JP2594104B2 - Transmitter for ground fault detection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a ground fault used for transmitting an exploration signal to the high-voltage distribution line when detecting a ground-fault accident point occurring in the high-voltage distribution line. The present invention relates to a transmitter for detecting accident points.

[Conventional technology]

2. Description of the Related Art There is a transmitter for searching for a ground fault point, which transmits an AC signal having a period capable of operating a display attached to a high-voltage distribution line.

[Problems to be solved by the invention]

This conventional ground fault accident point transmitter is convenient because the display can be operated by a signal from the transmitter. However, since it is an AC signal, there are the following problems in the case of searching for an accident point. That is, when there is a ground fault point in the distribution line, both the current flowing at the point of the fault and the current flowing to the ground capacitance of the distribution line are sent out. Even when there is no fault point, the latter current is sent out. In particular, the latter always accompanies each case of transmitting a signal in various places in order to search for an accident point. For these reasons, the transmitting stomach requires a large capacity. Such transmitters are large and heavy, and pose a problem in transporting to the site to be explored. Further, as described above, since the signal current is output regardless of the presence or absence of the ground fault point, even if there is no fault point, it is troublesome to go to check whether the indicator is inactive or not.

The present invention has been made in view of the above points, and it is an object of the present invention that the current of a signal to be transmitted throughout the entire work of searching for a ground fault point can be a small current or substantially zero. , Can reduce its own capacity and size,
In addition, it is an object of the present invention to provide a ground fault point exploration transmitter capable of determining the presence or absence of an accident point at the location of the transmitter.

[Means for solving the problem]

In order to achieve the above object, the present invention employs the means described in the claims, and the operation is as follows.

[Action]

When a pulsating voltage is applied to the output terminal and the voltage there rises, the earth capacitance of the distribution line is charged and the voltage of the distribution line rises. Next, during the period when the voltage value becomes zero V in the pulsating flow, backflow from the distribution line into the transmitter is prevented.
Therefore, when there is no ground fault point in the distribution line, the distribution line remains charged, and thereafter, no current flows from the transmitter to the distribution line. If there is a ground fault in the distribution line, current will flow there. Therefore, the transmitter only needs to transmit the current flowing at the point of the ground fault.

〔Example〕

Prior to the description of the embodiment of the present application, a ground fault point detecting display used in combination with a ground fault point transmitting transmitter will be described. In the display 1 shown in FIGS. 1 and 2, reference numeral 2 denotes a detection unit, and reference numeral 3 denotes a display unit, which is formed integrally with (or separately from) the detection unit 2.

In the detecting section 2, reference numeral 4 specifically shown in FIG. 5 denotes a substrate, which is formed by molding an aluminum alloy. In the base 4, reference numeral 5 denotes a substrate, 6 denotes an electric wire receiving portion bulging upward from the substrate 5, 7a and 7b denote connecting pieces, and 8 denotes a core mounting recess.

Next, reference numeral 10 shown in detail in FIGS.
2 shows the presser body in FIG. In the holding body 10, reference numeral 11 denotes a main body, which is formed by press-forming a metal plate into a U-shaped cross section as shown in FIG. In the main body 11, reference numeral 12 denotes a bolt insertion hole formed at one end thereof, reference numeral 13 denotes an inlet, and reference numeral 14 denotes a stopper. Next, reference numeral 15 denotes a mounting seat portion provided at an intermediate portion of the main body 11, which is formed so as to project right and left as shown in FIGS. Reference numeral 16 denotes a support attached to the seat 15, which is made of polyethylene. 17 is the support 16
The wire holder is attached to the wire, and is formed of a rubber material having elasticity, and has a concave portion 18 for applying to the wire on the lower surface.

Next, a description will be given of two fasteners provided on both sides of the space 20 where the distribution line is located in order to fasten the holding body 10 to the base 4. Reference numeral 21 denotes one of the fasteners, which is configured with a butterfly attachment. As shown in FIGS. 1 and 3, a shaft pin is used as the screwing tool 21, and the pressing body 10 is screwed to the base 4 so as to be freely opened and closed. Next, reference numeral 22 denotes another fastener, one end of which is connected to the base 4 and the other end is constituted by an engaging rod adapted to engage with the presser body 10. In this fastener 22, reference numeral 23 denotes Bolts, one end of which is the first, second,
As shown in FIG. 3, it is pivotally attached to the connecting piece 7b with a shaft 24. Reference numeral 25 denotes a seat formed at an intermediate portion of the bolt 23, which is formed in a flange shape as shown in the figure. 26 is the bolt 23
Shows a tightening nut screwed into FIG.

Next, the current detecting current transformer 28 shown in FIG. 1 and the structure for fastening the current transformer 28 to the base 4 and the holding body 10 in the detecting section 2 will be described. Numeral 30 denotes a current transformer core, which is formed in an annular shape surrounding the space 20 where the distribution line is located. The core 30 is made of ferrite. In the core, reference numeral 31 denotes a U-shaped first element, and reference numeral 32 denotes an inverted U-shaped second element. In the first element 31, reference numerals 31a and 31b shown in FIG. 5 denote legs, respectively, and reference numeral 31c denotes a connecting portion for connecting both legs, which is shown in FIG. As shown in FIGS. 5 and 12, it is fixed to the substrate 5 with a holding member 34 and a set screw 35 as shown in FIGS. Reference numerals 31a 'and 31b' indicate connection end faces, respectively.

Next, the second element 32 will be described. In particular, in FIGS. 1 and 4, 32a and 32b are legs, 32c is a connecting portion, and the back or upper surface 32c 'is formed as a flat surface as shown in FIG. 32a 'and 32b' indicate connecting end faces, respectively.

