JPH02234073A - Searching device for electricity leakage - Google Patents

Abstract

PURPOSE:To detect/display a direction of electricity leakage and a leak current and to perform a search for the leakage accurately and efficiently by providing each circuit such as one for leak current detection in a neutral line, detection of voltage against the earth, detection of phase shift/rectangular wave, phase comparison, etc. CONSTITUTION:The device consists of a DC power supply 2, switching circuit 3 changing-over the aforementioned power to output, current detection circuit 4 detecting/ phase-shifting the leak current to output a pulse signal, voltage detection circuit 5 detecting the voltage against the earth to output a rectangular wave signal, phase comparator circuit 6 for outputs of the circuits 4, 5, storage circuit 7 holding/ transferring the aforementioned output, display circuit 8 displaying this output by an output of the circuit 3, and recovering circuit 9 initializing the circuit 7 by the output of the circuit 3. Then, the leakage direction of a detected point is displayed by a comparison with a logical product of one pulse signal in both detected signals for the current/voltage, in which either one phase of the detected leak current or of voltage against the earth is shifted and rectified to the rectangular wave, and another detected signal, and also the existence of the leak current is displayed by the current detection signal. The search for leakage can be thus performed efficiently in high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an earth leakage detector for detecting earth leakage points occurring in a power supply area from a low-voltage distribution line. [Prior Art] Usually, low-voltage distribution lines extending from the secondary side of a distribution transformer (hereinafter referred to as a pole transformer) are of single-phase two-wire type, single-phase three-wire type, three-phase three-wire type, Various Sanwa four-wire power distribution systems are used, but in each system, one wire (or neutral point) is grounded at the location where the pole transformer is installed, in order to suppress the voltage rise on the low voltage side in the event of cross contact. It has been done. In order to maintain the grounding resistance of this grounding wire at a predetermined value, the grounding wires of multiple pole transformers are often connected in parallel (hereinafter, the wire that connects the grounding wires in parallel is called a neutral gland). To investigate the leakage occurring in the distribution line provided with this neutral wire, for example, the phase of the current detection signal obtained by shaping the leakage current detected by the current transformer connected to the neutral wire into a rectangular wave, Compare the phase of the voltage detection signal obtained by shaping the ground voltage into a rectangular wave, which is detected through the neutral wire and the lead wire connected to the ground, and the period when both phases are in the same phase is positive, and the period when the phases are opposite is negative. A smoothed rectangular wave signal is applied to the meter, and the pointer of the meter is swung left and right around the center of the scale in proportion to the polarity and amplitude of the input signal, and the direction of the sway of this pointer and the direction of the leakage are determined. A method has been proposed in which the leakage direction can be determined by matching the numbers (see Japanese Patent Publication No. 53-39579). [Problem to be Solved by the Invention] However, in the case of the configuration as described above, since the pointer of the meter is caused to swing by an analog signal that compares the phases of the current detection signal and the voltage detection signal, both of the above detections are performed. When the phase difference of the signals is 0 degrees or 180 degrees, the period of in-phase or anti-phase is maximum and the pointer swings greatly, so it is relatively easy to determine the direction of leakage, but the circuit constant of the circuit where the leakage current flows As the ratio of inductance or capacitance increases, the above phase difference approaches 90 degrees, so the difference between the in-phase and anti-phase periods becomes small, and the pointer swings slightly, making it impossible to accurately determine the direction of leakage. There was a problem. In addition, since the direction of leakage is detected by comparing the phase of the ground voltage of the neutral wire and the leakage current, it is not possible to detect leakage current only, as in the case of leakage detection in customer service lines, for example. First, this detection required a separate earth leakage probe designed to detect only leakage current, which caused the problem that the leakage detection was complicated and time-consuming. The purpose of the present invention is to solve the above-mentioned problems, to clearly detect and display the direction of leakage, and also to detect and display only the leakage current, thereby enabling accurate and efficient leakage detection. Our goal is to provide an earth leakage detector that can (Means for solving !II!) In order to solve the above problems, the present invention provides a current detection circuit that detects leakage current flowing in a neutral wire and outputs a rectangular wave current detection signal, A phase shift circuit is provided in either one of the voltage detection circuits that detect the voltage to ground and output a rectangular wave voltage detection signal, and a pulse signal is output from the rectangular wave detection signal to at least one of the two detection circuits. A rectangular wave detection circuit is provided, this pulse signal and the rectangular wave signal from the other detection circuit are input to a phase comparison circuit, the phases of both detection signals are compared, and the leakage direction is indicated by the output signal of this phase comparison circuit. At the same time, the presence or absence of leakage current is displayed using the current detection signal. [Function] The phase of either the detected leakage current or the ground voltage is shifted, and the current is shaped into a rectangular wave.・The voltage detection signals are phase-compared by logical product of the pulse signal generated by one of the signals and the other detection signal, and this comparison signal indicates the direction of the leakage at the detection point,
The presence or absence of leakage current is independently displayed using the above current detection signal. [Examples] Examples of the present invention will be explained below using figures. In Figure 1, 1 is an earth leakage detector, and 2 is a DC power source consisting of a battery, etc.
and a switching circuit 3 that switches and outputs this DC power supply 2,
A current detection circuit 4 that detects leakage current, shifts the phase to generate a pulse signal, and outputs this as a current detection signal; and a voltage detection circuit 5 that detects ground voltage and outputs a rectangular voltage detection signal. A phase comparator circuit 6 that compares the phases of the outputs of the current and voltage detection circuits 4 and 5, a storage circuit 7 that holds and sends out the output of this circuit, and a storage circuit 7 that stores and transmits the output of this circuit, and the output of this circuit that uses the output of the switching circuit 3 It is comprised of a display circuit 8 for displaying images, and a recovery circuit 9 for initializing the storage circuit 7 with the output of the switching circuit 3. The changeover circuit 3 is composed of a changeover switch formed by a two-circuit, four-contact rotary switch, etc., and the changeover switch's movable contacts (alga!) are interlocked and the corresponding fixed contacts b Il+ b I
f b 13+ b +a and t) H, bg
t, b*s+bx4 are switched sequentially. The movable contact a, is connected to the positive pole of the DC power supply 2, and the fixed contact bl1 is used as an idle contact, b + x + b
13+ b 14 is a movable contact a. is connected to.

