JPS59220015A - Leakage detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an earth leakage detection device such as an earth leakage breaker that detects earth leakage current in an electric circuit and interrupts the electric circuit, and an earth leakage alarm that issues a warning alarm.

An example of a conventional device of this type is shown in FIG. 1 and will be explained as follows.
In the figure, (1) is an AC voltage source, and this AC voltage source (
1) has electrical circuit breaking contacts (2a), (2b) and electrical circuit (3).
A load (4) is connected via a) and (3b).

(5) is a zero-phase current transformer whose primary windings are electrical circuits (3a) and (3b).

(6) A load resistor connected in parallel to the secondary output of the zero-phase current transformer (5), (8) is a diode, and this diode (force, (8) is connected in the opposite direction. and load resistance (6
), and is configured to control the voltage across the load resistor (6).

(9) is impressed when current flows and is connected to the circuit breaking contact (2a).
), (2b), (101 is a thyristor, this thyristor 00) connects the trip coil (9), anode and cathode in series, and connects the electric circuit (3).
a).

(3b) When a gate current is passed between the gate and cathode of the five thyristors θ0) connected between the trip coils (3b), the thyristor OQ is turned on and current can be passed through the trip coil (9). aυ is the resistance that limits the current flowing through it, and 0 is this resistance a1)
A rectifier diode is connected in series to the rectifier diode, (+3) is a capacitor, and a resistance Ql is connected between the 5 electric circuits (3a) and (3b).
The anode and cathode of diode 0 and the capacitor 0 are connected in series to obtain a smoothed voltage across the capacitor o9. (+4) is a reference point provided for the convenience of the following explanation, and this reference point is the electric line (
3b) and is used as the reference for each voltage unless otherwise specified.

051 is a stabilized power supply circuit that inputs the voltage across the capacitor (13) and outputs a stabilized DC voltage VCC;
Q is a threshold generation circuit, and this threshold generation circuit (16
) are the reference voltage generation circuit (16a) and R1111, respectively.
) + R16e resistor (16b), (16
e). This reference voltage generation circuit (16a) outputs a reference voltage vR, and its output end is connected to one end of a resistor (6), and the output end of the output terminal is connected to one end of a resistor (6).
, (16c) are connected between the output end of the reference voltage generation circuit (16a) and the reference point (14).

(17) connects its input terminal (+) to a resistor (16b), (16
Connect to the connection point c) and set the voltage VR + VTH as the input voltage, and connect the input terminal (→ to the resistor (6) and set the voltage at the other end of the resistor (6) with the reference voltage VR as the reference, that is, the earth leakage signal voltage This is a voltage comparator circuit that takes the input voltage as the voltage VR+VLK, where VTI is a threshold value and is expressed by a linear equation.

The output of this voltage comparator circuit a7) is in the ``H'' state when the earth leakage signal voltage VLK is lower than the threshold value VTR, and is in the 1L'' state when it is in the ``H'' state.

0υ is a current switching circuit that takes the output of this voltage comparison circuit as an input, and this current switching circuit (17) has an input state of −byn.
'When the current I flows out to the output, the input state is 'L''
When , the structure is such that a current, a larger current I, flows into the output. (191 is a capacitor with a value of C4, and this capacitor α1 is current switching circuit 08)
is connected between the output end of and the reference point (+41), and the current ■,
It is configured to be charged at the current source and discharged at the current source. (2() is a latch circuit that receives and stores the output of the current switching circuit 03, and its input terminal is connected to the output terminal of the current switching circuit (1), and the input voltage is the launch-on voltage ■TL
(■) The output that was in the 'L' state when the level rose to '
It is configured to set it to H' and maintain that state. Q
υ is a thyristor drive circuit which receives the output of the latch circuit (a) as an input, and its output end is connected to the gate of thyristor 0ω when the input state is 1H'.

At the output, current flows out, and when 1L', current flows out. is configured to allow inflow of

The operation of the earth leakage detection device configured as described above will be explained with reference to FIG. 2.

