch matrix adopts big current programmed switch matrix.

Described voltage changeover switch matrix adopts low thermoelectrical potential programmed switch matrix.

Adopt described earth cord network branch resistance measurement mechanism to ask for the method for the resistance value of each branch road of earth cord network, comprise the following steps:

1) first, described computer for controlling arranges i counter and j counter parameter initial value is 1:i=1, j=1;

2) i-th output terminal controlling current changeover switch matrix is connected with i-th node of tested earth cord network, i=1,2,3 ..., n;

3) control criterion DC current source exports measuring current I _i, i=1,2,3 ..., n;

4) a jth input end of control voltage change-over switch matrix is connected with a jth node for tested earth cord network, j=1,2,3 ..., n;

5) control figure nV shows to measure DC voltage, reads the measurement result U that digital nV shows _ij, and test result is kept in the internal register of computing machine in a matrix fashion;

6) if repeat 4 ~ 6 steps after j ≠ n, j counter adds 1;

7) if j=n, if i ≠ n, j counter is put after 1, i counter adds 1 again repeat 2 ~ 7 steps;

8) work as i=n, j=n, complete test, calculate the parameters of [R] matrix according to formula (5):

$r_{\mathrm{ij}}=\frac{u_{\mathrm{ij}}}{I_i}---\left(5\right)$

9) inverse matrix [G] adopting Gauss-about to try to achieve [R] when elimination method according to matrix [R] can calculate each branch resistance R according to formula (6), (7) _ij.

As i=j,

$R_{\mathrm{ii}}=-\frac{1}{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{G}_{\mathrm{ij}}}---\left(6\right)$

As i ≠ j,

$R_{\mathrm{ij}}=-\frac{1}{G_{\mathrm{ij}}}---\left(7\right)$

Technique effect of the present invention:

A kind of earth cord network branch resistance measuring method provided by the invention and device, will entirely spider lines as a multiterminal pure resistance passive linear network, integrated testability is carried out to the direct current resistance characteristic of earth cord network, the direct current resistance characteristic of complete characterization entirely spider lines in the matrix form, and achieve the measurement to earth cord network direct current resistance feature matrix parameter; By direct current resistance feature matrix [R], obtain inverse matrix [G], and then try to achieve the resistance value of each branch road of earth cord network.Thus can after earth cord network have been laid, by the direct current resistance feature matrix [R] of calibration gained earth cord network, directly obtain the resistance value of each branch road, the measured data that utilization obtains and design data compare, and judge actual earth cord network laying quality; Identify the mistake in of material, Miswire, grafting quality, the laying quality of reflection earth cord network, can also reflect the topological structure of earth cord network simultaneously, for checking the laying quality of earth cord network, provides reliable Data support for giving the design and simulation of earth cord network.

Accompanying drawing explanation

Fig. 1 is n node line resistance schematic network structure.

Fig. 2 is the schematic diagram that n node line resistance network applies current generating nodes voltage.

Fig. 3 is earth cord network branch resistance measurement mechanism schematic diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing, embodiments of the invention are described in further detail.

Earth cord network branch resistance is measured, and adopts " network analysis " overall plan.After measuring equipment earth cord network has been laid, before measuring equipment power supply and load access, will entirely spider lines as a multiterminal pure resistance passive linear network, utilize network analysis technique to carry out characteristic calibration to entirely spider lines, provide the DC impedance characteristic of entirely wire system in the matrix form.This network analysis technique, adopt " superposition principle ", utilize normalized current source at the scene, encourage to respectively each node, measure the current potential of corresponding each each node of current excitation simultaneously, utilize the dependence between the node voltage of resistor network and branch current, obtain earth cord network direct current resistance feature matrix, calculate the resistance value between each node further, the performance data that utilization obtains and design data compare, and judge actual earth cord network laying quality.

As shown in Figure 1, be n node line resistance schematic network structure.Comprise a reference mode P ₀and n isolated node P ₁, P ₂p _ip _n-1, P _n, be called n node earth cord network.R _iifor node P _iwith reference mode P ₀between resistance, R _i1for node P _iwith node P ₁between resistance, R _i2for node P _iwith node P ₂between resistance, R _infor node P _iwith node P _nbetween resistance.

