JPS631808B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Application) The present invention is applicable to AC single-phase three-wire distribution lines or AC three-phase four-wire
The present invention relates to a neutral wire missing detection device that outputs a signal when a missing wire such as a disconnection or loosening occurs in a neutral wire of a power distribution line having a neutral wire such as a wire type power distribution line.

(Problems with the Prior Art) In general, this type of neutral line missing detection device is configured as shown in FIG.
A series circuit of impedance elements A and B with equal values is connected between the impedance elements A and B.
The difference voltage between the virtual neutral point C, which is the connection point of B, and the neutral wire N is input to the comparator circuit D, and if a disconnection or looseness occurs at one point A of the neutral wire N, the load H, If the balance between F and F is poor, a voltage difference will occur between the virtual neutral point C and the neutral wire N, and this voltage difference will be input to the comparator circuit D, which will output a signal to the timer circuit G, which will set a certain time limit on this output signal. Then, a signal is outputted from the time limit circuit G to the amplifier circuit H, and this output signal is amplified by the amplifier circuit H, and the switching circuit RI is operated to operate the electromagnetic tripping device NU, and the voltage lines L1 and L2 are
The circuit contacts L and O of the neutral wire N and the circuit contact W of the neutral wire N were opened.

Therefore, if it is as described above, the voltage lines L1,
When either one of L2, for example voltage line L1, is broken or loosened, the voltage between voltage line L2 and neutral line N is connected to impedance element A, impedance element B, and load E in series. When applied to the circuit, a voltage difference between the virtual neutral point C and the neutral wire N is generated, opening the circuit contacts L, O, and W.
It operates even though no abnormal voltage is applied to the load. For example, at a temporary construction site, AC voltage is applied only between one of the voltage lines L1, L2 and the neutral line N, and the load is connected during this period. Since it cannot be connected and used, when it is installed in a circuit breaker such as a circuit breaker or circuit breaker due to electrical leakage, disconnection, or overcurrent, the voltage line is L1,
There was a problem in that voltage had to be applied to both L2 and the neutral wire N. And this distribution line L1,L
At the beginning of applying voltage to 2 and N, voltage lines L1 and L2
There was also a problem that the device would operate if there was a delay in the application of either one of the voltage lines.

Furthermore, when a one-off electrical surge occurs on the distribution lines L1, L2, N, such as a lightning surge or a switching surge when opening/closing a device contact, the time limit circuit 5 determines whether the surge continues for a certain period of time to reduce malfunctions. Therefore, the longer this certain period of time, the fewer malfunctions occur, but the neutral wire N
It was undesirable that there was a delay in operation when the function was missing.

(Object of the present invention) In view of the above-mentioned points, the present invention eliminates the need to output a signal when at least one of the voltage lines is missing, and further eliminates the need to output a signal only between at least one of the voltage lines and the neutral line. It eliminates the need to output a signal even when an AC voltage is applied to the distribution line and a load is connected, and it also outputs a signal when the application of voltage to at least one of the voltage lines is delayed in the initial stage of applying voltage to the distribution line. This makes it possible to output a signal even when the neutral wire is missing, and also prevents malfunctions when a one-off electrical surge occurs in the distribution line, such as a lightning surge or a surge when opening/closing a device contact. The purpose of this is to reduce the delay in operation when the neutral wire is missing.

