JP2008206360A - Earth leakage relay - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire an earth leakage relay for entering a test simulation waveform to an earth leakage detection circuit or prompting the input by a user in a state that a normal connection to a zero-phase current transformer is confirmed without using a switch on a signal line within the earth leakage detection circuit. <P>SOLUTION: The earth leakage relay includes: a Wheatstone bridge 41 provided between the earth leakage detection circuit 46 and the zero-phase current transformer 20, and having four detection resistors 42 disposed on four sides; a comparison circuit 50 for comparing a potential between middle points A, B in the Wheatstone bridge 41; and a simulation waveform generating circuit 53 biased in response to an operation of a test button 52 while the comparison circuit generates an output, and injecting the test simulation waveform into the earth leakage detection circuit 46. If the zero-phase current transformer 20 is normally connected, the Wheatstone bridge 41 is configured so as to generate the potential between the middle points A, B which causes the comparison circuit 50 to generate the predetermined output. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a leakage relay that is connected to a zero-phase current transformer that detects a zero-phase current of an electric circuit and monitors an electric leakage state of the electric circuit based on the detected current.

  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 configured by, for example, an integrated circuit, and is detected by the zero-phase current transformer in the earth leakage detection circuit. As is well known, the signal level is determined, and if a predetermined value is exceeded, a 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 it is inconvenient if the main circuit is opened immediately for earth leakage fire protection. Keep the main circuit energized at the location (for example, hospital operating room or smoke evacuation device), and only issue an alarm that a leakage has occurred. For example, the time when the main circuit can be opened. It is known to take appropriate measures in the band. 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, this earth leakage relay is also equipped with a test device, but 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 the signal line from the zero-phase current transformer is connected, it is possible to confirm the operation as a single leakage relay.
This is because the zero-phase current transformer and the earth leakage relay are not necessarily installed at the same time in distribution construction, and as described above, the core components related to the earth leakage detection function such as an integrated circuit are mounted on the earth leakage relay. Therefore, it is thought that there is a need to be able to quickly grasp the failure in the unlikely event.
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. That is, even if there is a disconnection or breakage of the signal line with the zero-phase current transformer, if there is no problem even in the earth leakage relay, an earth leakage alarm by operating the test button will be issued. For this reason, even if it is an earth-leakage relay, the reliability improvement of the test apparatus equivalent to an earth-leakage circuit breaker is calculated | required.

However, if attention is paid to the test itself, for example, if a short-circuit is made across the different poles of the zero-phase current transformer with a variable resistor, and the resistance value of this variable resistor is gradually reduced, the zero-phase For current transformers, it is recognized that this is a simulated increase in leakage current, so it is possible to check the leakage detection function including the zero-phase current transformer without relying on the test equipment, but in terms of safety or simplicity. When considering gender, it is not very good.
Therefore, the signal line in the leakage detection circuit is provided with a switch that opens and closes the signal line in the leakage detection circuit in conjunction with the operation of the test button, and the reference potential generated in the leakage relay when the switch is opened, or The pseudo signal from the oscillation circuit is injected into the secondary winding of the zero-phase current transformer via the signal line with the zero-phase current transformer, and then returned to the leakage detection circuit, so that the signal itself is a leakage current. It is known that a leakage alarm is issued by recognizing that this is a simulated increase (see, for example, Patent Document 1).

JP 2003-274550 A (paragraphs 0014 to 0020)

The conventional leakage relay test apparatus as described above requires a connection with a zero-phase current transformer, so that the failure of this zero-phase current transformer or the disconnection of the signal line between the zero-phase current transformer and the leakage relay Since the presence or absence of a broken line can be confirmed by a test operation, it goes without saying that the reliability is further improved if attention is paid only to the act of monitoring leakage.
However, in order to realize this, since a switch is required for the so-called weak signal line in the leakage detection circuit, and in the normal use state other than during the test, energization at the b contact (normally closed contact) is unavoidable. There was a problem that the reliability of the leakage detection circuit due to poor contact and the reliability of the product itself declined.

  The present invention was made to solve the above-described problems, and without using a switch for the signal line in the leakage detection circuit, in a state where normal connection with the zero-phase current transformer was confirmed, It is an object of the present invention to obtain a leakage relay that can input a simulated waveform for testing into a leakage detection circuit or can prompt the user to input the waveform.

  An earth leakage relay according to the present invention is connected to a zero-phase current transformer that detects a zero-phase current in an electric circuit, and detects the zero-phase current transformer in the earth-leakage relay that monitors an electric current leakage state based on the detected current. A detection resistor for converting a current into a voltage signal, a leakage detection circuit for determining a level of the voltage signal and detecting a leakage of the electric circuit, and provided between the leakage detection circuit and the zero-phase current transformer, A Wheatstone bridge consisting of four resistances with one side of the detection resistor, a comparison circuit that compares the potential between the midpoints of the Wheatstone bridge, and operation of the test button while the comparison circuit generates a predetermined output And a simulated waveform generation circuit that injects a simulated waveform for testing into the leakage detection circuit, and the Wheatstone bridge is connected to the zero-phase current transformer normally. Between the middle point, the comparator circuit is configured to produce a potential difference such as to generate the predetermined output.

