DE3711593A1 - Burn-out unit for locating cable faults - Google Patents

Abstract

Published without abstract.

Description

The invention relates to a burner for locating cable faults according to the preamble of claim 1.

Such known burners with a high voltage stage, consisting of a high voltage transformer with subsequent Rectification, use on the high voltage side of the Transformer a tap changer, which taps the Switching up the transformer on the secondary side until at the fault location of the Ignition occurs.

A pulse originating from the pulse echo measuring device becomes at the fault location reflected and returned to the beginning of the cable. Parallel to The burning process is the pulse echo meter via a Capacitor coupled, the pulses of the pulse echo meter run into the cable to be tested. Only when the This then becomes the fault location due to the occurrence of an arc reflected at the beginning of the cable and evaluated by measuring technology. The impulse is not generated by the burning, but proceeds from Pulse echo meter off.

From the transit time of the reflected voltage pulse Fault location determined. The duration of the arc on the Fault in the cable can also be maintained for some time to burn in a low-resistance bridge at the fault location. To the changeover switch on the High voltage side of the high voltage level gradually downwards switched to a lower voltage, preferably always on  decreasing burning voltage. By lowering the burning voltage a low-impedance, possibly metallic, arises at the fault location Bridge that advantageously has a low characteristic impedance and so far can be easily located with the pulse echo meter. A disadvantage of the known burner is that Step switch on the high voltage side of the high voltage step because of the high voltage there, relatively complex and is prone to failure. The switching process itself makes itself particularly noticeable in the step-down regulation in voltage jumps, whereby the arcs to be maintained could easily tear off. The Arc must then be ignited again, which is expensive and could cause high frequency interference.

The object of the present invention is to provide the known type of voltage control easier and cheaper design while avoiding high-frequency interference and in particular to provide the output voltage largely to slide to prevent the arc from breaking off.

To achieve the object, the invention provides that three High-voltage levels with gradually increasing levels Output voltage are provided, which on the output side over Coupling rectifiers are connected and on the input side a switch, the center tap on another Switch of a line-side variable transformer is present.

The essence of the invention is that gradual tensions to provide, but interconnect them so that a single Output voltage runs largely smoothly without the Switching would be complex and prone to failure. In the invention on the primary side of the transformers of the high voltage stages Regulation made and a combination of a gradual and  a sliding regulation, being structurally simple and cost-free, trouble-free, a voltage range from 0 to about 20 kV can be coated. The arrangement of individual voltage levels is advantageous because the individual stages are inexpensive for the current or voltage requirements can be designed. The Switches on the high voltage stages are on their input sides on, which uses relatively small and inexpensive switches can be. By switching on the primary side of the High voltage levels in connection with the switching of the mains-side variable transformers become disadvantageous voltage jumps largely avoided at the common output of the high-voltage stages, since with primary switching with sliding control on In this respect, the variable transformer creates a sliding output voltage is, especially because the primary side switch Output voltage at the output of the burner is only sluggish succeeds, so that voltage jumps are therefore suppressed can.

To this extent, the switch according to the invention only has to be used low voltages are switched on the primary side, which is inexpensive and is not very expensive. By arranging three High voltage levels can vary these inexpensively be provided, in particular taking into account that mainly the ignition stage has a low power requirement at high Has voltage, while the actual firing stages are advantageous can be provided with low voltage at higher Power output to maintain the arc burning time. In this respect, a single high voltage transformer, the at the same time the high ignition voltage and the high combustion current low arc arc voltage should be avoided will.  

In the invention, the first with a rotary switch desired burning voltage of a high voltage level selected. Then the wiper of the variable transformer is starting from zero like this turned up until the selected high-voltage level ignites the fault location of the cable. After ignition, the the next lower high voltage level the combustion current, which has a Coupling rectifier is fed. With current then flowing from the variable transformer via a switch provided there the full mains voltage is applied on the primary side and is simultaneously the voltage at the variable transformer by means of the grinder downwards regulated to slow the burning voltage down to lower Bring voltage values. With further current flow the last voltage level with low operating voltage the actual one Combustion current, which is now connected to another coupling rectifier the fault of the cable is fed. From there, the Grinder of the variable transformer another step-down control made until the arc at too low an arc voltage goes out. This is an uninterrupted burning process ensured. By avoiding switches on the High voltage side malfunctions are largely avoided and in particular, the emergence of high frequency interference largely suppressed.

In a further embodiment of the invention it is provided that the High-voltage stages each have a current transformer assigned to them Output signals are applied to an actuator, which after ignition of the arc when current flows through a high-voltage stage switch on the primary side is the next high voltage stage lower output voltage switches on gradually.

