DE1591877A1 - Method and device for locating faults in electrical lines, in particular telecommunications lines - Google Patents

Description

Method and device for locating faults on electrical lines, in particular telecommunication lines.

The invention relates to a method for simplifying the measurement and evaluation when locating faults in electrical lines with contact wire measuring bridges or combined double-cube measuring backs. It is applicable to resistance ratios ratio and resistance difference bridge circuits.

When locating insulation faults on electrical lines In addition to the actual fault location measurement, auxiliary measurements are carried out if necessary, with the help of which the resistance of the measuring leads, the asymmetry of measuring; and Fault wire conductor resistance and the asymmetry of measuring and fault wire insulation resistance must be taken into account.

If there is a test object whose peculiarity the consideration of all three 0.g. Factors, results from the equation for the distance of the fault location from the near end when using the resistance ratio bridge circuit: In this equation 1 = total length of the faulty line section 2x = distance of the fault from the near end of the line section M1 = measured value to take into account the lead resistance M2 = measured value to locate the fault M2 '= measured value to detect the insulation resistance asymmetry X3 = measured value to detect the conductor resistance asymmetry P = bridge half resistance If the measuring wire and the fault wire have the same conductor resistance and the resistance of the measuring wire to the insulation resistance of the line is very small compared to the fault wire very small compared to the wire resistance over the measuring wire, the fault wire, this results in M2 - M2 'M2-M1 1x = 1 1x = 1 P / 2-M2 '(Eq. 2) P / 2-M1 (Eq. 3) Equations of the form of Eq. 2 and 3 also occur when locating insulation faults in the compensated bridge current measuring circuit and when locating wire breaks and coupling faults (double swap, contact with unknown conductors, defective compensating capacitor, point of resistance).

In the case of sliding wire measuring bridges, which are used to implement the resistance ratio -Bridge circuit, only half of the sliding wire is mostly used coated on the tap designed as a grinder. The other half of the grinding wire is therefore generally replaced by a fixed resistor. From which two Partial resistances existing DUT must therefore have the lower resistance the contact wire and the higher resistance are connected to the fixed resistor, if a bridge adjustment should be possible. Otherwise the polarity of the test object must be reversed be connected. In order to enable a bridge adjustment without reversing the polarity, when the partial resistance of the test object connected to the sliding wire is slight is greater than the partial resistance connected to the fixed resistor, usually hosts slightly more than half of the total bridge half resistance P as a sliding wire resistance educated.

With the usual resistance difference measuring devices for fault location on the other hand, the polarity must be reversed in any case, if the variable balancing resistor lying partial resistance of the Ueßobjektes is greater than the other partial resistance.

The common formulas shown above for calculating the Removal of errors from the measured values with resistance ratio bridge circuits are relatively unwieldy. The calculation requires a relatively large amount of time and calculation errors can easily occur. For the differential resistance bridge circuits other formulas with a different structure are required.

In the case of the differential resistance bridge circuit, even with small Differences in the partial resistances of the device under test have reversed polarity in many cases so that a bridge adjustment can be achieved.

The invention serves to simplify and facilitate the calculation the removal of faults in electrical lines in the resistance ratio bridge circuit as well as to simplify the resistor differential bridge circuit.

The invention is based on the object through appropriate simplification the known formulas for calculating the fault location in electrical lines With the help of the resistance ratio bridge circuit and suitable equipment Tools to simplify the determination of the fault location.

For by far the most common form of equation, a Simplification done in such a way that the relative error distance with the help of a single arithmetic operation (division) can be determined in which the two to dividing measured values can be read off on the sliding wire scale or on the crank resistors are.

Furthermore, a possibility should be created for fault location to significantly reduce the cases in the resistance difference bridge circuit, which can only be calibrated after reversing the polarity of the cable. It is supposed to be achieved will also meet the above requirements, without the need for an additional scale on the sliding wire.

The object is achieved according to the invention in that, instead of the measured values Y, the corresponding arithmetic values resulting from the relationship N n P / 2 -M are used and not the error distance lx from the near end, but the error distance ly from the far end of the faulty line section from the sieving is calculated. If the sliding wire is provided with two opposing M and N scales to simplify the determination of the calculated values N, then, according to the invention, the scale that is not required can be covered by a rotatable or displaceable scale cover.