First, when a leakage current flows through the electrical circuits (3m) and (3b),
Detected by the zero-phase current transformer (5), the leakage signal voltage MA
K occurs. As shown in Fig. 2 (, ), when this voltage YLK becomes lower than the threshold value V'rH, the output of the voltage comparator circuit (17) becomes 1H'', which is before the input state of the stain current switching circuit o barrel. At 1H', a person charges the capacitor 01 with the current 1 as shown in Figure 2 (1).Then, the voltage vc1 across the capacitor (II) increases as shown in Figure 2 (c
), when the lateon voltage VTL is reached, the output state B of the launch circuit changes to % as shown in FIG. 2(d).
Without Ht, Cyrisk drive circuit (current I3 from 2υ
flows out, thyristor 001 turns on, the trip coil (9) is moved, and the circuit interrupting contact (4a),
(4b) is tripped to cut off the electrical circuit.

Then, the current switching circuit (input condition (input condition) of 1) A
As shown in Fig. 2(b), after changing from ``L'' to ``H'', the output state (output condition) B of the latch circuit (a)
As shown in FIG. 2(d), the time interval jLK+ at which the transition from 'L' to 'H' occurs is expressed by the following equation.

Therefore, the leakage signal voltage "LK" is the threshold value v'r■r
The leakage current whose lower period corresponds to the time interval tLKl is the sensitivity current of this earth leakage detection circuit.

Since the conventional earth leakage detection device operates as described above, it has the disadvantage that even if a single large electrical surge or noise is superimposed on the earth leakage signal voltage vLK, it will be erroneously detected and the electrical circuit will be cut off.

In view of the above points, the present invention has been made in order to solve such problems and eliminate such drawbacks, and its purpose is to provide an earth leakage detection device that can reduce malfunctions due to surges, noise, etc. It is in.

In order to achieve such an object, the present invention inputs an earth leakage signal obtained from the secondary output of a zero-phase current transformer provided for detecting earth leakage in an electric circuit, and has an amplitude value that is equal to or less than a predetermined threshold value. The output signal is sent by detecting that at least two cycles of an earth leakage signal whose duration exceeds a predetermined first set time has occurred within a predetermined second set time.

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 3 is a configuration diagram showing an embodiment of the earth leakage detection device according to the present invention.

In Fig. 3, the same reference numerals as in Fig. 1 indicate corresponding parts, and 6D is a first current switching circuit having an X input and an The X input is the output of the voltage comparator circuit (17). The first current switching circuit 6D outputs a current of I when both the X input and the X input are in the 1H'' state.
, and when the input condition is 'L# state, a current is generated, and a larger current is generated.

is configured to allow inflow of 6 is a capacitor having a value of C52, which is connected between the output terminal of the first current switching circuit 61) and the reference point α4), and is configured to be charged by the current ■ and discharged by the current I6. has been done.

6311 is a first voltage discrimination circuit that receives the output of the first current switching circuit 6p, and includes a voltage comparison circuit (53a) and diodes (53b), (53c), (53d), and (53f).
), (53g), a constant current source (53e), and a transistor (53h). and,
The input end (+) of this voltage comparison circuit (53a) is connected to the output end of the first current switching circuit 61), and the input end (-) is connected to the output end of the stabilized power supply circuit (output end of 151 and reference point 04). A constant current source (53e) and a diode (53
f), (53g) constant current source (53e) and diode (
This diode (53f) is connected to the connection point of the diode (53f).
) and the diode (53g) are connected to the transistor (53g).
This transistor (53h) is connected to the collector of this transistor (53h).
The emitter of h) is connected to the reference point αa, and the pace is connected to the output end of the voltage comparison circuit (53a). Also,
The input terminal (+) of the voltage comparator circuit (53a) and the reference point (14
), there are diodes (53b), (53c), (5
3d) are connected in series.

The first voltage discrimination circuit 5□□□ is constituted by, for example, a Schmitt trigger circuit, and the voltage comparison circuit (
When the input voltage applied to the input terminal (+) of the voltage comparator circuit (53a) is lower than the negative threshold voltage VT-+, the voltage comparator circuit (53a)
The output of transistor (53) is in the "L" state.
h) is off. In addition, this voltage comparison circuit (53a)
The input terminal (-) of the diode (53f) and (53g) has a forward voltage of 2 VF (V) when the forward voltage of each diode (53f) and (53g) is vF, and a positive threshold voltage of VT++, which is larger than this value. When the input voltage is 1, the output of the voltage comparator circuit (53a) is 1.
In H'' state, the transistor (53h)
turns on, and if the voltage between the collector and emitter of the transistor (53h) at this time is sufficiently small, the voltage comparator circuit (
The voltage at the inverting input terminal (-) of the diode (53a)
f) becomes the forward direction voltage VF (V), and the negative direction threshold V
T.

