JPH03107775A - Method and apparatus for measuring position of resistant disturbance used for electric cable - Google Patents

Abstract

PURPOSE: To measure the distance to a faulty point on a conductor easily and accurately by measuring voltage and current at both terminals of the faulty conductor. CONSTITUTION: The position of a faulty point 12 between both terminals A and B of an electrical conductor 10 is measured. At this time, a power supply device 18A is connected to one terminal A, a power supply device 18B at the opposite terminal B is separated, and current is fed to the faulty point 12 through the conductor 10. Then, after voltage and current are stabilized, the voltage and current at the self terminal A are measured by a voltmeter 14A and an ammeter 16A and at the same time the voltage of the opposite terminal B is measured by the voltmeter 14B. The opposite terminal B is electrically open and no current flows and the voltage is equal to the voltage of the faulty point 12. Similarly, the voltage at the terminal B is measured. Then, based on the measurements, resistance between the faulty point 12 and at least one terminal is calculated. Based on the result, the distance between the faulty point 12 and at least one terminal is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION Electrical cables used for communication or power transmission are often
Causes a disturbance between insulated conductors, between an insulated conductor and a metal shield or sheath, between an insulated conductor and the earth, or between a metal shield or sheath and the earth. These failures usually occur as a result of insulation damage or deterioration that creates electrical failures in the presence of groundwater. Another issue is that the resistive damage caused by water varies with time and voltage. Conductors that are partially shorted due to water damage vary with applied voltage, polarity of the applied voltage, and time because electrolysis changes the presence of ions and exposed conductor surfaces. This variable fault resistance is unpredictable and makes simple loop resistance methods unusable.

Several calculations using various bridging methods are available to measure the electrical resistance of a conductor to a point of failure, which can be used to calculate the distance to the point of failure. The bridge method requires parallel conductors or pairs of conductors to be strapped back from the far end of the fault conductor to the arm of the measuring bridge, especially where the fault resistance is high with respect to the conduction resistance. Bridge measurements are not possible unless a fault-free conductor is available.

Another fault location flN method uses short electrical pulses sent to the faulty line. At the point of failure, some of the transmitted energy is reflected back to the transmitting end where it is detected. The time delay from origination to return gives an estimated distance to the point of failure. This method only works for certain types of conductors and cannot easily detect high resistance faults.

11 The present invention is thus directed to solving the above-mentioned problems in the prior art, and it is possible to easily reduce the distance to a fault point on a conductor without being subject to the inherent limitations of previously known methods. It is an object of the present invention to provide a novel and highly useful measuring method and device that can accurately determine the amount of information.

That is, in one aspect of the invention, a method of measuring the position of a resistive gt* between a first end and a second end of an electrical conductor comprises: (a) applying a DC voltage to a first end of the conductor; (b)
Measure the steady state DC voltage and mi at the first end of the conductor, and virtually simultaneously measure the steady state D at the second end of the conductor.
C? Measure the t1 pressure, (C) DCf at the second end of the conductor.
t2 pressure is applied, (d) steady state D at the second end of the conductor.
C voltage and ? [measuring the current and virtually simultaneously measuring the steady state DC voltage at the first end of the conductor; (C)
(f) from the calculated resistance of the conductor, calculate the resistance of the conductor between the resistive fault of the conductor and at least one end of the conductor; The measuring method is provided, characterized in that the distance between the two is calculated.

In another aspect of the invention, an apparatus for measuring the location of a resistive fault between a first end and a second end of an electrical conductor comprises a first Ti force that applies a DC voltage to the first end of the conductor. a supply device; a fourteenth measuring device for measuring the voltage and current at a first end of the conductor; a second power supply device for applying a DC voltage to a second end of the conductor; and a fourteenth measuring device for measuring the voltage and current at the second end of the conductor. a second measuring device operatively connected to the first and second if measuring devices for measuring the resistance across each end of the conductor and any fault therein from the voltage and current measured thereby; The measuring device is characterized in that it comprises: a total of n devices for calculating the distance along the conductor from at least one end to the fault.

