阅读说明：本技术 触点部异常监视装置及使用触点部异常监视装置的电路断路器 (Contact part abnormality monitoring device and circuit breaker using the same ) 是由 原田幸树 野村敏光 泷川雄介 近井圣崇 于 2019-03-13 设计创作，主要内容包括：本发明提供一种非接触地对开闭触点部的电压降异常进行监视的触点部异常监视装置。触点部异常监视装置具有：变流器(3),其检测在将电路(1)进行开闭的开闭触点(2)为闭合状态的情况下流过电路(1)的负载电流；负载电流检测部(4),其输出负载电流的信号；电源侧电压检测电阻(5),其与开闭触点的电源侧的电路连接；负载侧电压检测电阻(6),其与开闭触点的负载侧的电路连接；异常检测用变流器(7),其对由于流过电源侧电压检测电阻及负载侧电压检测电阻的电流而产生的差分电流进行检测；电压降检测部(8),其基于差分电流而将成为开闭触点处的电压降的实测值的输出信号进行输出；波形比较部(10),其基于负载电流的值及开闭触点的接触电阻的初始值对电压降的正常值进行计算,基于电压降的正常值及电压降的实测值对电压降差分值进行计算而与预先设定的警报等级值相比较,在电压降差分值超过警报等级值的情况下,判定为在开闭触点的接触电阻存在异常,输出警报信号。(The invention provides a contact part abnormity monitoring device for monitoring voltage drop abnormity of an opening and closing contact part in a non-contact way. The contact portion abnormality monitoring device includes: a current transformer (3) that detects a load current flowing through the circuit (1) when an opening/closing contact (2) that opens/closes the circuit (1) is in a closed state; a load current detection unit (4) that outputs a signal of a load current; a power supply side voltage detection resistor (5) connected to a power supply side circuit that opens and closes the contact; a load side voltage detection resistor (6) connected to a load side circuit that opens and closes the contact; an abnormality detection current transformer (7) that detects a differential current generated by currents flowing through the power supply side voltage detection resistor and the load side voltage detection resistor; a voltage drop detection unit (8) that outputs an output signal that is an actual measurement value of the voltage drop at the opening/closing contact point, based on the differential current; and a waveform comparison unit (10) that calculates a normal value of the voltage drop based on the value of the load current and the initial value of the contact resistance of the opening/closing contact, calculates a voltage drop difference value based on the normal value of the voltage drop and the actual value of the voltage drop, compares the voltage drop difference value with a preset alarm level value, determines that there is an abnormality in the contact resistance of the opening/closing contact when the voltage drop difference value exceeds the alarm level value, and outputs an alarm signal.)

1. A contact portion abnormality monitoring device includes:

a current transformer that detects a load current flowing through a circuit that connects a power source and a load when an open/close contact that opens and closes the circuit is closed;

a load current detection unit that outputs a signal of the load current;

a power supply side voltage detection resistor connected to the power supply side circuit of the opening/closing contact;

a load-side voltage detection resistor connected to a circuit on the load side of the opening/closing contact;

an abnormality detection current transformer that detects a differential current generated by currents flowing through the power supply side voltage detection resistor and the load side voltage detection resistor;

a voltage drop detection unit that outputs an output signal that is an actual measurement value of the voltage drop at the open/close contact point based on the differential current; and

and a waveform comparing unit that calculates a normal value of a voltage drop based on a value of the load current and an initial value of the contact resistance of the opening/closing contact, calculates a voltage drop difference value based on the normal value of the voltage drop and an actual value of the voltage drop, compares the voltage drop difference value with a preset alarm level value, determines that there is an abnormality in the contact resistance of the opening/closing contact when the voltage drop difference value exceeds the alarm level value, and outputs an alarm signal.

2. The contact portion abnormality monitoring device according to claim 1,

the alarm device is provided with an alarm part which gives an alarm when the alarm signal is output.

3. The contact portion abnormality monitoring device according to claim 1 or 2,

the initial value of the contact resistance is a preset resistance value of a normal closed state at the opening and closing contact,

the alarm level value is an allowable range of a voltage difference based on a normal value of the voltage drop at the opening/closing contact and an actual measured value of the voltage drop when an abnormality occurs,

the touch panel includes an alarm level setting unit that stores an initial value of the contact resistance and sets an alarm level value.

4. The contact portion abnormality monitoring device according to any one of claims 1 to 3,

the power supply side voltage detection resistor and the load side voltage detection resistor are formed of resistor members having the same specification and are disposed on the same substrate.

5. A circuit breaker, having:

an opening/closing contact provided in a circuit for connecting a power source and a load, and opening/closing the power source and the load;

a current transformer that detects a load current flowing through the circuit when the opening/closing contact is in a closed state;

a load current detection unit that outputs a signal of the load current;

a power supply side voltage detection resistor connected to the power supply side circuit of the opening/closing contact;

a load-side voltage detection resistor connected to a circuit on the load side of the opening/closing contact;

an abnormality detection current transformer that detects a differential current generated by currents flowing through the power supply side voltage detection resistor and the load side voltage detection resistor;

a voltage drop detection unit that outputs an output signal that is an actual measurement value of the voltage drop at the open/close contact point based on the differential current;

a waveform comparing unit that calculates a normal value of a voltage drop based on a value of the load current and an initial value of the contact resistance of the opening/closing contact, calculates a voltage drop difference value based on the normal value of the voltage drop and an actual value of the voltage drop, compares the voltage drop difference value with a preset alarm level value, determines that there is an abnormality in the contact resistance of the opening/closing contact when the voltage drop difference value exceeds the alarm level value, and outputs an alarm signal; and

and a trip device capable of opening the opening and closing contact.

6. The contact portion abnormality monitoring device according to claim 5,

the alarm device is provided with an alarm part which gives an alarm when the alarm signal is output.

7. The contact portion abnormality monitoring device according to claim 5 or 6,

the initial value of the contact resistance is a preset resistance value of a normal closed state at the opening and closing contact,

the alarm level value is an allowable range of a voltage difference based on a normal value of the voltage drop at the opening/closing contact and an actual measured value of the voltage drop when an abnormality occurs,

the touch panel includes an alarm level setting unit that stores an initial value of the contact resistance and sets an alarm level value.

8. The contact portion abnormality monitoring device according to any one of claims 5 to 7,

the power supply side voltage detection resistor and the load side voltage detection resistor are formed of resistor members having the same specification and are disposed on the same substrate.

Technical Field

The present invention relates to a contact portion abnormality monitoring device for monitoring an abnormality of an opening/closing contact portion, and a circuit breaker using the contact portion abnormality monitoring device.

Background

As the abnormality monitoring of the opening and closing contact portions of the circuit breaker, a method of measuring the contact resistance of the opening and closing contact portions by a voltage drop method is adopted, that is, a method of calculating the resistance value of the contact portions by the voltage of the contact portions detected via an insulated amplifier connected to both ends of the opening and closing contact portions to be monitored in the circuit and the current flowing in the circuit detected via a current transformer, and comparing the resistance value with a reference value of the resistance to determine whether there is an abnormality (for example, patent document 1).