Next, the mounting structure of the second element 32 to the holding body 10 will be described with reference to FIGS. A receiving member 36 is formed integrally with the support plate 16 and has a V-shaped concave portion 36a on the upper surface, in which a connecting portion 32c of the second element 32 is provided.
Of the receiving member 36 in the left-right direction in FIG.
The second elements 32 are formed so as to be substantially equal to or slightly shorter than the dimension between the second elements 32b so that the second element 32 can be positioned in the left-right direction in FIG. Next, 37 is a leaf spring, and
Is attached to the main body 11 with a fastener 38.
The distal end 37a of the leaf spring 37 is in contact with the main body 11, and
The intermediate portion 37b elastically contacts the upper surface 32c 'of the second element 32 to urge the second element 32 toward the base 4.
With such a configuration, the second element 32 is elastically movable toward and away from the base 4. Reference numeral 39 denotes a stopper attached to the main body 11 for preventing excessive deformation of the spring 37. 40 is a leg 32a 'of the second element 32,
A guide member provided around the end surfaces 32a 'and 32b' at the distal end of 32b 'is formed of a synthetic resin material, and the inner surface thereof is a tapered guide surface 40a as shown in FIG. It is attached to the legs 32a, 32b with an adhesive 40b. The guide member 40 may be provided on the leg of the first element 31. Next, reference numeral 42 shown in FIGS. 1 and 5 denotes a detection coil in the current transformer 28. The coils are further numbered 6 through
This will be described with reference to FIG. 43 is a coil case made of a synthetic resin material. In this case, reference numeral 44 denotes a core insertion hole, and reference numeral 45 denotes a coil storage portion. Reference numeral 46 denotes a lead wire, one end of which is integrally attached to the case 43 at an attachment portion 47. In the lead wire 46, a core wire 48 is a plurality of twisted wires, and one end thereof is exposed in the coil case 43. Reference numeral 49 denotes a cover, which is formed of the same material as the case 43. Reference numeral 50 denotes a fastening member provided at an intermediate portion of the lead wire, which is formed integrally with the covering 49. In the fastening member 50, reference numeral 51 denotes a fixing flange, and reference numeral 52 denotes an insertion portion, which is formed in a tapered shape as shown. The core wire 48c at the position of the fastening member 50 is in a state where there is no twist so that water is hardly transmitted therethrough.

Next, the lead wire lead-in portion formed on the base 4 will be described. Reference numeral 53 denotes a lead wire insertion hole formed in the side wall of the receiving portion 6, which is formed in a tapered shape as shown in the figure. Reference numeral 54 denotes a recess formed on the periphery of the insertion hole 53 for retaining the flange.
Reference numeral 55 denotes a holding piece which is formed of a metal material and is fixed to the side wall of the electric wire receiving portion 6 by a fastening screw 56. In the fixed state, the flange portion 51 is pressed against the bottom surface of the concave portion 54 to prevent water from entering the insertion hole 53. 57 is concave 54
The adhesive poured into the gap between the and the flange portion 51, which is used as an auxiliary to maintain the waterproofness in the same manner as described above. Then 5
Reference numerals 8 and 58 'denote coil windings provided in the storage section 45 of the coil case 43.

Next, reference numeral 61 shown in FIGS.
Is shown on the cover member so as to cover it, and is formed of a rubber material having a good tracking property. In the cover member 61, reference numeral 62 denotes a flat plate portion, which is formed in a plate shape, and is mounted on the wire receiving portion 6 of the base 4. In the flat plate portion 62, 63, 63 are core insertion holes, 6
Reference numeral 4 denotes a distribution line mounting portion, which is located on the upper surface of the receiving portion 6. Reference numeral 65 denotes a positioning piece for positioning the distribution line. Next, reference numeral 67 denotes a cylindrical portion integrally formed with the flat plate portion 62, which is configured to hang down from the peripheral edge of the flat plate portion 62, and has a lower end portion 67a covering the outside of the display unit case described below.

Next, the display unit 3 will be described. Reference numeral 71 shown in FIGS. 1 to 3 and 5 denotes a case body, which is constituted by a bottom wall 72 of the base 4 formed by the base 5 and a cylindrical side wall 73 extending downward from the periphery of the bottom wall. . Reference numeral 74 denotes a mounting frame fixed to the case body 71. 75 is the mounting frame
The drive circuit is mounted on the printed circuit board 74 and has well-known circuit elements mounted thereon. Next, reference numeral 76 denotes a display body. In the display, 77 is a base frame attached to the mounting frame 74, 78 is a display member, which is rotatably mounted on the base frame 77, and the display member 78 is shown in FIGS. As described above, the white portions 78a and the black portions 78b are separately painted. Although not shown, a drive member for driving the display member 78 is attached to the base frame 77. Next, reference numeral 80 denotes a shielding frame which is formed in black, and windows 81 and 82 are formed on a side surface and a lower surface, respectively. 83 is a fitting piece provided in the shielding frame 80, and the case body 71
The shielding frame is formed by fitting with a fitting portion 84 formed in
80 positioning is performed. Next, reference numeral 85 denotes a display body cover, which is formed of a transparent material and has a fastening ring 86.
Thus, it is fixed to the case body 71. 87 is watertight O
Show the ring.

In the display unit 3 as described above, when no signal is given from the detection unit 2, the display member 78 is in a normal position as shown in FIG. The white portion 78a of the member 78 is hidden by the shielding frame 80 and cannot be seen (the whole is seen black). On the other hand, when a detection signal is given from the detection unit 2 to the display unit 3, the signal is given to the drive member of the display body 76 via the drive circuit 75, and the display member 78 rotates. as a result,
As shown in FIG. 15, from the outside of the display body cover 85, the white portion 78a of the display member 78 passes through the windows 81 and 82 in the shielding frame 80.
Can be recognized.

Next, reference numeral 90 shown in FIGS. 2 and 18 denotes an auxiliary member. This is because insulated wires used for high-voltage distribution lines generally have diameters of 5 mm (outer diameter 9 mm) to about 200 SQ (outer diameter 24.5 mm), and indicators are used for all of these insulated wires. It is necessary to mount it. In this case, it is used when a display is attached to a thin distribution line. In the auxiliary member 90, reference numeral 91 denotes a mounting surface for the mounting surface 64, and reference numeral 92 denotes a wire receiving portion, which is formed in a concave shape. Reference numeral 93 denotes an overhang portion, which is a positioning piece in the cover member 61.
The position of the auxiliary member 90 is determined between the positions 65 as shown in FIG. Such auxiliary members 90 having different heights from the mounting surface 91 to the receiving portion 92 are prepared according to electric wires having various diameters.

In the display device 1 having the above configuration, the first element 31 and the detection coil 42 in the current transformer core 30 are assembled as follows. First, the first element 31 is fixed to the substrate 5 with the adhesive 33 and the holding member 34. On the other hand, in the detection coil 42,
The coil windings 58, 58 'are housed in the housing portion 45, and each terminal of the coil winding is connected to each terminal 48a of the core wire 48 of the lead wire. Next, the detection coil 42 is attached to the first element 31 with the legs 31a, 31b inserted through the insertion holes 44, 44. Next, the other end of the lead wire 46 is inserted into the lead wire insertion hole 53, and the insertion portion 52 is inserted into the insertion hole 53,
And, with the flange portion 51 located in the concave portion 54, the fastening member 50
Is fixed to the side surface of the electric wire receiving portion 6 with the holding piece 55. In addition, insertion hole 53
The terminal 48b of the lead wire inserted from above is connected to the drive circuit 75. Next, the cover member 61 is put on the core insertion hole 63 in a state where the leg of the first element 31 is inserted. Thus, the assembly of the first element 31 and the detection coil 42 is completed.

