CN102928735B - Cable failure location method - Google Patents

Abstract

The invention discloses a cable failure location method. Step voltage detection points A, B, C and D are respectively arranged on an axis X and an axis Y of a rectangular coordinate system in a cable failure point region, and distances between the step voltage detection points A, B, C and D and the original point of the rectangular coordinate system are equal, potential difference values Uba, Uca and Uda of the step voltage detection points A, B, C and D are measured, and according to a formula R=K.L, and a median-of-a-triangle formula AP2+CP2=2OP2+2a2, coordinate values of X and Y of a failure point P can be figured out through calculation, wherein R represents resistance per unit length, L represents a length, K is a proportion coefficient, and a represents a length of AO. The invention is applied to the detection of the cable failure point.

Description

A kind of localization method of cable fault

Technical field:

The present invention relates to a kind of trouble spot and determine method, particularly a kind of localization method of cable fault.

Background technology:

Conventional step voltage method is when cable fault position application, be characterized in adding in power cable pulse or ac and dc current, the feature of utilizing discharge current to disperse ringwise outside trouble spot, at different directions, find respectively 2 isopotential points, trouble spot must be positioned on the perpendicular bisector point of crossing of 2 groups of isopotential point lines.

Step voltage method needs repeated multiple times measurement to cable fault location, wastes time and energy.

Summary of the invention:

The object of the invention is to provide a kind ofly can determine the localization method of a kind of cable fault of Method of Cable Trouble Point fast.

Realizing the object of the invention technical scheme is, a kind of localization method of cable fault, comprise step voltage check point, it is characterized in that: step voltage check point is A, B, C and D, these four check points are located at respectively on the X and Y-axis of the rectangular coordinate system in Method of Cable Trouble Point region, and the distance of rectangular coordinates initial point is equal therewith respectively for A, B, C and D, record A, B, C and D current potential difference: Uba, Uca and Uda, according to formula R=KL, in formula, R is resistance, unit ohm, L is length, unit rice, K is scale-up factor, median of a triangle formula: AP ²+ CP ²=2OP ²+ 2a ², the length that in formula, a is AO, can calculate the X of trouble spot P, the coordinate figure of Y by calculating.The present invention has localization of faults remarkable advantage fast compared with the prior art.

Accompanying drawing explanation:

Fig. 1 is voltage distribution schematic diagram, and Fig. 2 is the schematic diagram of the present invention four grounded probe points and trouble spot P on rectangular coordinate X, Y.

Embodiment:

The present invention's Method And Principle used is also " step voltage " method, but measurement point is different, in the P region, trouble spot of prediction (hypothesis), arranging and establishing initial point on the X and Y coordinates line of a rectangular coordinate system is O, on X and Y-axis line, establish respectively measurement point: A, B, C and D, make AO=BO=CO=DO, and establish grounded probe on above-mentioned A, B, C and tetra-points of D.Can apply voltage or electric current to cable, by the magnitude of voltage of above-mentioned four probe points, with following formula, can calculate the position of trouble spot P.

P point is trouble spot.A, B, C, D is four grounded probe.(can record the current potential difference Uba of four points, Uca, Uda)

R=kL (R is resistance, unit ohm, L is length, unit rice, k scale-up factor, i.e. resistance per unit length, unit ohm/meter)

U=RI (U voltage, R resistance, I electric current)

L＝R/k＝U/(I·k)

R (unit ohm) L (unit rice) I (unit ampere) U (unit volt)

If P point coordinate (x, y)

S=Ik (being convenience of calculation)

M=1/s (being convenience of calculation)

L＝R/k＝U/S 《1》

Known: OA=OB=OC=OD=a (a for regular length is set, unit rice)

Uba (B, A point two voltage differences, after method for expressing the same), Uca, Uda

By < < 1 > >, can be obtained

AP＝Uap/s＝Uap·m

BP＝Ubp/s＝Ubp·m

CP＝Ucp/s＝Ucp·m

DP＝Udp/s＝Udp·m

s＝Uap/AP＝Ubp/BP＝Ucp/CP＝Udp/DP

According to median of a triangle formula, in triangle APC

AP ²+CP ²＝2OP ²+2a ²

In triangle BPD

DP ²+BP ²＝2OP ²+2a ²

∴AP ²+CP ²＝DP ²+BP ²

《2》

(Uap/s) ²+(Ucp/s) ²＝(Udp/s) ²+(Ubp/s) ²

Uap ²+Ucp ²＝Udp ²+Ubp ² 《3》

Known according to Fig. 2

Udp＝Uda+Uap 《4》

Ubp＝Uba+Uap 《5》

Ucp＝Uca+Uap 《6》

By < < 4 > > < < 5 > > < < 6 > > substitution < < 3 > >

Uap ²+(Uca+Uap) ²＝(Uda+Uap) ²+(Uba+Uap) ²

Uap ²＝(Uda+Uap) ²+(Uba+Uap) ²-(Uca+Uap) ²

Uap ²＝Uda ²+2Uda·Uap+Uap ²+

Uba ²+2Uba·Uap+Uap ²-

Uca ²-2Uca·Uap-Uap ²

Uda ²+Uba ²-Uca ²＝2Uca·Uap-2Uda·Uap-2Uba·Ｕap

Uap＝(Uba ²+Uda ²-Uca ²)/2(Uca-Uba-Uda)