The present invention will be explained below based on the circuit block diagram shown in FIG. 1 and the time operation characteristic diagrams shown in FIGS.
is an AC single-phase three-wire distribution line, and the voltages V1 and V2 of the voltage lines L1 and L2 with respect to the neutral line N are applied with equal AC voltages, respectively, and the voltage between the voltage lines L1 and L2 is twice the AC voltage. Voltage is applied.
1a and 1b are a pair of rectifiers, which rectify the voltages of voltage lines L1 and L2 with respect to the neutral line N in the same direction and output them to one point A. Reference numeral 2 denotes a reference voltage setting circuit, which sets the reference voltage to a voltage higher than the maximum voltage of the output voltage to the neutral wire N at one point A during normal operation. 3 is a comparison circuit which inputs the output voltage of one point A with respect to the neutral line N, compares this output voltage with the reference voltage of the reference voltage setting circuit 2, and outputs a signal only when the output voltage is higher than this reference voltage. Output. A clip circuit 4 clips the input voltage of the comparison circuit 3 to a voltage higher than the reference voltage of the reference voltage setting circuit 2. Reference numeral 5 denotes a time limit circuit which outputs a signal when the output signal of the comparator circuit 3 continues for a certain period of time. 6 is an amplifier circuit, 7 is a switching circuit, and 8 is an electromagnetic tripping device, which amplifies the output of the timer circuit 5 in the amplifier circuit 6.
In response to the output signal, the switching circuit 7 performs a switching operation to operate the electromagnetic tripping device 8. Reference numerals 9a, 9b, and 9c are electrical circuit contacts provided on the voltage lines L1, L2 and the neutral line N, which are tripped from a closed state to an open state by an electromagnetic tripping device 8. 10a, 10
b is a load connected between the voltage line L1 and the neutral line N, and between the voltage line L2 and the neutral line N.

In addition, Fig. 2 is a time behavior characteristic diagram of the output voltage with respect to the neutral line N at one point A under normal conditions, and Fig. 3 is a graph of the output voltage at the neutral line N.
One point A when there is a disconnection or looseness at point B.
A time behavior characteristic diagram of the output voltage with respect to the neutral line N,
Fig. 4 is a time behavior characteristic diagram of the output voltage with respect to the neutral line N of one point A when one of the voltage lines L1 and L2, for example, the voltage line L1 is missing, and Fig. A is a state in which a one-off electrical surge such as a lightning surge or a switching surge when a device contacts is opened/closed, and a is the voltage line L with respect to the neutral line N.
1 and L2, and b shows a time behavior characteristic diagram of the output voltage at one point A with respect to the neutral line N. In the figure, SV is the reference voltage of the reference voltage setting circuit 2.

To explain this operating state based on FIG. 1, under normal conditions, the voltages of the voltage lines L1, L2 and the neutral line N are approximately equal, and the maximum output voltage with respect to the neutral line N at one point A. is lower than the reference voltage SV of the reference voltage setting circuit 2 as shown in FIG.

Furthermore, if a disconnection occurs at point B of the neutral wire N than in normal conditions and the loads 10a and 10b are unbalanced, the balance between the AC voltages V1 and V2 of the voltage lines L1 and L2 with respect to the neutral wire will be lost, and the voltage at point A will be lost. The output voltage to the neutral line N is alternately high and low every half cycle, and when this high voltage exceeds the reference voltage SV of the reference voltage setting circuit 2 as shown in FIG. A time limit circuit 5 determines whether this output signal continues for a certain period of time, and if this output signal continues for a certain period of time, an output signal is output, and the output signal of this time limit circuit 5 is amplified by an amplifier circuit 6. The switching circuit 7 is operated to operate the electromagnetic tripping device 8, and the circuit contacts 9a, 9 are operated.
b, 9c are opened and the distribution lines L1, L2, N are cut off.

However, the voltage lines L1 and L are lower than the normal state mentioned above.
2, for example, when the voltage line L1 is missing, only the voltage V2 is applied between the voltage line L2 and the neutral line N, and is supplied to the load 10b, and the output voltage with respect to the neutral line N at one point A. As shown in FIG. 4, there is a half-wave pulsating current lower than the reference voltage SV of the reference voltage generating circuit 2, and the comparator circuit 3 does not output an output signal and the circuit contacts 9a, 9b, and 9c continue to be closed. That is, the voltages V1, V of the voltage lines L1, L2 with respect to the neutral line N
Even if either one of 2 is not applied, the comparator circuit 3
does not output an output signal, so the voltage lines L1 and L2
This eliminates the need to output a signal when either one of the voltage lines L1 or L2 is missing, and in addition, AC voltage is applied only between either voltage line L1 or L2 and the neutral line N, and the signal is output even if a load is connected. In addition, it eliminates the need to output a signal when the application of voltage to one of the voltage lines L1, L2 is delayed in the initial stage of applying voltage to the distribution lines L1, L2, and N. N
It is possible to make it possible to output a signal when a signal is missing.