It is configured so that.

64) is a second current switching circuit that also has an input and an X input,
Its X input receives the coincidence output of an AND gate, which will be described later, and its Y input receives the output of the first voltage discrimination circuit (53). This second current switching circuit 64) also causes the current to flow into the output when the input is 'L' and the Y input is 'H', and flows the current I8 under other input conditions. It is composed of 6 is a capacitor having a value of C55, which is connected between the output terminal of the second current switching circuit 64) and the reference point αa.

66) is a second voltage discrimination circuit that receives the output of the second current switching circuit 64), and includes a voltage comparison circuit (56a) and diodes (56b), (56e), (56d), and (56f).
), (56g), a constant current source (56e), and a transistor (56h). and,
The non-inverting input terminal (+) of this voltage comparison circuit (56a) is connected to the output terminal of the second current switching circuit 64), and the inverting input terminal (-) is connected to the output terminal of the stabilized power supply circuit (151) and the reference point. α
A constant current source (56e) and a diode (56f) are connected in series between the constant current source (56e) and the diode (56f). The connection point of 56g) is connected to the collector of the transistor (56h), the emitter of this transistor (56h) is connected to the reference point (14),
The base is connected to the output end of the voltage comparison circuit (56a). Also, the non-inverting input terminal (
+) and the reference point (14) is a diode (56b).
, (56c), and (56d) are connected in series. The second voltage discrimination circuit (2) is constituted by, for example, a Schmint trigger circuit, has the same configuration and operation as the first voltage discrimination circuit al, and has a voltage comparison circuit (2).
56a) corresponds to the voltage comparison circuit (56a), and diodes (56b) to (56d), (56f), (56
g) are diodes (53b) to (s3a), (s3t
), (s3g), the constant current source (56e) is connected to the constant current source (56e).
3e), the transistor (56h) is the transistor (56h)
3h) respectively, and the input voltage ■cL2.
Positive threshold voltage V'r+2+negative threshold voltage V
It has the characteristics of D-2.

t57) is a flip-flop whose reset input terminal R
is connected to the output of the second voltage discrimination circuit (156), that is, the output terminal of the voltage comparison circuit (56a), and the trigger input terminal T is connected to the output of the first voltage comparison circuit (Zheng), that is, the voltage comparison circuit (53m). ) is connected to the output terminal of 5 when the input applied to the reset input terminal R is 'H'.

It is a positive edge trigger type that inverts the states of the Q output and Q output when the input applied to the trigger input terminal T changes from 1L' to ``H''. The six barrels are configured to be supplied to the voltage comparison circuit (56a) in the second voltage discrimination circuit 6e.
) and the four outputs of the flip-flop G7), and its output terminal is configured to be supplied to the X input of the second current switching circuit 6a.

Next, the operation of the embodiment shown in FIG. 3 will be explained with reference to FIG. 4. This figure 4 is an explanatory diagram of the operation, (,) shows the earth leakage signal voltage VLK, (b) shows the output state A of the voltage comparator circuit (17), and (c) shows both ends of the capacitor 6. Voltage (V1452), (a) is the output state C1 of the first voltage discrimination circuit c53) (el is the capacitor 65)
) indicates the output state of the second voltage discrimination circuit +561, and (gl indicates the output state E of the flip-flop 5?).

First, when a leakage current flows through the electrical circuits (3a) and (3b), it is detected by the zero-phase current transformer (5), and a leakage signal as shown in FIG. A voltage 'LK is generated. During the period when this leakage signal voltage V□, K is lower than the threshold voltage VTR, the voltage comparison circuit (
17), the output state A is %H'' as shown in Fig. 4(b).
Since the X input of the first current switching circuit 61) is 1H', the current flows out from the output of the first current switching circuit 51 and charges the capacitor (5).
The voltage across this capacitor 6 (V (4J) is shown in Figure 4 (C
) as shown in Clangmi pressure VCLI'! Although it is charged with.