Fixed contact b again! l * b 14 is a play contact, and big is ? A fixed contact bts is connected to the input end of the return circuit 9 and the input end of the display circuit B. And the movable contact alga! of the changeover switch mentioned above! is the fixed contact b l l +
b! When connected to 1, earth leakage detector 1
The power supply to each circuit is stopped, and the movable contacts al+al switch to the fixed contacts b1. btz, the DC power supply 2 is supplied to other circuits except the display circuit 8 (power supply lines are omitted except those shown in FIG. 1), and the memory circuit 7 is initialized at this time. It is supposed to be done. Movable contact al
Ga! is the fixed contact b+3+1)! 3, the DC power supply 2 is supplied to other circuits other than the human power end of the recovery circuit 9 to perform earth leakage detection operation. Movable contact alga! When the switch is connected to the fixed contacts b14+b14, DC current #2 is supplied to other circuits other than the input terminals of the display circuit 8 and the return circuit 9 to perform a leakage detection operation.

The current detection circuit 4 will be explained. Reference numeral 10 denotes a leakage current detection unit, which is formed by dividing an annular core so as to be expandable, and winding a secondary winding around the annular core. It consists of a current transformer CT for detecting leakage current that is passed through a lead-in line, etc., and a resistor R1 inserted between its secondary output terminals.The leakage current is converted into voltage from between the terminals of this resistor R1. It is designed to be output as follows. 1l is a phase shift circuit, which has a capacitor C1 and a resistor R.1 between the output terminals of the current detection circuit 4. are inserted in series to form a differentiating circuit, and the phase of the input signal is advanced by, for example, 60 degrees between the terminals of the resistor R, and then output. l
2 is an amplifier circuit, which includes an operational amplifier OP. The connection point between the capacitor C and the resistor R of the phase shift circuit Bll is connected to the inverting input terminal of the circuit via the input resistor R, and the resistor R4 is connected to the negative feedback circuit. The other end of R2 is connected to invert and amplify the input signal and output it. Then, the amplification degree R4/R of this amplifier circuit l2
3 is set so that when a leakage current equal to or higher than the detection level (for example lomA) is input to the leakage current detection unit 10, a rectangular wave with a steep rise and a peak value approximately equal to the power supply voltage is formed. 13 is a rectangular wave detection circuit, and a capacitor C2 and a resistor R are connected between the output terminal of the amplifier circuit 12 and the ground.
．． are connected in series to form a differentiation circuit with a small time constant 02 ・R, and a diode D is connected across the resistor R in the opposite direction, and at the rising edge of the input, the capacitor C and the resistor R,
A positive pulse is generated at the connection point of the not circuit NI, and when the level of the pulse exceeds the threshold of the NOT circuit NI, an L level output signal is sent from its output terminal. 14 is a delay circuit, which is a movable contact a. of the changeover switch of the switching circuit 3; and ground, a resistor R. and a capacitor C are connected in series to form an integrating circuit with a time constant Rh"Cs, and the connection point between the resistor R. and the capacitor C3 is connected to the rectangular wave detection circuit 13 through a diode D8 whose anode is connected to the connection point. A resistor R, and a capacitor C4 are connected in series between the output terminal of the knot circuit N2 and the ground, and a time constant R, . An integrating circuit C4 is provided, and a diode D3 is connected in the opposite direction to both ends of the resistor R?.
It is designed to be output from the connection point (output end) of the above resistor R and capacitor C4. The above time constant R,・C, is
The period T of the input signal to the delay circuit l4 (T in Fig. 4e)
), capacitor C3 connects to resistor R. Direct current +
Even if it is charged from flX2, it does not reach the threshold of the nosoto circuit N2, and it is set so that the threshold is reached within the charging time of the cycle TX2. In addition, the above time constant R,・C4 is such that for a time longer than the above period TX4, the capacitor C4 is connected to the resistor R.
, is set so that when it is charged from the NOT circuit N2 through the AND circuit A1, the threshold value of the AND circuit A1 is reached. Then, the capacitor C2 and the resistor R of the rectangular wave detection circuit l3
The connection point of S and the output terminal of the delay circuit 14 are connected to an AND circuit A.
1, and a current detection signal is sent from the output terminal of this AND circuit A+. Next, the voltage detection circuit 5 will be explained. 16 is a voltage detection section, and terminals 15a each have a removable connection fitting attached to one end and are connected to the other end of a connecting wire (not shown).
, 15b are inserted in series, and the input voltage is divided and output between the terminals of the resistor R.
The terminal 15a is removably connected to the neutral wire and the terminal 15b is connected to the ground via the connection wire (not shown), so that a ground voltage can be input. Reference numeral 17 denotes an amplifier circuit, which, like the amplifier circuit 12 described above, has an input resistor R, connected to the inverting input terminal of the operational amplifier OP3. via the voltage detection section 16
At the same time, a resistor Rl1 is connected to the negative feedback circuit, and the non-inverting input terminal is connected to the terminal 1.