However, from the normal state mentioned above, the distribution lines L1 and L
2. A one-off electrical surge, such as a lightning surge or a surge when opening/closing a device contact, occurs in the neutral line N.
When an electrical surge is superimposed on the voltage of one of the voltage lines L1 and L2 as shown in FIG. The signal is input to the reference voltage setting circuit 2 and becomes higher than the reference voltage SV of the reference voltage setting circuit 2, and a signal is output.
Since the input voltage of the time limit circuit 5 is clipped at a voltage higher than the reference voltage SV of the reference voltage setting circuit 2 by the clip circuit 4 to prevent a voltage higher than this voltage from being input to the comparator circuit 3, the fixed time of the time limit circuit 5 is
Since the time is not shorter than that without using the circuit, malfunctions due to electrical surges can be reduced in the time limit circuit 5.

Further, drawing No. 6 shows the present invention as an embodiment.
To explain based on the specific circuit diagram in the figure, voltage lines L1 and L2 and one point A are connected to each other.
Forward rectifiers 2a and 2b are connected to the 1 and L2 sides, voltage dividing resistors R1 and R2 of the comparator circuit 3 are connected between this point A and the neutral line N, and the reference voltage setting circuit 2 is connected to this voltage dividing point. The gate of the thyristor SCR, which also serves as the amplifier circuit 6 and the switching circuit 7, is connected through the constant voltage diode ZD1, and the resistor R3 and capacitor C1 of the time limit circuit 5 are connected in parallel between this gate and one point A. The cathode of the thyristor SCR is connected to one point A, and forward rectifiers D1 and D2 are connected between the anode of the thyristor SCR and the voltage lines L1 and L2 on the anode side of each other via the trip coil TC of the electromagnetic tripping device 8. Furthermore, a constant voltage diode ZD2 of the clip circuit 4 is connected between the voltage dividing points of the voltage dividing resistors R1 and R2 and one point A.
A disconnection occurs at one point B of the neutral wire N, and the loads 10a, 10
If b is unbalanced, the balance between the AC voltages V1 and V2 with respect to the neutral line N of voltage lines L1 and L2 will be lost, and the output voltage with respect to the neutral line N of one point A will change between high and low voltages every half cycle. The voltage is alternately outputted and applied to the voltage dividing resistors R1 and R2, and when the voltage at one point A of the voltage dividing point exceeds the reference voltage of the constant voltage diode ZD1 and continues for a certain period of time in the time limit circuit 5, the thyristor SCR performs a switching operation. The rectifier D is turned on from one of the voltage lines L1 and L2.
1. Current flows to the other voltage line L1, L2 through one side of D2, the trip coil TC, the thyristor SCR, and the other side of the rectifiers 2a, 2b, and the trip coil TC is moved to close the circuit contacts 9a, 9b, 9c. .

Moreover, when one of the voltage lines L1 and L2, for example voltage line L1, is missing, only the voltage V2 is applied between the voltage line L2 and the neutral line N, and is supplied to the load 10b. The output voltage to the normal conductor N becomes a half-wave pulsating current and is applied to the voltage dividing resistors R1 and R2. The SCR does not perform any switching operation and remains off, and the circuit contacts 9a, 9b, and 9c continue to be open.

Furthermore, if a single electrical surge occurs in the distribution lines L1, L2, and N, and the output voltage at one point A to the neutral line N becomes a high voltage due to the superimposition of the electrical surge,
The voltage with respect to one point A of the voltage dividing point of the voltage dividing resistors R1 and R2 exceeds the reference voltage of the voltage regulator diode ZD1 and is clipped to the constant voltage of the voltage regulator diode ZD2, and this clipped voltage is applied to the voltage regulator diode. Since the continuation of a certain period of time is determined by resistor R3 and capacitor C1 via ZD1, this certain period of time is not shortened compared to a voltage that is not clipped, and malfunctions can be reduced.