This advantageously automates the burner in the downward regulation with a relatively smooth course of the output voltage  reached. Any switching leaps occur on the output side hardly noticeable, because the interposition of the Transformer and the rectifier stage the output voltage runs relatively sluggishly. To ignite the arc, the primary-side switch selected a high voltage level and then the wiper of the variable transformer is slowly turned up, until an ignition occurs at the fault location of the cable. Then it will be the wiper of the variable transformer slowly descends again regulated, with the primary-side switch automatically High voltage stage with an ever lower output voltage switches on. The current transformers deliver via known per se And / Or gate a signal to an actuator, which then Current flow of the selected high voltage level to ignite the Arcing possibly the next high voltage level via a timing element switches on lower voltage. In this respect, the operation of the The burner is partly automatic, creating an uninterrupted Burning process is ensured.

In a further development of the invention it is provided that the High-voltage stages each have a current transformer assigned to them Output signals are supplied to actuators, an actuator the variable transformer with changeover switch and grinder for the Ignition voltage regulates up and down for the burning voltage and on other actuator the primary-side switch after reaching the Ignition voltage switches down gradually.

This is a complete automation of the burner for Burning in of bridges is achieved with an almost smooth course output high voltage. To this extent, will automatically Reaching the ignition voltage reduces the output voltage, whereby the arc voltage is maintained, however is continuously reduced until after complete downward regulation  the burn voltage advantageously a burned-in bridge on the There is a fault in the cable.

In the following, the invention is based on only one Execution path illustrating drawings explained in more detail.

The subject matter of the present invention results not only from the subject of the individual claims, but also from the combination of the individual claims among themselves.

All information and features disclosed in the documents - including the summary - , in particular the spatial design shown in the drawings, are claimed to be essential to the invention insofar as they are new to the prior art, individually or in combination.

Show it:

Fig. 1 is a schematic circuit diagram of an inventive combustion device,

Fig. 2 is a schematic circuit arrangement of an inventive burner with actuators for automatic operation of the burner.

According to Fig. 1, three high voltage levels 1, 2, 3 with gradually increasing voltage in the manner of a voltage cascade provided whose primary network-side coils 4, abut 5 and 6 to a change-over switch 7 to switch circuits 8, 9 and 10. The grinder of the switch 7 is guided to the grinder of a further switch 11 , which in turn has switching stages 12 and 13 on a variable transformer 14 . The variable transformer 14 is connected in the manner of an autotransformer on the primary side to a 220 volt mains voltage and the controllable tap 15 of the variable transformer 14 is applied to the switching stage 13 of the changeover switch 11 .

The high-voltage stages 1 , 2 and 3 are connected to one another on the output sides via coupling rectifiers 16 , 17 , so that a single high-voltage output 18 is produced. Only one single high-voltage stage 1 , 2 or 3 is operated via the changeover switch 7 .

At the high-voltage output 18 , a network 19 can be connected, consisting of a resistor 20 which is bridged by a switch 21 after the ignition. Furthermore, a coupling capacitor 22 is provided with an output 23 for coupling an echo pulse measuring device. At the output 24 of the network 19 , the cable 25 to be tested is connected, in which an arc 27 occurs at an error point 26 after the ignition voltage has been reached. From there, a pulse initially emitted by the pulse echo measuring device runs back to the input of the cable 25 and is fed back to the pulse echo measuring device via the network 19 via the coupling capacitor 22 . There the reflected impulse is made visible on a screen. The transit time of the reflected pulse is then a measure of the location of the fault in the cable to be tested. For repetitive measurements or for later measurements, a bridge can also be burned into the cable at the fault location in order to create an advantageously low transition area, at which measuring pulses can be reflected in a favorable manner.

. The inventive fuel unit according to Figure 1 operates as follows:

The desired operating voltage is selected with the changeover switch 7 , preferably the high voltage stage 1 with the highest output voltage is switched on at the switching stage 8 .

The switch 7 has further options according to the switch positions 9 and 10 , which are assigned to the high-voltage stages 2 and 3 , each with a lower final voltage.

In the invention, the following switching stages with final voltages can be provided at the high voltage stages:
Switching stage 8 + 9 + 10 for the final voltage 10/20 kV
Switching stage 9 + 10 for the final voltage 2/4 kV
Switching stage 10 for the final voltage 100/200 volts.