With constant application of the arithmetic values N one after the usual To obtain a running N-scale arrangement, willow after the further training of the Invention the adjustment elements of the measuring bridge with otherwise unchanged spatial Polarity reversed arrangement switched on. In order to avoid two scales with this arrangement and nevertheless the calculated values N or the measured values for the various measurements To be able to read Y easily, are in a further embodiment of the invention over two fixed or one adjustable reading thread arranged on the scale, whereby the distance between the two threads or thread positions the maximum negative value on the N-scale is equivalent to.

In a further embodiment of the invention, a two-fold Scale lettering or the double reading thread are omitted if the grinding wire the measuring bridge at the point that corresponds to the scale value N - 0 ohms Having tapping that can optionally be switched on for measurement can.

To use the differential resistance bridge circuit is after a further embodiment of the invention in the one opposite to the sliding wire Bridge arm a fixed resistor arranged switchable, the size of the maximum The value of the negative resistance corresponds to the N-scale.

The invention is to be explained in more detail with the aid of the drawing Fig. 1 shows a sliding wire measuring bridge for use in the resistance ratio bridge circuit, 2 shows a sliding wire double crank measuring bridge for use in the resistance ratio bridge circuit, in which the balancing elements are switched on with reversed polarity, Fig. Da and 3b possibilities for using two reading threads or one adjustable reading thread, Fig. 4 a sliding wire measuring bridge with sliding wire tap for use in conductor resistance measurement, 5 shows a sliding wire measuring bridge for use in the resistor difference bridge circuit, in which an additional resistor is switched on in a bridge branch.

In Fig. L, a conventional sliding wire measuring bridge for use in the resistance ratio bridge switching is shown with the terminals x1, x2 and E, in which z * B. the sliding wire with a sliding wire resistance Rs = 102 ohms is supplemented by a fast resistance of 98 ohms to the bridge half resistance P = 200 ohms. The test object Stollt represents a three-pole, which should be characterized by the resistors RA, R3 and RC, whereby the third resistor RC is for the bridge balancing our influence, it only influences the sensitivity of the circuit. The purpose of the circuit is to determine the RA / RB ratio by measuring. The position that the contact wire tap has after bridge adjustment for the case in which the partial resistances RA and RB of the test object are of the same size has been designated as the "point of symmetry". The scale for reading the measured value M begins at the terminal @@. to count the facing end of the sliding wire with 0 and in our example runs over the symmetry point 100 Ohm to the highest possible value of the sliding wire resistance RS = 102 Ohm. With this anoromul. is the application of Glt 1 to locate faults in electrical. lines possible. To simplify matters, stelole. Whoever introduces measured values M the corresponding values N = P / 2 - M and does not calculate the distance lx of the fault from the near end of the line section, but the distance ly from the far end. With these quantities the equation results It does not matter whether 1x or ly is calculated. If the fault is near the far end of the line section, or if the trimmings (splices, etc.) start to pay from the far end, it is obvious to calculate the distance ly anyway.

If the distance is desired 1x, it can be done with the help of the relationship 1x 5 1 - ly to be converted.

The values N cannot be directly applied to the normal loop wire measuring bridge but are from the above relationship N s P / 2 - M, in our example N = 100 ohms - M, to be calculated.

To avoid this calculation, the slip wire can be added to the existing from 0 to the largest possible value, in our example 102 ohms, running M-scale can be provided with a counter-rotating scale, which is in the point of symmetry starts to run @@ with O and at the end of the key @@@ facing terminal x1 @@ tes reaches the largest possible value P / 2, trj in our example f. For the abrasive wire section from the symmetry pole to the largest possible neßwert M, in our example 1 @@@ @ 2, e @@@@@ ben Values running from 0 to negative for the N-scale, in ours Example 0 to -2 ohms. Using this inert N and the given Eq. 4 results in a significantly simplified calculation of the error distance, thus the possibility of computational errors occurring is greatly reduced.

Another advantage is that Eq. 4, on the resistance ratio circuit applied in constructing the equation used in the differential resistance circuit corresponds, so that there are clear relationships for the user.

