JPS604802A - How to measure the distance to the disconnection point - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a distance measuring method to a disconnection point that is effective for detecting a disconnection point in, for example, underground or undersea cables.

←) Prior Art Generally, when a breakage occurs in an insulating cape/I/(electric wire, etc.), it is extremely difficult to find the breakage point without removing the cable sheath. In particular, underground power lines are difficult to handle directly.

It is almost impossible to know the distance to the point of disconnection in submarine power lines, etc. In recent years, attempts have been made to solve this problem by introducing a pulse voltage into the Keff voltage and detecting the delay in the 5-fault voltage, or by calculating the delay by comparing it with the capacitance of the line under the same conditions. However, reliable measurement results have not yet been obtained.

(c) Purpose The purpose of this invention is to prevent cable breakage in the case where the cable includes at least one core wire, even if the cable core wire is covered with an outer sheath, or even if the cable is buried underground or laid on the seabed. Accurate location.

It is an object of the present invention to provide a method for measuring the distance to a disconnection point that can be easily discovered.

In order to achieve the objective of IM Completion Note 1, this invention short-circuits one terminal of the pair of wires, and reduces the capacitance CA, CB between each of the pair of wires and another identical target object, and the pair of wires. Measure the capacitance CW of both lines together and the same target object, and from these measured capacitances CA, CB, CW and the known total length of the cable, LS = (CW + CB4C
A) The distance LS to the disconnection point is calculated by calculating LT/CW.

(g) Examples Hereinafter, the present invention will be explained in detail by way of examples.

FIG. 1 is a schematic diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes a cable whose distance to the disconnection point is to be measured, and is composed of a pair of core wires 2 and 3 and a shield conductor 4. 5 is a capacitance measurement calculator, and each core wire 2
, 3 and the shield conductor, and calculates the distance to the disconnection point based on the measured capacitance. One ends A and B of the core wires 2 and 3 are connected to the capacitance measuring calculator 5 through switches SA and SB, respectively, and one ends A and B of the core wires 2 and 3 are still commonly connected to each other through a switch SW. It has become. Furthermore, during measurement, the other ends of the core wires 2 and 3 are short-circuited (point F).

Of course, a low impedance circuit such as an electronic circuit is connected to the other end, and in the case of a substantially short-circuited state, it is sufficient.

Now, suppose that point D of the core wire opening is broken, and from one end B to D
We will explain how to calculate the distance LS to the point.

First, with switches SW and SB open, switch S
A is turned on, and the capacitance CA between the core wire 2 and the shield conductor 4 is measured by the capacitance measurement calculator 5.

Next, the switch SB is turned on, the switches SW and SA are turned off, and the capacitance CB between the core wire 6 and the shield conductor 4 is measured. Next, turn on switch SW, turn on either switch SA or switch SB,
The capacitance CW between the core wires 2 and 3 collectively and the shield conductor 4 is measured. These capacitances CA, CB, CW
When , the capacitance measurement calculator 5 calculates the following equation using the known cable 1) length LT and the capacitances CA, CB, and CW that are input separately.

L3=(CW+CB-CA)・LT/CW...(1
) Calculate the distance LS from one end A, B to the point where the wire breaks.

Next, the reason why the distance LS to the disconnection point can be calculated using the two-line equation (1) will be explained.

In FIG. 1, the electrostatic field ji between point A and the shield conductor 4
ljcA is the CAE capacitance of the core wire 2 (one point F: the position of the core wire 2 corresponding to the point where the wire is broken).

Let CEDF be the capacitance at points EF and DF of the pair of core wires 2 and 3.

CA: CAE+CEDF ・−・−(2). On the other hand, the capacitance CB between point B and the shield conductor 4 is the capacitance CBD of the core wire BD.

The core wires 2 and 6 of the pair of wires are z1 for the 71 capacitance measurement end.
Because it is a nickname.

CAE=CBD=CB .=. (a). Cape/V 1 has the same shape throughout.

The collective capacitance CW of the core wires 2 and 3 is proportional to the length L of the cable. Therefore, if the capacitance per unit length υ of the cable is Co, then CW = Co X LT (4) CEDF
=Co X LR--(5) However, LR: DF (
EF). From equation (2), CEDF=CA-C1...(6), equation (3) and (
From formula 6), CEDF-CA-CB =, -9 (7) Distance LS from point B to the point of disconnection is LS = LT-LR...
・(8) If we insert LT and LR from equations (4) and (5) into equation (8), and CEDF from equation (7) into equation (9), we get LS
= (cw+ CB −CA)/Co −−−−−−
Q (1 or from equation (4), Co = CW / LT --- = -0υ this θ1)
If we put Co in the formula into the formula (1C1).

