JP5631852B2 - Zero-phase voltage monitoring device, test terminal with zero-phase voltage monitoring function, and zero-phase voltage monitoring system - Google Patents

Description

  In the power transmission and distribution system, the present invention monitors a zero-phase voltage at the time of occurrence of a ground fault, and when it detects that the zero-phase voltage has become equal to or higher than a set value, the transmission / distribution line that sequentially shuts off a circuit breaker or the like The present invention relates to a zero-phase voltage monitoring device applicable to a protection system, a test terminal with a zero-phase voltage monitoring function, and a zero-phase voltage monitoring system.

  Conventionally, according to a ground fault protection system for a bus on the secondary side (66 kV circuit, etc.) of an interconnection substation, a ground fault sequence interrupting device (hereinafter referred to as a BGF device) is provided. And the zero-phase current io (current value) that flows to the neutral grounding resistor (hereinafter referred to as NGR device) connected to the neutral point of the interconnection transformer. It works based on the above.

  For example, an overvoltage relay (OVG) and a ground fault overcurrent relay (51G) are provided in the BGF device, and when it is detected that the zero phase voltage Vo and the zero phase current i0 are equal to or higher than a set value, a circuit breaker (CB ) Etc. are cut off sequentially (trip; order cut off) to protect the transmission lines, interconnection transformers, NRG equipment, etc. However, when checking or replacing the BGF device, checking the NGR equipment, etc., if the transmission line protection relay is changed to operate only with the OGV set value, and it is detected that the zero-phase voltage Vo has exceeded the set value. The CB is tripped to protect the transmission and distribution lines, but the interconnecting transformer does not trip, so it is handled by hand-cutting to protect the interconnecting transformer, NGR equipment, and the like.

  Moreover, in the primary test of the ground fault direction relay of the 6 kV distribution line, both the ground fault direction relay (67F) to be tested and the ground fault protection relay (10G) are locked together, and the test time is 1.5 hours to It takes 2.0 hours. Protection of the line during the test is handled by a hand-cutting operation by the operating staff to operate the CB under the monitoring of the zero-phase voltage Vo and to disconnect the line from the distribution transformer.

  The zero-phase voltage Vo generated at the time of an accident such as a one-line ground fault is measured via an instrument transformer such as a zero-phase transformer (GPT). The zero-phase voltmeter is connected to a test terminal of a test terminal tool (PTT test plug) that can be fitted to a socket electrode such as a switchboard.

  11A and 11B are a front view and a cross-sectional view showing a configuration example of a PTT test plug 50 according to a conventional example. A PTT test plug 50 shown in FIG. 11A includes a terminal body 25, four-pole test terminals 1a, 2a, 3a, and 4a and eight-pole contact terminals 1b, 2b, 3b, 4b, 1c, and 2c, shown in FIG. 3c and 4c. The terminal main body 25 has a terminal block part 26 and a plate-like part 27.

  The test terminals 1a, 2a, 3a, and 4a shown in FIG. 11B are provided in the terminal block portion 26 of the terminal main body 25, and an instrument such as a zero-phase voltmeter can be connected. Test terminal 1a is connected to contact terminals 1b and 1c, test terminal 2a is connected to contact terminals 2b and 2c, test terminal 3a is connected to contact terminals 3b and 3c, and test terminal 4a is connected to contact terminals 4b and 4c, respectively. Connected.

  The contact terminals 1b, 2b, 3b, and 4b shown in FIG. 11B are provided on the lower surface of the plate-like portion 27 of the terminal body 25, and the contact terminals 1c, 2c, 3c, and 4c are provided on the upper surface of the plate-like portion 27.

  The plate-like portion 27 can be connected to and removed from the socket electrode of the switchboard. The socket electrode of the switchboard is connected to an output terminal (secondary side or tertiary side; Vmax = 110V) such as an instrument transformer (PT). In the figure, 11, 12, 13, 14, 21, 22, 23, 24 are electrode numbers.

  Here, a connection example of the PTT test plug 50 will be described with reference to FIG. FIG. 12 shows a circuit diagram in which a portion where the PTT test plug 50 is connected to the socket electrode of the switchboard is developed. According to the PTT test plug 50 shown in FIG. 12, the electrode numbers 11, 12, 21, 22 and the electrode number 11 of the socket electrode of the switchboard (hereinafter referred to as the PTT socket 60) to which the PTT test plug 50 is fitted. , 12, 21, 22 are extracted.

  The zero-phase voltmeter 29 shown in FIG. 12 has a test terminal 1a in which the terminals of electrode numbers 11 and 21 are short-circuited through the short-circuit bar 5 and a terminal of electrode numbers 12 and 22 are short-circuited through the short-circuit bar 8. It is connected to a PTT test plug 50 having a test terminal 2a. The PTT test plug 50 to which the zero-phase voltmeter 29 is connected is fitted (inserted) into the PTT socket 60 of the switchboard.

  According to the external connection example of the zero-phase voltmeter 29, the lead wire in1 and the lead wire out1 are connected to the lead wire in2 and the lead wire out2 through the PTT test plug 50. The lead-in wires in1 and in2 are connected to the tertiary winding of the instrument transformer (PT). For example, a voltmeter 29 ′ provided in the switchboard is connected to the sending-out lines out <b> 1 and out <b> 2.

  In this example, the lead-in wire in1 is connected to the sliding electrode of electrode number 11 of the PTT socket 60. The lead-in wire in2 is connected to the sliding electrode of electrode number 12. The lead-out line out1 is connected to the sliding electrode of electrode number 21 of the PTT socket 60. The lead-out line out2 is connected to the sliding electrode of electrode number 22.

  By fitting (inserting) the PTT test plug 50 into the PTT socket 60, the same electrode numbers such as the electrode number 11-11, the electrode number 12-12, the electrode number 21-21, and the electrode number 22-22 Is connected. A test terminal 1a having terminals of electrode numbers 11 and 21, a lead-in line in1 having a sliding electrode of electrode number 11, and a lead-out line out1 having a sliding electrode of electrode number 21 are connected.

  Similarly, a test terminal 2a having terminals with electrode numbers 12 and 22, a lead-in wire in2 having a sliding electrode with electrode number 12, and a lead-out wire out2 having a sliding electrode with electrode number 22 are connected. As a result, the PTT test plug 50 connected to the zero-phase voltmeter 29 is connected to the PTT socket 60 connected to the tertiary winding of the instrument transformer (PT). The operating staff monitors the zero-phase voltmeter 29 and monitors whether the zero-phase voltage Vo is detected.