5b to send out an inverted and amplified output signal from the output terminal of the operational amplifier OP, and the amplification degree Rll/Rl@ of this amplifier circuit 17 is higher than the detection level (for example IV). When the voltage is input to the voltage detection unit 16, it is set so that it becomes a rectangular wave with a steep rise and a peak value approximately equal to the power supply voltage. 18 is a rectangular wave detection circuit, which, like the rectangular wave detection circuit 13 described above, has a capacitor C and a resistor Rlf connected in series between the output terminal of the amplifier circuit 17 and the ground, and has a time constant C. −R is a small differentiator circuit, and the resistance R
A diode D4 is connected in the opposite direction to both ends of lm to generate a positive pulse at the rising edge of the input, and when this level exceeds the threshold of the not circuit N, the output terminal of L
It is designed to send out a level signal. 19 is a delay circuit, and like the delay circuit 14, a resistor R. and capacitor C. are connected in series to form an integrating circuit with a time constant Rl3・Ch, and the connection point between the resistor RI3 and the capacitor Ch is
It is connected to the output terminal of the NOT circuit N of the rectangular wave detection circuit 18 through a diode D, whose anode is connected to the connection point, and also connected to the NOT circuit N4, and between the output terminal of this NOT circuit N4 and the ground. A resistor RI4 and a capacitor C are connected in series to form an integrating circuit with a time constant Rl4·C, and a diode D. are connected in the opposite direction, and the output is output from the connection point (output end) between the resistor R14 and the capacitor C▼. The above time constant Rl3・C. and the time constant Rl4·C, are the time constant Rh”Cw and the time constant R.· of the delay circuit 14 mentioned above.
The settings are the same for C4. Voltage detection signals are sent out from the output terminals of the amplifier circuit l7 and delay circuit l9, respectively. The phase comparison circuit 6 includes an AND circuit A8 connected from the output terminal of the AND circuit A1 of the current detection circuit 4 and the output terminal of the delay circuit 19 of the voltage detection circuit 5, and an output terminal of the AND circuit A8 and the voltage detection circuit. AND circuit A4 connected to the output terminal of the amplifier circuit 17 of No. 5, and the output terminal of the NOT circuit Ns connected to the output terminal of the AND circuit A and the output terminal of the amplifier circuit I7. It is formed of AND circuits A and A, and pulse signals are output from the output terminals of the AND circuits A and A, respectively. Describing the memory circuit 7, SR+. SRISR. is, for example, an 8-bit shift register that holds and outputs an H-level signal when eight or more pulses are input. This shift register SR+, SRt
．． Is the data terminal D of SRs the movable changeover switch of the changeover circuit 3? It is connected to point at so that it becomes H level when detecting earth leakage. shift register SR
, the output terminal of the AND circuit A1 of the current detection circuit 4 is connected to the clock terminal CK of the shift register SR. ,SR
The output terminals of AND circuits A and A4 of the phase comparator circuit 6 are connected to the clock terminal CK of s. Shift register SR. The reset terminal R of the shift register SR. is connected to the output terminal of the recovery circuit 9, and the shift register SR. , SR3's reset terminal R is connected to a diode D? , DI to the output terminal of the recovery circuit 9, and the recovery circuit 9 outputs a reset signal (L
level), shift register SR+
SRg, SR. s is designed to be initialized. In addition, shift registers SR■, SR. The glue set terminals R are each connected to a high resistance resistor R+s. R,. It is connected to the movable contact at of the changeover switch through the terminal, and is set to the H level when detecting earth leakage. Not circuits N, Ny, and Ns are connected to the output terminals Q of the shift registers S R+ and S RtSR s, respectively, and the output terminals Q? It inverts and outputs the H level output signal sent from shift register SR. Connect the glue set terminal R to the knot circuit N through the diode D. Also, a shift register SR. Reset terminal R of
diode D1. are connected to the output terminals of the NOT circuits N, respectively through shift registers SR. (or SR
, ) outputs an earth leakage detection signal (H level), shift register SR. (or SR.) is set to L level so that the earth leakage detection signal is not output from both at the same time. The display circuit 8 includes NOT circuits NN, , N of the storage circuit 7.
, a limiting resistor Rl ? + R + I +
Light emitting diode LD. via RI9. LD*
The cathodes of the light emitting diodes LD. ,LD■,LD! The anode of is switching circuit 3
The shift registers SR, SRt, SR are connected to the fixed contact b0 of the changeover switch and the movable contact a8 of the changeover switch is connected to the fixed contact bus
s to knot circuit Nh, NqN. When receiving an L level output signal through the light emitting diodes LD1 and LDg
, LDs are turned on to display the information. The light emitting diodes LD+, LDt, and LD3 are the second
As shown in the figure, for example, a symbol "A" is placed on one side of the distribution line penetration part of the current transformer and is arranged so as to be visible from the outside of the earth leakage probe l. For example, the symbol r3J is attached to the other side surface, and when the leakage detection operation is performed, the leakage current detection is indicated by lighting up the light emitting diode LD, and the light emitting diode LD. If it lights up, the light emitting diode LD. If it lights up, it will indicate that there is a leakage point towards the B side. The return circuit 9 has its input end connected to the fixed contact btt of the switch of the switching circuit 3, and also has a resistor R,
. is inserted and output to the storage circuit 7 via the NOT circuit N.