After selecting the desired operating voltage at the changeover switch 7 , the wiper 15 of the variable transformer 14 is now turned on starting from zero until the high-voltage stage 1 causes the arc 27 to ignite at the fault location 26 of the cable 25 to be tested. This switchover can also be provided automatically, the grinder 15 being automatically turned up until a signal occurs in a current transformer at the high-voltage stage which causes the ignition, which limits the further up-regulation of the voltage.

After the ignition, a current transformer 28 known per se, which is only shown symbolically in FIG. 1, indicates a current flow, which can be represented by an optical display using a lamp or a voltmeter or the like. The high-voltage stage 2 is then switched on by switching to the switching stage 9 . The high-voltage stage 9 now takes over the current for maintaining the arc 27 . This switchover can also take place automatically, actuators being actuated on the basis of a voltage or current flow in a drum.

With current of the high-voltage stage 2 now flowing, the current transformer 29 responds there and, starting from the switching stage 9 of the switch 7 , the switch 11 is connected to the full mains voltage corresponding to the switching stage 12 . This changeover can also take place automatically with a changeover relay which, when current flows through a converter 29, activates the excitation coil of a changeover relay via an amplifier circuit and gate. A slow downward regulation now takes place from the variable transformer 14 via the grinder 15 . After current flow in the converter 29 , the high voltage stage 3 , here provided as a voltage stage with a low operating voltage, takes over the actual combustion current, which now reaches the output side 18 via the coupling capacitor 17 and the coupling capacitor 16 and via the network 19 to the fault location 26 of the cable 25 is fed.

The high-voltage stages 2 and 3 can be regulated continuously when the switching stages 9 and 10 are switched on via the wiper 15 of the variable transformer 14 . In order to burn in a bridge at the fault location 26 of the cable 25 , the grinder 15 is regulated downwards until a low-resistance bridge has formed through carbonization at the fault location or a metal bridge in the manner of a short circuit through a melting process.

The changeover switch 7 in connection with the stepless regulation on the grinder 15 thus results in a slipping or rising output voltage at the output 18 , thereby ensuring an uninterrupted burning process.

The variable transformer is advantageously stepped up from zero to 220 volts when the highest high-voltage stage is in the switch position 8 of the changeover switch 7 . When the high-voltage stages 2 and 3 are operated , a stepless regulation from 220 volts down to zero can then take place, thereby ensuring an uninterrupted burning process.

For an almost stepless output voltage, only the switchover at the changeover switch 7 can be provided, without the additional stepless regulation on the grinder 15 of the variable transformer 14 . The gradual changeover on the primary side manifests itself relatively smoothly on the output side owing to the inertia of the intermediate circuit elements, as a result of which the arc is prevented from being torn off.

On the variable transformer 14 is an additional smoothing the curve of the output-side high voltage is obtained at the output 18, in particular during the downward control when the level changeover of the changeover switch 7 to the sliding switch 15 at the wiper of the variable transformer 14 is combined.

FIG. 2 shows extensive automation of the burning operation, the same reference numerals designating the same switching elements according to FIG. 1.

The effect according to the combustion device according to FIG. 2 is trouble-free operation with a smooth course of the output voltage according to FIG. 1, but with a largely automatic operating sequence.

According to FIG. 2, the switch 7 is used to preselect an advantageous ignition and operating voltage at the output 18 and for this purpose the grinder 15 of the variable transformer 14 is slowly regulated up until the ignition starts at the fault location 26 according to FIG. 1.

In the following, the automatic system according to the invention then takes over the further regulation of the operating voltage at the fault location 26 according to FIG. 1.

Incidentally, up-regulation until ignition by means of the grinder 15 can also take place automatically, a current transformer 28 reporting the ignition process and stopping the possibly motorized drive of the grinder 15 .

After the ignition, a voltage arises at the current transformer 28 or 29, depending on the selection of the switch 7 , which is led to a gate of an actuator 31 . This actuator 31 switches the changeover switch 7 to the next lower high voltage stage 2 or 3 via the control output 32 . At the same time, a further actuator 33 is connected via known and / or gate, which switches on the full mains voltage at the switching stage 12 via the control output 34 and regulates the mains voltage downwards on the grinder 15 via a motorized regulator by means of the regulating output 35 .

If the current in the converter 29 continues to flow, the last high-voltage stage 3 takes over the actual combustion current here in connection with timing elements, with the operating voltage actually low, the actuator 31 activating the switching stage 10 via the control output 32 and the further actuator 33 in the absence of the voltage of the current transformer 28 . 29 regulates the voltage further down, possibly down to zero, via the gates (not shown here) in the actuators 31 , 33 at the control output 35 by means of the grinder 15 and possibly by switching the switch 11 by means of the control output 34 .