  In connection with the protection of this type of power transmission / distribution system, Patent Document 1 discloses a ground fault sequence interruption device (BGF device). The ground fault sequence interrupting device is provided in a connected substation in which a plurality of lines are connected to a bus via a line switch. When a ground fault occurs, the ground fault sequence interrupting device sequentially shuts down the lines, and identifies the line where the ground fault occurred, based on whether or not the ground fault is resolved.

  The ground fault sequence interruption device determines whether or not the line is connected to a system fault by reading a signal indicating the connection status of the line switch. Based on these assumptions, the ground fault sequence interrupting device outputs the disconnection command only to the line connected to the system fault. By configuring the ground fault sequence interrupting device in this way, it is possible to reduce the time required for detecting and disconnecting the accident line, and to suppress the unnecessary disconnection of the healthy line, thereby minimizing damage caused by the ground fault. It can be suppressed.

  On the other hand, in connection with the PTT test plug 50, Patent Document 2 discloses a test terminal cover. According to the test terminal cover, it can be attached to and detached from a PTT terminal having a covering portion, a leg portion or the like, a CTT terminal, or the like. The covering portion covers the test plug receiving ports of the PTT terminal and the CTT terminal. The leg portion is provided on the covering portion, and is inserted into the test plug receiving port so as to be locked with the test terminal.

  The covering portion has a display portion, a fixing portion, and locking means. In the covering unit, the display unit displays and hides the message. The fixing unit holds the display unit in an operable manner. Based on these assumptions, the display unit and the fixing unit are selectively locked at the display position where the locking unit displays the message and the concealment position where the message is not displayed. When the test terminal cover is configured in this way, display and non-display of the test plug insertion can be repeatedly executed easily and reliably.

JP 2010-074866 Gazette (FIG. 4 on page 7) JP 2007-171750 A (page 3 FIG. 10)

By the way, according to the transmission and distribution line protection system according to the conventional example, there are the following problems.
i. The BGF device as found in Patent Document 1 has a function of detecting the generation of the zero-phase voltage Vo (OVG operation) and outputting an external alarm and display. However, when inspecting or replacing the BGF device, the function of operating the BGF device to trip the CB, the function of outputting an external alarm and display, etc. do not work. For this reason, under the monitoring of the zero-phase voltage Vo by operating personnel, the CB must be operated to cope with a manual cutting operation such as disconnecting the interconnection transformer from the line. As a result, it is necessary to constantly monitor the zero-phase voltage Vo, and if the monitoring time of the zero-phase voltage Vo by operating personnel is long, the monitoring place cannot be left and the mental burden becomes excessive. .

  ii. In addition, according to the transmission and distribution line protection system to which the BGF device is applied, since the rating of the NGR device is a short time such as 15 seconds or 30 seconds, a ground fault continues and leads to a CB manual cutting operation. If it takes a long time to complete, there is a concern that NGR equipment will be damaged. From this point as well, it is necessary to inform the operation staff early of the occurrence of the ground fault.

  iii. Furthermore, in the primary test of the ground fault relay of the 6 kV distribution line, both the ground fault direction relay (67F) to be tested and the ground fault protective relay (10G) are locked together, and the test time is 1.5 hours to 2 hours. It takes 0 hours. If an accident such as a single-line ground fault occurs during the test, these protective relays will not function (does not work). If a ground fault such as a single-line ground fault occurs during the test, the accident will continue until the hand-cut operation is completed, which will affect public safety.

  For this reason, when a ground fault occurs, the CB needs to be manually cut off at an early stage. For this purpose, a zero-phase voltmeter is connected to the PTT test plug as shown in Patent Document 2 during the test, and the CB is operated under the monitoring of the zero-phase voltage Vo by the operating personnel, and the distribution transformer The response will be taken by hand-cutting to disconnect the track from the vessel. Incidentally, regarding the zero-phase voltage Vo, the occurrence of a ground fault cannot be detected early unless the zero-phase voltmeter is continuously watched (monitored) (not known).

  iv. When a zero-phase voltage monitoring means is configured by combining a PTT test plug such as that disclosed in Patent Document 2 and an external alarm and display output function such as an overvoltage relay in a BGF device, simply a PTT test plug and an external alarm Even if combined with the function of the display output, it is not solved to sound an alarm or display an alarm during an inoperable time of the overvoltage relay.

  Accordingly, the present invention solves such a problem, and devise a circuit for monitoring the zero-phase voltage so that an alarm can be sounded even during an inoperable time of an overvoltage relay, etc. It is an object of the present invention to provide a zero-phase voltage monitoring device, a test terminal device with a zero-phase voltage monitoring function, and a zero-phase voltage monitoring system that can greatly reduce the mental burden of (local staff).

In order to solve the above-described problem, a zero-phase voltage monitoring device according to claim 1 is provided with an attachment member attachable to a pair of test terminals of a test terminal connected to an instrument transformer, and the attachment member A zero-phase voltage monitoring circuit connected to the measuring transformer, the zero-phase voltage monitoring circuit detects a zero-phase voltage appearing between the test terminals connected to the instrument transformer, and a detection voltage when a ground fault occurs An alarm operation is performed based on a drive power source obtained by AC / DC conversion .

According to the zero phase voltage monitoring apparatus of the first aspect, the attachment member is connected to the pair of test terminals of the test terminal tool of the instrument transformer. The zero phase voltage monitoring circuit is connected to the mounting member. Based on this assumption, the zero-phase voltage monitoring circuit detects the zero-phase voltage appearing between the test terminals connected to the instrument transformer, and the drive obtained by AC / DC conversion of the detected voltage when a ground fault occurs An alarm action is executed based on the power supply .

  During this alarm operation, for example, it is possible to confirm that a zero-phase voltage has appeared between the test terminals at the time of the occurrence of the ground fault by means of at least one of the ringing sound and the alarm color, so always watch the zero-phase voltmeter. There is no need. Therefore, since an alarm can be sounded even during an inoperable time of an overvoltage relay or the like, the mental burden on the operator (local response staff) can be greatly reduced.