As shown in FIG. 2, the earth leakage detector 1 configured in this manner has a main body part 40 in which the above-mentioned circuits are housed, similar to a measuring instrument commonly called a clamp-type ammeter.
and an annular core part 41 which is divided into two parts so that the current transformer CT of the current detecting part 10 can be expanded and retracted from the main body part 40, and which has a pivot part (not shown) inside the main body part 40 and protrudes from the current transformer CT. It is equipped with an operation button 42 that always protrudes, and the above operations! By pushing 042, the annular iron core 41 is expanded and the neutral wire 27 is inserted from the open end, and by releasing the push, the expansion is restored and the neutral wire 27 is inserted through the annular iron core 41. It is supposed to be done.

Further, the main body part 40 is equipped with a mounting string of an appropriate length equipped with a hook metal fitting (not shown), so that the hook metal fitting can be hung on a member near the attachment for hanging support. Next, the operation of the earth leakage detector 1 will be explained using an example in which it is applied to a single-phase three-wire low-voltage distribution line shown in FIG. In Figure 3,
21, 22, and 23 are pole transformers, and the neutral points of the secondary windings of the pole transformers 21, 22, and 23 are grounded through ground wires 24, 25, and 26, respectively. , 25.
26 are interconnected by a neutral wire 27. The grounding wires 24, 25.26 are connected to grounding resistors 28, 29.26, respectively.
It has 30. The voltage lines connected from both ends of the secondary winding of the pole transformer 21, 22, 23 are connected to the neutral gland 2.
7 and extending to the supply area of each pole transformer, and power is supplied to a load (not shown) in a single-phase three-wire distribution system.

The supply areas are separated by boundary points 31 and 32, so that no load current flows through the neutral wire 27 of these boundary points 3l and 32. In the above distribution line, P of the voltage line in the supply area of the pole transformer 22
If a leakage occurs at a point, the path of the leakage current is as shown by the arrow in Figure 3, from the point P through the ground,
Divided into the ground wires 24, 25, and 26 and passed through the neutral wire 27,
It flows through the pole transformer 22 and returns to point P. At this time, the leakage current is caused by the ground resistance 28 of the ground wires 24, 25, 26
．． 2930, a ground voltage is generated in the neutral wire 27. Furthermore, only leakage currents flow in the neutral vA2 7 of the boundary points 31, 32 in opposite directions, as shown in FIG.

When attaching the earth leakage probe 1 to the neutral wire 27, first,
The movable contacts a and a8 of the changeover switch of the changeover circuit 3 are connected to the fixed contacts b l l + b! l to fixed contact b+i.
When switched to b■, the DC power supply 2 is supplied to each circuit other than the display circuit 8. In response to this, the input terminal of the return circuit 9 becomes H level, and an L level recent signal is sent to the memory circuit 7 from the output terminal of the NOT circuit N. The shift register SR that received this. The reset terminal R of the shift register SR. , S.R. Is each glue set terminal R a diode D? , DI conduction causes L
level, and the shift registers S Rr , S
Rz and S Rs are initialized.