At the end of the charging period, the capacitor 6 is discharged by the current flow.

On the other hand, the output state C of the first voltage discrimination circuit (to) is, as shown in FIG. 4(d), the voltage across the capacitor 2 while the capacitor 6 is being charged. , 2 becomes higher than the positive threshold voltage vT, , until the voltage across the capacitor 62 during discharge becomes lower than the negative threshold voltage VT-+. Become.

(See Figure 4 (e) l (d)) Then, the output state C of the first voltage comparator circuit is as shown in Figure 4 (
When the current becomes 'H' as shown in d), the first current switching circuit (54) flows out the current because the X input is 'L#' and rapidly charges the capacitor (59). As shown in FIG. 4(e), when the voltage across the six capacitors vC, . . . reaches the positive threshold voltage vT, . . . of the second voltage discrimination circuit (a), this second voltage The output state of the discrimination circuit is not 'H' as shown in Fig. 4 (fl).

Along with this, and gate l! The output of iQ becomes ``H'', and the output of the second current switching circuit 5 is also switched to current I8, causing the six capacitors to slowly discharge.During this discharge, the capacitor 65) ), the leakage current is detected before reaching the negative threshold voltage VT-2 of the second voltage discrimination circuit (a), and the first voltage discrimination circuit 63
), the output state C of ′■(′
Then, in the flip-flop 7), since the recent human power R is 1H'', the Q and Q output states are reversed, and the Q output state E becomes 'H'' as shown in Figure 4(g).
'', the thyristor drive circuit Cυ outputs a current, turns on the thyristor (10), touches the trip coil (9), and connects the circuit breaking contacts (4a) and (4b).
By tripping the electric circuits (3a) and (3b), the AC voltage source (
1).

When the state E of the Q output of the flipflop 5η becomes 1H' as shown in FIG. 4(g), the first current switching circuit 51) switches the output current from the current I to the current I6, The capacitor 621 is discharged, and the output state C of the first voltage discriminator circuit 6 is changed to '''L as shown in Figure 4 (dl).
Return to '. During this period, the output state C is 11 (' shown in FIG. 4(d), the capacitor 55) is as shown in FIG. 4(e).
As shown in Figure 4(d), it is charged by the input clamp voltage VCL2t of the second Schmitt trigger discharge circuit 6e, and discharged by the current generator at the same time as the output state C becomes ``L'' as shown in Figure 4(d). Then, when the voltage VC55 of the six capacitors shown in FIG. 4(e) becomes less than the negative threshold voltage vT- of the second voltage discrimination circuit (a),
The output state C of the first voltage discrimination circuit 5 returns to 1L' as shown in FIG. 4(d), the flip-flop 6η is reset, and the output state E of the Q output is changed to FIG. 4(g). As shown, return to ``L'' and turn on the thyristor drive circuit (2
+) output current as current 1. From the current I,. Switch to
By stopping the supply of gate current to the thyristor α0), the period during which the gate current is supplied is set to a time width tow determined by the following equation (3).

And the sensitivity current is the same as the conventional circuit.

The electric circuits (3a) and (3b) are cut off from the AC voltage source (1) only when the first cycle of the leakage current is detected and the next cycle is detected within the time width tDET determined by the following equation (4). Ru.

In this way, the output signal has a predetermined time width.