Patent document 1: japanese Kokai publication Hei-1-179281

Disclosure of Invention

However, in the conventional method, in an apparatus for opening and closing the contacts such as a circuit breaker, in order to directly measure the voltage drop of the opening and closing contact portion, the contacts are also electrically connected to each other via a voltage measuring instrument connected to both ends of the contacts after the opening and closing contacts are opened, and therefore, it is substantially impossible to ensure insulation between the contacts at the time of opening the contacts.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a contact portion abnormality monitoring device and a circuit breaker using the contact portion abnormality monitoring device, which can safely monitor an abnormality of an opening/closing contact portion by measuring a voltage drop of the opening/closing contact portion in a non-contact manner.

The contact portion abnormality monitoring device according to the present invention includes: a current transformer that detects a load current flowing through a circuit that connects a power source and a load, when an open/close contact that opens and closes the circuit is closed; a load current detection unit that outputs a signal of a load current; a power supply side voltage detection resistor connected to a power supply side circuit that opens and closes the contact; a load side voltage detection resistor connected to a load side circuit that opens and closes the contact; an abnormality detection current transformer that detects a differential current generated by currents flowing through the power supply side voltage detection resistor and the load side voltage detection resistor; a voltage drop detection unit that outputs an output signal that is an actual measurement value of the voltage drop at the open/close contact point based on the differential current; and a waveform comparing unit that calculates a normal value of the voltage drop based on the value of the load current and an initial value of the contact resistance of the opening/closing contact, calculates a voltage drop difference value based on the normal value of the voltage drop and an actual value of the voltage drop, compares the voltage drop difference value with a preset alarm level value, determines that there is an abnormality in the contact resistance of the opening/closing contact when the voltage drop difference value exceeds the alarm level value, and outputs an alarm signal.

The circuit breaker according to the present invention comprises: an opening/closing contact provided in a circuit for connecting a power source and a load, and opening/closing the power source and the load; a current transformer that detects a load current flowing through the circuit when the open/close contacts are in a closed state; a load current detection unit that outputs a signal of a load current; a power supply side voltage detection resistor connected to a power supply side circuit that opens and closes the contact; a load side voltage detection resistor connected to a load side circuit that opens and closes the contact; an abnormality detection current transformer that detects a differential current generated by currents flowing through the power supply side voltage detection resistor and the load side voltage detection resistor; a voltage drop detection unit that outputs an output signal that is an actual measurement value of the voltage drop at the open/close contact point based on the differential current; a waveform comparing unit that calculates a normal value of voltage drop based on a value of the load current and an initial value of contact resistance of the opening/closing contact, calculates a voltage drop difference value based on the normal value of voltage drop and an actual value of voltage drop, compares the voltage drop difference value with a preset alarm level value, determines that there is an abnormality in the contact resistance of the opening/closing contact when the voltage drop difference value exceeds the alarm level value, and outputs an alarm signal; and a trip device capable of opening the opening and closing contacts.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the contact portion abnormality monitoring device and the circuit breaker using the contact portion abnormality monitoring device of the present invention, the presence or absence of an abnormality of the contact portion can be monitored by comparing an actual measurement value of a voltage drop of the opening/closing contact calculated from a difference between currents flowing through voltage detection resistors connected between the power source side and the load side lines of the opening/closing contact, respectively, with a normal value of a voltage drop of the opening/closing contact calculated from a load current and an initial value of a contact resistance of the opening/closing contact. Since the voltage drop of the opening/closing contact part can be measured in a non-contact manner, the safety of the circuit breaker can be improved without affecting the insulation between the opening/closing contacts.

Drawings

Fig. 1 is a block diagram of a circuit breaker according to embodiment 1 of the present invention.

Fig. 2 is a simulation result showing the operation of the circuit breaker according to embodiment 1 of the present invention.

Fig. 3 is a block diagram of a circuit breaker according to embodiment 2 of the present invention.

Fig. 4 is a block diagram of a circuit breaker according to embodiment 3 of the present invention.

Detailed Description

Hereinafter, an embodiment of a circuit breaker according to the present invention will be described with reference to the drawings. In the drawings, the same reference numerals denote the same or equivalent parts.

Embodiment 1.

Fig. 1 is a block diagram of a circuit breaker according to embodiment 1, and shows a configuration for detecting an abnormality of a contact portion in a three-phase 4-wire circuit.

As shown in fig. 1, the circuit breaker according to embodiment 1 includes a contact portion abnormality monitoring device including an opening/closing contact 2, a current transformer 3, a load current detection unit 4, a power source side voltage detection resistor 5, a load side voltage detection resistor 6, an abnormality detection current transformer 7, a voltage drop detection unit 8, an alarm level setting unit 9, and a waveform comparison unit 10, which are provided in an electric circuit 1, and an alarm portion 11 and a trip device 12.

The circuit 1 is connected to a power source and a load, and includes circuits 1a, 1b, 1c, and 1 d. The opening/closing contact 2 is provided in the electric circuit 1 for opening/closing between the power source and the load, and has opening/closing contacts 2a, 2b, 2c, and 2 d.

The inverter 3 has inverters 3a, 3b, 3c, and 3d, and outputs an output signal (current signal) proportional to a load current flowing from a power supply to a load when the open/close contacts 2 are closed.

The load current detection unit 4 converts the output signal from the converter 3 into a load current signal (analog signal or digital signal) and outputs the load current signal.

The power supply side voltage detection resistor 5 is connected to the power supply side with respect to the opening/closing contact 2, and converts the power supply side voltage (potential difference formed by power supply side potentials V1, V2, V3, and V4) into power supply side voltage detection currents (power supply side voltage detection currents i1, i2, i3, and i 4). The power source side voltage detection resistors 5a, 5b, and 5c respectively correspond to the power source side voltage detection currents i1, i2, and i 3.

The load-side voltage detection resistor 6 is connected to the load side with respect to the opening/closing contact 2, and converts a load-side voltage (a potential difference formed by the load-side potentials V5, V6, V7, and V8) into a load-side voltage detection current (load-side voltage detection currents i5, i6, i7, and i 8). Load side voltage detection resistors 6a, 6b, and 6c corresponding to the load side voltage detection currents i5, i6, and i7, respectively, are provided.

The abnormality detection current transformer 7 outputs an output signal (voltage signal) proportional to a differential current generated by a power supply side voltage detection current flowing through the power supply side voltage detection resistor 5 and a load side voltage detection current flowing through the load side voltage detection resistor 6. The abnormality detection converter 7 can be, for example, a zero-sequence converter.

The voltage drop detection unit 8 converts an output signal proportional to the differential current from the abnormality detection current transformer 7 into a differential voltage signal (analog voltage signal or digital voltage signal), and outputs an output signal that is an actual measurement value of the voltage drop.