The voltage routing of the current transformers 28 , 29 , 30 via and / or comparisons by means of gates (not shown here) in the actuators 31, 33 is known per se. In each case with current flow in the current transformers 28 , 29 , 30 , the changeover switch 7 is switched down and in the switching stages 9 and 10 via gates in the actuator 33 , if the current flow of the current transformer 28 is absent, the actuator 33 , the grinder 15 and the changeover switch 11 operated. The changeover takes place depending on the current profile in the current transformers, here in particular with reference to the current transformer 28 , possibly in connection with timing elements.

Automated burning process:

The high-voltage stage 1 is only controlled via the stepless regulation of the variable transformer on the grinder 15 . The supply is via switch 8 .

Switch 7 is initially on both 9 and 10 . The medium voltage level 2 and the low voltage level 3 are connected directly to the network via switches 7 and 11 .

If the ignition of the cable fault 26 now takes place when the variable transformer 14 is turned up and the arc 27 is stopped, the medium-voltage stage 2 first takes over the power supply to the arc 27 . A control voltage then arises in the converter 29 , which causes an interruption of the switch 8 via the logic circuit 31 and the actuator 32 when a predetermined value is reached. The arc 26 is now fed by the medium voltage stage 2 .

When the arc resistance is further reduced, the low-voltage stage 3 begins to feed current into the arc as well. This is done via the coupling diodes 17 and 16 . A further control voltage arises at the converter 30 , which also brings the switch 7 into position 10 via the logic circuit 31 and the actuator 32 . The combustion current is now only supplied by low voltage level 3 .

When a predetermined combustion current is exceeded, the control voltage rises at the converter 30 and causes the control transformer to move into the largest voltage stage 12 via the logic 33 . When the grinder 15 touches the contact 12 , the actuator 34 automatically switches the switch 11 and the power supply via the sliding contact 15 is removed. By comparing the predetermined combustion current with the measurement voltage coming from the converter 30 , the variable transformer is set to the optimized combustion current via the actuator 35 .

The automatic sequence of the individual is advantageous Switching operations depending on the cable type and depending on the current for one intended intended burning effect. This will create a Optimization of the burning process achieved.

To this extent, a combustion device is created, the output voltage of which can advantageously be regulated slowly and without interference until the fault point is ignited. After the ignition, the output voltage at output 18 is slowly, advantageously, automatically regulated downwards, possibly until a zero range of the output voltage is reached. This advantageously creates a bridge at the point of failure, without fear of special high-frequency interference from tearing off the arc or other interference on the high-voltage side of the high-voltage stages.

The switch arrangement is on the primary side of the high voltage stages inexpensive and runs smoothly with no interference Voltage curve of the output voltage. To that extent one reliable, uninterrupted burning process ensured will.

Claims (4)

1. Burner for locating cable faults by means of a pulse echo meter and with a DC high-voltage source, which is present on the cable to be tested, the voltage being increased until ignition occurs at the fault location in the cable, the pulse emanating from the pulse echo meter for The beginning of the cable is reflected and evaluated by measurement technology, characterized in that three high-voltage stages ( 1 , 2 , 3 ) are provided, each with a step-wise increasing output voltage, which are connected on the output side via coupling rectifiers ( 16 , 17 ) and on the input side at a changeover switch ( 7 ), the center tap of which rests on a further changeover switch ( 11 ) of a mains-side variable transformer ( 14 ). 2. Burner according to claim 1, characterized in that the high-voltage stages ( 1 , 2 , 3 ) each have a current transformer ( 28 , 29 , 30 ) assigned, the output signals of which are applied to an actuator ( 31 ) which, after ignition of the arc ( 27 ) with current flow of a high-voltage stage ( 1 ) or ( 2 ) via the switch ( 7 ) the next high-voltage stage ( 2 or 3 ) of lower output voltage is switched on in stages. 3. Burning device according to claim 1, characterized in that the high-voltage stages ( 1 , 2 , 3 ) each have a current transformer ( 28 , 29 , 30 ) assigned, the output signals of which are fed to actuators ( 31 , 33 ), an actuator ( 33 ) regulates the variable transformer ( 14 ) with changeover switch ( 11 ) and grinders ( 9 ) for the ignition voltage up and for the burning voltage downward and another actuator ( 31 ) switches the changeover switch ( 7 ) downwards gradually after reaching the ignition voltage. 4. Burning device according to claim 1, characterized characterized in that the automatic sequence of individual switching operations depending on the cable type and depending on Electricity is provided for an intended burning effect.