  The zero-phase voltage monitoring device according to claim 2, wherein the zero-phase voltage monitoring circuit is connected to the test terminal via the mounting member and detects a zero-phase voltage appearing between the test terminals. A voltage detection unit that is connected to the voltage detection unit and compares a detection voltage output from the voltage detection unit with a threshold voltage that is a determination reference, and determines whether or not a zero-phase voltage appears. It is characterized by having.

  A zero-phase voltage monitoring device according to a third aspect of the present invention includes, in the second aspect, an alarm unit that is connected to the voltage determination unit and generates a ringing sound based on a determination output voltage output from the voltage determination unit. It is characterized by.

  A zero-phase voltage monitoring device according to a fourth aspect of the invention is the zero-phase voltage monitoring device according to the second or third aspect, wherein the display unit is connected to the voltage determination unit and displays an alarm color based on a determination output voltage output from the voltage determination unit. It is characterized by having.

  The zero-phase voltage monitoring device according to claim 5 is characterized in that, in claim 2, the voltage detection unit and the voltage determination unit are sealed with mold resin in the housing.

  The zero-phase voltage monitoring device according to claim 6 is characterized in that, in claim 1, a terminal with a claw that can be connected to a test terminal of the test terminal tool is used as the attachment member. .

The test terminal device with a zero-phase voltage monitoring function according to claim 7 can be connected to a terminal main body portion having a terminal block portion and a plate-shaped portion, and to a terminal block portion of the terminal main body portion. A pair of first terminals and a pair of terminals that are provided on the plate-like portion of the terminal body and connected to the first terminal and connectable to the output terminal connected to the instrument transformer. A zero-phase voltage monitoring apparatus according to any one of claims 1 to 6 , wherein the zero-phase voltage monitoring apparatus is connected to the first terminal or the second terminal, and the zero-phase voltage monitoring apparatus includes a power supply unit and a voltage. The detection part is shared and provided in the terminal main body part.

According to instrument transformer test terminal device according to claim 7, since one of the zero phase voltage monitoring apparatus according to the present invention is a power supply unit and the voltage detecting unit is provided in the terminal body portion is shared, zero Without supplying the driving power of the phase voltage monitoring circuit from the outside , zero phase between the first or second terminal at the time of occurrence of ground fault by at least one of ringing sound and alarm color when connecting with instrument transformer It becomes possible to confirm that the voltage has appeared.

The zero-phase voltage monitoring system according to claim 8 is a terminal main body portion having a terminal block portion and a plate-like portion, and a pair of first devices that are provided in the terminal block portion of the terminal main body portion and can be connected to an instrument. 1 terminal and a pair of second terminals which are provided at the plate-like portion of the terminal main body and connected to the first terminal and connectable to the output terminal connected to the instrument transformer And a zero-phase voltage monitoring device according to any one of claims 1 to 6, which is connectable to a first terminal of the test terminal tool.

According to the test terminal device for an instrument transformer according to claim 8, the zero phase voltage monitoring device according to the present invention is provided, and the zero phase voltage monitoring device is connected to the second terminal of the test terminal tool. Because it is possible, the second power supply at the time of the occurrence of the ground fault is generated by connecting at least one of the sounding sound and the alarm color when the instrument transformer is connected , without supplying the driving power of the zero-phase voltage monitoring circuit from the outside . It can be confirmed that a zero-phase voltage has appeared between the terminals.

According to the zero-phase voltage monitoring apparatus according to the present invention, the pair of test terminals of the test terminal connected to the instrument transformer is provided with an attachable attachment member, and this attachment member has a zero-phase voltage monitoring circuit. The zero-phase voltage monitoring circuit detects the zero-phase voltage that appears between the test terminals connected to the instrument transformer, and converts the detected voltage at the time of the occurrence of the ground fault into an AC-DC converter. Based on the above, an alarm action is executed.

With this configuration, the zero phase voltage appears between the test terminals at the time of the occurrence of the ground fault by at least one of the ringing sound and the alarm color without supplying the driving power of the zero phase voltage monitoring circuit from the outside. It becomes possible to confirm. Thereby, since it is not always necessary to watch the zero-phase voltmeter, the mental burden on the operator (local staff) can be greatly reduced. Moreover, not only can an alarm be sounded even during an inoperable time of an overvoltage relay or the like, but since it is only connected to an existing PTT test plug, it is easy to handle and does not require special adjustments and is very convenient to use.

According to the test terminal device with a zero-phase voltage monitoring function according to the present invention, any one of the zero-phase voltage monitoring devices according to the present invention is provided in the terminal main body, so that the drive power source of the zero-phase voltage monitoring circuit is externally provided. Without connecting, when connecting an instrument transformer, it is possible to confirm that a zero-phase voltage has appeared between the first and second terminals at the time of occurrence of a ground fault by at least one of ringing sound and alarm color Become. Since it is not always necessary to look closely at the zero-phase voltmeter, the mental burden on the operator (local response staff) can be greatly reduced. This makes it possible to provide a simple OVG alarm built-in test plug in which the power supply unit and the voltage detection unit are shared .

According to the zero-phase voltage monitoring system according to the present invention, any one of the zero-phase voltage monitoring devices according to the present invention is provided, and the zero-phase voltage monitoring device can be connected to the first terminal of the test terminal tool. Therefore, without supplying the driving power of the zero-phase voltage monitoring circuit from the outside, when connecting the instrument transformer, at least one of the ringing sound and the alarm color, between the first terminal at the time of the occurrence of the ground fault It becomes possible to confirm that the zero phase voltage has appeared. Thereby, since it is not always necessary to watch the zero-phase voltmeter, the mental burden on the operator (local staff) can be greatly reduced. In addition, since the power supply unit and the voltage detection unit are shared and can be easily connected to an existing PTT test plug, it is versatile. In addition, there is no hindrance to the attached shorting bar and lead connection method, and the feeling of use is the same as the conventional method.