The alarm level setting unit 9 is composed of a storage element such as a nonvolatile memory, and stores an initial value of a contact resistance value, which is a resistance value in a normal closed state at an open/close contact point set in advance at the time of factory adjustment, and an alarm level value. Here, the alarm level value is an allowable range of a voltage difference based on a normal value of a voltage drop at the opening/closing contact and an actual measured value of the voltage drop when an abnormality occurs. The alarm level value can be changed as necessary and can be input to the alarm level setting unit 9.

The waveform comparing unit 10 calculates a normal value of the voltage drop in the closed state based on the value of the load current signal output from the load current detecting unit 4 and the initial value of the contact resistance recorded in the alarm level setting unit 9, obtains an actual measurement value of the voltage drop at the open/close contact 2 based on the differential voltage signal output from the voltage drop detecting unit 8, calculates a voltage drop difference value from the normal value of the voltage drop and the actual measurement value of the voltage drop, compares the voltage drop difference value with a preset alarm level value, determines that the contact resistance of the open/close contact 2 is deviated from the initial value when the voltage drop difference value exceeds the alarm level value, and outputs an alarm signal.

The alarm unit 11 generates an alarm when receiving the alarm signal output from the waveform comparison unit 10.

The trip device 12 can open the opening and closing contacts in accordance with the current flowing through the circuit 1.

Next, an operation of the circuit breaker according to embodiment 1 of the present invention configured as described above will be described with reference to fig. 1.

In the normally closed state, load currents Ia, Ib, Ic, and Id flowing through the circuits 1a, 1b, 1c, and 1d are detected by the inverters 3a, 3b, 3c, and 3d, respectively, and current signals proportional to the load currents Ia, Ib, Ic, and Id are output to the load current detection unit 4 as output signals.

The load current detection unit 4 converts the obtained output signals proportional to the load currents Ia, Ib, Ic, and Id into load current signals, and outputs the load current signals to the waveform comparison unit 10.

The alarm level setting unit 9 records initial values Xa, Xb, Xc, and Xd of the contact resistance of the opening/closing contacts 2a, 2b, 2c, and 2d, which are input in advance, and outputs the initial values Xa, Xb, Xc, and Xd of the contact resistance to the waveform comparing unit 10. Here, the initial value of the contact resistance is a contact resistance value measured at the time of factory adjustment of the circuit breaker. Note that, a method of calculating a voltage drop difference value when an abnormality occurs based on a normal value of a voltage drop and an actually measured value of the voltage drop will be described later.

The waveform comparing unit 10 derives normal values Δ Ua, Δ Ub, Δ Uc, and Δ Ud of the voltage drop of the open/close contacts 2a, 2b, 2c, and 2d in the normal closed state from the acquired initial values Xa, Xb, Xc, and Xd of the contact resistance and the load currents Ia, Ib, Ic, and Id, respectively, by using expressions (1-1), (1-2), (1-3), and (1-4).

[ formula 1-1]

ΔUa＝Ia×Xa (1-1)

[ formulae 1-2]

ΔUb＝Ib×Xb (1-2)

[ formulae 1 to 3]

ΔUc＝Ic×Xc (1-3)

[ formulae 1 to 4]

ΔUd＝Id×Xd (1-4)

Power supply side voltage detection resistors 5a, 5b, and 5c are connected between the power supply side lines of the circuits 1a, 1b, and 1c and the circuit 1 d. The power supply side potentials of the circuits 1a, 1b, 1c, and 1d are defined as V1, V2, V3, and V4, respectively, the currents flowing through the power supply side voltage detection resistors 5a, 5b, and 5c are defined as power supply side voltage detection currents i1, i2, and i3, respectively, and the current flowing through the circuit 1d via the power supply side voltage detection resistors is defined as a power supply side voltage detection current i 4.

Here, as shown in fig. 1, if wiring is performed such that the wiring connected to the power supply side voltage detection resistor 5a and the power supply side voltage detection resistor 5b is connected to the power supply side of the circuit 1d wound around the abnormality detection current transformer 7, and the wiring connected to the power supply side of the circuit 1d is connected to the wiring of the power supply side voltage detection resistor 5c wound around the abnormality detection current transformer 7, the total current i of the power supply side voltage detection currents output from the abnormality detection current transformer 7 is expressed by equation (2).

[ formula 2]

i＝N×(i1+i2-i3) (2)

Here, N represents the number of turns of the power supply side wiring wound around the abnormality detection current transformer 7.

When the power source side voltage detection currents i1, i2, i3 are represented by the power source side potentials V1, V2, V3, V4 and the resistance values R1, R2, R3 of the power source side voltage detection resistors 5a, 5b, 5c, the power source side voltage detection currents become expressions (3-1), (3-2) and (3-3), respectively, and the power source side voltage detection current i4 becomes expression (3-4). The total current i of the power supply side voltage detection currents output from the abnormality detection current transformer 7 is expressed by equation (4).

[ formula 3-1]

i1＝(V1-V4)/R1 (3-1)

[ formula 3-2]

i2＝(V2-V4)/R2 (3-2)

[ formula 3-3]

i3＝(V3-V4)/R3 (3-3)

[ formulas 3 to 4]

i4＝-i1-i2-i3

＝-(V1-V4)/R1-(V2-V4)/R2-(V3-V4)/R3

＝-1/(R1R2R3)×(R2R3V1+R1R3V2+R1R2V3(R1R2+R2R3+R3R1)V4) (3-4)

[ formula 4]

i＝N×1/(R1R2R3)×(R2R3V1+R1R3V2-R1R2V3+(R1R2-R2R3-R3R1)V4) (4)

On the other hand, load-side voltage detection resistors 6a, 6b, and 6c are connected between load-side lines of the circuits 1a, 1b, and 1c and the circuit 1 d. The load-side potentials of the circuits 1a, 1b, 1c, and 1d are defined as V5, V6, V7, and V8, respectively, the currents flowing through the load-side voltage detection resistors 6a, 6b, and 6c are defined as load-side voltage detection currents i5, i6, and i7, respectively, and the current flowing through the circuit 1d via the load-side voltage detection resistors is defined as a load-side voltage detection current i 8.

Here, as shown in fig. 1, if wiring is performed such that the wiring connected to the load side voltage detection resistor 6a and the load side voltage detection resistor 6b is connected to the load side of the circuit 1d wound around the abnormality detection current transformer 7, and the wiring connected to the load side of the circuit 1d is connected to the wiring of the load side voltage detection resistor 6c wound around the abnormality detection current transformer 7, the total current i10 of the load side voltage detection current output from the abnormality detection current transformer 7 is expressed by equation (5).

[ formula 5]

i10＝N10×(i5+i6-i7) (5)

Here, N10 represents the number of turns of the wire on the load side of the winding of the abnormality detection current transformer 7.