Next, the mounting of the display having the above configuration to the high-voltage distribution line 95 will be described. As shown in FIG. 2, with the holding body 10 opened with respect to the base 4, the base 4 is applied to the overhead high-voltage distribution line 95 from below. In other words, the distribution line 95 is positioned at the mounting portion 64 between the positioning pieces 65, 65 on the cover member 61. Next, the presser body 10 is put on the distribution line 95. The work is performed by pressing the holding body 10 with an arrow 96 in FIG.
This can be easily done by pushing up slightly in the direction. When the holding body 10 is put on the distribution line 95 in this way, the connecting end surface of the second element 32 with respect to the connecting end surfaces 31a 'and 31b' of the first element 31 by the tapered guide surface 40a of the guide member 40. The positioning of 32a 'and 32b' is properly performed, and the end faces 31a 'and 32a' and the end faces 31b 'and 32b' are exactly overlapped without displacement. Then bolt
23 is raised as shown by the arrow 97 in FIG. 2, and it is positioned in the insertion hole 12 through the inlet 13. After that nut 26
To move the presser body 10 to the side of the base 4 in sequence.
95 is firmly sandwiched between the distribution line mounting portion 64 and the contact portion 18 of the wire retainer 17. In this case, the presser body
Even if the main body 11 of 10 moves to the side of the base 4, the second element 32 whose end face has already contacted does not move in the same direction as described above, but only the leaf spring 37 bends. Therefore, in this state,
The second element 32 is pressed against the first element 31 by the urging force of the leaf spring 37. As a result of the above, the first member is located between the receiving member 36 and the lower surface 32c "of the connecting portion of the second element 32.
As shown in the figure, a gap is created.

When the nut 26 is tightened as described above, the movement due to the tightening is caused by the front end of the main body 11 in the holding body 10 being a seat.
It is limited to the position where it touches 25. This makes the presser body
It is possible to prevent the state where the main body 11 of the 10 moves excessively to the side of the base 4 and the leaf spring 37 is crushed (the state where elasticity cannot be exhibited).

In the case where the mounting to the electric wire 95 is performed as described above, when the holding body 10 is opened with respect to the base 4 as shown in FIG. 17 is elastically held by the leaf spring 37 of the second element 32, the second element 32 can be inclined as shown by the imaginary line in FIG. The force is prevented from being damaged. After the second element 32 is tilted as described above, the leaf spring 37
To press the flat upper surface 32c 'of the element 32, the second element 32
Returns to the original state shown by the solid line in FIG.

Next, the operation of the display having the above configuration will be described. When the exploration signal current flows through the high-voltage distribution line 95 in the above mounting state,
The resulting magnetic flux is generated in the core 30. The magnetic flux is detected by the coil winding 58 of the detection coil 42, and the detection signal is transmitted to the drive circuit 75 through the core wire 48 of the lead wire 46 as described above. As a result, the display member rotates as described above. In addition, the above-mentioned display performs the same operation as described above when a short-circuit current flows through the high-voltage distribution line 95.
When the return signal current flows through the display 95, the display 76 performs a return operation. For those, refer to the following circuit description and its operation description.

Next, the circuit configuration of the display will be described. As shown by the block in FIG. 19, this indicator detects a current flowing through the distribution line and generates a DC output of a magnitude corresponding to the magnitude of the current, and the current detection mechanism 256 The display energy storage capacitor C2 and the open energy storage capacitor C7 that store the DC output of 256, the first to third switches 259 to 261 that are normally open, and the current detection mechanism 256 are connected to the overhead distribution line. When a large current at the time of a short circuit and a small current at the time of a ground fault are detected, a closing command is given to the second switch 260, and when a medium current at a normal load of the overhead distribution line is detected, the third switch 261 is closed. The determination means 262 for giving the generation command and the charging voltage of the display energy storage capacitor C2
The first switch 259
Switch control means 263 for giving a closing command to
And a signal current detection circuit 263a of the switch control means 263. One end of the series circuit of the first and second switches 259 and 260 is connected to the display energy storage capacitor C2, and the other end is capable of energizing the coil 254 in the display energizing direction. While one end of the third switch 261 is connected to the open energy storage capacitor C7.
Connected to the current detection mechanism 256 via
The other end is connected so that the coil 254 can be energized in the return energizing direction. The above current detection mechanism
256 is the current transformer 28 and the coil windings 58, 5 in it.
8 ′ half-wave and full-wave rectifier circuits 264 and 265, respectively,
And a resonance circuit 266 attached to the one winding 58.
One winding 58 in the current transformer 28 has, for example, 6000 turns, to which a capacitor C1 is connected in parallel to a resonance circuit.
266 are formed. The resonance circuit 266 is for efficiently detecting and outputting a search signal of 180 cycles arriving from the transmitter via the distribution line, and for reducing the output of the commercial frequency signal. The other winding 58 'has, for example, 1500 turns. The determination mechanism 262 includes a search signal current detection circuit 267, a normal load current detection circuit 268, a short-circuit current detection circuit 269, and a suppression circuit 270. The configuration of each circuit and each switch is as shown in FIG. 20.
Next, the operation will be described together with the operation.

The operation of the display device when the search signal current flows through the distribution line 95 will be described with reference to FIG. 20 showing the circuit configuration. The current flowing through the distribution line 95 and the waveforms at each point in FIGS. 20 (a) to (e) are as shown in FIG. Exploration signal current is distribution line
When flowing through 95, the current is detected by winding 58 in current transformer 28. In this case, the output signal obtained from the winding 58 is sufficiently large due to the resonance caused by the capacitor C1. The output signal is rectified by the diode D1 and the storage capacitor for display
Stored in C2.

The output signal is input to the search signal current detection circuit 267. In the circuit 267, the signal passes through a differentiating circuit 257 including a capacitor C5 and a resistor R1, and is supplied to a voltage detecting element 271 via a diode D4. The voltage detection element 271 is
When there is an input signal having a detection level V1 or higher at the input terminal 271a indicated by the suffix a, the signal is transmitted from the output terminal 271b indicated by the suffix b as an output signal. Is an element having a characteristic that does not generate an output signal at the output terminal. As such an element, there is, for example, a commercially available C-MOS-8502ALB. The same applies to other voltage detection elements described below. The output signal of the voltage detecting element 271 is input to the pulse transformer T1, and further transmitted from the transformer T1 to the gate of the SCR 292, so that the SCR 292 becomes conductive.