As shown in Figure 2, after ground net system has been laid, with P ₀point is reference, applies electric current, then form a unique group node voltage U at n isolated node at n isolated node ₁, U ₂u _iu _n-1, U _n;

To n node application Kirchhoff's current law (KCL), one group of independently nodal voltage equation can be obtained:

$\left(\begin{array}{c}{U}_1\\ U_2\\ .\\ .\\ U_n\end{array}\right)=\left(\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& .& .& .& r_{\mathrm{nn}}\end{array}\right)\left(\begin{array}{c}{I}_1\\ I_2\\ .\\ .\\ I_n\end{array}\right)---\left(8\right)$

[U]＝[R][I] (9)

In formula, U _i----the be voltage of node i;

I _i---the exciting current of-node i;

Matrix [R]:

$\left[R\right]=\left[\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& r_{n2}& .& .& r_{\mathrm{nn}}\end{array}\right]$

Can obtain according to expression formula (9) conversion

[G][U]＝[I] (10)

Wherein [G] is the inverse matrix of [R].

Expression is as follows

$\left(\begin{array}{ccccc}{G}_{11}& G_{12}& .& .& G_{1n}\\ G_{21}& G_{22}& .& .& G_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ G_{n1}& G_{n2}& .& .& G_{\mathrm{nn}}\end{array}\right)\left(\begin{array}{c}{U}_1\\ U_2\\ .\\ .\\ U_n\end{array}\right)=\left(\begin{array}{c}{I}_1\\ I_2\\ .\\ .\\ I_n\end{array}\right)$

In formula, U _i----(node i is relative to reference point P for the voltage of node i ₀node voltage);

I _i---the exciting current of-node i;

G _iithe self-conductance that-----is node i;

G _ijthe mutual conductance of----be between node i and node j; For linear system, G _ij=G _ji;

All self-conductances and mutual conductance are all the functions of resistance in network, reflect the direct current resistance characteristic of network, have uniqueness.

According to Kirchhoff's current law (KCL), for any one node P _i, the electric current flowing into this node is I _i, the voltage of this node is U _i, obtain according to Kirchhoff's current law (KCL):

$\frac{U_i}{R_{\mathrm{ii}}}+\frac{U_i-U_1}{R_{i1}}+\frac{U_i-U_2}{R_{i2}}+.....+\frac{U_i-\mathrm{Un}}{R_{\mathrm{in}}}=I_i---\left(12\right)$

$\frac{-1}{R_{i1}}{U}_1+\frac{-1}{R_{i2}}{U}_2+..(\frac{1}{R_{\mathrm{ii}}}+\frac{1}{R_{i1}}+\frac{1}{R_{i2}}...+\frac{1}{R_{\mathrm{in}}})U_i+...+\frac{-1}{R_{\mathrm{in}}}{U}_n=I_i---\left(13\right)$

Wherein, R _iifor node P _iwith reference mode P ₀between resistance, R _i1for node P _iwith node P ₁between resistance, R _i2for node P _iwith node P ₂between resistance, R _infor node P _iwith node P _nbetween resistance.

Can obtain from formula (12) (13)

As i=j,

$R_{\mathrm{ii}}=-\frac{1}{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{G}_{\mathrm{ij}}}---\left(14\right)$

As i ≠ j,

$R_{\mathrm{ij}}=-\frac{1}{G_{\mathrm{ij}}}---\left(15\right)$

A kind of earth cord network branch resistance measuring method, comprises the following steps:

1) entirely as a multiterminal pure resistance passive linear network, a reference mode P will be comprised by spider lines ₀and n isolated node, be called n node earth cord network;

2) with P ₀point is reference, applies electric current, then form unique group node voltage at n isolated node at n isolated node:

$\left(\begin{array}{c}{U}_1\\ U_2\\ .\\ .\\ U_n\end{array}\right)=\left(\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& .& .& .& r_{\mathrm{nn}}\end{array}\right)\left(\begin{array}{c}{I}_1\\ I_2\\ .\\ .\\ I_n\end{array}\right)---\left(1\right)$

Matrix [R]:

$\left[R\right]=\left[\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& r_{n2}& .& .& r_{\mathrm{nn}}\end{array}\right]---\left(2\right)$

Characterize the impedance operator of n node earth cord network, be called direct current resistance feature matrix, reflect the relation between earth cord network node Injection Current and each node voltage;

4) by being injected into the DC current of each node of earth cord network, the node voltage produced on each node is measured, by calculating the measurement realized described direct current resistance feature matrix [R] parameter;

5) by Gauss-about when elimination method tries to achieve the inverse matrix [G] of [R];

6) by conductance matrix [G], the resistance value of each branch road of earth cord network is asked for.