1 is a block diagram illustrating a schematic configuration example of a simple OVG alarm device 10 as a first embodiment according to the present invention. 4 is an operation flowchart showing a zero-phase voltage monitoring example in the simple OVG alarm device 10; (A) And (B) is sectional drawing which shows the structural example of the PTT test plug 20 as 2nd Embodiment. 3 is a circuit diagram showing an example of an internal configuration of a PTT test plug 20. FIG. It is a power transmission system diagram showing an application example of the PTT test plug 20 in the transmission and distribution line protection system 100. It is an external view which shows the structural example of the simple OVG warning device 30 in the zero phase voltage monitoring system 300 as 3rd Embodiment. It is a front view which shows the example of attachment of the simple OVG warning device. FIG. 4 is a partially broken sectional view showing a connection example between a simple OVG alarm device 30 and a PTT test plug 50. 2 is a circuit diagram showing an example of internal and external connections of a zero-phase voltage monitoring system 300. FIG. 3 is a circuit diagram showing an example of external connection of a zero-phase voltage monitoring system 300. FIG. (A) And (B) is the front and sectional drawing which show the structural example of the PTT test plug 50 which concerns on a prior art example. 4 is a wiring diagram showing an example of connection of a PTT test plug 50. FIG.

  Hereinafter, a zero-phase voltage monitoring device, a test transformer test instrument, and a test terminal device thereof will be described with reference to the drawings.

<Simple OVG Alarm Device as First Embodiment>
The simple OVG alarm device 10 shown in FIG. 1 constitutes an example of a zero-phase voltage monitoring device, and includes an attachment member 36, 47 and a zero-phase voltage monitoring circuit 10 ′. The attachment members 36 and 47 can be attached to a pair of test terminals 1a and 2a of a test terminal device (hereinafter referred to as a PTT test plug 50) connected to an instrument transformer. Depending on the specifications of the zero-phase voltage monitoring circuit 10 ′, a simple lead wire member is used for the mounting members 36 and 47, or a predetermined OVG alarm device 10 having a built-in zero-phase voltage monitoring circuit 10 ′ is supported to support its own weight. A flat conductive support member having a thickness of 1 mm is used.

  For example, the zero-phase voltage monitoring circuit 10 ′ is mounted on the printed circuit board 15, and the printed circuit board 15 can be connected to the PTT test plug 50 via the attachment members 36 and 47. The zero-phase voltage monitoring circuit 10 ′ detects the zero-phase voltage (ground fault voltage) Vo appearing between the test terminals 1a and 2a when the instrument transformer is connected, and performs an alarm operation based on the detection voltage at the time of occurrence of the ground fault. Run.

  The driving power for the zero-phase voltage monitoring circuit 10 'is not supplied from the outside, but is supplied from the tertiary winding circuit (PT tertiary circuit: Vmax = 110V) of the instrument transformer. The operating voltage of the zero-phase voltage monitoring circuit 10 'is around 20V, and the circuit constants are set so that the operating current is minimized. Incidentally, since the set value of the existing OVG relay is 64 V set value: 30 V and digital relay set value (fixed): 20 V, the simple OVG alarm device 10 operates sufficiently. In this example, the required characteristics were set so that the existing OVG settling value (30 V) or less was ensured and the previous alarm was not inferior.

  The zero-phase voltage monitoring circuit 10 ′ includes, for example, a power supply & voltage detection unit 31, a voltage limiter unit 32, a voltage setting unit 33, and an alarm & display unit 34. The power supply & voltage detector 31 constitutes an example of a voltage detector. The power source & voltage detector 31 has a full-wave rectifier circuit 31a. The full-wave rectifier circuit 31a has terminals + and − on the DC output side and terminals on the AC input side (hereinafter referred to as AC input terminals a1 and a2). The AC input terminals a1 and a2 are connected corresponding to the test terminals 1a and 2a of the PTT test plug 50.

  The power supply & voltage detection unit 31 is connected to a voltage limiter unit 32 that constitutes a part of the voltage determination unit. The voltage limiter unit 32 includes a resistance element R1 and a Zener diode ZD1. One end of the resistor element R1 is connected to the terminal + on the DC output side of the full-wave rectifier circuit 31a. The other end of the resistance element R1 is connected to one end of the Zener diode ZD1. The other end of the Zener diode ZD1 is connected to a terminal − on the DC output side of the full-wave rectifier circuit 31a. The resistance element R1 is about 1.0 kΩ, and the maximum current Irmax when energized is about 85 mA.

  The voltage limiter unit 32 is connected to a voltage setting unit 33 that constitutes the remaining part of the voltage determination unit. The voltage setting unit 33 has a Zener diode ZD2. One end of the Zener diode ZD2 is connected to the connection point between the resistor element R1 and the Zener diode ZD1. The forward voltage drop Vz of the Zener diode ZD1 is about 24V. The maximum operating current Imax is about 70 mA. The forward voltage drop Vz of the Zener diode ZD2 is about 7V. The maximum operating current Imax is about 135 mA. As described above, the simple resistance elements R1 and R2 and the Zener diodes ZD1 and ZD2 constitute a detection voltage stabilization circuit, thereby ensuring the simplification and reliability of the zero-phase voltage monitoring circuit 10 '.

  An alarm & display unit 34 is connected to the voltage setting unit 33. The alarm & display unit 34 includes a resistance element R2, a piezoelectric buzzer 34a that configures an example of an alarm unit, and an operation indicator lamp 34b that configures an example of a display unit. A light emitting diode (LED) or an indicator lamp is used as the operation indicator lamp 34b. One end of each of the resistance element R2 and the piezoelectric buzzer 34a is connected together, and is connected to the other end of the Zener diode ZD2. The other end of the resistance element R2 is connected to one end of the operation indicator lamp 34b. The other end of the operation indicator lamp 34b and the other end of the piezoelectric buzzer 34a are connected together and connected to the terminal − on the DC output side of the above-described full-wave rectifier circuit 31a.

  The resistance element R2 is about 3.0 kΩ, and the maximum current Irmax when energized is about 5 mA. The consumption current of the piezoelectric buzzer 34a is 8 mA (at 12 V), and the oscillation frequency is 3.0 ± 0.5 kHz. The current during the minimum operation is about 3.3 mA when the drive voltage is 5V. The maximum operating current Imax is 10 mA. The sound pressure is 75 dB. If the volume during operation of the piezoelectric buzzer 34a is ensured to be about 70 dB, the volume can be sufficiently monitored in the room even if it is slightly away from the zero-phase voltage monitoring circuit 10 '. The operation voltage of the operation indicator 34b is about 2.4 to 32V. The maximum operating current Imax is about 5 mA. These components constitute a zero-phase voltage monitoring circuit 10 '.