When the display energy storage capacitor C2 is sufficiently charged and reaches the operating voltage of the magsine coil 254 of the display body 76, that is, when the voltage becomes equal to or higher than the detection level V2 of the voltage detection element 272,
The voltage detecting element 272 detects this and sends a signal from its output terminal 272b to make the SCR 291 conductive. Since the SCR292 is already conducting when the SCR291 conducts, the display capacitor
The charge charged in the capacitor C2 is discharged through the path of C2 → SCR291 → SCR292 → magsine coil 254 → capacitor C2. This discharge causes an exciting current to flow through the coil 254 in the direction of arrow X. As a result, the display member 78 moves from the normal position (FIG. 14) as described above to the failure display device (FIG. 15).
(Fig.), And the display is in the display state. No. 20
In the figure, a signal current detection circuit 263a includes a Zener diode (8V) D3 for protecting the voltage detection element 272, and a voltage detection element
It comprises a Zener diode (6.2V) D2 for adjusting the detection level V2 of 272 to the operating voltage of the magsine coil 254, and a capacitor C4.

Next, when a return signal flows through the distribution line 95, the display state of the display unit returns as follows.

When a return signal current of a predetermined value, for example, 4 A or more, flows through the distribution line 95, the current is detected by the winding 58 'of the current transformer 28. The detected signal is connected to the output terminal of the full-wave rectifier circuit 265.
Rectified by the bridge-connected diode D7, and charged to the return energy storage capacitor C7 via the resistor R3. The above resistance
R3 is a resistor for securing an operation voltage of a relay Ry described later. As described above, the return capacitor C7 is charged by the signal from the current transformer 28 and the potential at the point (e) rises, and when the potential becomes equal to or higher than the detection level V3 of the voltage detection element 273, the output terminal of the voltage detection element 273 is output. A signal is sent from 273b to the pulse transformer T2, and a gate signal is sent from the transformer T2 to the gate of SCR293, so that SCR293 is turned on. When SCR293 conducts,
A return capacitor C7 → magsine coil 254 → relay contact Ryb → SCR293 → closed circuit of the return capacitor C7 is formed, and the charge of the capacitor C7 is discharged. Due to this discharge, a current flows through the coil 254 of the display body 76 in a direction opposite to that at the time of the ground fault display as shown by the arrow Y. As a result, in the display body 76, the display member 78 is driven to rotate in the reverse direction and returns to the normal position. The return operation can be performed in the same manner as described above by flowing a normal load current (4 A or more) of the commercial frequency through the distribution line 95.

D9 is a Zener diode (8V) for limiting the voltage of the input terminal 273a of the voltage detecting element 273 to a constant value, D8 is a Zener diode (13V) for keeping the voltage at the point (e) constant, and C8 is a Zener diode. This is a capacitor connected in parallel with the diode D9.

In the case of the above-described return operation and subsequent energization of the load current, the signal of the suppression circuit 270 is fed back to the ground fault detection signal detection circuit 267 to prevent the voltage detection element 271 of the circuit 267 from performing the detection operation. ing. That is, if the potential at the point a is set to the reference 0 potential when a load current is flowing through the line, the point c becomes-. So the diode
One terminal D7 'of D7 → point a → diode D5 → point (b) →
A current flows through the circuit of the Zener diode D6 → the resistor R2 → the point c → the other terminal D7 ″ of the diode D7.
Even if the point 58 detects the load current and the point b becomes positive, the potential at the point (b) becomes 0 and the voltage detecting element 271 does not operate. Therefore, even when the SCR 291 in which the display capacitor C2 is charged is in the conductive state, the detection operation of the voltage detecting element 271 is forcibly suppressed by the signal from the suppression circuit 270 as described above, and the SCR 292 is in the non-conductive state. , The current does not flow through the mag-sine coil 254, and the display mechanism does not enter the display state.

Also, the load current is very weak after recovery (for example, about 1A)
In such a case, since the output of the winding 58 'is small, the above-described suppression operation is not performed, and the points (a) and (b) are indicated by broken lines in the column of the load current in FIG. Such a signal appears. However, because the level is small, the voltage sensing element
271 does not detect it. Therefore, no erroneous display is made.

Next, the operation of the display when a large current (for example, a current of 800 A or more) flows through the distribution line 95 is as follows. 80 on tracks
When a short circuit current of 0 A or more flows, it is detected by the current transformer 28, and the output from the winding 58 'is connected to the diodes D7, D10.
It works, given to the relay Ry via the contact Rya
Is closed and the contact Ryb opens at the same time. The output from the winding 58 of the current transformer 28 is charged to the display capacitor C2 via the diode D1. When the display capacitor C2 is charged to a predetermined voltage, the voltage is detected by the voltage detection element 272, and the SCR 291 is turned on by the detection signal. SCR291
Is turned on, the display capacitor C2 → SCR291 → relay contact Rya → magsine coil 254 → closed circuit of the display capacitor C2 is formed, the electric charge of the capacitor C2 is discharged, and the coil 254 of the display body 76 has the ground fault. The current flows in the same direction as in the case. As a result, the display member 78 moves from the normal position to the failure display position, and enters the display state. The zener diode D10 has a voltage value that conducts when the output voltage of the diode D7 reaches the output voltage corresponding to the short circuit current of 800 A. The diode D11 is a diode for back electromotive force reflux.

In the above case, the differentiating circuit 257 in the ground fault detection signal detecting circuit 267 determines whether the signal (current) flowing through the line is a commercial frequency of 50 cycles or 60 cycles and an excessive current such as a short-circuit current at the point (a). Limit potential rise. In other words, if the above signal is a commercial frequency, even if the flowing signal is excessive, a sufficient detection signal (output) cannot be obtained because the signal is different from the resonance frequency set in the resonance circuit. Since the potential rise at the point (a) is restricted by the circuit, the first voltage detecting element 271
Does not reach the detection level V1, and the element does not operate.

Next, when the work of restoring the short-circuit fault point found as described above is completed, a normal load current is again supplied to the distribution line. Then, also in this case, the display state of the display is restored in the same manner as in the above description.