When the load-side voltage detection currents i5, i6, i7 and i8 are represented by the load-side potentials V5, V6, V7 and V8 and the resistance values R5, R6 and R7 of the load-side voltage detection resistors 6a, 6b and 6c, the load-side voltage detection currents are expressed by the formula (6-1), the formula (6-2), the formula (6-3) and the formula (6-4), respectively. The total current i10 of the load-side voltage detection currents output from the abnormality detection current transformer 7 is expressed by equation (7).

[ formula 6-1]

i5＝(V5-V8)/R5 (6-1)

[ formula 6-2]

i6＝(V6-V8)/R6 (6-2)

[ formula 6-3]

i7＝(V7-V8)/R7 (6-3)

[ formula 6-4]

i8＝-i5-i6-i7

＝-(V5-V8)/R5-(V6-V8)/R6-(V7-V8)/R7

＝-1/(R5R6R7)×(R6R7V5+R5R7V6+R5R6V7-(R5R6+R6R7+R7R5)V8) (6-4)

[ formula 7]

i10＝N10×1/(R5R6R7)×(R6R7V5+R5R7V6-R5R6V7+(R5R6-R6R7-R7R5)V8) (7)

Here, if R1, R2, R3, R5, R6, R7, R Ω, and N1, M turns are used, the differential current signal Δ i, i-i10 generated by the current output from the abnormality detecting converter 7 is expressed by formula (8).

[ formula 8]

Δi＝M×1/R×((V1-V5)+(V2-V6)-(V3-V7)-(V4-V8)

＝M×1/R×(ΔVa+ΔVb-ΔVc-ΔVd) (8)

Further, Δ Va, Δ Vb, Δ Vc, and Δ Vd represent voltage drops at the opening/closing contacts 2a, 2b, 2c, and 2d, respectively, and are expressed by expressions (9-1), (9-2), (9-3), and (9-4).

[ formula 9-1]

ΔVa＝V1-V5 (9-1)

[ formula 9-2]

ΔVb＝V2-V6 (9-2)

[ formulas 9-3]

ΔVc＝V3-V7 (9-3)

[ formulas 9-4]

ΔVd＝V4-V8 (9-4)

An output signal proportional to the differential current signal Δ i detected by the abnormality detection current transformer 7 is output to the voltage drop detection unit 8. The voltage drop detection unit 8 outputs an output signal proportional to the obtained differential current signal Δ i to the waveform comparison unit 10.

The waveform comparing unit 10 calculates the actual measurement value Δ V of the voltage drop at the open/close contacts 2a to 2d by equation (10) based on the value of the obtained differential current signal Δ i.

[ formula 10]

ΔV＝Δi×R/M

＝ΔVa+ΔVb-ΔVc-ΔVd (10)

If the measured values of the contact resistances at the opening/closing contacts 2a, 2b, 2c, 2d are Ra, Rb, Rc, Rd, the formula (10) is the formula (11) using the load currents Ia, Ib, Ic, Id described above.

[ formula 11]

ΔV＝(Ia×Ra)+(Ib×Rb)-(Ic×Rc)-(Id×Rd) (11)

On the other hand, the waveform comparing unit 10 estimates the normal value Δ U of the voltage drop of the contact portion at the opening/closing contacts 2a, 2b, 2c, 2d by the equation (12) using the normal values Δ Ua, Δ Ub, Δ Uc, Δ Ud of the voltage drop in the normal closed state derived by the equations (1-1), (1-2), (1-3) and (1-4).

[ formula 12]

ΔU＝ΔUa+ΔUb-ΔUc-ΔUd

＝(Ia×Xa)+(Ib×Xb)-(Ic×Xc)-(Id×Xd) (12)

Here, fig. 2 is an example of a simulation result of the operation of the circuit breaker according to embodiment 1. In fig. 2, the horizontal axis represents time, and the vertical axis represents voltage level.

As shown in fig. 2(a), when the open-close contacts 2a, 2b, 2c, 2d are in the normally closed state, the actually measured values Ra, Rb, Rc, Rd of the contact resistance substantially match the initial values Xa, Xb, Xc, Xd of the contact resistance, and therefore the voltage drop difference value Δ V — Δ U becomes equation (13).

[ formula 13]

When the open/close contacts 2a, 2B, 2c, 2d are abnormal and the actually measured values Ra, Rb, Rc, Rd of the contact resistance increase, the actually measured values Ra, Rb, Rc, Rd of the contact resistance and the initial values Xa, Xb, Xc, Xd of the contact resistance become more deviated from each other, and therefore, as shown in fig. 2(B), the amplitude of the voltage drop difference value Δ V- Δ U increases with the actually measured values of the contact resistance, and becomes greater than or equal to the positive direction alarm level value and the negative direction alarm level value.

Therefore, by monitoring the magnitude of the voltage drop difference value Δ V- Δ U and comparing it with the alarm level value set in the alarm level setting unit 9, it is possible to detect an abnormality in the opening/closing contact.

When the magnitude of the voltage drop difference value Δ V- Δ U exceeds the alarm level value, the waveform comparing unit 10 outputs an alarm signal to the alarm unit 11. Upon receiving the alarm signal output from the waveform comparing unit 10, the alarm unit 11 outputs an alarm to an external device, thereby being able to notify an abnormality of the opening/closing contacts 2a, 2b, 2c, 2 d.

In embodiment 1, when there is fluctuation in the resistance values of the power source side voltage detection resistors 5a, 5b, and 5c and the load side voltage detection resistors 6a, 6b, and 6c, since a measurement error occurs in the actual measurement value Δ V of the voltage drop at the open/close contacts 2a, 2b, 2c, and 2d due to the fluctuation in the resistance values, the waveform comparison unit 10 has a function of correcting the fluctuation in the resistance values of the power source side voltage detection resistors 5a, 5b, and 5c and the load side voltage detection resistors 6a, 6b, and 6c, and thus the measurement accuracy can be further improved.

The fluctuations in the resistance value are caused by the temperature, humidity environment, and aging deterioration, but the reliability of the measurement can be further improved because the constants of the power source side voltage detection resistors 5a, 5b, and 5c and the load side voltage detection resistors 6a, 6b, and 6c are made uniform, and the circuit is configured by the resistor members of the same specification, so that all the members obtain uniform resistance value changes with respect to the temperature, humidity environment, and aging deterioration.

Further, by disposing the power source side voltage detection resistors 5a, 5b, and 5c and the load side voltage detection resistors 6a, 6b, and 6c on the same substrate, the influence of the temperature and humidity environment due to the position can be made less likely to occur, and the reliability of the measurement can be further improved.

According to the contact portion abnormality monitoring device according to embodiment 1 and the circuit breaker using the same, the presence or absence of an abnormality of the contact portion can be monitored by comparing an actual measurement value of a voltage drop of the opening/closing contact calculated from a difference between currents flowing through the voltage detection resistors connected between the power supply side and the load side lines of the opening/closing contact, respectively, with a normal value of the voltage drop of the opening/closing contact calculated from the load current and an initial value of the contact resistance of the opening/closing contact. Since the voltage drop of the opening/closing contact part can be measured in a non-contact manner, the safety of the circuit breaker can be improved without affecting the insulation between the opening/closing contacts.