Thus, the present invention allows the location of faults to be determined without using bridges or signal crossing techniques, but rather by measuring the voltages and currents across certain conductors, and also allows sequential DC signals with opposite potentials to be determined. A set of measurements is carried out which has the particular advantage of being able to correct ground-induced errors and obtain a statistical average of the measurements, as explained below with reference to the examples. It will become clear.

1 emperor 1 Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

From the drawings, FIG. 1 shows an unconventional measurement circuit connected to ground g[hazardous conductor 10 at 12]. Digital voltmeter 14
A1 ammeter 16A, DOT! A force supply device 18A1 switching mechanism 5W(a) and a ground reference G(a) are connected to the A end of the faulty conductor. Similarly, a digital voltmeter 1413, an ammeter 1681, a DC power supply unit 18
B. Switching mechanism 5W (b) and ground reference G (
b) is connected to the 8 ends of the conductor. Conductor failure point 12
The conductor resistance from to end A and end B is R(a), respectively.
and R(b). The fault resistance is R(f).

The resistances of the grounding points G(a) and G(b) are R(
Ga) and R (Gb).

When an electric potential (bias voltage) is applied to one end of a faulty conductor with respect to ground, current flows through the conductor to the fault, and also through adjacent conductors and directly to the surrounding ground. If the opposite ends B of the conductor are electrically connected, no current will flow in the second portion of the conductor.

Therefore, the voltage V(b) at the 8 end of the cable is equal to the voltage V(f) at the fault. Using these values,
The resistance of the cable section can be calculated from the following formula: where V(a) represents the applied line voltage and V(b)
represents the voltage at the fault, and (a) represents the line current.

The measured ffi current is driven through ground resistances R (Ga) and R (Gb). Earth resistance is generally unknown, but
Critical measurements, if not taken into account? ! May produce an axe. To avoid this possible error, the present invention uses reference grounds 22(a) and 22(b) that are placed outside the voltage gradient area of local grounds G(a) or G(b). Local ground resistance voltage drops and errors are thereby minimized. In addition to earth resistance, other factors often appear that can lead to measurement errors. As shown in FIG. 2, large mine currents 1 (01) and I (a2) from external shadows and other electrochemical processes often apply voltages and 24 to the faulty body. In order to cancel the errors arising from these external influences, switching mechanisms 5W(a) and swcb> are used to first apply an influence to the measuring wheel and then subtract it from the measured value. The errors of these effects are then removed in the averaging algorithm used. , the measurement is carried out as follows: 1. The power supply bag "fi18B is disconnected, and the power supply device 18A is connected to the A of the conductor 10 via the switch 5W(a).
Connected to the end, making the conductor positive.

2. v! At some implicitly precise point, once the voltage and current have stabilized, the readings of vca>, v(b), and 1(a) are measured simultaneously.

34 Switch 5(a)1. The second step is repeated so that the te body becomes negative.

4. Stages N2 and 3 are (V (a) - V (b)
)/i (a) is repeated until the mean of (a) is known within a given statistical accuracy.

5. Power supply 18A is disconnected and power supply 18B is connected to the 8 end of conductor 10 via switch 5W(b), making the conductor positive.

6, V (b>, V (a) Oyohii (b) wo3
11 Steps 1@2 to 4 are repeated to ensure consistency.

The conductor resistance to the point of failure is then measured as follows: where N is the number of measurements taken during the test routine at each end of the conductor.

Using conductor resistance calculation, the distance to the Fii harm point is calculated as follows:
) 131D(b)=D(t)R(b)/
(II(a)+R(b)) (4) However, D
<a) is the distance from end A to the failure point, D (b) is the distance from end B to the failure point, and D(t
) is the total distance of the cable from point A to 8.

The calculation assumes that the conductor resistance per unit length of cable is constant.

Alternatively, if the conductor resistance per medium length is known, the distance to the point of conductor fault can be calculated by hand: D(a) = R(a)/R(n)
f! ,il(b)=R(b)/R(n)
(6 mabutashi R' (n >
is the characteristic resistance of the conductor in ohms per unit length.