For the case often encountered in the prairie, that the lead resistance is very small compared to the line resistance and between the measuring and fault wires If there is no difference in resistance, Eq. 4 to N2 ly = 1 N2 '(eq. 5) To carry out the procedure and use the simplified Equations, it is too cumbersome to use the necessary arithmetic values N in each case Help to calculate the relationship N = P / 2 - 1. For such cases it is known a existing scale, here the M-scale, with a second scale label, in ours Example of the N-scale, provided with ru. To avoid errors when reading the scale, It is advantageous to rotate the scale labeling that is not required by means of a or to cover slidably arranged scale diaphragms. Analogous to a double The scale labeling of the sliding wire can also have double labeling of the switch positions the double crank resistors can be provided.

By using two scale markings, the measuring bridge becomes confusing. It is also disadvantageous if one scale is opposite to the general one usual arrangement of the scale runs. To avoid this, be expedient the The polarity of the balancing elements of the measuring bridge is reversed if the spatial arrangement is otherwise undamaged turned on. The principle is shown in Fig. 2, with a sliding wire double Kusbelmeßbrücke for use in the resistor ratio bridge circuit. the The scale then begins with the value N = P / 2 - Rs, in the selected example with N = - 2 Ohm, and runs over the symmetry point N = 0 Ohm to the maximum value N = 100 Ohm.

Count to zero a value corresponding to the actual resistance but the beginning scale is required for those measuring circuits with those absolute values such as capacitance, inductance, earth resistance are to be determined, as well as for measuring circuits that are used for fault location, but not on a Bridge method are based on e.g. current branching measurement.

For this purpose, a second would be starting with zero, i.e. by the amount Rs - P62 offset scale with the same graduation required, whereby again the respective scale that is not required could be covered by a scale cover. Around To avoid the second scale, however, one can also set two fixed values above the first scale Arrange the reading threads with the distance Rs - P / 2, in the selected example 2 ohms. Of the the same effect can be achieved with a by the amount Rs = P / 2 compared to the zero position rotatable reading thread can be achieved. These possibilities are shown schematically in 3a and 3b indicated.

Another way to avoid a double scale is to use it by providing the contact wire with a fixed tap at the point N = O Ohm, to which the output of the measuring bridge can be switched for measurements where absolute Sizes are to be determined. An application example is shown in Fig. 4, wherein the circuit is provided for measuring the loop resistance.

When using the resistance andsdifferenz-Brädkenschaltung for locating of insulation and resistance difference faults can also refer to the previously described Possibilities are dispensed with if in the opposite of the loop wire Bridge arm a resistor of the size Rs - P / 2 is provided so that it can be switched on is. This possibility also has the advantage that even with the differential resistance bridge circuit a bridge adjustment without reversing the polarity of the device under test or leads to the device under test can be achieved if the partial resistance connected to the balancing resistor slightly larger than the other partial resistor connected to the fixed resistor of the test object is. This possibility is for the use of the differential resistance bridge circuit for locating insulation faults can be seen from FIG. 5.

Claims (6)

Patent claims: t. Method for locating faults in electrical lines, in particular telecommunications lines, with loop wire or combined 4 loop wire double crank measuring bridges, characterized in that the error distance is determined using the equation is calculated, where 1 the total length of the faulty line segment ly the distance of the fault location from the far end M1 the measured value for taking into account the lead resistance X2 the measured value for the fault location M2 'the measured value for the detection of the insulation resistance unbalance M3 the measured value for the detection of the line resistance unbalance and the for The calculation value N corresponding to the respective measured value M results from the relationship N = P / 2 -> 1, in which P means the bridge half resistance. 2. Arrangement for performing the method according to claim 1, characterized characterized in that the scale that is not required is replaced by a rotatable or displaceable The scale cover is covered. 3. arrangement for performing the method according to claim 1, characterized marked that the adjustment elements of the Mebbrücke $ with otherwise unchanged spatial arrangement are switched on without polarity. 4. Arrangement according to claim 3, characterized in that over the Scale two fixed or one adjustable reading thread are arranged, with the distance between the two threads or thread positions the maximum negative value on the N-scale is equivalent to. 5. Arrangement according to claim 3, characterized in that the grinding wire at the point that corresponds to the scale value N. O Ohm, an optionally switchable having fixed tap. 6. Arrangement according to claim 3, characterized in that in the dem A fixed resistor can be switched on on the opposite side of the bridge branch is arranged, the size of which corresponds to the maximum value of the negative resistance on the N-scale is equivalent to.