Next, the movable contacts at, a. Fixed contact b, 3, b
2, the DC power supply 2 is supplied to each circuit except the input terminal of the return circuit 9, and the NOT circuit N of the return circuit 9 has its input terminal connected to the resistor R. The output signal is inverted to H level because it is grounded through the terminal. Therefore, the reset terminals R of the shift registers S Rt and S R3 are connected to high resistance resistors R+s and R, respectively, since the diodes Dt and C++ become non-conductive. , receives DC power supply 2 through , and is inverted to H level, and the shift register SR! ，
S.R. is SR. At the same time, the device enters a standby state and becomes capable of detecting earth leakage, storing information, and displaying information. At this time, if the earth leakage probe l is installed and left unattended for a long time for investigation, the movable contacts a,,at of the changeover switch
If the power supply to the display circuit 8 is stopped by switching and connecting it to the fixed contact b14+bza, the light emitting diodes LD,,t, of the display circuit 8 during the leakage detection operation can be
n*, LD. The consumption of DC power supply 2 due to lighting is reduced. (b) Exploration of the direction of electrical leakage. Neutral 1! of multiple boundary points (3l32 in this example) to be detected using multiple earth leakage probes l in the above state!
! j127, for example, by changing the position of the operating chain 42 shown in FIG. 2 to the front side in FIG.
A) on the right side), and install it through the pillar. Next, the terminals 15a and 15b of the voltage detection circuit 5 are connected to neutral! through a tangent M wire having a connecting fitting (not shown). Connect to 1127 and earth respectively. ■ If there is no electrical leakage. Since there are no input signals to the current detection circuit 4 and voltage detection circuit 5, and there are no input/output signals to the phase comparison circuit 6 and memory circuit 7, shift registers SR, SRz, SR. All of the output terminals Q of the not circuit N. ，
Nff, N. Light emitting diode LD+, LD via
The cathodes of t and LDs are all held at H level, and even if power is supplied to these anodes, there is no earth leakage detection display. ■ Micro leakage that does not reach the detection level is the third cause.
If it occurs at point P in the diagram. A small current is detected by the leakage current detection section 10 of the current detection circuit 4, and is amplified and outputted by the amplifier circuit 12 via the phase shift circuit 11, but since the input level is small, the output waveform has a steep rise. Even if it does not become a rectangular wave and is input to the rectangular wave detection circuit 13, a pulse exceeding the thresholds of the NOT circuit N1 and the AND circuit A1 will not be generated.
The output signal of the not circuit IR N + remains at H level, and the output signal of AND circuit AI remains at L level. On the other hand, the voltage detection circuit 5 detects a minute voltage at the voltage detection section l6, but as described above, the output waveform of the amplifier circuit 17 is not a square wave with a steep rise, so the square wave detection circuit 18 is not Since no pulse exceeding the threshold of circuit N is output, the output signal of NOT circuit Ns remains at H level, and the output signal of delay circuit 19 remains at L level. At this time, the output signal of the amplifier circuit 17 is
The input terminals of AND circuits As and Aa are sent to AND circuits A and A, respectively.
Since the output signal of the mustard level is being received, the output signal of the phase comparison circuit 6 remains at the L level. Therefore, as in the case where the above-mentioned leakage does not occur, the light emitting diode L
Even if power is supplied to D+, LDt, and LDs, there is no earth leakage detection display.

■ If an electric leakage exceeding the detection level occurs at point P in Figure 3. The earth leakage probe l attached to the boundary point 31 detects the leakage current at this time with the leakage current detection unit 10 (Fig. 4a, Fig. 5d), and phase-shifts it by, for example, 60 degrees by the phase shift circuit 1l. (
(Fig. 4b). Amplifier circuit 12 that received this
is inverted and amplified, and sends out a rectangular wave signal with a steep rise and a peak value approximately equal to the power supply voltage (Figure 4C and Figure 5C). Rectangular wave detection circuit 13 receives this and generates a pulse at the rising edge of the input (Fig. 4d), which is sent to AND circuit A.
At the same time, the inverted output signal is sent to the delay circuit 14 via the NOT circuit N1 (Fig. 4e) e The delay circuit 14 receives this, and the diode D8 becomes conductive at the fall of the input signal. So, capacitor C, is DC power supply 2
When the charge stored in the resistor R is instantly discharged by the resistor R, and the diode DO becomes non-conductive at the rising edge of the input signal, the capacitor C is transferred to the resistor R. is charged via,
Repeat charging and discharging operations. During this charging/discharging operation, the capacitor C repeats the operation of being discharged before its charging voltage reaches the threshold of the NOT circuit Nx, so the output signal of the NOT circuit Nt is held at H level. This results in
Capacitor C4 has a time constant of 04 through resistor R, R7
The charging voltage is the same as that of the rectangular wave detection circuit 13.
When, for example, five pulse signals are input in succession (that is, within the charging time of Shuho TX4 of the above input signal), the threshold of AND circuit A1 is reached, and delay circuit I4 sends out an H level output signal. (FIG. 4B, AND circuit A) receives this and uses the pulse signal having the same phase as the output pulse of the rectangular wave detection circuit 13 as the current detection signal of the current detection circuit 4, and outputs the AND circuit of the phase comparison circuit 6. It is output to the circuit As and the shift register SR of the memory circuit 7 (FIG. 4g, FIG. 5f).

