JP4926015B2 - Earth leakage relay - Google Patents

Description

  The present invention relates to a leakage relay that detects a leakage of a main circuit in combination with a zero-phase current transformer and outputs the occurrence of the leakage to the outside. More specifically, the present invention relates to an improvement of a test apparatus for confirming the function.

  An earth leakage breaker, which is one of the circuit breakers, incorporates an earth leakage detection circuit, a zero-phase current transformer, and an electromagnet device, for example, configured by an integrated circuit. As is well known, the level of the signal detected by the current transformer is determined, and if it exceeds a predetermined value, the drive signal is output to the electromagnet device and the main circuit is opened. It is also well known that a test device (test button) is installed to check whether this leakage detection function can operate normally.

This earth leakage breaker will be installed in accordance with the electrical equipment technical standards from the viewpoint of electric shock prevention or earth leakage fire protection, but in some cases, the main circuit was not opened immediately in earth leakage fire protection. In inconvenient locations (eg hospital operating rooms and smoke evacuation devices), keep the main circuit energized and only give an alarm that a leakage has occurred. For example, the main circuit may be opened. It is known to take appropriate measures in the absence of time.
As a means for issuing this alarm, a separate zero-phase current transformer disposed in the main circuit and a leakage relay to which a signal line from this zero-phase current transformer is connected are used. In view of the “leakage monitoring”, it is generally installed in an electrical management room, for example, away from the main circuit.

  By the way, although this earth leakage relay is also equipped with a test device, it differs from the above-described earth leakage circuit breaker test device in the following points. In other words, the earth leakage relay can be tested alone, and this test makes it possible to confirm the function or operation of a built-in integrated circuit or relay (equivalent to an electromagnetic device in an earth leakage breaker). ing. In other words, even before connecting the signal line from the zero-phase current transformer, it can be confirmed as a single earth leakage relay. This is not necessarily the case when installing the zero-phase current transformer and the earth leakage relay at the same time in distribution construction. In addition, as mentioned above, since the core components related to the leakage detection function such as an integrated circuit are mounted on the leakage relay as described above, it is possible to quickly grasp the emergency failure. It is thought to be in the background. However, in other words, this means that the zero-phase current transformer itself cannot be confirmed by a test even in actual use, that is, in a connected state with the zero-phase current transformer. In other words, even if there is a disconnection or breakage of the signal line, if there is no problem even within the leakage relay, a leakage alarm will be issued by pushing the test button. As a result, even if it is a leakage relay, Therefore, it is necessary to improve the reliability of the test equipment equivalent to the earth leakage breaker.

  However, even if it is an earth leakage relay, it is not limited as long as a test winding for supplying a test current by pushing a test button is passed through the zero-phase current transformer (for example, refer to Patent Document 1). Further, in this Patent Document 1, it is possible to easily determine whether the malfunction of the earth leakage alarm due to the pressing of the test button is due to a malfunction of the built-in integrated circuit or relay, or due to disconnection or disconnection. The detection resistor that converts the output current obtained by the phase current transformer into a voltage is disconnected by the transistor circuit only during disconnection diagnosis, and in the meantime, a resistor is connected to the connection line with the zero-phase current transformer. It is known that the potential difference obtained in step (1) is determined, and if it exceeds a predetermined value, it is determined that the wire is disconnected (or not connected) and an electric leakage alarm (in this case, a wire disconnection alarm) is issued.

JP 2002-44856 A (column 5, lines 24 to 30)

  The conventional earth leakage relay test equipment entrusts the test operation to the test winding wound around the zero-phase current transformer, and the earth leakage relay itself is disconnected or disconnected from the zero-phase current transformer. It goes without saying that the reliability is further improved in view of the point of detecting a so-called self-check function. However, in realizing this, it goes without saying that it is troublesome to wind the test winding from the earth leakage relay around the zero phase current transformer, and further to the signal line between the zero phase current transformer and the earth leakage detection circuit. Faced with the challenge of increasing circuit scale by requiring functions such as a transistor circuit that switches the connection of resistors including a detection resistor, a reset circuit for a leakage detection circuit, and a waveform generation circuit that controls their timing . Further, in terms of performance, there is still room for improvement, for example, by inserting a transistor in series with the detection resistor, a change in impedance due to the temperature of the transistor affects the sensitivity current.

  The present invention has been made in order to solve the above-described problems, and an object thereof is to provide a highly reliable leakage relay that performs reliable leakage monitoring.

The earth leakage relay according to the present invention is a first detection resistor that is connected to a zero-phase current transformer installed in the main circuit via a connection lead wire and converts an output current obtained by the zero-phase current transformer into a voltage. A leakage detection circuit for determining the level of the voltage, an output circuit for driving the leakage display element in response to the output of the leakage detection circuit, and the leakage detection circuit in the main circuit by pressing the test button. A simulated waveform generating circuit that generates a simulated waveform determined to have a level equivalent to the occurrence of leakage, and the first detection resistor and the leakage detection circuit are interposed between the first detection resistor and the leakage detection circuit. An amplifier circuit to which a voltage obtained by dividing the voltage at one end of the detection resistor by the first detection resistor and the second detection resistor is input; a comparator that compares a signal amplified by the amplifier circuit with a reference potential ; According to the comparison output of the above comparator And a switching means for turning on and off of the signal injection from the simulated waveform generating circuit to said leakage detecting circuit.