The procedure described above represents the basic idea of the fault location process. As mentioned above, it is important that the measurements are taken simultaneously as data is recorded at opposite ends of the cable under test. Communication between opposite ends of the conductor under test is therefore required.

To achieve the required accuracy, timing and communication,
A computer-based automated drag resistance fault locator has been developed. The locator is designed to measure the location of one li'5 point of harm in an external shut of a cable that includes at least one metal jacket, armor or conductor. 1 - Fault is the breakdown of the electrically insulating outer jacket due to a mechanical or other failure that creates a micro electrical path (high resistance) to the surrounding land or one or more adjacent conductors.

The locator does not require the use of a separate dedicated conductor pair. Instead, this device is designed specifically for this application.
You can use the law. The end-to-end communications of the group are performed on the conductor under test. The use of conductors other than those used for communications signals will prevent cable faults from being detected before service interruption.
“, and allows testing while the cable is in use. An identical locator device is used at each end of the cable under test.

From FIG. 3, each locator device 24 consists of a microcomputer 26 and an operator interface 28. As shown in FIG. The interface is a data display and keyboard. Computer 26 is connected to a multi-channel analog-to-digital converter 30, an Igoshi'J conditioner 32, and a line interface 34.

Custom software program 36 exercises the test sequence and displays the data results. External connections are made to the conductor under test at line connections 38, to ground at 40, and to 1tp at 42.

FIG. 4 is a schematic diagram of the line interface components of the locator device. The line interface has
A separate 50 VD (power supply 18 is included) connected via an on/off switch 46 to the polarity of a transfer switch 48. The transfer switch is a double pole double throw switch;
One throw 50 is connected to the negative terminal of the power supply via an on/off switch. Throw 50 connects to either terminal 51 or terminal 52. The other throw 54 is connected to the positive terminal of power supply 18 and to either terminal 55 or 56 of the switch.

Terminals 51 and 56 are connected to line connector 38 of the locator device via enable switch 58. Terminals 42J3 and 45 are connected to ground terminal 40 of the device via resistor 60.

Thus, when the enable switch is turned on and terminals 41 and 45 are coupled, line end F38 is at a negative potential with respect to ground terminal 40. When switch terminals 42 and 46 are coupled, line end f3B is rounded to ground terminal 40 and becomes positive.

An amplifier 61 is connected in parallel across resistor 60 and serves to provide a signal representative of the line current in the Inl path between line terminal 38 and ground terminal 40. A line voltage amplifier 64 is connected upstream of enable switch 58 and to calculation reference terminal F42 to produce a signal representing tfXjJ- between line terminal 38 and calculation reference terminal 42.

This is equal to voltage V(a) in FIG.

Another amplifier 66 has a ground terminal 40 and a calculation reference terminal 4.
2 to produce a signal representative of the voltage across these terminals. The outputs from the three amplifiers are sent to the locator device's signal conditioner 32. Shunt switch 70
is connected between the line terminal 38 and the ground terminal 40.

To conduct a test using this device, 211! locator devices are connected to opposite ends of the couple conductor to be tested as shown in FIG.
One end is referred to as a "local" or "master" device, while the other end is referred to as a "remote" or "flave" device.

There are many external connections to each locator device that must be made prior to testing. The quality of these connections affects the accuracy of the fault position measurement process.

Still referring to FIG. 5, a bias voltage is applied between line connector 38 and ground connector 40. A line connection is a direct electrical connection to the metal conductor under test. A ground connection is a return path from the actual point of failure through a ground or local ground connection. Test S lightning current flows between these two points. The resistance of the earth connection must be as low as possible. It is desirable to use existing large grounding structures, such as water pipes and existing grounding devices.

The third connection is the calculation reference connection 42. The 71 standard is 1
It is a dedicated ground outside of any earth potential field 72 that may be created by a secondary ground. Calculation ml11! The sowing area is 1
Since it is next grounded, low impedance is not required, but it must be kept as low as possible to ensure the MO-free standard. No other connections are made to this ground.