The above shift register S receives this at the clock terminal CK.
R, is set and shifted one bit at a time at each rising edge of the input pulse, and this shift register SR, for example, has 8 bits.
If it is a bit, when 8 pulse signals are input, the output terminal Q is inverted to H level (Fig. 4h), and the NOT circuit N is inverted.
．． The light emitting diode LD. of the display circuit 8 is connected to the display circuit 8 through the light emitting diode LD. The cathode side of the shift register SR is set to the level ■, and even if the leakage current disappears, the shift register SR holds (memorizes) this level until a reset signal is input. On the other hand, the voltage detection section 16 of the voltage detection circuit 5
The amplification circuit 17 that receives this detects the voltage to ground (Fig. 5a), inverts and amplifies it, and sends out a rectangular wave signal with a steep rise (Fig. 5b). Rectangular wave detection circuit 1B receiving this generates a pulse signal at the rising edge of the input, similar to the above-mentioned rectangular wave detection circuit 13, and sends this to the knot circuit N,
Output via . The delay circuit 19 receiving this includes a capacitor C. is the knot circuit N. By repeating charging and discharging operations at a charging voltage that does not reach the threshold value of , the output signal of the NOT circuit N4 is held at H level, and the time constant C? is connected to the capacitor C via the resistor R.・
R. The charging voltage changes when, for example, five pulse signals are input in succession (i.e., the period TX of the input signal
4), the output signal becomes H level. The AND circuit Am of the phase comparator circuit 6 receives this and outputs the logical product with the output signal of the AND circuit A1 of the current detection circuit 4. That is, AND circuit At outputs a pulse signal (FIG. 5f) having the same phase as the output signal of AND circuit A to AND circuits A3 and A4.

The AND circuits A and A4 which received this input the rectangular wave output signal (Fig. 5b) of the amplifier circuit 17 of the voltage detection circuit 5 to the other input terminal, and the AND circuits A and A4 receive the rectangular wave output signal (Fig. 5b) of the amplifier circuit 17 of the voltage detection circuit 5 through the NOT circuit Ns. (FIG. 5C), and since the AND circuit A4 is directly inputted, only one of them (AND circuit A in this example) outputs the pulse signal as the output signal of the phase comparator circuit 6. Become. In this way, the phase comparator circuit 6 activates the AND circuit Am only when both the leakage current and the ground voltage exceed the detection level.
outputs a pulse signal (so that it is possible to accurately compare the phases of both signals.Moreover, the phase comparison circuit 6 is configured to output either the leakage current or the ground voltage (in this example). Since the current and voltage detection signals are inputted by shifting the phase of the leakage current (leakage current), due to constant failure of the circuit in which the leakage current flows, for example, the leakage current may be in a phase relationship that is slightly ahead of the ground voltage. If so, the level of the voltage waveform at the time of the above pulse generation is L level, and on the contrary, if the leakage current is in a phase relationship slightly delayed from the ground voltage, the level of the voltage waveform at the time of the above pulse generation is H level. Therefore, even if the topological relationship between the two is homeomorphic, it will not be possible to distinguish between them《,
It becomes possible to perform a phase comparison that accurately determines the phase relationship between the two. The shift register SR8 of the storage circuit 7 receives the pulse signal (FIG. 5f) from the AND circuit A3 of the phase comparison circuit 6, and the shift register SR. Similarly, when, for example, eight pulse signals are input, the output terminal Q is inverted to the ■ level (Fig. 5g), and the NOT circuit N. The light emitting diode LD. of the display circuit 8 is connected to the display circuit 8 through the light emitting diode LD. The cathode side of the shift register SR is set to L level, and even if the leakage current disappears, the shift register SR is held until the reset signal is input (
Remember. At this time, the shift register SR. When the output signal of the shift register S becomes H level, the diode I)to becomes conductive via the NOT circuit N't, and the input of the reset terminal R of the shift register SR3 becomes the L level.
R3 is reset. Furthermore, in the operation of the delay circuit 14, if five consecutive pulse signals are not input from the rectangular wave detection circuit 13 (for example, an instantaneous leakage occurs due to incorrect operation of electrical equipment), the diode D ,but,
The capacitor C and the resistor R. In response to this, the output of the NOT circuit Nt becomes an L level, and the diode D becomes conductive, and the capacitor C is charged at a high voltage.
Since it is discharged before the charging time of the period T x 4 reaches the level, the AND circuit A. , the input end is L
It remains at the same level and no pulse signal is sent out. This operation is exactly the same in the delay circuit 19 as well.