  Next, a zero-phase voltage monitoring example in the simple OVG alarm device 10 will be described with reference to FIG. In this example, the power source & voltage detector 31 is connected to the test terminals 1a and 2a of the PTT test plug 50 via the attachment members 36 and 47, and the zero appearing between the test terminals 1a and 2a when the instrument transformer is connected. It is assumed that the phase voltage Vo is detected. In the simple OVG alarm device 10, the power supply unit and the voltage detection unit are shared, and the circuit is configured such that the piezoelectric buzzer 34a, the operation indicator lamp 34b, and the like operate when the power supply voltage rises to the target value.

  Under these operating conditions, in step ST1 shown in FIG. 2, the power supply & voltage detection unit 31 detects the zero-phase voltage Vo appearing between the test terminals 1a and 2a when a ground fault occurs. At this time, a power supply voltage (zero phase voltage Vo = detection voltage Vx) exceeding the voltage drop (9V) due to the rectifier voltage drop (2V) + ZD2 voltage (7V) + buzzer operating voltage (5V) + R1 is detected. However, the voltage drop (9 V) of the resistance element R1 is a value when the buzzer minimum current 3.3 mA + LED lighting 5 mA is energized.

  In step ST2, the voltage limiter unit 32 compares the zero-phase voltage Vo with the determination reference value Vth. At this time, the voltage limiter 32 compares the detection voltage Vx output from the power supply & voltage detection unit 31 with the forward voltage drop Vz1 of the Zener diode ZD1 serving as a determination reference, and whether or not the zero-phase voltage Vo appears. Is determined.

  In the voltage setting unit 33, the forward voltage drop Vz1 of the Zener diode ZD2 is set as the determination reference value Vth. In the voltage limiter 32, a Zener current Iz flows based on the forward voltage drop Vz1 of the Zener diode ZD1. If the detection voltage Vx is equal to or lower than the determination reference value Vth as a result of this energization, the process returns to step ST1 and the power supply & voltage detection unit 31 detects the zero-phase voltage Vo.

  When the detected voltage Vx exceeds the determination reference value Vth in step ST2, the detected voltage Vx = zero phase voltage Vo is detected, so that the process proceeds to step ST3 and the alarm & display unit 34 performs an alarm operation. At this time, the piezoelectric buzzer 34 a generates a ringing sound based on the determination output voltage output from the voltage setting unit 33. If comprised in this way, it will become easy to confirm that the zero phase voltage Vo appeared between the test terminals 1a and 2a at the time of occurrence of a ground fault accident by a ringing sound.

  At the same time, the alarm & display unit 34 performs a display operation in step ST4. At this time, the operation indicator lamp 34b displays an alarm color such as red or orange based on the determination output voltage (operating voltage 2.4 to 32V) output from the voltage setting unit 33. If comprised in this way, it will become easy to confirm with the alarm color that the zero phase voltage Vo appeared between the test terminals 1a and 1b at the time of the occurrence of a ground fault.

  As described above, according to the simplified OVG alarm device 10 as the first embodiment, the voltage limiter unit 32 and the voltage setting unit 33 serve as the determination reference and the detection voltage Vx output from the power source & voltage detection unit 31. The determination reference voltage Vth is compared to determine whether the zero-phase voltage Vo appears. Based on this assumption, the alarm & display unit 34 generates a ringing sound based on the determination output voltage by the voltage limiter unit 32 and the voltage setting unit 33, and displays an alarm color.

  Therefore, it becomes possible to confirm that the zero-phase voltage Vo has appeared between the test terminals 1a and 2a at the time of occurrence of the ground fault by at least one of the ringing sound and the alarm color. Thereby, since it is not always necessary to watch the zero-phase voltmeter, the mental burden on the operator (local staff) can be greatly reduced.

<PTT Test Plug as Second Embodiment>
Next, a configuration example of the PTT test plug 20 as the second embodiment will be described with reference to FIGS. 3A and 3B. In this embodiment, a zero-phase voltage monitoring circuit 10 ′ such as a power source & voltage detection unit 31, a piezoelectric buzzer 34 a, and an operation indicator lamp 34 b is installed in the PTT test plug 20, and the zero-phase voltage Vo has exceeded the target. In some cases, an alarm sound and a color display are used. The electronic components constituting the zero-phase voltage monitoring circuit 10 'are the minimum necessary, and circuit elements having a simple function are used, so that the reliability of the entire apparatus can be ensured.

  The PTT test plug 20 shown in FIG. 3A constitutes an example of a test terminal having a built-in OVG alarm function. The PTT test plug 20 has a terminal main body 25. The terminal main body 25 has a terminal block part 26 and a plate-like part 27. The terminal block portion 26 has, for example, a housing whose upper surface is open. The terminal body 25 is made of an insulating member such as hard resin or ceramic.

  The test terminals 1a and 2a (test terminals) constituting an example of the first terminal are provided on the terminal base part 26 side of the terminal body 25 and a pair of sliding types constituting an example of the second terminal. Are connected to the contact terminals 1b, 2b, 1c, and 2c, and a meter such as a voltmeter is connectable. A coaxial double structure terminal is used as the test terminals 1a and 2a. Short-circuit bars 5 and 8 are also used for the test terminals 1a and 2a (see FIG. 8).

  In this example, the contact terminals 1b and 2b are provided on the lower surface of the plate-like portion 27 of the terminal main body portion 25, and the contact terminals 1c and 2c are provided on the upper surface of the plate-like portion 27 of the terminal main body portion 25. It is possible to connect to and remove from the sliding electrode (output terminal: PTT socket) of the switchboard connected to the device. The contact terminals 1b, 2b, 1c, and 2c include spare terminals 3b, 4b, 3c, and 4c (remained as spares for existing compatibility), for example, a shape in which the plate shape is divided into four parts in the upper and lower sides. have.

  The plate-like part 27 is configured to extend from the opposite side of the terminal base part 26 to the relay connection terminal surface. The contact terminals 1b, 2b, 1c, 2c and the spare terminals 3b, 4b, 3c, 4c are provided with an insulation distance from each other in the opposite direction to the relay contact terminal surface of the terminal block part 26 of the plate-like part 27. . The contact terminals 1b, 2b, 1c, and 2c are inserted into the PTT socket of the instrument transformer, and are brought into electrical conduction by contacting an internal electrode (hereinafter also referred to as a socket electrode) of the PTT socket. In this conductive state, the lead-in line and the feed line are made conductive (ON) and a branch terminal is configured.