  According to this invention, by operating the test button, it is possible to confirm whether there is an abnormality in the connection with the zero-phase current transformer, as well as whether there is a fault in the zero-phase current transformer itself, as well as whether there is a fault inside the leakage relay, It is possible to provide a user with a reliable leakage relay that performs leakage monitoring.

Embodiment 1 FIG.
1 is a circuit diagram including a leakage relay in Embodiment 1 of the present invention.
The earth leakage relay 40 is provided in the electric circuit 10 of the main circuit, and is connected to both ends of the zero-phase current transformer 20 that detects the zero-phase current in the electric circuit 10 via the connection lead wires 30. A detection resistor 42 for converting the output current of the current into a voltage signal, a leakage detection circuit 46 for determining the level of the voltage signal from the detection resistor 42 and detecting leakage in the electric circuit 10, and an output of the leakage detection circuit 46 is amplified. When the leakage detection circuit 46 detects a leakage, the output circuit 47 turns on the leakage display LED 48 and drives the leakage alarm output relay 49.

  And the earth-leakage relay 40 is equipped with the Wheatstone bridge 41 which made the detection resistance 42 one side, and formed the other three sides with resistance 43,44,45, and when the zero phase current transformer 20 is connected, the Wheatstone bridge 41 is provided. The resistance values of the resistors 43, 44, and 45 are set so that the potential at the detection resistor side midpoint A becomes lower than the potential at the other midpoint B and the relationship of the A point potential <the B point potential. That is, in the present invention, the Wheatstone bridge 41 is interposed between the zero-phase current transformer 20 and the leakage detection circuit 40, and in a normal Wheatstone bridge, the current flowing through the galvanometer is zero in order to measure the unknown resistance. The resistance values of the resistors 43, 44, and 45 are set so as to generate a predetermined potential difference at the midpoints A and B to which the galvanometer is connected.

Further, a comparison circuit 50 for comparing the potentials of the Wheatstone bridge 41 is provided at the midpoints A and B. When the relationship of the A point potential <the B point potential, the comparison circuit 50 generates a predetermined output. As a result, the transistor 51 is turned on, and the test button 52 via the transistor 51 and the simulated waveform generating circuit 53 that is energized by the pressing operation of the test button 52 to generate a test simulated waveform are It is configured to be connected to the input.
The earth leakage relay 40 includes a power circuit 54 for supplying a predetermined voltage to each internal circuit.

In the earth leakage relay 40 according to the first embodiment, when the zero-phase current transformer 20 is connected as described above, the resistors 43, 44, and 45 have a relationship of A point potential <B point potential in the Wheatstone bridge 41. Therefore, at this time, the transistor 51 is turned on by the output of the comparison circuit 50, the simulated waveform generation circuit 53 is connected to the input of the leakage detection circuit 46, and the simulated waveform for testing is supplied to the leakage detection circuit 46. inject.
Therefore, when the zero-phase current transformer 20 is normally connected to the leakage relay 40, it is possible to confirm that the leakage detection circuit 46 is normal by pushing the test button 52.

When the zero-phase current transformer 20 is not connected or the connection lead wire 30 is disconnected, the A point potential> the B point potential in the Wheatstone bridge 41, the transistor 51 is turned off by the comparison circuit 50, and the simulated waveform generating circuit 53 is disconnected from the input of the leakage detection circuit 46.
Therefore, even if the test button 52 is operated, the earth leakage relay 40 does not operate, so it can be confirmed that there is an abnormality in the connection with the zero-phase current transformer 20 or the zero-phase current transformer 20.

  As described above, according to the leakage relay of the first embodiment, detection is provided between the leakage detection circuit 46 and the zero-phase current transformer 20 and converts the detected current of the zero-phase current transformer 20 into a voltage signal. A Wheatstone bridge 41 composed of four resistances with the resistor 42 as one side, a comparison circuit 50 that compares the potential between the midpoints A and B of the Wheatstone bridge 41, and the comparison circuit 50 generate a predetermined output. And a simulated waveform generating circuit 53 that is energized in response to the operation of the test button 52 and injects a simulated waveform for testing into the leakage detection circuit 46. In the Wheatstone bridge 41, the zero-phase current transformer 20 operates normally. When connected, since the comparison circuit 50 is set so as to generate a potential difference between the midpoints A and B so as to generate a predetermined output, the zero-phase current transformer is connected to the signal line of the leakage detection circuit b. contact By using the test button without using a switch, it is possible to check whether there is a fault inside the ground fault relay, whether there is an abnormality in the connection with the zero-phase current transformer, and whether there is a fault in the zero-phase current transformer itself. It is possible to realize a highly reliable leakage relay that performs leakage monitoring.