As explained above, according to the present invention, the device operates upon detecting that at least two cycles of leakage current greater than the sensitivity current occur within a predetermined time.
Since malfunctions caused by surges and noise can be reduced, the practical effects are extremely significant.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of a conventional earth leakage detection device, FIG. 2 is an explanatory diagram of the operation of FIG. The figure is an explanatory diagram of the operation of FIG. 3. (5)...Zero-phase current transformer, 00)...Thyristor, (I■...Capacitor, (1!51...Stabilized power supply circuit, (le...) Threshold generation circuit, (lη
... Voltage comparator circuit, 0I) ... Thyristor drive circuit, 61), ...-Current switching circuit, ■,
tss...Capacitor, (to), C(1)...
Voltage discrimination circuit, 6η...flip-flop, e5e
...Gate circuit. Agent Masuo Oiwa T, Continued Sleeve iE 9F (voluntary) 59 3 21 Showa year rl 0 f1゛Accepted J1 Director-General 1, Indication of the incident Special) Tosho 58-93632 No. 2,
Title of the invention: Earth leakage detection device (f's, j3) Relationship with the case of the person making the amendment: Patent applicant fl-Place: Chiyo 1.11-ku, Kunouchi 2 Ii, Tokyo
2127fi'; 3 Name (601,) Mitsubishi Electric Corporation Representative Kata 111 Jin Hachibe 4, Agent address 2-1 Marunouchi, Chiyoda-ku, Higashi JK”+
2 sounds: 3';',. Pack 6 of the detailed explanation of the invention in the specification, and amend the content of the amendment. (2) "Control" on page 3, line 10 of the same book is amended to "restriction." (Correct "leakage" in line 11 of page 6 of the 31st lecture to "leakage of electricity". (4) r (4a), (4b) in line 2 of page 7 of the same book.
)j to [(2a). (2b) Correct as J. (5) On page 8, line 19 of the same book, add the sentence ``any input'' after ``flow,''. (6) Delete the sentence "For example, it consists of..." in lines 3 and 4 of page 10 of the same book. (7) Delete "match" in line 20 of the same page of the same ministry. (8) "Non-reversal" in the 14th section of page 11 of the same book is deleted. (9) Delete "1-Reverse" on line 15 of the same page of the same book. 00) Delete "non-inversion" from the 3rd and 4th negative lines of No. 12 of the same ministry. (11) In lines 6 and 7 of the same page of the same book, delete the sentence ``For example, it consists of...''. Oz Same book, same page, line 9 TJ (56a) J to r
(53a) Correct as J. (1) Correct "RI" in the 17th line of the same book to "R". 04) Correct rRl in the 1st line of the 13th page of the same book to rRJ. (151 Correct rXJ in the 9th line of the same page of the same book to rXJ. (16) Correct “1st” in the 1st line of the 15th page of the same book to “2nd”. (17) In the 2nd line of the same page of the same book Correct I'll to [X-1. 0 Kyu Correct R-1 to "1-R" in line 16 of the same page of the same book. ■ 1 (4a), (4b) of line 20 of the same page of the same ministry
J to r (2a). (2b) Correct as J. QO) Change the "Schmitt trigger" in line 9 of page 16 of the same book to "
"voltage discrimination". (21) Same book, same page, lines 14-15 [1st...4th
The output state of the second voltage discriminator circuit c16) is corrected as shown in FIG. 4(f). that's all

Claims (1)

[Claims] 2 of the zero-phase current transformer installed to detect leakage in the electrical circuit
A threshold generation circuit that inputs the leakage signal obtained from the next output and generates a threshold; a voltage comparison circuit that compares the output voltage of this threshold generation circuit with a reference voltage; a first current switching circuit that switches the input and output current; and a current switching circuit that is connected between the output end of the first current switching circuit and a reference point that serves as a voltage reference, and that is responsive to the input conditions of the first current switching circuit. a first voltage discriminator circuit that uses the output of the first current switching circuit as an input, and a second voltage discriminator circuit that uses the output of the first voltage discriminator circuit as an input and switches the output current. current switching circuit and this second
The second current switching circuit is connected between the current switching circuit and the reference point.
a second capacitor that charges and discharges according to input conditions of the current switching circuit; a second voltage discrimination circuit that receives the output of the second current switching circuit; and an output of the first voltage discrimination circuit. a flip-flop that is triggered by and reset by the output of the second voltage discrimination circuit and supplies the voltage to the input terminal of the first current switching circuit; a gate circuit for supplying an AND with the output of the circuit to the input terminal of the second current switching circuit; and means for cutting off the AC voltage source supplied to the electric circuit based on the Q output of the flip-flop. and a stabilized power supply circuit for supplying a stabilized DC voltage to each of the above-mentioned circuits, the period when the amplitude value exceeds a predetermined threshold value set by the threshold generation circuit is a predetermined period. If the earth leakage signal exceeds the first set time, the
At least 2 within the set time? 1. An earth leakage detection device characterized in that it detects the occurrence of a cycle and sends out a signal.