Next, a drawing showing an embodiment of a transmitter for searching for a ground fault accident point of the present application will be described. In FIG. 22, reference numeral 101 denotes a ground fault accident point detecting transmitter. In this case, reference numeral 102 denotes an output terminal to which the distribution line 95 is connected via the connection line 102b. 103 is a ground terminal, which is grounded. 104 is a search signal forming circuit. In the circuit 104, 105 is a pulsating flow forming circuit,
A DC-A converter that converts a low-voltage direct current into a high-pressure (for example, 10 KV) pulsating flow and outputs the same is used. 105a indicates its input terminal, and 105b indicates its output terminal. Reference numeral 106 denotes a DC power supply, for example, a storage battery. Reference numeral 107 denotes a backflow prevention unit, which includes, for example, a diode configured to pass a current only from the pulsating flow forming circuit 105 to the output terminal 102 and to prevent passage in the reverse direction. Reference numeral 108 denotes a display means, for example, one whose display changes in response to the voltage of the output terminal 102.

The operation of transmitting a search signal in the transmitter for searching for a ground fault will be described. When a direct current is supplied from the power supply 106 to the pulsating flow forming circuit 105, the circuit 105 is adapted to operate the indicator described below only in one polarity (for example, plus or minus) with respect to zero V. A pulsating flow oscillating at a period of, for example, 180 or 170 Hz is output. The pulsating flow is sent to the output terminal 102 through the backflow prevention means 107 as a search signal.

Next, a description will be given of FIG. 23 showing a voltage state of the distribution line when a search signal is transmitted from the output terminal 102 of the transmitter to the distribution line 95. First, the output waveform of the transmitter as described above is as shown in FIG.

If there is no ground fault in the distribution line in the above case, it is as follows. The voltage of the distribution line 95 is instantaneously charged to the earth capacitance of the distribution line at the time (a) as shown in (b), and reaches the output voltage (for example, 10 KV) of the transmitter. Next, at the time (b), the backflow into the transmitter is prevented by the backflow prevention circuit 107, so that the voltage is maintained as described above. Thereafter, the state of charge is maintained as shown.

Next, the case where the distribution line 95 has the fault point of the resistance ground fault is as follows. The current of the search signal sent to the distribution line 95 flows to the ground fault point. Therefore, the voltage of distribution line 95 is (c)
It becomes as shown in. The voltage V1 differs depending on the magnitude of the ground fault resistance. When the ground fault resistance is about 6KΩ, the voltage V1 is about 3KV and 1KΩ.
In the case of about 2KV.

Next, the case where the distribution line 95 has an intermittent and irregular ground fault due to a crack of an insulator or a tree contact is as follows. As shown in (d), a voltage is applied to the distribution line 95 in the same manner as in (a) above. In this state, when a ground fault occurs (discharge at a crack, contact of a tree) at the time shown in (c), a current flows instantaneously there and the voltage drops. Then, when the insulation is restored, the voltage is applied again at the time (d) in the same manner as in the case (a). Such an operation is repeated irregularly as shown.

Next, in FIG. 24 showing one circuit example of the display means 108, reference numeral 111 denotes a voltage-dividing resistor circuit for detecting voltage.
11b. As shown, one end of the circuit 111 is connected to the output terminal 102, and the other end is connected to the ground terminal 103. Reference numeral 112 denotes a voltage display device, one end of which is connected to the voltage dividing resistor circuit 1 described above.
11 is connected to the middle point, and the other end is connected to the ground circuit. In the display device 112, 113 is a rectifying diode, 114 is a smoothing capacitor, 115 is a display, and a microammeter is used. 116 is an adjusting resistor.

In the display means 108, the voltage of the output terminal 102 is extracted at a low voltage value by passing through the voltage dividing resistor circuit 111. The extracted voltage is rectified by the diode 113, smoothed by the capacitor 114, and applied to the display 115.
Then, the hand of the indicator 115 swings according to the voltage.

According to the display means as described above, when the search signal is transmitted to the distribution line 95, each state of the distribution line is displayed as follows.

First, when there is no ground fault point, the needle of the indicator 115 keeps swinging to the maximum value (voltage value of the search signal).

If there is a resistance ground fault in the distribution line, it swings to an intermediate voltage value corresponding to the magnitude of the ground fault resistance and stabilizes. When there is an intermittent ground fault due to a crack or the like of the insulator, the needle repeatedly swings and returns irregularly.

Since the display state of the display 115 changes in this way, the presence or absence of a ground fault and the type of the accident can be determined by looking at the display 115.

Next, regarding the search for the ground fault using the above transmitter,
This will be described with reference to FIG. In Fig. 25, 99 is a substation, CB is a circuit breaker, and 100 is a distribution line (length is, for example, 20 km).
And a fictitious high-voltage distribution line 95 for three phases is provided. SS1 ~ S
S4 is a section switch, for example, provided every 4 km. H1 to H10 indicate the presence of an indicator attached to each power pole (about every 50 m) of the distribution line 100. As is apparent from FIG. 25, the indicators are attached to the distribution lines at a distance from each other.

For example, when a ground fault occurs at the point P1 in FIG. 25 in the above distribution line, a known ground fault relay at the substation 99 is activated, the segment switches SS3 and SS4 are opened, and the section is in a power failure state. Becomes In such a state, the user goes to the site with the ground fault accident point detecting transmitter 101 having the above configuration.

At the site, the output terminal 102 of the transmitter 101 is connected in three phases and the ground terminal 103 is connected to the ground with respect to the high-voltage distribution line in the power failure state divided into the measurable line length. Next, the search signal is transmitted as described above, and the determination as described above is performed by looking at the display on the display 115 in that case. After that, a measure corresponding to the determination result may be taken.

When the transmitter is removed from the distribution line after the exploration work as described above, there is the following safety. That is, if there is no accident point, the distribution line remains charged with a high voltage as shown in FIG. 23 (b). However, in the transmitter 101, since the voltage dividing resistor circuit 111 is connected between the output terminal 102 and the ground terminal 103, the high voltage is discharged through the voltage dividing resistor circuit 111. The discharge state can be confirmed by looking at the support of the display 115. Therefore, it is possible to prevent an electric shock accident caused by accidentally touching a charged distribution line. It is preferable that the time constant of the discharge be sufficiently long (several seconds to several tens of seconds) as compared with the cycle of the terminal signal so as not to hinder the determination of the presence or absence of the fault point as described above.

Next, FIG. 26 showing a different example of the display means will be described. This example shows an example of a display unit whose display changes in response to the current output to the output terminal 102. In the figure, 117 is a current detection current transformer, and 118 is a current display device. In the device 118, 119 is a rectifying diode, 120
Is a smoothing capacitor, 121 is a display, and 122 is an adjusting resistor. Reference numeral 123 denotes a current detection circuit which generates an output when the input exceeds a predetermined value. Reference numeral 124 denotes a buzzer shown as another example of the display.