Embodiment 2.

Fig. 3 is a block diagram of the circuit breaker according to embodiment 2, and shows a configuration for detecting an abnormality of a contact portion in a single-phase 3-wire circuit and a three-phase 3-wire circuit.

As shown in fig. 3, the circuit breaker according to embodiment 2 is configured, similarly to embodiment 1, by a contact portion abnormality monitoring device including opening and closing contacts 2, a current transformer 3, a load current detection unit 4, a power supply side voltage detection resistor 5, a load side voltage detection resistor 6, an abnormality detection current transformer 7, a voltage drop detection unit 8, an alarm level setting unit 9, and a waveform comparison unit 10, which are provided in an electric circuit 1, and an alarm portion 11 and a trip device 12.

The circuit 1 is connected to a power source and a load, and includes circuits 1a, 1b, and 1 c. The opening/closing contact 2 is provided in an electric circuit 1 for opening/closing between a power source and a load, and has opening/closing contacts 2a, 2b, and 2 c.

The inverter 3 has inverters 3a, 3b, and 3c, and outputs an output signal (current signal) proportional to a load current flowing from a power supply to a load when the open/close contacts 2 are closed.

The load current detection unit 4 converts the output signal from the converter 3 into a load current signal (analog signal or digital signal) and outputs the load current signal.

The power supply side voltage detection resistor 5 is connected to the power supply side with respect to the opening/closing contact 2, and converts the power supply side voltage (potential difference formed by the power supply side potentials V1, V2, and V3) into power supply side voltage detection currents (power supply side voltage detection currents i1, i2, and i 3). The power source side voltage detection resistors 5a, 5b, and 5c respectively correspond to the power source side voltage detection currents i1, i2, and i 3.

The load side voltage detection resistor 6 is connected to the load side with respect to the opening/closing contact 2, and converts a load side voltage (a potential difference formed by the load side potentials V4, V5, and V6) into a load side voltage detection current (load side voltage detection currents i4, i5, and i 6). Load side voltage detection resistors 6a, 6b, and 6c corresponding to the load side voltage detection currents i4, i5, and i6, respectively, are provided.

The abnormality detection current transformer 7 outputs an output signal (voltage signal) proportional to a differential current generated by a power supply side voltage detection current flowing through the power supply side voltage detection resistor 5 and a load side voltage detection current flowing through the load side voltage detection resistor 6. The abnormality detection converter 7 can be, for example, a zero-sequence converter.

The voltage drop detection unit 8 converts an output signal proportional to the differential current from the abnormality detection current transformer 7 into a differential voltage signal (analog voltage signal or digital voltage signal), and outputs an output signal that is an actual measurement value of the voltage drop.

The alarm level setting unit 9 is composed of a storage element such as a nonvolatile memory, and stores an initial value of a contact resistance value, which is a resistance value in a normal closed state at an open/close contact point set in advance at the time of factory adjustment, and an alarm level value. Here, the alarm level value is an allowable range of a voltage difference based on a normal value of a voltage drop at the opening/closing contact and an actual measured value of the voltage drop when an abnormality occurs. The alarm level value can be changed as necessary and can be input to the alarm level setting unit 9.

The waveform comparing unit 10 calculates a normal value of the voltage drop in the closed state based on the value of the load current signal output from the load current detecting unit 4 and the initial value of the contact resistance recorded in the alarm level setting unit 9, acquires an actual measurement value of the voltage drop at the open/close contact 2 based on the differential voltage signal output from the voltage drop detecting unit 8, calculates a voltage drop difference value from the normal value of the voltage drop and the actual measurement value of the voltage drop, compares the voltage drop difference value with a preset alarm level value, determines that the contact resistance of the open/close contact 2 is deviated from the initial value when the voltage drop difference value exceeds the alarm level value, and outputs an alarm signal.

The alarm unit 11 generates an alarm when receiving the alarm signal output from the waveform comparison unit 10.

The trip device 12 can open the opening and closing contacts in accordance with the current flowing through the circuit 1.

Next, the operation of the circuit breaker according to embodiment 2 of the present invention configured as described above will be described with reference to fig. 3.

In a normally closed state, load currents Ia, Ib, and Ic flowing through the circuits 1a, 1b, and 1c are detected by the inverters 3a, 3b, and 3c, respectively, and current signals proportional to the load currents Ia, Ib, and Ic are output to the load current detection unit 4 as output signals.

The load current detection unit 4 converts the obtained output signals proportional to the load currents Ia, Ib, and Ic into load current signals, and outputs the load current signals to the waveform comparison unit 10.

The alarm level setting unit 9 records initial values Xa, Xb, and Xc of the contact resistance of the opening/closing contacts 2a, 2b, and 2c, which are input in advance, and outputs the initial values Xa, Xb, and Xc of the contact resistance to the waveform comparing unit 10. Here, the initial value of the contact resistance is a contact resistance value measured at the time of factory adjustment of the circuit breaker. Note that, a method of calculating a voltage drop difference value when an abnormality occurs based on a normal value of a voltage drop and an actually measured value of the voltage drop will be described later.

The waveform comparing unit 10 derives normal values Δ Ua, Δ Ub, and Δ Uc of the voltage drop of the open-close contacts 2a, 2b, and 2c in the normal closed state from the obtained initial values Xa, Xb, and Xc of the contact resistance and the load currents Ia, Ib, and Ic described above by using expressions (14-1), (14-2), and (14-3), respectively.

[ formula 14-1]

ΔUa＝Ia×Xa (14-1)

[ formula 14-2]

ΔUb＝Ib×Xb (14-2)

[ formula 14-3]

ΔUc＝Ic×Xc (14-3)

Power supply side voltage detection resistors 5a, 5b, and 5c are connected between the power supply side lines of the circuits 1a, 1b, and 1 c. The power supply side potentials of the circuits 1a, 1b, and 1c are defined as V1, V2, and V3, respectively, and the currents flowing through the power supply side voltage detection resistors 5a, 5b, and 5c are defined as power supply side voltage detection currents i1, i2, and i3, respectively.

Here, as shown in fig. 3, if wiring connected to the power supply side voltage detection resistor 5a and the power supply side voltage detection resistor 5b is wound around the abnormality detection current transformer 7 and wiring connected to the power supply side voltage detection resistor 5c connected to the power supply side of the circuit 1c wound around the abnormality detection current transformer 7 is connected, the total current i of the power supply side voltage detection currents output from the abnormality detection current transformer 7 is expressed by equation (15).

[ formula 15]

i＝N×i3 (15)

Here, N represents the number of turns of the power supply side wiring wound around the abnormality detection current transformer 7.

When the power source side voltage detection currents i1, i2, i3 are represented by power source side potentials V1, V2, V3 and resistance values R1, R2, R3 of the power source side voltage detection resistors 5a, 5b, 5c, the power source side voltage detection currents become expressions (16-1), (16-2), and (16-3), respectively. The total current i of the power supply side voltage detection currents output from the abnormality detection current transformer 7 is expressed by equation (17).