The distance that the shield reference is required from the ground connection to ensure that the calculated reference is outside any earth potential field 72 depends on the conductivity of the soil and the resistance of the main ground terminal. Typical values are 5-10 feet (15-30 meters).

If there is a fault in the two conductor circumferences and an inner conductor is available at each end of the cable, the locator device includes a ground connector 40 and a reference connector 4 coupled to the respective ends of the second conductor.
2, so the second conductor serves as a ground reference.

Communication between the two devices uses the same hardware and connections as the main test routine. Commands and data are first 2
converted to a hexadecimal code. The '-' code is sent by applying a test potential to the conductor under test and then alternating the applied polarity according to a binary code.

Data is recovered by using the main measurement channel of the analog-to-digital converter. The data is then processed by a microcomputer. The use of ^ level signals, very slow data transmission, and advanced processing of received data ensures minimal error rates and reliable communication under harsh conditions.

The software program controls the microcomputer, operates the analog subsystem circuits, performs the prescribed measurement sequence, and outputs the results. Once the test has begun (complete test), no further operator intervention is required. Several stages occur in automatic fishing without the need for manipulation. Total line length (D(t)) and line resistance (Ω/KJR
) must also be input into the microcomputer.

Prior to the actual test, the device performs a self-test according to the flow diagram of FIG. In addition to monitoring internal computer performance,
This test also measures local and remote earth voltage transient levels. If this test passes, the unit that initiated the test requests that it be identified as a mask device and as a remote S device as a slave FA control. Once these steps are completed, the program proceeds to active testing according to Figure 7.

An active test is a test sequence that determines the value of R(a). When active testing is requested, the number of test samples is sent by the mask and agreed upon by the slave. When the test begins, the microcomputer bases its timing on the last data signal sent. From this point until the end of the active test, events are carefully synchronized to ensure simultaneous measurements.

The test procedure is a ttiW4 adjustment stage in which a negative polarity is simply added to the first positive sampling line. When the first positive value is applied, both microcomputers measure and record the line voltage (V(a) at the mask and V(b) at the slave) and the line current (1(a) at the mask).

Then the polarity is reversed and the same values V (a> , V (b
) and i (a) are measured and recorded. Each current Lt measurement is for the calculated reference connection, but the current is the Wi current flowing in the line connection.

After the required number of test cycles, the device enters data transfer mode. All data values recorded by the slave device are sent back to the mask. Upon completion of this stage, a passive test mode is entered.

A passive test is similar to an active test except that the slave device applies a voltage to the line under test and measures and records the line ff current. The values measured and recorded are V (a),
V (b) t3yo U i (b) ': J tochar.

As a result of this test order, the recorded values are sent from the slave to the mask.

Once all the data is received by the mask, the microcomputer calculates R(a) and R(b), R(f), and D(a) and D(t)) based on the structural gradient of D(t).
The value of is used as a sieve.

The accuracy of fault location is influenced by many parameters. Assuming good grounding and homogeneous conductors, the accuracy of the location is equal to the accuracy of the measurement plus the ratio of the resistance at the point of failure to the resistance of the line (Ω/unit distance) by 11 orders of magnitude! be reached. Measured viscosity is 0.05% (0,0005), failure resistance is 20
．． 0000, and the line resistance is 20Ω/K11, the resulting error is as follows.

Error -0,0005X20.000/20=O,0O0
5X1000 -0.57Qw The addition of several other factors, such as poor grounding and the effects of electrical tlL noise and voltage offsets on the fault line, worsens the results. Even small changes in resistance over the length of the line directly affect the result by 4 degrees.

Since these effects represent a percentage of the total line length, subsequent testing at shorter distances 1II (eg, slightly before and after the predicted fault location) increases the ability to predict the exact fault location.

Although one embodiment of the invention is illustrated above, it will be appreciated that other embodiments are possible within the scope of the invention. Therefore, the invention is limited only by the scope of the claims.
II+ should be considered limited.