LS=(CW-1-CB-CA), LT/CW,
The original equation (1) is obtained. i.e. known cable 1
Total length LT and measured capacitance CA.

The distance LS to the disconnection point can be calculated from CB and CW.

An example of a capacitance measuring calculator used in the embodiment of FIG. 1 is shown in FIG. This capacitance measurement calculator is effective when the cable length is long.

In Figure 2, CX is an unknown capacitance, and Nichitsu S
1, the power supply 10 and the resistor R are switched in parallel and connected to each other.

11 is a comparator, and the input voltage E (terminal voltage of resistor R) is +, which is smaller than the limit voltage EO, and the lower limit 71 engineering pressure E.
When C is a dog, an output signal VG is output.

12 is a pulse train generator that outputs a pulse train signal VP;
3 is a gate circuit that outputs the pulse (word VC) from the pulse train generator 12 while the output signal VC from the comparator 11 is input; 14 is a counter that receives and counts the pulse signal VC from the gate circuit 13; 15; is counter 1
Memorize the Curran I value of 4 as the measured capacitance, and
This is a memory calculation circuit that performs calculations such as the following equation (1).

In this capacitance measurement calculator, first, the switch S1 is turned to the a side, and the constant capacitance CX is charged with the voltage ES of the power supply 10. Next, when the switch S1 is turned to the b side, the charge stored in the capacitance to be measured CX is discharged through the resistor R. In this case, the voltage E across the resistor R is from time ts to the time when the voltage E reaches the upper limit voltage Eo, as shown in FIG. 6(a).

jc indicates the point in time when the voltage E reaches the lower limit voltage Ec. During the period from time to to tc, the comparator 11 outputs the output signal VG [see (b) in FIG. 6], and this output signal VG Gate circuit 1 Loha pulse signal VC [
(See FIG. 6(d))] is output. This output pulse signal is counted by the counter 14, and the count value has a long period from to to tc. Since the period from to to tc is proportional to the capacitance to be measured CX, the counter 14's counter 14 is the capacitance to be measured CX.
Therefore, from the count value, it is possible to know that the capacitance to be measured fi<CX. Capacitance to be measured CX
As shown in FIG. 1, the capacitances CA, CB, and CW are measured and the pulse count values NA, NB, and NW of the counter 14 are obtained as those corresponding to the capacitances CA, CB, and CW. 1) Corresponding to equation LS-(NW-NA4-
NB)・LT/NW ・・・・・・Distance LS to the disconnection point can be calculated.

Instead of measuring the number of pulses NW, NA, and NB.

From to to tc in Figure 6(a) when each capacitance is connected
Measure the times LW, tA, and tB at l.

LS, -(tW-LA+tB)・LT/lW...
... Even if you calculate the distance LS to the disconnection point from the formula 0, the above formula 02 converts each capacitance to Pärnu number, and the θ1 formula converts the distance LS to time. It was designed to make it easier to read.

Regarding the measurement of unknown capacitance, as shown in FIG. Other measurement principles may be used to measure the capacitance.

In addition, in the above embodiment, a method for measuring the distance to the disconnection point of a cable having one row of core wires and a shield conductor was explained, but even if the cable does not have a shield conductor,
By measuring the capacitance between a pair of core wires and a conduit conductor pipe or the ground, the distance to the disconnection point can be similarly measured.

(F) Effect According to the present invention, since only the capacitance at one end of each of the two core wires of the cable and the capacitance at one end when both core wires are bundled are measured, the distance to the disconnection point can be easily determined. can be measured. Moreover, since the capacitance can be measured relatively accurately, the distance to the disconnection point can also be measured with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention. FIG. 2 is a block diagram showing an example of the capacitance measurement calculator used in the same embodiment, and FIG. 6 is a signal time chart for explaining the operation of the capacitance measurement calculator. , 2 ・3: Core wire, 4
: Shield conductor, 5: Capacitance measurement calculator. Patent applicant Shimadzu Corporation Representative Patent attorney Shigeru Nakamura Figure 1 Figure 3 (d) Vc

Claims (1)

[Claims] (1) A method for measuring the distance to a break point in a cable consisting of a pair of wires covered with an outer sheath. AiJ is the capacitance CA between each pair of wires and another identical target object when the terminals of the pair of wires are short-circuited. CB, the capacitance CW of both the column lines collectively, and the capacitance CW between the same target object were measured. Using these measurements CA, CB, CW and the known total length LT of the cable, LS = (CW + CB - CA) · LT
By calculating /CW, the distance L to the disconnection point can be calculated.
A distance measurement method to a disconnection point that calculates S. (2+ mJ) A distance measuring method to a disconnection point according to claim 1, wherein the same target object is a shield conductor of a cable.