  According to the present invention, a leakage test can be performed without winding a test winding around the zero-phase current transformer, and a disconnection or a broken line with the zero-phase current transformer can be detected without increasing the circuit scale. An earth leakage relay can be obtained.

Embodiment 1 FIG.
1 is a circuit diagram including a leakage relay in Embodiment 1 of the present invention. The output current of the zero-phase current transformer 20 installed in the electric circuit 10 of the seed circuit is caused by the first detection resistor 41 via the connection lead wire 30 connecting the zero-phase current transformer 20 and the leakage relay 40. When converted to voltage input and input to the leakage detection circuit 46 and reaches the reference level, the leakage circuit LED 48 is turned on by the output circuit 47 and the leakage alarm output relay 49 is driven.

  Here, the process in which the voltage (potential at point A in the figure) obtained by the first detection resistor 41 is injected into the leakage detection circuit 46 will be described in detail. The potential at point A is input to the non-inverting input terminal of the operational amplifier 43 constituting the amplifier circuit 50. Utilizing the fact that the inverting input terminal of the operational amplifier 43 becomes a constant voltage circuit having a voltage amplification factor of 1, the potential at the point A, that is, the level voltage of leakage detection, is the first and second constituting the voltage dividing resistor. It is input to the leakage detection circuit 46 through the resistors 44 and 45.

When the test button 55 is pressed, a simulated waveform that is determined to have a level equivalent to the occurrence of leakage in the main circuit is input from the simulated waveform generation circuit 56 to the leakage detection circuit 46 and output from the output circuit 47 as described above. .
The above description is a so-called normal state in which the connection lead wire 30 is not disconnected or broken, but the earth leakage display LED 48 and the earth leakage alarm output relay 49 are not affected unless the main circuit leakage or the test button 55 is pushed. Do not drive. Further, as is apparent from the figure, the simulated waveform from the simulated waveform generation circuit 56 is not injected into the zero-phase current transformer 20. That is, the earth leakage relay 40 and the zero-phase current transformer 20 are connected only by the connection lead wire 30.

Next, the operation of the earth leakage relay 40 when the connection lead wire 30 is disconnected or broken or when it is not connected (hereinafter collectively referred to as the disconnection of the connection lead wire). explain.
Between the non-inverting input terminal of the operational amplifier 43 and the ground, there is a second detection resistor 42 for inputting the voltage divided by the first detection resistor 41 to the non-inverting input terminal of the operational amplifier 43 when the connection lead wire is disconnected. It is connected.
The relationship between the internal impedance of the zero-phase current transformer 20, the first detection resistor 41, and the second detection resistor 42 is set as follows.
Internal impedance (several tens of Ω) <first detection resistor 41 (several kΩ) <second detection resistor 42 (several hundred kΩ)
That is, under normal conditions, the potential at point A and the potential at point B (reference potential output from the leakage detection circuit 46: VREF (for example, 2.5 V) by the combined impedance of the internal impedance and the first detection resistor 41 )) Is almost equivalent (because the internal impedance of the zero-phase current transformer 20 is extremely low). On the other hand, when the connection lead wire is disconnected, the internal impedance does not contribute to the combined resistance, that is, the potential at the point A is divided by the first detection resistor 41 and the second detection resistor 42. The potential at the point is lower than the potential at the point B. By utilizing this difference in potential difference, as will be described later, the earth leakage display LED 48 and the earth leakage alarm output relay 49 are driven at the time of the disconnection, and the user is informed of the disconnection state.

  In making use of the difference in potential difference, in order to clarify the difference, the entire secondary side of the zero-phase current transformer 20 may be made to have a high impedance. The entire side must be low impedance, and therefore the difference in potential difference between normal and disconnected is small. Therefore, in the present invention, the amplifier circuit 50 is provided. More specifically, in addition to the operational amplifier 43, a minute voltage (several tens of mV) at the time of disconnection of the connection lead wire is amplified by a current flowing through the first resistor 44 of the inverting input terminal. The minute voltage is amplified (for example, several V) by the second resistor 45 (feedback resistor) (with this, the signal for detecting the disconnection is gained by the amplifier circuit 50, gain 1 + second resistor 45 / second resistor. Treated as a single resistor 44).

  Since the amplified voltage naturally includes an AC component due to leakage, the DC component obtained by removing the AC component by the low-pass filter 51 is input to the comparator 52. In the comparator 52, the output of the comparator 52 becomes Hi (high) by comparing the DC voltage with the reference potential set by the reference potential determining resistors 53 and 54. That is, this Hi output is output to the output circuit 47, and the leakage indicator LED 48 and the leakage alarm output relay 49 are driven. Needless to say, the reference potential is set so that the output of the comparator 52 becomes Lo (low) during normal operation.

  In this way, the method of using the amplifier circuit 50 is devised, and the presence or absence of disconnection can be confirmed in real time only by adding parts such as the second detection resistor 42, the low-pass filter 51, the comparator 52, or a small circuit. It becomes possible to detect.