In the display means, the current transformer 117 is detected by the current flowing to the output terminal 102 and the current flowing to the ground terminal 103. The operation after detection is the same as that shown in FIG. 24, and the current to the output terminal 102 is displayed on the display 121. The buzzer 124 also sounds according to the presence or absence of the current.

The display operation of the display means will be described with reference to FIG.
27A shows the output voltage waveform of the transmitter 101,
(B)-(d) are the waveforms of the current output from the output terminal to the distribution line.

When there is no ground fault in the distribution line, the charging current to the distribution line momentarily flows from the output terminal of the transmitter 101 at the time (e) as shown in (b), and the current becomes zero after charging. Therefore, the pointer of the display 121 only swings momentarily for a moment.
The buzzer 124 only sounds for a moment.

When the distribution line has a resistance ground fault, a current I1 (0.4 A for 6 kΩ, about 0.6 A for 1 kΩ) flows according to the ground fault resistance as shown in (c). Therefore, the pointer of the display 121 stably indicates the deflection according to the ground fault resistance. The buzzer 124 sounds continuously.

If the distribution line has intermittent and irregular ground faults,
Current flows irregularly as shown in FIG. Therefore, the pointer of the display 121 fluctuates irregularly. The buzzer 124 also sounds irregularly. In (d), (f) indicates the discharge current of the crack of the insulator or the discharge current due to the tree contact with the distribution line.
(G) shows a state when the above-mentioned discharge continues.

Parts that are functionally considered to be the same as or equivalent to those in the preceding figure are given the same reference numerals as in the preceding figure, and redundant description is omitted. (Also, the same reference numerals will be used in the following drawings and the same reference numerals will be used, and redundant description will be omitted.) Next, FIG. 28 showing another example of the circuit configuration of the ground fault accident point detecting transmitter will be described. I do. A signal output unit 131 includes both of the two types of display means 108 and 108 '. Means 108
159 is a voltage detection circuit. 132 is a switching unit, 133 is a gate drive unit, 134 is a control unit, 135 is a transmission unit, 1
36 indicates a timer unit, and 137 indicates a power supply unit.

In the signal output unit 131, Tr1 is an output transformer for an exploration signal, 138 is a full-wave rectifier circuit exemplified as a pulsating flow forming circuit and a backflow preventing unit, and an output voltage is induced in a secondary winding of the transformer Tr1. Sometimes it acts to rectify it to form a pulsating current, and when the output voltage of the secondary winding is zero, a current flows from the output terminal 102 to the ground terminal 103 through the secondary winding of the transformer. It acts to prevent things. Tr2 is an output transformer for return signal, 139
Indicates an output terminal of the return signal.

Next, in the switching unit 132, 141 and 142 are switching elements, and use a GTO (gate turn-off thyristor). 143,144 are protection circuits (snubber circuits), GTO14
GTOs 141 and 142 are connected in parallel with each other so as to cope with reverse withstand voltage caused by surge at the time of ON-OFF of 1,142.
Next, in the gate drive unit 133, reference numerals 145 and 146 denote gate drive circuits for controlling ON / OFF of the GTOs 141 and 142 of the switching elements.

Next, the control unit 134 controls the gate drive unit 133 based on signals from the transmission unit 135 and the timer unit 136. Reference numerals 147 and 148 denote OR circuits, and reference numerals 149 to 152 denote AND circuits.

Next, in the transmitting unit 135, reference numeral 153 is a transmitting circuit for a search signal, and in this example, a frequency (90 Hz) which is half the frequency of the search signal.
Is used. Reference numeral 154 denotes a return signal transmitting circuit which transmits 50 Hz (same as the commercial frequency).

Next, in the timer section 136, reference numeral 156 is a timer for setting the transmission time of the search signal, and the time is set to, for example, 30 seconds. Reference numeral 157 denotes a timer for setting the return signal transmission time, which is set to, for example, 10 seconds.

Next, in the power supply unit 137, E is a DC power supply, for example, 24V
Storage battery, S1 is a power switch, 160 is a voltage detection circuit,
When the voltage of the power supply E reaches the detection level, the power is output to display the presence / absence state (level) of the power supply. 161 is DC
A DC converter that forms ± 12 V DC from 24 V DC.

Next, S2 is a power auxiliary switch, S3 is a changeover switch,
The three sets of switches S3-1 to S3-3 are linked to switch the circuit from 90 Hz side a to 50 Hz side b or vice versa. S4 is a start switch, which uses an interlocking push button switch composed of switches S4-1 and S4-2 provided on the timer 156 and the timer 157. Next, L1 and L2 are power indicator lamps, Le is a transmission indicator lamp, and 158 is an AND circuit.

Next, the operation (operation method) of the transmitter having the above configuration will be described.

First, the case of transmitting a search signal will be described with reference to FIGS. 29 (A) and 29 (B). As in the previous embodiment, the output terminal 102 is connected to the distribution line, and the ground terminal 103 is grounded. Next, the power switch S1 is turned on. Then, the DC-DC converter 161 is connected to the DC power supply E and operates. The switches S3-1 to S3-3 of the changeover switch S3 are switched to the 90 Hz side. Next, when the power auxiliary switch S2 is turned on, the power indicator lamp L1 is turned on to indicate that the power is turned on.

Next, when the start switch S4 is turned ON, the switch S4−
1 to S4-2 turn ON, timer 156 operates and time (seconds)
And outputs a signal from the output terminal of the timer 156 (see waveform diagram).

The output signal of the timer 156 is input to the 90 Hz transmitting circuit 153. Since the transmission circuit 153 is connected to the power supply E,
From the output terminal, a transmission signal of 90 Hz is output to AND circuits 149 and 150 (see waveform diagrams).

The output signals from the timer 156 are input to the AND circuits 149 and 150, and the signals from the AND circuits 149 and 150 are 9
Output alternately at 0 Hz intervals (see waveform diagram).

The output signals from the AND circuits 149 and 150 are then input to the OR circuits 147 and 148. Signals from the output terminals are respectively input to gate drive circuits 145 and 146, and GTO14
For each of the 1,142 data, an ON signal (a signal that changes to 0V + 12V. This + 12V actually drops to 3V due to the ON resistance of the GTO) as shown by (h) and (h ') in the waveform diagrams. Are output alternately at 90 Hz intervals. Also, the output of the OR circuits 147 and 148 causes the transmission display lamp Le to light up to indicate the transmission state. In the above case, however, the OFF signals (from 0 V to -1) are applied to the gates of the GTOs 141 and 142 as shown in (I) and (I ′) in the waveform diagrams, respectively.
Signal that changes to 2V).