  A simple OVG alarm device 10 is connected to the test terminals 1a, 2a or the contact terminals 1b, 2b. The simple OVG alarm device 10 is provided in the terminal block part 26. As the simple OVG alarm device 10, the one described in the first embodiment is used. The simple OVG alarm device 10 is hardened with resin and is incorporated in the terminal block part 26 (housing).

  For example, a hole having a predetermined volume is provided in the terminal block portion 26, and the zero-phase voltage monitoring circuit 10 'mounted on the printed board 15 shown in FIG. 1 can be accommodated in the hole. In FIG. 3A, the terminal block part 26 has a cubic shape (casing), and has a square-shaped lid portion 28 that can cover the entire open upper surface of the terminal block part 26 when viewed from above. Test terminals 1a and 2a are arranged on the left side of the upper surface (relay connection terminal surface) of the lid 28.

  An operation indicator lamp 34b is disposed substantially below the center of the line segment connecting the test terminals 1a and 2a on the left and right sides, and it is easy to confirm in which circuit the zero-phase voltage Vo is generated. A light emitting diode (LED) is used for the operation indicator lamp 34b, and the LED emits light with a small current.

  A piezoelectric buzzer 34a is disposed below the operation indicator lamp 34b and on the lower side of the front surface of the lid portion 28, and a buzzer ring (alarm sound extraction port) is opened. For example, the alarm sound outlet is provided with a plurality of slits on the right side of the upper surface of the lid portion 28, and a necessary amount of gap (lattice structure) is secured so that the alarm sound does not stay inside.

  Here, an example of the internal configuration of the PTT test plug 20 will be described with reference to FIG. According to the internal configuration example of the PTT test plug 20 shown in FIG. 4, the test terminals 1a and 2a, the contact terminals 1b, 1c, 2b and 2c, and the zero-phase voltage monitoring circuit 10 'are configured.

  One end of the test terminal 1a is connected to the contact terminal 1b on the lower surface of the plate-like portion 27 of the terminal body 25 shown in FIG. The other end of the test terminal 1a is connected to the contact terminal 1c on the upper surface provided in the plate-like portion 27 and to the AC input terminal a1 of the full-wave rectifier circuit 31a of the simple OVG alarm device 10.

  Further, one end of the test terminal 2a is connected to the contact terminal 2b on the lower surface of the plate-like portion 27 of the terminal body 25 shown in FIG. The other end of the test terminal 2a is connected to the contact terminal 2c on the upper surface provided in the plate-like portion 27 and to the AC input terminal a2 of the full-wave rectifier circuit 31a of the simple OVG alarm device 10.

  Note that the simple OVG alarm device 10 described in the first embodiment is used for the zero-phase voltage monitoring circuit 10 '. Refer to the first embodiment for an internal configuration example of the zero-phase voltage monitoring circuit 10 '. The PTT test plug 20 was developed based on the commercially available PTT test plug 50 and may be inserted into the secondary circuit of the instrument transformer (PT). That is, the PTT test plug 20 is always in a charged state and has a continuous alarm operation. Therefore, in order to prevent misuse, the PTT test plug 20 is dedicated to the tertiary circuit as a two-pole configuration.

  Next, an application example of the PTT test plug 20 in the transmission and distribution line protection system 100 will be described with reference to FIG. In the power transmission / distribution line protection system 100 shown in FIG. 5, two PTT test plugs 20 (indicated as PTT1, PTT2, and PTT3 in the figure) according to the present invention are ground faults at the portions indicated by 中 in the figure. It is connected to an overvoltage relay (64V) or a ground fault direction relay (67G in the figure). Actually, the wiring drawn from the ground fault overvoltage relay (64V) or the ground fault direction relay (67G) is led to the switchboard, and the PTT test plug 20 is used by being fitted to the socket electrode of the switchboard.

  The transmission / distribution line protection system 100 is applied to a ground fault protection system for a radial transmission line in a connected substation. The interconnected substation is, for example, 110 kV bus (Bus), 66 kV bus (Bus), two transformers (1MTr, 2MTr), two primary side bus switches (BLS), four secondary side switches Bus switch (BLS), two line switches (LLS) on the transmission line side, two circuit breakers on the primary side (CBa, CBb), two circuit breakers on the secondary side (CBc, CBd), two circuit breakers for power transmission lines (CBe, CBf), two transformer secondary side neutral point switching switches (LS), one bus section switching switch (LS) ) Three zero-phase current transformers (ZCT; hereinafter referred to as ZCT1 to ZCT3), one instrument transformer (PT), one zero-phase voltmeter 29, one neutral wire grounding resistor (NGR equipment) One ground fault overvoltage relay (64V), one ground fault overcurrent relay (51G), two ground faults It consists of direction relay (67G).

  The primary side of the transformer (1MTr) is connected to the 110 kV bus (Bus) via BLS and CBa. Its secondary side is connected to a 66 kV bus (Bus) via CBc and BLS. The primary side of the transformer (2MTr) is connected to the 110 kV bus (Bus) via BLS and CBb. Its secondary side is connected to a 66 kV bus (Bus) via CBd and BLS.

  A 66 kV first bus A (Bus) is connected to the first A line of 66 kV via BLS, CBe and LLS. The 66 kV bus (Bus) is connected to a second B line of 66 kV via other BLS, CBf and LLS. On the 66 kV bus (Bus), a switch (LS) for switching the bus section is connected between the first A-line power transmission system and the second B-line power transmission system.

  One end of a neutral point ground resistance (NGR device) is connected to the neutral point of the Y connection on the secondary side of the transformer (1MTr) via one switch (LS). The other end of this NGR device is grounded. One end of the NGR device is connected to the neutral point of the Y connection on the secondary side of the transformer (2MTr) via another switch (LS). A ZCT 3 is attached to the wiring leading to the NGR device. A ground fault overcurrent relay (51G) is connected to this ZCT3 via a CTT (current transformer test terminal).

  A ground fault overvoltage relay (64V) is connected to the ground fault overcurrent relay (51G). The ground fault overvoltage relay (64V) is connected to the tertiary winding of the instrument transformer (PT) via PTT1. The zero-phase voltmeter 29 is connected to the tertiary winding of the instrument transformer (PT) via the PTT 4. The ground fault direction relay 671 is connected to ZCT1 and CBe, and is connected to the tertiary winding of the instrument transformer (PT) via PTT2. The ground fault direction relay 672 is connected to ZCT2 and CBf, and is connected to the tertiary winding of the instrument transformer (PT) via PTT3. These constitute the transmission / distribution line protection system 100.