Embodiment 2. FIG.
In the first embodiment, when the connection lead wire is disconnected, the leakage indicator LED 48 and the leakage alarm output relay 49 are driven as a “break alarm”, so that the disconnection can be notified to the user. On the other hand, if a power supply voltage is applied to the earth leakage relay 40 in a temporary installation before the start of energization of the main circuit, that is, in a state where the earth leakage relay 40 and the zero-phase current transformer 20 are not yet connected, this is regarded as a disconnection. The disconnection alarm is also activated. In particular, if alarm means such as a buzzer is in the wiring / live line state on the user side in the leakage alarm output relay 49, the influence cannot be overlooked. An improvement of this will be described as a second embodiment.

FIG. 2 is a circuit diagram showing Embodiment 2 of the present invention.
As shown in FIG. 2, the simulation signal of the simulation waveform generation circuit 56 is configured to be injected into the leakage detection circuit 46 via the switch means, for example, the transistor 57, and the base of the transistor 57 is the comparator 52. The connection to the output is the difference from the first embodiment.
In other words, since the output of the comparator 52 is Lo at normal time, the transistor 57 is turned on, and if the test button 55 is pushed, the leakage indicator LED 48 and the leakage alarm output relay 49 are driven. On the other hand, at the time of disconnection, as in the first embodiment, the output of the comparator 52 becomes Hi, and as a result, the transistor 57 is turned off. Since the alarm output relay 49 is not driven, the user can recognize the disconnection.

  In this case, the application of power to the earth leakage relay 40 when the zero-phase current transformer is not connected, and immediately the disconnection alarm drive are avoided. Needless to say, unless the test button 55 is pushed, the disconnection will occur. Therefore, daily inspection by pressing the test button 55 is indispensable.

In general, the leakage relay is the same as the leakage breaker, the user selects the rated sensitivity current according to the length to the load device at the installation location, the distance between the wiring and the ground, or the installation standards such as laws and regulations. However, in setting the rated sensitivity current, in consideration of the convenience, the manufacturer also provides a rated sensitivity current selection type in addition to the rated sensitivity current fixed type (for example, 100). -200/500 mA switching type).
In the above description, the first resistor 44 constituting the voltage dividing resistor is fixed as a so-called rated sensitivity current fixed type. However, as shown in FIG. 1 or 2, the first resistor 44 is variable. In consideration of the configuration of the electronic circuit so that, for example, a rotary switch can be arranged outside the leakage relay 40, the divided variable voltage obtained by the first resistor 44 is supplied to the leakage detection circuit 46. By inputting, a rated sensitivity current selection type is also possible, and a more convenient leakage relay can be obtained.

It is a circuit diagram containing the earth-leakage relay in Embodiment 1 of this invention. It is a circuit diagram containing the earth-leakage relay in Embodiment 2 of this invention.

Explanation of symbols

10 circuit, 20 zero-phase current transformer, 30 connection lead, 40 earth leakage relay, 41 first detection resistor, 42 second detection resistor, 43 operational amplifier, 44 first resistor, 45 second resistor, 46 earth leakage Detection circuit, 47 Output circuit, 48 Earth leakage display LED, 49 Earth leakage alarm output relay, 50 Amplifier circuit, 51 Low pass filter, 52 Comparator, 53, 54 Reference potential determination resistor, 55 Test button, 56 Simulated waveform generation circuit, 57 Transistor

Claims (4)

A first detection resistor that is connected to a zero-phase current transformer installed in the main circuit via a connecting lead, converts the output current obtained by the zero-phase current transformer into a voltage, and determines the level of the voltage. The leakage detection circuit to be performed, the output circuit that drives the leakage display element in response to the output of the leakage detection circuit, and the test button being pressed, the leakage detection circuit determines that the level is equivalent to the occurrence of leakage in the main circuit. A simulated waveform generating circuit for generating a simulated waveform, interposed between the first detection resistor and the leakage detection circuit, and the voltage at one end of the first detection resistor when the connection lead wire is disconnected. An amplifier circuit to which a voltage divided by the first detection resistor and the second detection resistor is input, a comparator for comparing a signal amplified by the amplifier circuit with a reference potential, and a comparison output of the comparator Above simulated waveform generator Leakage relay, characterized in that a switch means for turning on and off of the signal injected into the electric leakage detection circuit. The internal impedance of the zero-phase current transformer, the first detection resistor and the second detection resistor are:
Leakage relay of claim 1 Symbol mounting, characterized in that it is configured to have an internal impedance <relationship of the first resistance value of the sense resistor <resistance value of the second detection resistor.   The amplifier circuit includes an operational amplifier and a voltage dividing resistor that divides the output of the operational amplifier, inputs the output of the operational amplifier to the comparator, and supplies the potential obtained by the voltage dividing resistor to the leakage detection circuit. The ground-fault relay according to claim 1 or 2, wherein the ground-fault relay is configured to input to the relay. The earth leakage relay according to claim 3 , wherein the voltage dividing resistor comprises a variable resistor.

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