[ formula 16-1]

i1＝1/(R1R2+R2R3+R3R1)×((R2+R3)V1-R3V2-R2V3) (16-1)

[ formula 16-2]

i2＝1/(R1R2+R2R3+R3R1)×(-R3V1+(R1+R3)V2-R1V3) (16-2)

[ formula 16-3]

i3＝1/(R1R2+R2R3+R3R1)×(-R2V1+R1V2+(R1+R2)V3) (16-3)

[ formula 17]

i＝N×1/(R1R2+R2R3+R3R1)×(-R2V1-R1V2+(R1+R2)V3) (17)

On the other hand, load-side voltage detection resistors 6a, 6b, and 6c are connected between load-side lines of the circuits 1a, 1b, and 1 c. The load-side potentials of the circuits 1a, 1b, and 1c are defined as V4, V5, and V6, respectively, and the currents flowing through the load-side voltage detection resistors 6a, 6b, and 6c are defined as load-side voltage detection currents i4, i5, and i6, respectively.

Here, as shown in fig. 3, if the wiring connected to the load side voltage detection resistor 6a and the load side voltage detection resistor 6b is wound around the abnormality detection current transformer 7 and the wiring connected to the load side voltage detection resistor 6c connected to the load side of the circuit 1c wound around the abnormality detection current transformer 7 is connected, the total current i10 of the load side voltage detection currents output from the abnormality detection current transformer 7 is expressed by equation (18).

[ formula 18]

i10＝N10×i6 (18)

Here, N10 represents the number of turns of the power supply side wiring wound around the abnormality detection current transformer 7.

When the load-side voltage detection currents i4, i5, i6 are represented by the load-side potentials V4, V5, V6 and the resistance values R4, R5, R6 of the load-side voltage detection resistors 6a, 6b, 6c, the load-side voltages become expressions (19-1), (19-2), and (19-3), respectively. The total current i10 of the load-side voltage detection currents output from the abnormality detection current transformer 7 is equation (20).

[ formula 19-1]

i4＝1/(R4R5+R5R6+R6R4)×((R5+R6)V4-R6V5-R5V6) (19-1)

[ formula 19-2]

i5＝1/(R4R5+R5R6+R6R4)×(-R6V4+(R4+R6)V5-R4V6) (19-2)

[ formula 19-3]

i6＝1/(R4R5+R5R6+R6R4)×(-R5V4-R4V5+(R4+R5)V6) (19-3)

[ formula 20]

i10＝N10×1/(R4R5+R5R6+R6R4)×(-R5V4-R4V5+(R4+R5)V6) (20)

Here, if R1, R2, R3, R4, R5, R6, R Ω, and N10, M turns are used, the differential current signal Δ i, i-i10 generated by the current output from the abnormality detecting converter 7 is expressed by formula (21).

[ formula 21]

Δi＝M×1/3R×(-ΔVa-ΔVb+2ΔVc) (21)

Further, Δ Va, Δ Vb, and Δ Vc represent voltage drops at the open/close contacts 2a, 2b, and 2c, respectively, and are expressed by expressions (22-1), (22-2), and (22-3).

[ formula 22-1]

ΔVa＝V1-V4 (22-1)

[ formula 22-2]

ΔVb＝V2-V5 (22-2)

[ formula 22-3]

ΔVc＝V3-V6 (22-3)

An output signal proportional to the differential current signal Δ i detected by the abnormality detection current transformer 7 is output to the voltage drop detection unit 8. The voltage drop detection unit 8 outputs an output signal proportional to the obtained differential current signal Δ i to the waveform comparison unit 10.

The waveform comparing unit 10 calculates an actual measurement value Δ V of the contact voltage drop at the open/close contacts 2a to 2c by equation (23) based on the value of the obtained differential current signal Δ i.

[ formula 23]

ΔV＝Δi×3R/M

＝-ΔVa-ΔVb+2ΔVc (23)

If Ra, Rb, and Rc are actually measured values of the contact resistance at the opening/closing contacts 2a, 2b, and 2c, equation (23) is expressed as equation (24) using the load currents Ia, Ib, and Ic.

[ formula 24]

ΔV＝-(Ia×Ra)-(Ib×Rb)+2(Ic×Rc) (24)

On the other hand, the waveform comparing unit 10 estimates the normal value Δ U of the voltage drop of the contact portion at the open/close contacts 2a to 2c by the equation (25) using the normal values Δ Ua, Δ Ub, and Δ Uc of the voltage drop in the normal closed state derived by the equations (14-1), (14-2), and (14-3).

[ formula 25]

ΔU＝-ΔUa-ΔUb+2ΔUc

＝-(Ia×Xa)-(Ib×Xb)+2(Ic×Xc) (25)

When the open-close contacts 2a, 2b, and 2c are in the normally closed state, the actually measured values Ra, Rb, and Rc of the contact resistance and the initial values Xa, Xb, and Xc of the contact resistance substantially match each other, and therefore the voltage drop difference value Δ V — Δ U is expressed by expression (26).

[ formula 26]

When the open/close contacts 2a, 2b, 2c are abnormal and the actually measured values Ra, Rb, Rc of the contact resistance increase, the actually measured values Ra, Rb, Rc of the contact resistance and the initial values Xa, Xb, Xc of the contact resistance become more divergent, and therefore the amplitude of the voltage drop difference value Δ V- Δ U becomes larger according to the actually measured values of the contact resistance and becomes larger than or equal to the positive direction alarm level value and the negative direction alarm level value.

Therefore, by monitoring the magnitude of the voltage drop difference value Δ V- Δ U and comparing it with the alarm level value set in the alarm level setting unit 9, it is possible to detect an abnormality in the opening/closing contact.

When the magnitude of the voltage drop difference value Δ V- Δ U exceeds the alarm level value, the waveform comparing unit 10 outputs an alarm signal to the alarm unit 11. Upon receiving the alarm signal output from the waveform comparing unit 10, the alarm unit 11 outputs an alarm to an external device, thereby being able to notify an abnormality of the opening/closing contacts 2a, 2b, and 2 c.

In embodiment 2, similarly to embodiment 1, when there is fluctuation in the resistance values of the power source side voltage detection resistors 5a, 5b, and 5c and the load side voltage detection resistors 6a, 6b, and 6c, a measurement error occurs in the actual measurement value Δ V of the voltage drop at the open/close contacts 2a, 2b, and 2c due to the fluctuation in the resistance values, and therefore, the waveform comparison unit 10 has a function of correcting the fluctuation in the resistance values of the power source side voltage detection resistors 5a, 5b, and 5c and the load side voltage detection resistors 6a, 6b, and 6c, thereby making it possible to further improve the measurement accuracy.

As for the power source side voltage detection resistors 5a, 5b, 5c and the load side voltage detection resistors 6a, 6b, 6c, it is preferable to use resistor members of the same specification as in embodiment 1. Further, by being disposed on the same substrate, the measurement device is less likely to be affected by the temperature and humidity environment due to the position, and the reliability of the measurement can be further improved.

According to the contact portion abnormality monitoring device according to embodiment 2 and the circuit breaker using the same, the presence or absence of an abnormality of the contact portion can be monitored by comparing an actual measurement value of a voltage drop of the opening/closing contact calculated from a difference between currents flowing through the voltage detection resistors connected between the power supply side and the load side lines of the opening/closing contact, respectively, with a normal value of the voltage drop of the opening/closing contact calculated from the load current and an initial value of the contact resistance of the opening/closing contact. Since the voltage drop of the opening/closing contact part can be measured in a non-contact manner, the safety of the circuit breaker can be improved without affecting the insulation between the opening/closing contacts.

Embodiment 3.

Fig. 4 is a block diagram of the circuit breaker according to embodiment 3, and shows a configuration for detecting an abnormality of a contact portion in a single-phase 2-wire circuit.

As shown in fig. 4, the circuit breaker according to embodiment 3 is configured by a contact abnormality monitoring device including opening and closing contacts 2, a current transformer 3, a load current detection unit 4, a power supply side voltage detection resistor 5, a load side voltage detection resistor 6, an abnormality detection current transformer 7, a voltage drop detection unit 8, an alarm level setting unit 9, and a waveform comparison unit 10, which are provided in an electric circuit 1, as in embodiments 1 and 2, and an alarm unit 11 and a trip device 12.

The circuit 1 is connected to a power source and a load, and includes circuits 1a and 1 b. The opening/closing contact 2 is provided in an electric circuit 1 for opening/closing between a power source and a load, and has opening/closing contacts 2a and 2 b.

The inverter 3 has inverters 3a and 3b, and outputs an output signal (current signal) proportional to a load current flowing from a power source to a load when the open/close contacts 2 are closed.

The load current detection unit 4 converts the output signal from the converter 3 into a load current signal (analog signal or digital signal) and outputs the load current signal.

The power supply side voltage detection resistor 5 is connected to the power supply side with respect to the opening/closing contact 2, and converts the power supply side voltage (potential difference formed by the power supply side potentials V1 and V2) into power supply side voltage detection currents (power supply side voltage detection currents i1 and i 2). The power supply side voltage detection resistors 5a and 5b are provided corresponding to the power supply side voltage detection currents i1 and i2, respectively.

The load side voltage detection resistor 6 is connected to the load side with respect to the opening/closing contact 2, and converts a load side voltage (a potential difference between the load side potentials V3 and V4) into load side voltage detection currents (load side voltage detection currents i3 and i 4). Load side voltage detection resistors 6a and 6b corresponding to the load side voltage detection currents i3 and i4, respectively, are provided.

The abnormality detection current transformer 7 outputs an output signal (a current signal or a voltage signal) proportional to a differential current generated by a power supply side voltage detection current flowing through the power supply side voltage detection resistor 5 and a load side voltage detection current flowing through the load side voltage detection resistor 6. The abnormality detection converter 7 can be, for example, a zero-sequence converter.

The voltage drop detection unit 8 converts an output signal proportional to the differential current from the abnormality detection current transformer 7 into a differential voltage signal (analog voltage signal or digital voltage signal), and outputs an output signal that is an actual measurement value of the voltage drop.

The alarm level setting unit 9 is composed of a storage element such as a nonvolatile memory, and stores an initial value of a contact resistance value, which is a resistance value in a normal closed state at an open/close contact point set in advance at the time of factory adjustment, and an alarm level value. Here, the alarm level value is an allowable range of a voltage difference based on a normal value of a voltage drop at the opening/closing contact and an actual measured value of the voltage drop when an abnormality occurs. The alarm level value can be changed as necessary and can be input to the alarm level setting unit 9.

The waveform comparing unit 10 calculates a normal value of the voltage drop in the closed state based on the value of the load current signal output from the load current detecting unit 4 and the initial value of the contact resistance recorded in the alarm level setting unit 9, obtains an actual measurement value of the voltage drop at the open/close contact 2 based on the differential voltage signal output from the voltage drop detecting unit 8, calculates a voltage drop difference value from the normal value of the voltage drop and the actual measurement value of the voltage drop, compares the voltage drop difference value with a preset alarm level value, determines that the contact resistance of the open/close contact 2 is deviated from the initial value when the voltage drop difference value exceeds the alarm level value, and outputs an alarm signal.

The alarm unit 11 generates an alarm when receiving the alarm signal output from the waveform comparison unit 10.

The trip device 12 can open the opening and closing contacts in accordance with the current flowing through the circuit 1.

Next, an operation of the circuit breaker according to embodiment 3 of the present invention configured as described above will be described with reference to fig. 4.

In the normally closed state, load currents Ia and Ib flowing through the circuits 1a and 1b are detected by the current transformers 3a and 3b, respectively, and current signals proportional to the load currents Ia and Ib are output to the load current detection unit 4 as output signals.

The load current detection unit 4 converts the obtained output signals proportional to the load currents Ia and Ib into load current signals, and outputs the load current signals to the waveform comparison unit 10.

The alarm level setting unit 9 records initial values Xa and Xb of contact resistance of the opening and closing contacts 2a and 2b, which are input in advance, and outputs the initial values Xa and Xb of the contact resistance to the waveform comparing unit 10. Here, the initial value of the contact resistance is a contact resistance value measured at the time of factory adjustment of the circuit breaker. Note that, a method of calculating a voltage drop difference value when an abnormality occurs based on a normal value of a voltage drop and an actually measured value of the voltage drop will be described later.

The waveform comparing unit 10 derives normal values Δ Ua and Δ Ub of voltage drops of the open-close contacts 2a and 2b in the normal closed state from the obtained initial values Xa and Xb of the contact resistance and the load currents Ia and Ib, respectively, by using equations (27-1) and (27-2).

[ formula 27-1]

ΔUa＝Ia×Xa (27-1)

[ formula 27-2]

ΔUb＝Ib×Xb (27-2)

Power supply side voltage detection resistors 5a and 5b are connected between power supply side lines of the circuits 1a and 1 b. The power supply side potentials of the circuits 1a and 1b are defined as V1 and V2, respectively, and the currents flowing through the power supply side voltage detection resistors 5a and 5b are defined as power supply side voltage detection currents i1 and i2, respectively.

Here, as shown in fig. 4, the wiring connected to the power supply side voltage detection resistor 5a and the power supply side voltage detection resistor 5b is wound around the abnormality detection current transformer 7, and the total current i of the power supply side voltage detection currents output from the abnormality detection current transformer 7 is represented by equation (28).

[ formula 28]

i＝N×i1 (28)

Here, N represents the number of turns of the power supply side wiring wound around the abnormality detection current transformer 7.

When the power supply side voltage detection currents i1, i2 are represented by the power supply side potentials V1, V2 and the resistance values R1, R2 of the power supply side voltage detection resistors 5a, 5b, the power supply side voltage detection currents become expression (29-1) and expression (29-2), respectively. The total current i of the power supply side voltage detection currents output from the abnormality detection current transformer 7 is expressed by equation (30).

[ formula 29-1]

i1＝(V1-V2)/(R1+R2) (29-1)

[ formula 29-2]

i2＝-(V1-V2)/(R1+R2) (29-2)

[ formula 30]

i＝N×(V1-V2)/(R1+R2) (30)

On the other hand, load-side voltage detection resistors 6a and 6b are connected between load-side lines of the circuits 1a and 1 b. The load-side potentials of the circuits 1a and 1b are defined as V3 and V4, respectively, and the currents flowing through the load-side voltage detection resistors 6a and 6b are defined as load-side voltage detection currents i3 and i4, respectively.

Here, as shown in fig. 4, the wiring connected to the load side voltage detection resistor 6a and the load side voltage detection resistor 6b is wound around the abnormality detection current transformer 7, and the total current i10 of the load side voltage detection currents output from the abnormality detection current transformer 7 is expressed by equation (31).

[ formula 31]

i10＝N10×i3 (31)

Here, N10 represents the number of turns of the power supply side wiring wound around the abnormality detection current transformer 7.

When the load-side voltage detection currents i3, i4 are represented by the load-side potentials V3, V4 and the resistance values R3, R4 of the load-side voltage detection resistors 6a, 6b, the load-side voltage detection currents are expressed by the equations (32-1) and (32-2). The total current i10 of the load-side voltage detection currents output from the abnormality detection current transformer 7 is equation (33).

[ formula 32-1]

i3＝(V3-V4)/(R3+R4) (32-1)

[ formula 32-2]

i4＝-(V3-V4)/(R3+R4) (32-2)

[ formula 33]

i10＝N10×(V3-V4)/(R3+R4) (33)

Here, if R1 ═ R2 ═ R3 ═ R4 ═ R [ Ω ], and N ═ N10 ═ M [ turns ], the differential current signal Δ i ═ i-i10 generated by the current output from the abnormality detection current transformer 7 becomes formula (34).

[ formula 34]

Δi＝M×1/2R×(ΔVa-ΔVb) (34)

Further, Δ Va and Δ Vb represent voltage drops of the open/close contacts 2a and 2b, and are expressed by expressions (35-1) and (35-2).

[ formula 35-1]

ΔVa＝V1-V3 (35-1)

[ formula 35-2]

ΔVb＝V2-V4 (35-2)

An output signal proportional to the differential current signal Δ i detected by the abnormality detection current transformer 7 is output to the voltage drop detection unit 8. The voltage drop detection unit 8 outputs an output signal proportional to the obtained differential current signal Δ i to the waveform comparison unit 10.

The waveform comparing unit 10 calculates the actual measurement value Δ V of the voltage drop at the open/close contacts 2a to 2b by equation (36) based on the value of the obtained differential current signal Δ i.

[ formula 36]

ΔV＝Δi×2R/M

＝ΔVa-ΔVb (36)

If Ra and Rb are actually measured values of the contact resistance at the opening/closing contacts 2a and 2b, equation (36) is equation (37) using the load currents Ia and Ib.

[ formula 37]

ΔV＝(Ia×Ra)-(Ib×Rb) (37)

On the other hand, the waveform comparing unit 10 estimates the normal value Δ U of the voltage drop of the contact portions at the open and close contacts 2a and 2b by the equation (38) using the normal values Δ Ua and Δ Ub of the voltage drop in the normal closed state derived by the equations (27-1) and (27-2).

[ formula 38]

ΔU＝ΔUa-ΔUb

＝(Ia×Xa)-(Ib×Xb) (38)

When the open-close contacts 2a and 2b are in the normally closed state, the actually measured values Ra and Rb of the contact resistance and the initial values Xa and Xb of the contact resistance substantially match each other, and therefore the voltage drop difference value Δ V- Δ U becomes equation (39).

[ formula 39]

When the actual measurement values Ra and Rb of the contact resistance increase due to an abnormality in the opening/closing contacts 2a and 2b, the actual measurement values Ra and Rb of the contact resistance and the initial values Xa and Xb of the contact resistance increase in deviation, and therefore the amplitude of the voltage drop difference value Δ V- Δ U increases with the actual measurement values of the contact resistance, and becomes greater than or equal to the positive direction alarm level value and the negative direction alarm level value.

Therefore, by monitoring the magnitude of the voltage drop difference value Δ V- Δ U and comparing it with the alarm level value set in the alarm level setting unit 9, it is possible to detect an abnormality in the opening/closing contact.

When the magnitude of the voltage drop difference value Δ V- Δ U exceeds the alarm level value, the waveform comparing unit 10 outputs an alarm signal to the alarm unit 11. Upon receiving the alarm signal output from the waveform comparing unit 10, the alarm unit 11 outputs an alarm to an external device, thereby being able to notify an abnormality of the opening/closing contacts 2a and 2 b.

In embodiment 3, similarly to embodiment 1, when there is fluctuation in the resistance values of the power supply side voltage detection resistors 5a and 5b and the load side voltage detection resistors 6a and 6b, since a measurement error occurs in the actual measurement value Δ V of the voltage drop at the open/close contacts 2a and 2b due to the fluctuation in the resistance values, the waveform comparison unit 10 has a function of correcting the fluctuation in the resistance values of the power supply side voltage detection resistors 5a and 5b and the load side voltage detection resistors 6a and 6b, and thus the measurement accuracy can be further improved.

As for the power supply side voltage detection resistors 5a and 5b and the load side voltage detection resistors 6a and 6b, it is preferable to use resistor members of the same specification as in embodiment 1. Further, by being disposed on the same substrate, the measurement device is less likely to be affected by the temperature and humidity environment due to the position, and the reliability of the measurement can be further improved.

According to the contact portion abnormality monitoring device according to embodiment 3 and the circuit breaker using the same, the presence or absence of an abnormality of the contact portion can be monitored by comparing an actual measurement value of a voltage drop of the opening/closing contact calculated from a difference between currents flowing through the voltage detection resistors connected between the power supply side and the load side lines of the opening/closing contact, respectively, with a normal value of the voltage drop of the opening/closing contact calculated from the load current and an initial value of the contact resistance of the opening/closing contact. Since the voltage drop of the opening/closing contact part can be measured in a non-contact manner, the safety of the circuit breaker can be improved without affecting the insulation between the opening/closing contacts.

Description of the reference numerals

1 circuit, 2 open/close contacts, 3 current transformer, 4 load current detection unit, 5 power source side voltage detection resistor, 6 load side voltage detection resistor, 7 abnormality detection current transformer, 8 voltage drop detection unit, 9 alarm level setting unit, 10 waveform comparison unit, 11 alarm unit, 12 trip device