Step 4) in, consider and apply normalized current to earth system n node simultaneously, system will be very huge, construction cost is very high, therefore, adopt " superposition principle " of linear circuit, inspiring standard electric current is applied in turn to earth system, measure each node voltage respectively, [R] matrix can be calculated.

Inspiring standard electric current is applied in turn to earth system, travels through each node, that is:

$\left[\begin{array}{c}{I}_{s1}\\ 0\\ .\\ .\\ 0\end{array}\right],\left[\begin{array}{c}0\\ I_{s2}\\ .\\ .\\ 0\end{array}\right],......\left[\begin{array}{c}0\\ 0\\ .\\ .\\ I_{\mathrm{sn}}\end{array}\right]$

Measure each node voltage respectively:

$\left[\begin{array}{c}{U}_{11}\\ U_{21}\\ .\\ .\\ U_{n1}\end{array}\right],\left[\begin{array}{c}{U}_{12}\\ U_{22}\\ .\\ .\\ U_{n2}\end{array}\right],......\left[\begin{array}{c}{U}_{1n}\\ U_{2n}\\ .\\ .\\ U_{\mathrm{nn}}\end{array}\right]$

Substitute into following formula respectively

$\left(\begin{array}{c}{U}_1\\ U_2\\ .\\ .\\ U_n\end{array}\right)=\left(\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& .& .& .& r_{\mathrm{nn}}\end{array}\right)\left(\begin{array}{c}{I}_1\\ I_2\\ .\\ .\\ I_n\end{array}\right)$

Obtain each parameter of [R] matrix:

$\left(\begin{array}{c}{r}_{11}\\ r_{21}\\ .\\ .\\ r_{n1}\end{array}\right)=\left(\begin{array}{c}\frac{U_{11}}{I_{S1}}\\ \frac{U_{21}}{I_{S1}}\\ .\\ .\\ \frac{U_{n1}}{I_{S1}}\end{array}\right),\left(\begin{array}{c}{r}_{12}\\ r_{22}\\ .\\ .\\ r_{n2}\end{array}\right)=\left(\begin{array}{c}\frac{U_{12}}{I_{S2}}\\ \frac{U_{22}}{I_{S2}}\\ .\\ .\\ \frac{U_{n2}}{I_{S2}}\end{array}\right).........\left(\begin{array}{c}{r}_{1n}\\ r_{2n}\\ .\\ .\\ r_{\mathrm{nn}}\end{array}\right)=\left(\begin{array}{c}\frac{U_{1n}}{I_{\mathrm{Sn}}}\\ \frac{U_{2n}}{I_{\mathrm{Sn}}}\\ .\\ .\\ \frac{U_{\mathrm{nn}}}{I_{\mathrm{Sn}}}\end{array}\right)$

Also namely:

$\left[R\right]=\left(\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& r_{n2}& .& .& r_{\mathrm{nn}}\end{array}\right)=\left(\begin{array}{ccccc}\frac{U_{11}}{I_{s1}}& \frac{U_{12}}{I_{s2}}& .& .& \frac{U_{1n}}{I_{\mathrm{sn}}}\\ \frac{U_{21}}{I_{s1}}& \frac{U_{22}}{I_{s2}}& .& .& \frac{U_{2n}}{I_{\mathrm{sn}}}\\ .& .& .& .& .\\ .& .& .& .& .\\ \frac{U_{n1}}{I_{s1}}& \frac{U_{n2}}{I_{s2}}& .& .& \frac{U_{\mathrm{nn}}}{I_{\mathrm{sn}}}\end{array}\right)$

Step 5) in, the inverse matrix [G] using Gauss-about to try to achieve [R] when elimination method is

$\left[G\right]=\left[\begin{array}{ccccc}{G}_{11}& G_{12}& .& .& G_{1n}\\ G_{21}& G_{22}& .& .& G_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ G_{n1}& G_{n2}& .& .& G_{\mathrm{nn}}\end{array}\right]$

[G] is conductance matrix, and i capable j row parameter is G _ij.