Further, the voltage line L
1, voltage dividing resistors R4, R between L2 and the neutral line, respectively.
5, R6, R7 are connected and this voltage dividing resistor R4, R5
and the respective voltage dividing points of voltage dividing resistors R6 and R7 and one point A
A forward rectifier 2a, 2b is connected between the point A and the neutral wire N, and a series circuit of a resistor R8, a constant voltage diode ZD1 of the reference voltage setting circuit 2, and a resistor R9 is connected between this point A and the neutral wire N. A series circuit consisting of a constant voltage diode ZD3 on the side of point A and a resistor R10 on the side of neutral line N is connected between this point A and the neutral wire N. A constant voltage diode ZD3 and a resistor R1 are connected between the
Transistor whose base is connected to the connection point with 0
A clip circuit 4 is constructed by connecting the collector and emitter of TR1 via a collector resistor on the A side, and the base of the transistor TR2 is connected to the connection point of the series circuit of the constant voltage diode ZD1 and the resistor R9. Connect to one point A and connect this collector to a photocoupler light emitting diode LED.
Furthermore, the emitter of the phototransistor TR3 for light reception of this photocoupler is connected to the gate of the thyristor SCR of the switching circuit 7, and a capacitor C2 and a resistor R12 are connected between the gate and cathode of the thyristor SCR. are connected in parallel, and the input of the diode bridge DB is connected between the voltage lines L1 and L2.
The anode of the thyristor SCR is connected to one of the outputs of the DB via the trip coil TC of the electromagnetic trip device 8, and the cathode of this thyristor SCR is connected to the other output of the diode bridge DB. The cathode of a constant voltage diode ZD4 is connected to one side via a resistor R13, the anode of this constant voltage diode ZD4 is connected to the other output of the diode bridge DB, and the cathode of this constant voltage diode ZD4 and the collector of the phototransistor TR3 are A resistor R13 is connected between them. Note that C3 is a capacitor connected in parallel to resistor R9, and this capacitor C3, transistor TR2, light emitting diode LED, phototransistor TR3, capacitor C2, and resistor R14 constitute an amplifier circuit 6 via a timer circuit 5. There is.

To explain this operating state, if a disconnection occurs at point B of the neutral wire N and the load 10a, 10b is unbalanced, the balance of the AC voltages V1, V2 of the voltage lines L1, L2 with respect to the neutral wire N becomes unbalanced. The output voltage with respect to the neutral wire N of the collapse point A is periodically outputted as a high voltage and a low voltage alternately, and when this high voltage exceeds the reference voltage of the voltage regulator diode ZD1, the resistor R9 and the voltage regulator diode ZD1 are connected in series. A current flows through the circuit and a voltage is output to this resistor R9, charging the capacitor C3, turning on the transistor TR2, causing the light emitting diode LED to emit light, and the phototransistor TR3 receiving this light, turning on the resistor R13 and the resistor R14. and phototransistor
A voltage is applied to the gate of the thyristor SCR via TR3. Furthermore, this voltage is applied for a certain period of time by capacitor C2 and resistor R12 to switch the thyristor SCR and turn it on, causing current to flow from one side of the diode bridge DB to the other via the trip coil TC and the thyristor SCR. The trip coil TC is moved and the circuit contact 9a,
9b and 9c are opened. Incidentally, a fixed time period is given to the capacitor C3 and the resistor R9, similarly to the capacitor C2 and the resistor R12.

Moreover, when one of the voltage lines L1 and L2, for example voltage line L1, is missing, only the voltage V2 is applied between the voltage line L2 and the neutral line N, and is supplied to the load 10b. The output voltage to the normal conductor N becomes a pulsating current lower than the reference voltage of the constant voltage diode ZD1, and no voltage is generated across the resistor R9, and the thyristor SCR does not perform a switching operation and continues to be off, and the circuit contacts 9a, 9b, and 9c are closed. Continue the pole.

Furthermore, when a single electrical surge occurs in the distribution lines L1, L2, and N, and the output voltage at one point A relative to the neutral wire N becomes a high voltage due to the superposition of the electrical surge, the series circuit of the resistor R9 and the voltage regulator diode ZD1 Current flows through the constant voltage diode ZD3 and the resistor R
Current flows through the series circuit with 10 and a voltage is generated across the resistor R10, turning on the transistor TR1 and clipping it to the constant voltage of the constant voltage diode ZD3. Since the continuation of a certain period of time is determined by the resistor R9 and the capacitor C3, this certain period of time is not shortened compared to a voltage that is not clipped, and malfunctions can be reduced.