Embodiment 2. FIG.
FIG. 2 is a circuit diagram showing Embodiment 2 of the present invention.
In the first embodiment, the simulated waveform generating circuit 53 that generates the simulated waveform for testing is controlled by the output of the comparison circuit 50 that compares the potential between the midpoints A and B of the Wheatstone bridge 41. When the leakage relay 40 does not operate due to the operation of the test button 52, it is unknown whether there is an abnormality in either the connection of the zero-phase current transformer 20 or the leakage detection circuit 46.
Therefore, in the second embodiment, when the zero-phase current transformer 20 is not connected (including the case where the connection lead wire 30 of the zero-phase current transformer 20 is disconnected), the midpoint A of the Wheatstone bridge 41 is , B is set such that A point potential> B point potential, and the comparison circuit 50 generates a predetermined output.

Then, the transistors 55 and 56 forming the output circuit are turned on by the output of the comparison circuit 50, the abnormality display LED 57 is turned on, and the abnormality alarm output relay 58 is driven, whereby the connection of the zero-phase current transformer 20 is abnormal. Inform that there is.
If the abnormality display LED 57 is not lit and the leakage indicator LED 48 is not lit even if the test button 52 is operated, it can be determined that an abnormality is recognized after the leakage detection circuit 46.

  As described above, according to the leakage relay of the second embodiment, detection is provided between the leakage detection circuit 46 and the zero-phase current transformer 20 and converts the detected current of the zero-phase current transformer 20 into a voltage signal. A Wheatstone bridge 41 consisting of four resistances with one side of the resistor 42, a comparison circuit 50 for comparing the potential between the midpoints A and B of the Wheatstone bridge 41, and when the comparison circuit 50 generates a predetermined output. The Wheatstone bridge 41 has a potential difference that causes the comparison circuit 50 to generate a predetermined output between the middle points A and B when the zero-phase current transformer 20 is not connected. Since it is set to occur, in addition to confirming whether there is a fault inside the leakage relay by operating the test button without using the b-contact switch on the signal line of the leakage detection circuit from the zero-phase current transformer, Abnormality presence or absence of connection of the flow circuit, and further can be a failure existence of zero-phase current transformer itself can be confirmed, to achieve a high leakage relay reliable to perform a reliable leakage monitoring.

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

DESCRIPTION OF SYMBOLS 10 Electric circuit 20 Zero phase current transformer 30 Connection lead wire 40 Earth leakage relay 41 Wheatstone bridge 42 Detection resistance 43-45 Resistance 46 Earth leakage detection circuit 47 Output circuit 48 Earth leakage display LED
49 Leakage alarm output relay 50 Comparison circuit 51 Transistor 52 Test button 53 Simulated waveform generation circuit 54 Power supply circuit 55, 56 Transistor 57 Error indication LED
58 Abnormal alarm output relay

Claims (6)

In the leakage relay that is connected to the zero-phase current transformer that detects the zero-phase current of the circuit, and monitors the leakage status of the circuit based on the detected current,
A detection resistor for converting the detection current of the zero-phase current transformer into a voltage signal;
A leakage detection circuit for determining a level of the voltage signal and detecting a leakage of the electric circuit;
A Wheatstone bridge, which is provided between the leakage detection circuit and the zero-phase current transformer, and includes four-side resistances with the detection resistance as one side;
A comparison circuit that compares the potential between the midpoints of the Wheatstone bridge;
In a state where this comparison circuit is generating a predetermined output, it is energized according to the operation of the test button, and includes a simulated waveform generating circuit that injects a simulated waveform for testing into the leakage detection circuit,
The Wheatstone bridge is set such that when the zero-phase current transformer is normally connected, a potential difference is generated between the middle points so that the comparison circuit generates the predetermined output. An earth leakage relay.   The Wheatstone bridge is set such that when the zero-phase current transformer is normally connected, the potential at the midpoint of the detection resistor is lower than the potential of the other midpoint. The earth leakage relay according to claim 1.   The earth leakage relay according to claim 1, wherein the earth leakage detection circuit drives an earth leakage display element and detects an earth leakage alarm output relay when earth leakage is detected. In the leakage relay that is connected to the zero-phase current transformer that detects the zero-phase current of the circuit, and monitors the leakage status of the circuit based on the detected current,
A detection resistor for converting the detection current of the zero-phase current transformer into a voltage signal;
A leakage detection circuit for determining a level of the voltage signal and detecting a leakage of the electric circuit;
A simulated waveform generating circuit that is energized according to the operation of the test button and injects a simulated waveform for testing into the leakage detection circuit;
A Wheatstone bridge, which is provided between the leakage detection circuit and the zero-phase current transformer, and includes four-side resistors having the detection resistor as one side;
A comparison circuit that compares the potential between the midpoints of the Wheatstone bridge;
An alarm output circuit energized when the comparison circuit generates a predetermined output,
The Wheatstone bridge is set such that when the zero-phase current transformer is not connected, a potential difference is generated between the midpoints so that the comparison circuit generates the predetermined output. Earth leakage relay.   The Wheatstone bridge is set such that, when the zero-phase current transformer is normally connected, the potential of the midpoint of the detection resistor is higher than the potential of the other midpoint. The earth leakage relay according to claim 4.   5. The leakage relay according to claim 4, wherein the alarm output circuit drives an abnormality display element.

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