Step 6) in, for any one node P _i, node P _iwith reference mode P ₀between branch resistance be R _ii, node P _iwith node P ₁between branch resistance be R _i1, node P _iwith node P ₂between branch resistance be R _i2, node P _iwith node P _jbetween branch resistance be R _ij, node P _iwith node P _nbetween branch resistance be R _in; As i ≠ j,

$G_{\mathrm{ij}}=-\frac{1}{R_{\mathrm{ij}}}$

Obtain node P _iwith node P _jbetween branch resistance be:

$R_{\mathrm{ij}}=-\frac{1}{G_{\mathrm{ij}}}---\left(3\right)$

As i=j,

$R_{\mathrm{ii}}=-\frac{1}{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{G}_{\mathrm{ij}}}---\left(4\right)$

As shown in Figure 3, be earth cord network branch resistance measurement mechanism schematic diagram of the present invention.Comprise standard DC current source, digital nV table, current changeover switch matrix, voltage changeover switch matrix and computer for controlling and testing software thereof.Earth cord network also has n isolated node except a reference mode, is called n node earth cord network; Current changeover switch matrix has 1 input port and n delivery outlet, and voltage changeover switch matrix has 1, n input port delivery outlet; The output of standard DC current source is high-end to be connected with the input end of current changeover switch matrix, and n output terminal of current changeover switch matrix is connected with n node of tested earth cord network in order respectively; N input end of voltage changeover switch matrix is connected with n node of tested earth cord network in order respectively, and the input that output terminal and the digital nV of voltage changeover switch matrix show is high-end to be connected; Standard DC current source exports low side and is connected with the reference mode of tested earth cord network with digital nV table input low side simultaneously; Standard DC current source, digital nV table, current changeover switch matrix, voltage changeover switch matrix are all connected with computer for controlling by control interface (as GPIB); For controlling the switch on and off of current changeover switch matrix on described computer for controlling, the switch on and off of control voltage change-over switch matrix, the output state of control criterion DC current source, arranges the output current amplitude of standard DC current source, obtains the measurement data that digital nV shows.

Wherein, because the resistance of line resistance can be smaller, in order to reduce error, need to adopt large Impetus of Current Source, therefore, current changeover switch matrix adopts big current programmed switch matrix; Such as, adopt high-current relay array, add the big current programmed switch matrix of control circuit.

Due to very low by geodesic resistance value, if time the electric current of current source is also smaller, need the voltage measured can be very little, bring difficulty to Measurement accuracy voltage.The earth cord network of N number of node, corresponding N primary current excitation, need to measure N number of voltage, complete one-shot measurement needs N altogether at every turn ²secondary voltage measurement.Therefore need to adopt switch matrix to go voltage table to switch to each measuring junction, measure the magnitude of voltage of node one by one, so just relate to the impact that switch matrix switches the thermoelectrical potential voltage brought.If the magnitude of voltage measured is very little, the proportion that thermoelectrical potential accounts for will increase, and the impact that thermoelectrical potential is brought can not be left in the basket.Therefore, voltage changeover switch matrix adopts low thermoelectrical potential programmed switch matrix, and the switch that can adopt mainly contains following three kinds, and one is low thermoelectrical potential mechanical switch, and two is low thermoelectrical potential relays, and three is analog switches.These three kinds of switches respectively have relative merits, can the value of thermoelectrical potential be controlled in microvolt magnitude, can as the selection in design.

Device of the present invention, under control of the computer, selects node in order by big current programmed switch matrix, injects measuring current I at this node _si; Computing machine controls low-heat electromotive force programmed switch matrix, selects node in order, digital spc voltage table is accessed each node successively, measure the current potential U of each node _i1~ U _in; Utilize each parameter of direct current resistance feature matrix of formula (16) computation and measurement equipment ground system, determine the direct current resistance feature matrix [R] of whole earthed system.