Further, although the above embodiment uses an AC single-phase three-wire distribution line, an AC three-phase four-wire distribution line may also be used, and the neutral line N
There is no limitation as long as it is a distribution line owned by

(Effect) As described above, the present invention can reduce the voltage of a plurality of voltage lines with respect to the neutral line of a distribution line such as an AC single-phase three-wire distribution line or an AC three-phase four-wire distribution line. A reference voltage setting circuit standard in which the voltage is rectified in the same direction by a rectifier and output to one point, and the output voltage for the neutral line of this point is input to a comparator circuit and set to a voltage higher than the normal voltage of this output voltage. Since a signal is output only when the output voltage exceeds the voltage, it is no longer necessary to output a signal when one of the voltage lines is missing, and furthermore, an alternating current is generated only between one of the voltage lines and the neutral line. It eliminates the need to output a signal even when voltage is applied and a load is connected, but it also outputs a signal when there is a delay in the application of voltage to one of the voltage lines at the beginning of applying voltage to the distribution line. Without it, a signal can be output when the neutral wire is missing. In addition, the input voltage of the comparator circuit is clipped at a voltage higher than the reference voltage of the reference voltage setting circuit using a clip circuit, and when the output signal of the comparator circuit continues for a certain period of time, a signal is output by a time limit circuit. In contrast, when a one-off electrical surge occurs on the distribution line, such as a lightning surge or a surge when opening/closing the contacts of equipment, the fixed time of the timer circuit does not shorten, so malfunctions can be reduced, and the neutral line This has the effect of reducing the delay in operation when the data is missing.

[Brief explanation of the drawing]

Figures 1 to 5 show an embodiment of the neutral line missing detection device of the present invention, where Figure 1 is a circuit block diagram and Figure 2 is a normal state of the output voltage with respect to the neutral line N at one point A. Figure 3 is a diagram of the time behavior characteristics of the output voltage with respect to the neutral line N of one point A when the neutral line is missing, and Figure 4 is a diagram of the voltage line of the output voltage with respect to the neutral line N of one point A. Figure 5 shows the time behavior characteristic diagram when one of the voltage lines is missing, where electrical noise is generated in the distribution line, and a is the voltage time with respect to the neutral line N of either voltage line L1 or L2. Fig. 6 is a specific circuit diagram of an embodiment of the neutral line missing detection device of the present invention; A specific circuit diagram of another embodiment of the neutral line missing detection device according to the invention, FIG. 8 shows a circuit block diagram of a conventional neutral line missing detection device. L1, L2... Voltage line, N... Neutral line, 1a,
1b... Rectifier, A... One point, 2... Reference voltage setting circuit, 3... Comparison circuit, 4... Clip circuit,
5... Time limit circuit, 6... Amplifying circuit, 7... Switching circuit, 8... Electromagnetic tripping device, 9a, 9
b, 9c...Circuit contact, 10a, 10b...Load, SV...Reference voltage, R1 to R14...Resistance,
C1 to C3... Capacitor, D1, D2... Rectifier, ZD1 to ZD4... Constant voltage diode,
TR1 and TR2...transistor, TR3...phototransistor, SCR...thyristor, TC...
Trip coil, LED...light emitting diode, DB
...Diode bridge.

Claims (1)

[Claims] 1 A plurality of AC single-phase three-wire distribution lines or AC three-phase four-wire distribution lines that rectify the voltage of the voltage line with respect to the neutral line in the same direction and output it to one point. A comparison that outputs a signal only when the output voltage exceeds the reference voltage of a reference voltage setting circuit that inputs the output voltage of the rectifier and the neutral wire at this one point and sets the output voltage to a higher voltage than the normal voltage. a time limit circuit that outputs a signal when the output signal of the comparison circuit continues for a certain period of time; and a clip circuit that clips the input voltage of the comparison circuit to a voltage higher than the reference voltage of the reference voltage setting circuit. Neutral line missing detection device.