GTO141 and 142 turn on alternately at 90 Hz intervals as above
Therefore, currents i1 and i2 flow on the primary side of the output transformer Tr1 at intervals of 90 cycles through the following path.

i1 path DC power supply + side → power switch S1 → output transformer Tr
1 intermediate tap t10 → winding start terminal t11 of output transformer Tr1 → changeover switch S3-1 → GTO141 → ground e0 →-of DC power supply E
Side (see waveform diagram i1).

i2 path + side of DC power supply E → power switch S1 → output transformer Tr
1 intermediate tap t10 → winding terminal t12 of output transformer Tr1 → changeover switch S3-2 → GTO142 → ground e0 →-of DC power supply E
Side (see waveform diagram i2).

As described above, the currents i1 and i2 are on the primary side of the output transformer Tr1.
The output transformer will flow when alternating at 90 hertz intervals
On the secondary side (output end side) of Tr1, a positive output signal (see (nu) in waveform diagram v1) and a negative output signal ((nu ′) in waveform diagram v1) are spaced at intervals of 90 Hz. Alternately). Note that there is a pause between the positive output signal and the negative output signal ((l) in the waveform diagram v1).
See). Therefore, the output signal is output on the plus side and the minus side at an interval of 180 Hz.

The output signal of the transformer Tr1 is rectified by a rectifier circuit, becomes a search signal of a pulsating waveform, and is output to the output terminal 102.

Next, the operation corresponding to the situation of the distribution line accident when the above-mentioned search signal is output will be described.

(A) When the distribution line is sound (no ground fault) The signal current does not flow after the instantaneous current flows because the ground capacitance C0 of the distribution line is only charged (waveform diagram i3-
0), that is, the line is charged to 10 kv (see waveform diagram v2-1). This charging voltage (10 kv) can be confirmed by a display 115 (a voltmeter, which actually indicates the current in voltage) of the display means 108. That is, in the case where there is no accident, it is possible to determine the occurrence of a ground fault by checking the charging voltage (10 kv) of the distribution line.

This charged voltage is discharged to the ground (ground e0) via the voltage dividing resistor circuit 111 serving also as a discharging resistor. Therefore, the investigator (operator) confirms the discharge of this voltage with the display 115 and after the safety, the user proceeds to the next operation.

(B) When there is a ground fault in the distribution line (ground fault resistance is 0 to 6k
Ω) The output signal v1 of the output transformer Tr1 is shaped into a positive rectangular wave by the full-wave rectifier circuit 138 and output. This output is 18
It is output at intervals of 0 cycles (see waveform diagram v2-2). The voltage (several kv) in this case is indicated on the display 1 of the display means 108.
15 (voltmeter) is displayed as a lower voltage than the case without the ground fault, so that a ground fault accident can be confirmed. In addition, the current flowing through the distribution line can be confirmed by the display 121 (ammeter) of the display means 110 '(see the waveform diagram i3-1), and the buzzer 124 sounds in accordance with (interlocks with) the following, and the ground fault is also generated by voice. Accident can be confirmed. In other words, it can be determined that a ground fault has occurred.

(C) When the insulator of the distribution line has an intermittent ground fault (when an irregular ground fault occurs) When the insulator has cracks, etc., the insulation resistance decreases, and the intermittent ground fault occurs, It can be confirmed by the display means 108, 108 '. In this case, the voltage and current of the distribution line are as shown in waveform diagrams v2-3 and i3-2, respectively. Therefore, the voltmeter 115 or the ammeter 121 vibrates extremely irregularly. In this case, the buzzer 124 that rings following the output of the current detection circuit 123 also rings irregularly. In this way, the intermittent ground fault is also
5. It can be determined by the irregular vibration state of the ammeter 121 and the irregular intermittent sound of the buzzer 124.

When the exploration signal is sent as described above, if the high-voltage distribution line to be searched has a ground fault (b) or an intermittent ground fault (c), the signal flowing through the distribution line The current indicator 13- or i3-2 causes the display to indicate that an accident has occurred.

When the search signal is sent as described above, the transmitter stops the setting of the timer 156 in 30 seconds. Therefore, the transmission of the signal from the output terminal 102 stops after the elapse of the time. When the power switch S1 is opened, the output of the transmitter is immediately stopped immediately.

Next, after the ground fault detection is completed and the repair of the accident point is completed, the return signal is transmitted to the distribution line by the transmitter, and the display is restored.

That is, in the transmitter, the connection between the output terminal 102 and the distribution line is disconnected, and the ground terminal 103 is disconnected from the ground. Instead, one terminal of the return output terminal 139 is connected to one of the three lines of the distribution line, and the other is connected. Terminal is connected to one of the remaining two wires. At the point of accident, the following operations are performed after the three phases are connected together.

Switch the switch S3 of the transmitter to the 50 Hz side b,
Turn on the power switch S1 and the auxiliary power switch S2.
Then, the power indicator L1 goes off, the power indicator L2 at the 50 Hz side lights up, and the switching state of the transmission circuit is displayed.

By the switching, a signal is output from the timer 157 on the 50 Hz side (see the waveform diagram in FIG. 30). The output of the timer 157 is input to the transmission circuit 154 on the 50 Hz side, and the output signal from the transmission circuit 154 on the 50 Hz side (see waveform diagram).
Are input to the AND circuits 151 and 152, respectively, and the output signals (see the waveform diagram) from the timer 157 are also input to them. With the above input, the outputs of the AND circuits 151 and 152 are input to the OR circuits 147 and 148 (see waveform diagrams). With this input, the outputs from the OR circuits 147 and 148 are input to the gate drive circuits 145 and 146. In addition, the transmission display lamp Le is turned on by the output of the OR circuit to display the transmission state. The gate drive circuits 145 and 146 are operated by the input signals, and their output signals (waveforms 'and') are applied to the gates of the GTOs 141 and 142 so that the GTOs 141 and 142 are turned on alternately at intervals of 50 Hz. When the GTOs 141 and 142 are turned on alternately as described above, the current i4,
i5 flows alternately at 50 Hz intervals (waveform diagrams i4, i
5).

i4 current path Positive side of DC power supply E → middle tap t20 → winding start terminal t21
→ Switching switch S3-1 → GTO141 → Earth e0 → DC power supply E
Current path of i5 positive side of DC power supply E → middle tap t20 → winding start terminal t22
→ Switching switch S3-2 → GTO142 → Earth e0 → DC power supply E
When the negative side of, the secondary side of the output signal transformer Tr2 for the return signal is 5
A rectangular wave signal v3 of 0 Hz is output (see waveform diagram v3). Also, a return signal current i6 flows on the secondary side of the output transformer Tr2 for the return signal (see the waveform diagram i6).