$r_{\mathrm{ij}}=\frac{U_{\mathrm{ij}}}{I_{\mathrm{si}}}---\left(16\right)$

Consider that the test duration is longer, drift of thermo emf is also larger on the impact of measurement performance, therefore, for the measuring equipment earthed system of numerous node, the method that many group nodes voltage is measured simultaneously can be adopted, improve measuring speed, shorten Measuring Time, reduce the impact of drift of thermo emf.Also the way of clearing can be adopted to eliminate the impact of thermoelectrical potential.Specific practice is, before current excitation, first measures the voltage of each node, as a setting thermoelectrical potential, then measures the later magnitude of voltage of applying current source, and the latter deducts the former and just obtains the magnitude of voltage eliminating thermoelectric potential influence.Certainly can not remove the impact of thermoelectrical potential completely, be not only because thermoelectrical potential can slowly drift, twice measurement can not complete at the same time, and the temperature applying resistance after electric current also can along with change, and corresponding thermoelectrical potential also has faint change.Our final object the impact of thermoelectrical potential will be controlled within acceptable scope.

Adopt above-mentioned earth cord network branch resistance measurement mechanism to ask for the method for the resistance value of each branch road of earth cord network, comprise the following steps:

1) first, testing results software on computer for controlling, arranges i counter and j counter parameter initial value is 1:i=1, j=1;

2) i-th output terminal controlling current changeover switch matrix is connected with i-th node of tested earth cord network, i=1,2,3 ... .n;

3) control criterion DC current source exports measuring current Ii, i=1, and 2,3 ... .n;

4) a jth input end of control voltage change-over switch matrix is connected with a jth node for tested earth cord network, j=1,2,3 ... .n;

5) control figure nV shows to measure DC voltage, reads the measurement result U that digital nV shows _ij, and test result is kept in the internal register of computing machine in a matrix fashion;

6) if repeat 4 ~ 6 steps after j ≠ n, j counter adds 1;

7) if j=n, if i ≠ n, j counter is put after 1, i counter adds 1 again repeat 2 ~ 7 steps;

8) work as i=n, j=n, complete test, calculate the parameters of [R] matrix according to formula (17):

$r_{\mathrm{ij}}=\frac{u_{\mathrm{ij}}}{I_i}---\left(17\right)$

9) inverse matrix [G] adopting Gauss-about to try to achieve [R] when elimination method according to matrix [R] can calculate each branch resistance R according to formula (18), (19) _ij,

As i=j,

$R_{\mathrm{ii}}=-\frac{1}{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{G}_{\mathrm{ij}}}---\left(18\right)$

As i ≠ j,

$R_{\mathrm{ij}}=-\frac{1}{G_{\mathrm{ij}}}.---\left(19\right)$

It should be pointed out that the above embodiment can make the invention of those skilled in the art's comprehend, but do not limit the present invention in any way creation.Therefore, although this instructions and embodiment have been described in detail to the invention, it will be appreciated by those skilled in the art that and still can modify to the invention or equivalent replacement; And all do not depart from technical scheme and the improvement thereof of the spirit and scope of the present invention, it is all encompassed in the middle of the protection domain of the invention patent.

Claims (8)

1. an earth cord network branch resistance measuring method, is characterized in that, comprising:

1) entirely as a multiterminal pure resistance passive linear network, a reference mode P will be comprised by spider lines ₀and n isolated node, be called n node earth cord network;

2) with P ₀point is reference, applies electric current, then form unique group node voltage at n isolated node at n isolated node:

$\left(\begin{array}{c}{U}_1\\ U_2\\ .\\ .\\ U_n\end{array}\right)=\left(\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& .& .& .& r_{\mathrm{nn}}\end{array}\right)\left(\begin{array}{c}{I}_1\\ I_2\\ .\\ .\\ I_n\end{array}\right)---\left(1\right)$

Matrix [R]:

$\left[R\right]=\left[\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& r_{n2}& .& .& r_{\mathrm{nn}}\end{array}\right]---\left(2\right)$

Characterize the impedance operator of n node earth cord network, be called direct current resistance feature matrix, reflect the relation between earth cord network node Injection Current and each node voltage;

4) by being injected into the DC current of each node of earth cord network, the node voltage produced on each node is measured, by calculating the measurement realized described direct current resistance feature matrix [R] parameter;

5) by Gauss-about when elimination method tries to achieve the inverse matrix [G] of [R], i.e. conductance matrix [G];

6) by conductance matrix [G], the resistance value of each branch road of earth cord network is asked for.

2. earth cord network branch resistance measuring method according to claim 1, is characterized in that, described step 4) in, adopt the superposition principle of linear circuit, inspiring standard electric current is applied in turn to earth cord network, travels through each node, that is:

$\left[\begin{array}{c}{I}_{s1}\\ 0\\ .\\ .\\ 0\end{array}\right],\left[\begin{array}{c}0\\ I_{s2}\\ .\\ .\\ 0\end{array}\right],......\left[\begin{array}{c}0\\ 0\\ .\\ .\\ I_{\mathrm{sn}}\end{array}\right]$

Measure each node voltage respectively:

$\left[\begin{array}{c}{U}_{11}\\ U_{21}\\ .\\ .\\ U_{n1}\end{array}\right],\left[\begin{array}{c}{U}_{12}\\ U_{22}\\ .\\ .\\ U_{n2}\end{array}\right],......\left[\begin{array}{c}{U}_{1n}\\ U_{2n}\\ .\\ .\\ U_{\mathrm{nn}}\end{array}\right]$

Substitute into following formula respectively

$\left(\begin{array}{c}{U}_1\\ U_2\\ .\\ .\\ U_n\end{array}\right)=\left(\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& .& .& .& r_{\mathrm{nn}}\end{array}\right)\left(\begin{array}{c}{I}_1\\ I_2\\ .\\ .\\ I_n\end{array}\right)$

Obtain each parameter of [R] matrix:

$\left(\begin{array}{c}{r}_{11}\\ r_{21}\\ .\\ .\\ r_{n1}\end{array}\right)=\left(\begin{array}{c}\frac{U_{11}}{I_{S1}}\\ \frac{U_{21}}{I_{S1}}\\ .\\ .\\ \frac{U_{n1}}{I_{S1}}\end{array}\right),\left(\begin{array}{c}{r}_{12}\\ r_{22}\\ .\\ .\\ r_{n2}\end{array}\right)=\left(\begin{array}{c}\frac{U_{12}}{I_{S2}}\\ \frac{U_{22}}{I_{S2}}\\ .\\ .\\ \frac{U_{n2}}{I_{S2}}\end{array}\right).........\left(\begin{array}{c}{r}_{1n}\\ r_{2n}\\ .\\ .\\ r_{\mathrm{nn}}\end{array}\right)=\left(\begin{array}{c}\frac{U_{1n}}{I_{\mathrm{Sn}}}\\ \frac{U_{2n}}{I_{\mathrm{Sn}}}\\ .\\ .\\ \frac{U_{\mathrm{nn}}}{I_{\mathrm{Sn}}}\end{array}\right)$

Also namely:

$\left[R\right]=\left(\begin{array}{ccccc}{r}_{11}& r_{12}& .& .& r_{1n}\\ r_{21}& r_{22}& .& .& r_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ r_{n1}& r_{n2}& .& .& r_{\mathrm{nn}}\end{array}\right)=\left(\begin{array}{ccccc}\frac{U_{11}}{I_{s1}}& \frac{U_{12}}{I_{s2}}& .& .& \frac{U_{1n}}{I_{\mathrm{sn}}}\\ \frac{U_{21}}{I_{s1}}& \frac{U_{22}}{I_{s2}}& .& .& \frac{U_{2n}}{I_{\mathrm{sn}}}\\ .& .& .& .& .\\ .& .& .& .& .\\ \frac{U_{n1}}{I_{s1}}& \frac{U_{n2}}{I_{s2}}& .& .& \frac{U_{\mathrm{nn}}}{I_{\mathrm{sn}}}\end{array}\right).$

3. earth cord network branch resistance measuring method according to claim 2, is characterized in that, described step 5) in, the inverse matrix [G] using Gauss-about to try to achieve [R] when elimination method is

$\left[G\right]=\left[\begin{array}{ccccc}{G}_{11}& G_{12}& .& .& G_{1n}\\ G_{21}& G_{22}& .& .& G_{2n}\\ .& .& .& .& .\\ .& .& .& .& .\\ G_{n1}& G_{n2}& .& .& G_{\mathrm{nn}}\end{array}\right]$

[G] is conductance matrix, and i capable j row parameter is G _ij.