The delay circuits 14 and 19 have a predetermined number (for example, 5
(i.e., if more than one pulse signal is not input continuously)
Since an H level output signal is not sent unless charging is performed for the period of the input signal TX4, an induced current due to residual magnetism of the current transformer CT of the leakage current detection unit 10 may flow, or the voltage may change. Even if noise intrudes into the detection unit 16, it is possible to output both current and voltage detection signals without malfunctioning, and to perform accurate earth leakage detection display. On the other hand, as shown in FIG. 3, the earth leakage probe l attached to the boundary point 32 is connected to the boundary point 31.
Since the leakage currents flowing through the neutral 127 of 32 flow in opposite directions, if the polarities of the secondary windings of the current transformer CT of the leakage current detection unit IO are the same and are installed at the boundary points 31 and 32, both The phase difference between the output current waveforms is 180 degrees. Therefore, if the phase of the leakage current at the boundary point 31 described above is in phase (Figure 5 d) with respect to the phase of the ground voltage of the neutral I127 (Figure 5 a), which is common to both, then the boundary point The phase of the leakage current detected in 32 is in reverse phase (5th
Figure h). The subsequent operation of the current detection circuit 4 is almost the same as that of the current detection circuit 4 of the earth leakage probe l attached to the boundary point 31, but only the phase is different by 180 degrees (the fifth
figure'. J)+1 On the other hand, the output of the voltage detection circuit 5 is exactly the same as the voltage detection circuit 5 of the earth leakage probe 1 attached to the boundary point 31 (Fig. 5 a, b, c), and The output signal of the current detection circuit 4 (Fig. 5 j) and the output signal of the voltage detection circuit 5 (Fig. 5 b) of the earth leakage probe l installed on the
The phases are compared in the phase comparator circuit 6, and the logical product of both signals is output as a pulse signal from the AND circuit A4 (fifth
Figure j). Shift register SR of the storage circuit 7 that receives this
, for example, when 8 pulse signals are input manually, the output terminal Q
teeth! Inverted to l level (Fig. 5k), the not circuit N,
The light emitting diode LD. of the display circuit 8 is connected to the display circuit 8 through the light emitting diode LD. The cathode side of is set to L level and this is held (memorized). At this time, when the output signal of the shift register SR becomes H level, the NOT circuit N. through diode D
, becomes conductive and sets the input of the reset terminal R of the shift register SR to the L level to reset ? Let it run. As mentioned above, shift register SR. When the leakage detection is performed, the shift register SR3 is reset, and the shift register SR. When the leakage detection is activated, the shift register S
R. For example, both shift registers SR. , S.R. Malfunctions such as outputting earth leakage detection signals at the same time do not occur. Then, in the above state, the movable contact aa of the switching circuit 3 is connected from the fixed contact bl4+ bl4 to b ts+ b *s
"When switched, the light emitting diode LD.LD of the display circuit 8
■, Since the positive pole of the DC power supply 2 is connected to the anode of the LDs, the earth leakage detector 1 installed at the boundary point 3l lights up the light emitting diode LD which indicates leakage current detection, and the light emitting diode LD which indicates the direction of the leakage. The earth leakage probe l attached to the boundary point 32 is a light emitting diode LD. and L.D. lights up. At this time, as shown in FIG. 2, the light emitting diode LDt is in the A direction, and the light emitting diode LD. indicates the B direction, which is determined in advance from the leakage direction and the A or B direction above.
The polarity of the current transformer CT of the current detecting unit 10 is set so that the direction indicated by 4
2 is attached to the front side in Fig. 3, so A indicates that the leakage point is on the right side in Fig. 3, and B indicates that the leakage point is on the left side.
It can be seen that it is located in the supply area of the pole transformer 22 between 2 and 2. Note that, for example, only the earth leakage probe l at the boundary point 32 should be moved in the opposite direction from the above (the operation button 42 should be moved to the other side in FIG.
(in the figure, the left and right sides respectively) and the neutral wire 27
When the current detection circuit 4 is installed in
In the diagram, it is indicated that there is a leakage point to the left of the boundary point 32. Therefore, in actual use, the earth leakage detector 1
It doesn't matter which way you install it to the neutral wire 27.
In addition, since the presence or absence of leakage current and the direction of the leakage current are stored in the memory circuit 7, the switching operation of the switching circuit 3 to display the above display must be performed after removing the earth leakage probe l from the distribution line. You can. Next, the movable contact a. of the switching circuit 3. , a, to the fixed contact b I 1 + bR Z, a reset signal is sent from the recovery circuit 9 to the memory concave path 7, so that
When the memory circuit 7 returns to its initial state, the light emitting diode is turned off. Then, when the movable contact al+at is switched to the fixed contact b l l + b@ +, the supply of DC power 2 is stopped. As can be understood from the above operation, if the earth leakage detector l of the present invention is attached to the neutral wire at each boundary point of the low-voltage distribution line in the area where the earth leakage is estimated to occur, the earth leakage can be prevented. If it occurs even temporarily, it will operate to memorize and display the direction of the leakage, so this leakage direction display will indicate the location of the leakage within the supply area of the pole transformer sandwiched between the two probes pointing inward. It turns out that there is. The leakage point is usually in the load or wiring of a customer that receives power from the distribution line in the above power supply area by a drop-in line, so to identify this consumer, it is necessary to detect leakage current from the drop-in line. It's a good thing. (Example) Exploration of electrical leakage points. Next, we will explain the leakage detection of the above service wire. In this case, a lead-in wire is attached to pass through the current transformer CT of the leakage current detection section IO, and no ground voltage is input to the terminals 15a, 15b of the voltage detection section 16. A drop-in wire is usually a stranded wire consisting of two or three insulated wires, and when a leakage occurs on the load side of the drop-in wire, the current flowing through the drop-in wire becomes a faulty current, and the current of this faulty part is transferred to the above-mentioned leakage. If the leakage current is detected by the current detection unit 10 and is equal to or higher than the detection level as described above, the current detection circuit 4 transfers the shift register SR. A current detection signal is sent to shift register SR. The output becomes H level, and the NOT circuit Nh