As described above, when the return signal current i5 (about 5 A) flows into the distribution line, the display detects this and the display returns.
This return signal current i6 is flowing through the distribution line only when the ammeter 16
You can confirm by 3.

〔The invention's effect〕

As described above, in the present invention, when an exploration signal is sent to the distribution line 95 for exploration of an accident point, if there is an accident point, the signal sent from the transmitter 101 indicates a display attached to the distribution line. When the above signals are sent, as well as the operation of the heaters H7 and H8, the current flows only at the point of the ground fault (since the current flowing through the ground capacitance is substantially zero), so that the signals are output. The power current is small and has good characteristics.

On the other hand, when exploring signals are detected at various locations to search for the fault point, if there is no fault point, the current flowing to the fault point is also zero, so the power to be transmitted at each location is always substantially constant. There is a good feature that is zero.

As described above, according to the present invention, the current to be transmitted throughout the exploration work may be small or substantially zero, and there is an effect that the capacity and size of the transmitter can be reduced.

Furthermore, in the present invention, when sending a signal for exploration,
When there is no fault point, the current is substantially zero, and when there is a fault point, only the current flows.Therefore, the current flowing to the output terminal of the transmitter or the voltage of the output terminal corresponding to the current is determined. Thus, it is possible to determine whether or not there is an accident point while staying at the transmitter installation location. This has the effect that the useless confirmation work of the indicator as in the prior art can be omitted when there is no accident point.

(B) If there is an accident point, its type (resistance ground fault,
It is also possible to determine whether the insulator is cracked or a ground fault due to contact with a tree), so that there is an effect that it is possible to prepare for a countermeasure for the accident point in advance.

[Brief description of the drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a half sectional view of a display for detecting a ground fault point, FIG. 2 is a front view for explaining attachment to an electric wire, and FIG. FIG. 4 is an exploded perspective view of the presser body, FIG. 5 is a perspective view of an exploded state of the first element and the display unit in the detection unit, and FIG. Fig. 7 is a plan view.
FIG. 8 is a cross-sectional view of a state in which a cover member and a part of a coil case are broken at a position of a line VIII-VIII, FIG. 9 is a bottom view of a detection coil, and FIG. X-ray sectional view, FIG. 11 is an enlarged sectional view taken along line XI-XI, FIG. 12 is XII-XII
FIG. 13 is an exploded perspective view of a shield and a display body cover in the display unit, FIG. 14 is a perspective view of the display unit in a normal state, FIG. 15 is a perspective view of the display unit in a display state, FIG.
16 is a sectional view taken along line XVI-XVI, FIG. 17 is a sectional view taken along line XVII-XVII, FIG. 18 is a plan view of an auxiliary member, FIG. 19 is a block circuit diagram of a display, and FIG. 20 is a circuit of a display. Fig. 21, Fig. 21 is a waveform diagram for explaining the operation of the display, Fig. 22 is a block circuit diagram of a transmitter for searching for a ground fault, and Fig. 23 is a voltage waveform diagram when a search signal is transmitted to a distribution line. , FIG. 24 is a circuit diagram of the display means, FIG. 25 is a route diagram of the distribution line, FIG. 26 is a circuit diagram showing another example of the display means, and FIG. 27 is a state in which a search signal has been transmitted to the distribution line. , FIG. 28 is a circuit diagram showing another circuit example of the ground fault point locating transmitter, and FIGS. 29 (A) and 29 (B) explain the operation at the time of transmitting the locating signal. FIG. 30 is a waveform chart for explaining an operation at the time of sending a return signal. 101: Transmitter for ground fault detection, 102 ... Output terminal, 10
5 ... pulse flow forming circuit, 107 ... backflow prevention means, 108 ... display means.

Continued on the front page (72) Inventor Masahiro Oikawa 3-7-1 Ichibancho, Sendai City, Miyagi Prefecture Tohoku Electric Power Co., Inc. (72) Inventor Ryosaku Nakata 35 Shinkanma, Nagagusa-cho, Obu City, Aichi Prefecture Japan High Voltage Electric Stock (72) Inventor Masayuki Ota 35, Fukamama, Nagakusa-cho, Obu City, Aichi Prefecture Inside Japan High Voltage Electric Co., Ltd.

Claims (3)

(57) [Claims] A transmitter for searching for a ground fault point, comprising: a search signal forming circuit for forming a search signal having a period suitable for operating a display; and an output terminal for outputting the search signal to a distribution line. In the above, the exploration signal forming circuit includes a pulsating flow forming circuit that forms a pulsating signal that swings in the above cycle only in one positive or negative polarity with reference to zero V, and directs the pulsating flow to the output terminal. And a backflow prevention means for blocking passage in the opposite direction. 2. A transmitter for detecting a ground fault point, comprising: a search signal forming circuit for forming a search signal having a period suitable for operating a display; and an output terminal for outputting the search signal to a distribution line. In the above, the exploration signal forming circuit includes a pulsating flow forming circuit that forms a pulsating signal that swings in the above cycle only in one positive or negative polarity with reference to zero V, and directs the pulsating flow to the output terminal. Backflow preventing means for passing through, but preventing passage in the opposite direction, and display means for changing the display in response to the current output to the output terminal or the voltage of the output terminal. Transmitter for detecting fault points. 3. A transmitter for detecting a ground fault point, comprising: a search signal forming circuit for forming a search signal having a cycle suitable for operating a display; and an output terminal for outputting the search signal to a distribution line. In the above, the exploration signal forming circuit includes a pulsating flow forming circuit that forms a pulsating signal that swings in the above cycle only in one positive or negative polarity with reference to zero V, and directs the pulsating flow to the output terminal. Backflow blocking means for blocking the passage in the opposite direction, and connecting one end of a voltage-dividing resistor circuit for voltage detection to the output terminal and grounding the other end of the voltage-dividing resistor circuit to ground. A transmitter for detecting a ground fault, wherein a voltage indicating device whose display changes in response to the voltage at the intermediate point of the voltage dividing resistor circuit is connected.