  According to the transmission / distribution line protection system 100, two lines A and B are connected to a 66 kV bus Bus and power is supplied to the two lines A and B. For example, when a ground fault occurs on line B (X mark in the figure is a ground fault point), a ground fault current (zero phase current io) flows through the NGR device, and the ground fault overcurrent relay (51G) operates. . When a ground fault voltage (zero phase voltage Vo) is generated in the tertiary winding of the instrument transformer (PT), the zero phase voltmeter 29 displays the ground fault voltage. Moreover, a ground fault overvoltage relay (64V) operates via PTT1, and an alarm sound of an existing monitoring control device is generated and a failure is displayed.

  In the transmission and distribution line protection system 100, when the ground fault direction relays 671 and 672 do not operate for some reason, the ground fault overcurrent relay (51G), the ground fault overvoltage relay (64V), and the timer cut off the circuit of the 66 kV bus Bus. The circuit breakers CBe and CBf are cut in this order, and then the circuit breakers CBa and CBb of the 110 kV bus BUS are turned off. Thereby, it becomes possible to protect two transformers (1MTr, 2MTr), transmission / distribution lines, and the like from a ground fault.

  As described above, according to the PTT test plug 20 as the second embodiment, the zero-phase voltage monitoring circuit 10 ′ is provided in the terminal main body 25, and the zero-phase voltage monitoring circuit 10 ′ includes the simple OVG alarm according to the present invention. Since the device 10 is used, a zero-phase voltage Vo appears between the first and second terminals when a ground fault occurs due to at least one of a ringing sound and an alarm color when an instrument transformer (PT) is connected. You will be able to confirm that. Thereby, since it is not always necessary to watch the zero-phase voltmeter 29, the mental burden on the operator (local staff member) can be greatly reduced. A test plug with a built-in OVG alarm device can be provided.

  In addition, since the entire simple OVG alarm device 10 is molded with resin and incorporated into the PTT test plug 20, disconnection and damage due to vibration during transportation and handling can be prevented, ensuring reliability. And now it can be improved.

<PTT Test Terminal Device as Third Embodiment>
Next, a configuration example and a connection example of the zero-phase voltage monitoring system 300 according to the third embodiment will be described with reference to FIGS. A zero-phase voltage monitoring system 300 shown in FIG. 6 includes a test terminal device (hereinafter referred to as a PTT test plug 50) according to a conventional example and a simple OVG alarm device 30 according to the present invention.

  As described with reference to FIG. 11, the PTT test plug 50 includes the terminal body 25, the pair of test terminals 1a and 2a (first terminals), and the pair of contact terminals 1b and 2b (second terminals). It is configured. The terminal main body 25 has a terminal block part 26 and a plate-like part 27. The test terminals 1a and 2a are provided on the terminal base portion 26 of the terminal main body 25 and are connected to the contact terminals 1b and 2b, and an instrument such as a zero-phase voltmeter can be connected. The contact terminals 1b and 2b are provided on the plate-like portion 27 of the terminal body 25, and can be connected to the output terminal of the instrument transformer.

  The simple OVG alarm device 30 can be connected to the test terminals 1a and 2a of the PTT test plug 50 shown in FIG. In the simple OVG alarm device 30, the zero-phase voltage monitoring circuit 10 ′ including the power supply & voltage detection unit 31 and the voltage determination unit shown in FIG. 4 is sealed with mold resin inside the housing unit 35. On the outside of the housing part 35, a ringing opening of the piezoelectric buzzer 34a and a part of the operation indicator lamp 34b are exposed on a predetermined surface of the apparatus. The sound opening of the piezoelectric buzzer 34a and the operation indicator lamp 34b are provided on a surface that is easy for the user to visually confirm. If the simple OVG alarm device 30 is configured in this manner, the inside of the simple OVG alarm device 30 can be easily protected from the outside during transportation.

  In this example, the simple OVG alarm device 30 is provided with attachment members 36 and 47 dedicated to the PTT test plug. The attachment members 36 and 47 are pulled out to the outside of the housing portion 35 from, for example, a surface orthogonal to the surface of the housing portion 35 provided with the ringing opening of the piezoelectric buzzer 34a and the operation indicator lamp 34b. The attachment member 36 includes a flat insulating wire 3 having a predetermined thickness, and a terminal 6 with a claw having a C shape. The attachment member 47 includes a flat insulating wire 4 having a predetermined thickness and a claw-equipped terminal 7 having a C shape. The claw terminal 6 is connected to the terminal end of the insulated wiring 3, and the claw terminal 7 is connected to the terminal end of the insulating wiring 4.

  Here, a connection example of the simple OVG alarm device 30 will be described with reference to FIG. According to the simple OVG alarm device 30 shown in FIG. 7, the claw terminal 6 can be connected to the test terminal 1a of the PTT test plug 50, and the claw terminal 7 can be connected to the test terminal 2a. . For example, the claw terminal 6 is inserted into the test terminal 1a, and the claw terminal 7 is inserted into the test terminal 2a.

  In this example, the insulated wiring 3 is linearly arranged with respect to the test terminal 1a, whereas the insulated wiring 4 is arranged so as to bypass the test terminal 1a. The insulated wiring 4 is pulled out to the outside of the housing part 35 and then bent into a “<” shape in one direction, and further bent into a “<” shape in the opposite direction to the outside of the housing part 35. It arrange | positions so that it may become the same direction as the direction pulled out.

  When the zero-phase voltage monitoring system 300 is configured in this way, when the simple OVG alarm device 30 is attached, the attachment members 36 and 47 are connected to the test terminals 1a and 2a with the claws 6 and 7 from the upper direction to the lower direction. By being lowered to drop, it can be easily connected to the existing PTT test plug 50. In addition, the insulated wires 3 and 4 are ordered with respect to the test terminals 1a and 2a arranged in a column, and the simple OVG alarm device 30 can be maintained in a predetermined posture. The PTT test plug 50 is provided with versatility so that it can be used in the same manner as the conventional example. As a result, the operating staff only need to deal with normal work and are freed from the mental burden.