《7》

< < 7 > > substitution < < 4 > > < < 5 > > < < 6 > > can be obtained to Udp; Ubp; Ucp

Known according to Fig. 2 coordinate and Pythagorean theorem

OP ²＝x ²+y ²

AP ²＝Uap ²m ²＝x ²+(y-a) ² 《8》

BP ²＝Ubp ²m ²＝(x-a) ²+y ² 《9》

CP ²＝Ucp ²m ²＝x ²+(y+a) ² 《10》

DP ²＝Udp ^pm ²＝(x+a) ²+y ² 《11》

< < 8 > > < < 10 > > two equatioies are subtracted each other:

Ucp ²m ²-Uap ²m ²＝x ²+(y+a) ²-x ²-(y-a) ²

＝x ²+y ²+2ay+a ²-x ²-y ²+2ay-a ²

m ²＝4ay/(Ucp ²-Uap ²) 《12》

< < 9 > > < < 11 > > two equatioies are subtracted each other:

Udp ²m ²-Ubp ²m ²＝(x+a) ²+y ²-(x-a) ²-y ²

＝x ²+2ax+a ²+y ²-x ²+2ax-a ²-y ²

＝4ax

m ²＝4ax/(Udp ²-Ubp ²) 《13》

< < 12 > > < < 13 > > are merged:

4ay/(Ucp ²-Uap ²)＝4ax/(Udp ²-2Ubp ²)

x＝y(Udp ²-Ubp ²)/(Ucp ²-Uap ²) 《14》

< < 8 > > < < 10 > > equatioies are divided by:

Uap ²m ²/Ucp ²m ²＝(x ²+(y-a) ²)/(x ²+(y+a) ²)

Ucp ²(x ²+(y-a) ²)＝Uap ²(x ²+(y+a) ²

Ucp ²(x ²+y ²-2ay+a ²)＝Uap ²(x ²+y ²+2ay+a ²)

Ucp ²x ²+Ucp ²y ²-2ayUcp ²+Ucp ²a ²＝

Uap ²x ²+Uap ²y ²+2ayUap ²+Uap ²a ²

Ucp ²x ²-Uap ²x ²＝Uap ²y ²+2ayUap ²+Uap ²a ²-

Ucp ²y ²+2ayUcp ²-Ucp ²a ²

(Ucp ²-Uap ²)x ²＝(Uap ²+Ucp ²)2ay-

(Ucp ²-Uap ²)a ²-(Ucp ²-Uap ²y ²

x ²＝((Uap ²+Ucp ²)2ay)/(Ucp ²-Uap ²)-y2 ⁺a ²

《15》

By < < 14 > > substitution < < 15 > >

(y(Udp ²-Ubp ²)/(Ucp ²-Uap ²)) ²＝

((Uap ²+Ucp ²)2ay)/(Ucp ²-Uap ²)-y ²+a ²

(((Udp ²-Ubp ²)/(Ucp ²-Uap ²)) ²+1)y ²-

((Uap ²+Ucp ²)2ay)/(Ucp ²-Uap ²)-a ²

＝0

According to linear equation in two unknowns solution formula, obtain:

$\begin{array}{c}y=(2a({\mathrm{Ucp}}^2+{\mathrm{Uap}}^2)/({\mathrm{Ucp}}^2-{\mathrm{Uap}}^2)\&PlusMinus;\\ \sqrt{{4a}^2{({\mathrm{Ucp}}^2+{\mathrm{Uap}}^2)}^2/{({\mathrm{Ucp}}^2-{\mathrm{Uap}}^2)}^2+{4a}^2({({\mathrm{Udp}}^2-{\mathrm{Ubp}}^2/({\mathrm{Ucp}}^2-{\mathrm{Uap}}^2)}^2+1)}\\ )/\left(2\left((({\mathrm{Udp}}^2-{\mathrm{Ubp}}^2)/({\mathrm{Ucp}}^2-{\mathrm{Uap}}^2){)}^2+1\right)\right)\end{array}---<<16>>$

Wherein open root symbol and to get preceding paragraph identical

< < 16 > > substitution < < 14 > > are drawn to P point coordinate x, y.

Claims (1)

1. the localization method of a cable fault, comprise step voltage check point, it is characterized in that: step voltage check point is A, B, C and D, these four check points are located at respectively on the X and Y-axis of the rectangular coordinate system in Method of Cable Trouble Point region, and the distance of rectangular coordinates initial point is equal therewith respectively for A, B, C and D, record A, B, C and D current potential difference: Uba, Uca and Uda, according to formula R=KL, in formula, R is resistance, unit ohm, L is length, unit rice, K is scale-up factor, median of a triangle formula: AP ²+ CP ²=2OP ²+ 2a ², the length that in formula, a is AO, can calculate the X of trouble spot P, the coordinate figure of Y by calculating.