4. earth cord network branch resistance measuring method according to claim 3, is characterized in that, described step 6) in, for any one node P _i, node P _iwith reference mode P ₀between branch resistance be R _ii, node P _iwith node P ₁between branch resistance be R _i1, node P _iwith node P ₂between branch resistance be R _i2, node P _iwith node P _jbetween branch resistance be R _ij, node P _iwith node P _nbetween branch resistance be R _in; As i ≠ j,

$G_{\mathrm{ij}}=-\frac{1}{R_{\mathrm{ij}}}$

Obtain node P _iwith node P _jbetween branch resistance be:

$R_{\mathrm{ij}}=-\frac{1}{G_{\mathrm{ij}}}---\left(3\right)$

As i=j,

$R_{\mathrm{ii}}=-\frac{1}{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{G}_{\mathrm{ij}}}.---\left(4\right)$

5. an earth cord network branch resistance measurement mechanism, is characterized in that, comprises standard DC current source, digital nV table, current changeover switch matrix, voltage changeover switch matrix and computer for controlling; Described earth cord network also has n isolated node except a reference mode, is called n node earth cord network; Described current changeover switch matrix has 1 input end and n output terminal, and described voltage changeover switch matrix has n input end 1 output terminal; Described standard DC current source output is high-end to be connected with the input end of current changeover switch matrix, and n output terminal of current changeover switch matrix is connected with n node of tested earth cord network in order respectively; N input end of described voltage changeover switch matrix is connected with n node of tested earth cord network in order respectively, and the input that output terminal and the digital nV of voltage changeover switch matrix show is high-end to be connected; Standard DC current source exports low side and is connected with the reference mode of tested earth cord network with digital nV table input low side simultaneously; Described standard DC current source, digital nV table, current changeover switch matrix, voltage changeover switch matrix are all connected with computer for controlling by programmable interface; Described computer for controlling is for controlling the switch on and off of current changeover switch matrix, the switch on and off of control voltage change-over switch matrix, the output state of control criterion DC current source, arranges the output current amplitude of standard DC current source, obtains the measurement data that digital nV shows.

6. earth cord network branch resistance measurement mechanism according to claim 5, is characterized in that, described current changeover switch matrix adopts big current programmed switch matrix.

7. earth cord network branch resistance measurement mechanism according to claim 5, is characterized in that, described voltage changeover switch matrix adopts low thermoelectrical potential programmed switch matrix.

8. adopt described earth cord network direct current resistance characteristic test device to ask for the method for the resistance value of each branch road of earth cord network, comprise the following steps:

1) first, described computer for controlling arranges i counter and j counter parameter initial value is 1:i=1, j=1;

2) i-th output terminal controlling current changeover switch matrix is connected with i-th node of tested earth cord network, i=1,2,3 ..., n;

3) control criterion DC current source exports measuring current I _i, i=1,2,3 ..., n;

4) a jth input end of control voltage change-over switch matrix is connected with a jth node for tested earth cord network, j=1,2,3 ..., n;

5) control figure nV shows to measure DC voltage, reads the measurement result U that digital nV shows _ij, and test result is kept in the internal register of computing machine in a matrix fashion;

6) if repeat 4 ~ 6 steps after j ≠ n, j counter adds 1;

7) if j=n, if i ≠ n, j counter is put after 1, i counter adds 1 again repeat 2 ~ 7 steps;

8) work as i=n, j=n, complete test, calculate the parameters of [R] matrix according to formula (5):

$r_{\mathrm{ij}}=\frac{u_{\mathrm{ij}}}{I_i}---\left(5\right)$

9) inverse matrix [G] adopting Gauss-about to try to achieve [R] when elimination method according to matrix [R] can calculate each branch resistance R according to formula (6), (7) _ij.

As i=j,

$R_{\mathrm{ii}}=-\frac{1}{\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{G}_{\mathrm{ij}}}---\left(6\right)$

As i ≠ j,

$R_{\mathrm{ij}}=-\frac{1}{G_{\mathrm{ij}}}.---\left(7\right)$