[Brief explanation of drawings]

Figure 1 is a diagram of the basic measurement circuit according to the present invention, Figure 2 is a schematic diagram of a ground current that applies voltage or current to a faulty conductor, Figure 3 is a block diagram of the control unit, and Figure 4 is the control unit. A schematic diagram of the line interface included in the
FIG. 5 is a schematic diagram showing the ground connection of the device, and FIGS. 6, 7 and 8 are flow charts showing the sequence of operation of the device. Code explanation: 10-39 body; 12-g1 harm point: 14A, B-voltmeter:
16Δ, B-Ammeter: 18A, 13-Power supply device; 2
2 (a>, (b) - reference ground; 5W (a), (b) - switching 41HM: G (, a), (b) - ground base i;
R (a), (b) - conductor resistance 5R (f) - fault resistance: 2
4-Control unit

Claims (7)

[Claims] (1) A method of determining the location of a resistive fault between a first end and a second end of an electrical conductor, comprising: (a) applying a DC voltage with respect to ground to the first end of the conductor; (b) (c) measuring a steady state DC voltage and current with respect to earth at a first end of the conductor and substantially simultaneously measuring a steady state DC voltage with respect to earth at a second end of the conductor; (d) measuring a steady state DC voltage and current with respect to earth at a second end of the conductor and substantially simultaneously measuring a steady state DC voltage with respect to earth at a first end of the conductor; ) from the measured voltage and current calculate the resistance between the resistive fault of the conductor and at least one end; (f) from the calculated resistance of the conductor calculate the resistance between the resistive fault of the conductor and at least one end thereof; The measuring method, comprising: calculating a distance. 2. A method according to claim 1, characterized in that: (2) a DC voltage is applied to the conductor with respect to a first ground connection, and a steady state DC voltage is measured with respect to a second independent ground connection. (3) Repeat steps (a) and (b) half of the time with an applied DC voltage of positive polarity and half of the times with an applied DC voltage of negative polarity, half the time with an applied DC voltage of positive polarity, and repeating steps (c) and (d) another half time with an applied DC voltage of negative polarity, and calculating a plurality of values of the conductor resistance from the point of failure of the conductor to each end. and average the value of the resistance from the fault point to each end to obtain the average conductor resistance, and from the average conductor resistance the value of the resistance between the fault point and at least one of the ends of the first and second conductor. 2. A measuring method according to claim 1, characterized in that it comprises calculating a distance. (4) a device for measuring the location of a resistive fault between a first end and a second end of an electrical conductor, the first power supply device applying a DC voltage to the first end of the conductor with respect to a regulated ground connection; a first voltmeter side device for measuring a DC voltage at a first end with respect to a second ground connection of the conductor; a first current measuring device for measuring a current in the conductor at the first end; a second power supply device that applies a DC voltage with respect to a ground connection; a second voltage measurement device that measures a DC voltage at a second end with respect to a second ground connection of the conductor; and a second current that measures a current in the conductor with a second end. a measuring device, operatively connected to the measuring device for calculating the resistance between each end of the conductor and any fault therein from the voltage and current measured by the measuring device, and for calculating the resistance between each end of the conductor and any fault therein; The measuring device characterized in that it includes: a calculating device for calculating the distance traveled by the user; (5) first and second control units connected to the first and second ends of the conductor, each control unit having a device for sending signals to other control units on the conductor and a device for receiving signals from the same unit; 5. Measuring device according to claim 4, characterized in that it includes the control unit comprising: (6) The signal transmitting device includes a switch device for selectively reversing the polarity of the DC voltage applied to the conductor, thereby
6. Measuring device according to claim 5, characterized in that an advance signal is generated. (7) causing the first control unit to apply a DC voltage to the first end of the cable and then applying a steady state DC voltage and current to the first end of the cable;
measurement at the end, and the second control unit has steady state DC
a device for causing a voltage and a current to be measured at a first end at substantially the same time as a voltage is measured at a second end;
C voltage and current are measured at the second end, and apparatus for causing the first control unit to measure the voltage and current at the second end substantially simultaneously with measuring the steady state DC voltage at the first end. 6. Device according to claim 5, characterized in that: