JP2008305764A - Connection failure detecting circuit of electric wire and circuit breaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection failure detecting circuit capable of detecting a connection failure of an electric wire in an initial stage. <P>SOLUTION: The connection failure detecting circuit is equipped with a pair of voltage sensors 6a, 6b detecting wave forms of an input terminal 1 and an output terminal 2 of a circuit breaker; a memory 12 storing a peculiar wave form to the connection failure in the initial stage and a peculiar wave form of a serious connection failure; and a control part 16 comparing the difference of detected voltage wave forms with a memory wave form. The control part 16 decides the connection failure when the difference of the voltage wave forms is almost agreed with the stored connection failure wave form, inputs a signal, and trips a trip coil to perform breaking operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a connection failure detection circuit and a circuit breaker that detect a connection failure of an electric wire connected to a power distribution device such as a circuit breaker.

Conventionally, as a method of detecting a connection failure of an electric wire, a method of detecting a connection failure by detecting a temperature rise of a terminal portion is used. This is to detect a temperature rise caused by an increase in the resistance of the connection part due to loosening of the terminal screw. For example, in the circuit breaker having the configuration described in Patent Document 1, a temperature sensor is attached to the output terminal. When the temperature rises above a predetermined value, it is determined that the connection is defective and the disconnection operation is performed.
JP 2001-286052 A

  Thus, the configuration using the temperature sensor can determine a connection failure by detecting a temperature rise in the connection portion. However, the set temperature could not be lowered to prevent malfunction of the circuit breaker and the like, and the connection failure was not judged unless the temperature became high. For this reason, when incorporated in a circuit breaker, etc., connection failure cannot be detected in the initial stage, and even if the circuit breaker operates due to connection failure, the circuit breaker case deteriorates or the distribution board case There was a problem of deterioration.

  In view of the above problems, an object of the present invention is to provide a connection failure detection circuit capable of detecting a connection failure of electric wires at an initial stage, and a circuit breaker incorporating the circuit.

In order to solve the above-described problem, a wire connection failure detection circuit according to the invention of claim 1 includes a pair of voltage waveform detection means for detecting the voltage waveform of the input terminal and the output terminal of the power distribution device, and the detected voltage waveform. Inter-terminal voltage output circuit for extracting the difference as a terminal-to-terminal voltage waveform, waveform information storage means for storing a terminal voltage waveform peculiar to slight connection failure, and comparison judgment for comparing the extracted waveform with the stored waveform The comparison and determination unit determines that a connection failure has occurred and outputs a connection failure occurrence signal when the extracted waveform substantially matches the stored waveform.
According to this configuration, by detecting the difference in the voltage waveform between the input and output terminals, it is possible to cut the commercial frequency component that is the main component of the voltage waveform, and it is easy to detect the slight waveform component caused by the poor connection. Then, by storing a specific waveform generated in the initial stage of connection failure and determining that the connection is defective when the extracted waveform matches or is close to the stored waveform, the connection failure can be detected with a simple circuit. In addition, since the connection failure in the initial stage can be detected, the stage before heat generation can be detected.

According to a second aspect of the present invention, in the first aspect of the invention, the waveform information storage means stores not only a voltage waveform peculiar to a slight connection failure but also a waveform peculiar to a severe connection failure, and the comparison judgment means extracts The waveform information is output together with the connection failure occurrence signal in addition to the connection failure occurrence signal when the waveform that is substantially coincides with any of the stored waveforms.
According to this configuration, it is possible to determine whether the stage of connection failure that has occurred is mild or severe, and it is easy to deal with it.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein the voltage waveform detecting means is a pair of antennas installed near the input terminal and the output terminal, and the comparison judging means excludes commercial frequency components. It is characterized in that the connection failure is judged by comparing the high frequency components.
According to this configuration, the voltage waveform detecting means can be a loop antenna, for example, and the voltage waveform can be detected with a simple configuration.

According to a fourth aspect of the present invention, in the circuit breaker that operates to break when an electric leakage or overcurrent occurs, the electric wire connection failure detection circuit according to any one of the first to third aspects is provided, and the comparison and determination means determines that the connection is defective. Then, the circuit is cut off.
According to this configuration, the electric circuit can be interrupted at the initial stage of connection failure, and heat generation at the terminal portion and deterioration of the device can be prevented.

  According to the present invention, by detecting the difference in the voltage waveform between the input and output terminals, the commercial frequency component that is the main component of the voltage waveform can be cut, and it becomes easy to detect a slight waveform component caused by a connection failure. Then, by storing a specific waveform generated in the initial stage of connection failure and determining that the connection is defective when the extracted waveform matches or is close to the stored waveform, the connection failure can be detected with a simple circuit. In addition, since the connection failure in the initial stage can be detected, the stage before heat generation can be detected.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a circuit block diagram of an earth leakage circuit breaker which is one of circuit breakers incorporating an electric wire connection failure detection circuit according to the present invention, where 1 is an input terminal, 2 is an output terminal, and 3 is an electric circuit K. 4 is a tripping coil that detects the zero-phase current of the electric circuit K, 6a is a voltage sensor that detects the terminal voltage waveform of the input terminal 1, and 6b Is a voltage sensor that detects the voltage waveform of the output terminal 2, 7 is a tripping control unit that controls the coil 4 based on the detected current information and voltage waveform information, 8 is a power supply circuit that drives the cutoff control unit 7, Is a current detection circuit that amplifies and outputs current information detected by the zero-phase current transformer 5. In addition, L has shown the electric wire which is connected to the earth-leakage circuit breaker and comprises the electric circuit K. FIG.

  The interruption control unit 7 outputs the difference between the output signals of the two voltage sensors 6a and 6b, the inter-terminal voltage detection circuit 10, the current information output from the zero-phase current transformer 5, and the inter-terminal voltage detection circuit 10. A / D conversion circuit 11 that performs A / D conversion of voltage information, a storage unit 12 that includes an EPROM or the like that stores waveform information, a trigger circuit 14 of a thyristor 13 that drives a tripping coil 4, a notification LED 15 that performs a notification operation when shut off, It has the control part 16 which consists of MPU which judges electrical leakage and poor connection, and performs predetermined | prescribed control.

The storage unit 12 stores three types of waveforms as shown in FIG. 2A shows a normal waveform without connection failure (hereinafter referred to as waveform A1), and FIG. 2B shows a mild connection failure waveform (hereinafter referred to as waveform A2) that can be regarded as an initial stage of connection failure. 2 (c) shows a severe connection failure waveform (hereinafter referred to as waveform A3) at the stage where the connection failure has progressed and glow discharge has occurred.
The voltage waveform between terminals is a sine wave waveform of a commercial frequency generated by a slight voltage drop inside the circuit breaker during normal connection, and is a waveform A1 shown in FIG. When an initial connection failure occurs, a small discharge phenomenon occurs in the terminal portion. A large number of such discharges are generated during one cycle of the voltage, and the inter-terminal voltage waveform has a waveform as shown in FIG. Furthermore, when the connection failure deteriorates, the discharge changes to glow discharge, and changes to discharge once every half cycle. Due to this change, the voltage waveform between the terminals becomes a waveform A3 as shown in FIG.

  The control unit 16 compares the stored waveform with the extracted waveform to determine a terminal connection failure. First, the current inter-terminal voltage waveform is compared with the stored normal voltage waveform A1. If it is determined that the comparison is similar, the connection state of the electric wire is determined to be normal, and the comparison operation is continued.

  If it is not similar to the waveform A1, it is compared with the waveform A2. If it is determined that they are similar in this comparison, it is determined that there is a slight (initial) connection failure, the trigger circuit 14 is activated, the trip coil 4 is tripped, and the switching contact 3 is opened. Thus, the electric circuit K is interrupted. Then, the notification LED 15 is controlled to emit light and controlled to light for a predetermined time (the power supply to the power circuit 8 is stopped by the shut-off operation, but the power can be turned on for a certain time by the power storage of the power circuit 8).

If it is not similar to the waveform A2, it is finally compared with the waveform A3. If it is determined in this comparison that they are similar, it is determined that there is a severe connection failure. Similarly, the trigger circuit 14 is activated to cut off the electric circuit K. In addition, the notification LED 15 is controlled to blink and blink for a predetermined time.
In this embodiment, the voltage waveform A1 at normal time is stored in the storage unit 2, but the waveform A
The connection failure can be determined only by storing the two waveforms A2 and A3, or only the waveform A2 may be used. Further, when the current information output from the current detection circuit 9 is larger than the set value, the control unit 16 determines that leakage has occurred and operates the trigger circuit 14 to similarly cut off the electric circuit.

Thus, by detecting the voltage waveform difference between the input and output terminals, the commercial frequency component, which is the main component of the voltage waveform, can be cut, and it becomes easy to detect a slight waveform component caused by poor connection. Then, by storing a specific waveform generated in the initial stage of connection failure and determining that the connection is defective when the extracted waveform matches or is close to the stored waveform, the connection failure can be detected with a simple circuit. In addition, since the connection failure in the initial stage can be detected, the stage before heat generation can be detected.
Therefore, the electric circuit can be interrupted at the initial stage of poor connection, heat generation and discharge of the terminal portion can be prevented, and deterioration of equipment and the like can be prevented. In addition, it is easy to deal with because it is possible to determine whether the connection failure caused by the light emission of the notification LED is an initial stage or a severe stage.

  FIG. 3 shows another example of the connection failure detection circuit of the electric wire, and shows a state where it is incorporated in a circuit breaker as in FIG. The voltage waveform detection means is greatly different from the configuration of FIG. 1, and the voltage waveforms at the input terminal 1 and the output terminal 2 are detected by electromagnetic waves generated by the changes by the antennas 18a and 18b formed of loop antennas. In addition, since the other structure of a circuit breaker is the same as that of the said FIG. 1, it attaches | subjects the same code | symbol and abbreviate | omits description.

In this case, the voltage waveform stored in the storage unit 12 is a waveform as shown in FIGS. FIG. 4A is an explanatory diagram at the time of normal connection, and no waveform is detected, FIG. 4B is a waveform at an initial stage where connection failure occurs (hereinafter referred to as waveform B1), and FIG. 4C is a connection. A waveform (hereinafter referred to as waveform B2) at a stage where a defect has advanced and glow discharge has occurred is shown.
The voltage waveform information detected by the antennas 18a and 18b does not generate a spike-like waveform when a wire is normally connected to a terminal, and a commercial frequency that is a low frequency cannot be detected. ) Does not detect the waveform as shown in. Then, a waveform as shown in FIG. 4B is detected by a spike-like waveform generated with the occurrence of a slight connection failure. Further, in a severe connection failure in which glow discharge occurs, a discharge that occurs once in a half cycle is detected as shown in FIG.

The control unit 16 detects a connection failure of the terminal by comparing with the stored waveform. First, the waveform B1 is compared. If it is determined that they are similar in this comparison, it is determined that there is a slight (initial) connection failure, the trigger circuit 14 is activated, the trip coil 4 is tripped, and the switching contact 3 is opened. Thus, the electric circuit is interrupted. Then, similarly to the above embodiment, the notification LED 15 is controlled to emit light and controlled to light for a predetermined time.
If it is not similar to waveform B1, it is compared with waveform B2. If it is determined in this comparison that they are similar, it is determined that there is a severe connection failure. Similarly, the trigger circuit 14 is activated to cut off the electric circuit. In addition, the notification LED 15 is controlled to blink and blink for a predetermined time.

  In this way, the voltage waveform at the terminal portion may be detected using the antenna, and an initial connection failure can be detected. The antenna may be a loop antenna and can detect a voltage waveform with a simple configuration.

  The electric wire connection failure detection circuit can be applied not only to a circuit breaker as shown in the above embodiment but also to an electric circuit for transmitting and distributing electric power, so that a poor connection can be detected at an early stage. .

It is a circuit block diagram which shows an example of embodiment of the circuit breaker provided with the connection failure detection circuit of the electric wire which concerns on this invention. The comparison voltage waveform memorize | stored in the memory | storage part of FIG. 1 is shown, (a) is a waveform with a normal connection, (b) is a waveform with a mild connection failure, (c) is a waveform with a severe connection failure. It is a block diagram of the circuit breaker provided with the other structure of the connection failure detection circuit of an electric wire. (A) is explanatory drawing of the waveform detected by an antenna at the time of a normal connection, (b) is the waveform of the mild connection failure memorize | stored in the memory | storage part of FIG. 3, (c) is the severeness memorize | stored in the memory | storage part of FIG. This is a waveform of connection failure.

Explanation of symbols

  1 .... Input terminal, 2 .... Output terminal, 6 .... Voltage sensor (voltage waveform detection means), 7 .... Interrupt control unit, 10 .... Inter-terminal voltage detection circuit, 12 .... Storage unit (waveform information storage means) ), 16 .. Control part (comparison judgment means), 18a, 18b .. Antenna, L .. Electric wire.

Claims (4)

A pair of voltage waveform detecting means for detecting voltage waveforms at the input terminal and the output terminal of the power distribution device;
An inter-terminal voltage output circuit that extracts the difference between the detected voltage waveforms as an inter-terminal voltage waveform;
Waveform information storage means for storing a voltage waveform between terminals peculiar to mild connection failure;
Comparing and determining means for comparing the extracted waveform with the stored waveform,
The wire connection failure detection circuit, wherein the comparison determination means determines that a connection failure has occurred and outputs a connection failure occurrence signal when the extracted waveform substantially matches the stored waveform. The waveform information storage means stores not only a voltage waveform peculiar to a slight connection failure but also a waveform peculiar to a severe connection failure,
2. The electric wire connection failure detection circuit according to claim 1, wherein when the extracted waveform substantially matches any of the stored waveforms, the comparison determination means outputs the waveform information in addition to the connection failure occurrence signal. . 3. The voltage waveform detection means is a pair of antennas installed in the vicinity of the input terminal and the output terminal, and the comparison / determination means compares the high-frequency components excluding the commercial frequency component to determine a connection failure. The connection failure detection circuit of a description electric wire. In a circuit breaker that shuts off when a leakage or overcurrent occurs,
A circuit breaker comprising the electric wire connection failure detection circuit according to any one of claims 1 to 3, wherein the circuit is interrupted when the comparison / determination means determines that the connection is defective.

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