through the light emitting diode LD. The cathode of LD. is kept at L level, and the light emitting guide LD. lights up, indicating that leakage current has flowed through the service wire to which it is attached. Then, by successively performing the same exploration as described above for the load or wiring connected to this lead-in line and narrowing down the range of presence or absence of earth leakage current, the location of the earth leakage can be investigated (that is, discovered). In the above embodiment, it has been explained that the phase-shifting circuit l1 is formed by a differentiating circuit to advance the phase, but since it is sufficient to compare the relative phase relationship of both voltage and current detection signals, it can be formed by using an integrating circuit. The phase may be delayed, and
The phase shift circuit 11 may be provided not in the current detection circuit 4 but in the voltage detection circuit 5. In addition, in the embodiment, a rectangular wave detection circuit that outputs a pulse signal from a rectangular wave detection signal is provided in the current detection circuit 4, and the phase is compared with the rectangular wave output from the other voltage detection circuit 5. Alternatively, the voltage detection circuit 5 may be provided with a rectangular wave detection circuit that outputs a pulse signal from a rectangular wave detection signal, and the current detection circuit 4 may output a rectangular wave to compare the phases.
At this time, it goes without saying that it is necessary to match the polarity of the current transformer CT so that the leakage direction operation display and the actual leakage direction match. Further, in the above embodiment, a light emitting diode is used to display the leakage detection operation, but the present invention is not limited to this, and other display elements may be used. According to the embodiment, for example, an 8-bit shift register is used in the memory circuit 7, so in the investigation of the leakage direction, the phases of the leakage current and the ground voltage are compared in the phase comparator circuit 6, and the AND circuit A, Or, when the signal is being output from A4, the power of the load that is causing the leakage is turned off, or
Remove the current transformer CT from the neutral gland 27 or remove the voltage detector l.
At the moment when the connecting wires connected to terminals 15a and 15b of 6 are removed, only one of the output signals of the current detection circuit 4 or the voltage detection circuit 5 is cut off first, and for example, when the AND circuit At outputs a pulse. When the rectangular wave signal from the amplifier circuit l7 of the voltage detection circuit 5 is reversed from H level to L level and the phase relationship is momentarily reversed, the pulse signal that had been output from the AND circuit A momentarily changes. Pulses will be sent from the other AND circuit A, but since the output signal is not sent unless 8 pulses are input to the clock terminal CK of the shift register, the instantaneous signal shown above is Even if input, the display will not be caused by an incorrect detection operation. Furthermore, according to this embodiment, the leakage current detection display and the leakage direction display are performed using light emitting diodes LD,,t,ox, which are small and operate with minimal power.
Since LDs are used, conventional display devices (meters)
The volume and power capacity can be reduced compared to earth leakage detectors using In addition, when installing this earth leakage detection IT on the power distribution line, if the movable contacts a1, a of the switching circuit 3 are switched and connected to the fixed contact b tar b 14 position, it will be possible to detect and store the earth leakage. Since the light emitting diode does not light up, there is no battery consumption due to lighting, and by using elements such as complementary Mosyc with low power consumption in each circuit, even if small and compact batteries are used, The earth leakage detector 1 can be continuously attached to the power distribution line for a long time. Further, although a light emitting diode is used in the above embodiment, the present invention is not limited to this, and other display elements may be used. [
[Effects of the Invention] As explained above, the earth leakage detector of the present invention can clearly display the earth leakage direction by using an on/off display instead of an analog display, and can also display the earth leakage direction and detect only the leakage current. Since it can be displayed, highly reliable and efficient leakage detection can be performed.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of the structure of the earth leakage detector 1, FIG. 3 is an explanatory diagram of a single-phase three-wire distribution line to which the earth leakage detector is applied, and FIG. Figure 4 a % h
is a time chart showing leakage current detection operation, Fig. 5a
z k is a time chart showing the earth leakage direction detection operation. 1; Earth leakage detector 4; Current detection circuit 5; Voltage detection circuit 6; Phase comparison circuit 8; Display circuit 11
; Phase shift and same path l 2 2. Pole transformer 4, 2 5. Ground wire Neutral wire Patent applicant: Chubu Electric Power Co., Ltd. Mu Co., Ltd. Aichi Electric Co., Ltd. Mu Co., Ltd. Figure 2 Figure 4 Figure 8 Figure No. 5

Claims (1)

[Claims] A current detection circuit detects the leakage current flowing in a neutral wire connected in parallel with the ground wires of multiple low-voltage distribution transformers and outputs a rectangular wave current detection signal, and a current detection circuit detects the ground voltage of the neutral wire. An earth leakage detector comprising: a voltage detection circuit that outputs a rectangular voltage detection signal; and a phase comparison circuit that compares the phases of both of the detection signals; One of the current detection circuit and the voltage detection circuit is provided with a phase shift circuit, and at least one of the two detection circuits is provided with a rectangular wave detection circuit that outputs a pulse signal from the rectangular wave detection signal. The pulse signal and the rectangular wave detection signal from the other detection circuit are input to the phase comparator circuit to display the leakage direction, and the current detection signal is used to display the presence or absence of leakage current. Earth leakage detector.