  Here, a connection example between the simple OVG alarm device 30 and the PTT test plug 50 will be described with reference to FIG. According to the simple OVG alarm device 30 shown in FIG. 8, the test terminals 1 a and 2 a of the PTT test plug 50 are connected via the short-circuit bars 5 and 8. A coaxial double structure terminal is used as the test terminals 1a and 2a. Here, the electrode numbers of the two terminals of the test terminal 1a are 11 and 21, respectively. Similarly, the electrode numbers of the two terminals of the test terminal 2a are 12,22. As the short-circuit bars 5 and 8, those having a U-shape are used.

  In this example, the two terminals with electrode numbers 11 and 21 are short-circuited via the short-circuit bar 5 in a state where the claw terminal 6 of the simple OVG alarm device 30 is sandwiched between the test terminals 1 a of the PTT test plug 50. . The terminal of electrode number 11 of the test terminal 1a is connected to the contact terminal 1b on the lower surface provided in the plate-like part 27. The terminal of the electrode number 21 of the test terminal 1a is connected to the contact terminal 1c on the upper surface provided in the plate-like part 27.

  Similarly, the terminal 7 with the claw of the simple OVG alarm device 30 is short-circuited between the two terminals of the electrode numbers 12 and 22 of the test terminal 2 a of the PTT test plug 50 through the short-circuit bar 8. The terminal of electrode number 12 of the test terminal 2 a is connected to the contact terminal 2 b on the lower surface provided in the plate-like part 27. The terminal of the electrode number 22 of the test terminal 2a is connected to the contact terminal 2c on the upper surface provided in the plate-like part 27. Thus, the simple OVG alarm device 30 and the PTT test plug 50 are connected via the short-circuit bars 5 and 8.

  Here, an example of internal and external connections of the zero-phase voltage monitoring system 300 will be described with reference to FIGS. According to the internal connection example of the zero-phase voltage monitoring system 300 shown in FIG. 9, the test terminal 1 a is connected to the AC input terminal a <b> 1 of the simple OVG alarm device 30 via the attachment member 36. The test terminal 1a is connected to the AC input terminal a2 via the mounting member 47. For an internal connection example of the simple OVG alarm device 30, refer to an internal connection example of the simple OVG alarm device 10 shown in FIG.

  According to an external connection example of the zero-phase voltage monitoring system 300, the lead-in line in1 and the lead-out line out1 are connected via the PTT test plug 50 to the lead-in line in2 and the lead-out line out2. The lead-in wires in1 and in2 are connected to the tertiary winding of the instrument transformer (PT) as shown in FIG. For example, a zero-phase voltmeter 29 is connected to the delivery lines out1 and out2 (see FIG. 10). FIG. 10 is a circuit diagram in which a portion where the PTT test plug 50 is connected to the socket electrode of the switchboard is developed.

  The simple OVG alarm device 30 shown in FIG. 10 has a test terminal 1a in which the terminals of electrode numbers 11 and 21 are short-circuited through the short-circuit bar 5 and a terminal of electrode numbers 12 and 22 are short-circuited through the short-circuit bar 8. It is connected to a PTT test plug 50 having a test terminal 2a. The PTT test plug 50 to which the simple OVG alarm device 30 is connected is fitted (inserted) into a socket electrode (hereinafter referred to as a PTT socket 60) of the switchboard.

  In this example, the lead-in wire in1 is connected to the sliding electrode of electrode number 11 of the PTT socket 60. The lead-in wire in2 is connected to the sliding electrode of electrode number 12. The lead-out line out1 is connected to the sliding electrode of electrode number 21 of the PTT socket 60. The lead-out line out2 is connected to the sliding electrode of electrode number 22.

  By fitting (inserting) the PTT test plug 50 into the PTT socket 60, the same electrode numbers such as the electrode number 11-11, the electrode number 12-12, the electrode number 21-21, and the electrode number 22-22 Is connected. A test terminal 1a having terminals of electrode numbers 11 and 21, a lead-in line in1 having a sliding electrode of electrode number 11, and a lead-out line out1 having a sliding electrode of electrode number 21 are connected.

  Similarly, a test terminal 2a having terminals with electrode numbers 12 and 22, a lead-in wire in2 having a sliding electrode with electrode number 12, and a lead-out wire out2 having a sliding electrode with electrode number 22 are connected. These constitute the zero-phase voltage monitoring system 300. Refer to FIG. 5 for an application example thereof.

  Thus, according to the zero-phase voltage monitoring system 300 as the third embodiment, the simple OVG alarm device 10 according to the present invention is provided, and this simple OVG alarm device 10 is connected to the test terminals 1a and 2a of the PTT test plug. Because it is possible to connect, when the instrument transformer is connected, it is confirmed that the zero-phase voltage Vo has appeared between the test terminals 1a and 2a at the time of the ground fault by the ringing sound and / or alarm color become able to.

  Thereby, since it is not always necessary to watch the zero-phase voltmeter 29, the mental burden on the operator (local staff member) can be greatly reduced. Moreover, since it can be easily connected to the existing PTT test plug 50, it is versatile. Moreover, there is no trouble in the attached shorting bars 5 and 8 and the lead connection method, and the feeling of use is not different from the conventional method.

  INDUSTRIAL APPLICABILITY The present invention is extremely suitable when applied to a line protection system that monitors a zero-phase voltage when a ground fault occurs in a power generation / transformation and transmission system.

1a, 2a Test terminal (first terminal)
1b, 2b Contact terminal (second terminal)
3,4 Wiring member 5,8 Shorting bar
6, 7 Terminals with claws 10 Simple OVG alarm device 10 'Zero-phase voltage monitoring circuit 15 Printed circuit board 20, 50 PTT test plug 25 Terminal body part 26 Terminal block part 27 Plate-like part 28 Lid part 29 Zero-phase voltmeter 31 Power supply part 32 Voltage detection unit 33 Voltage determination unit 34 Determination output unit
34a Piezoelectric buzzer 34b Operation indicator 35 Housing 36, 47 Mounting member 60 PTT socket 100 Transmission / distribution line protection system 300 Zero-phase voltage monitoring system

Claims (8)

An attachment member attachable to a pair of test terminals of a test terminal connected to an instrument transformer;
A zero-phase voltage monitoring circuit connected to the mounting member,
The zero-phase voltage monitoring circuit is
Wherein detecting a potential transformer connected to the zero-phase voltage appearing across the test terminals, the AC detection voltage during ground fault occurs - performing an alarm operation based on the driving power obtained by DC converted A zero-phase voltage monitoring device. The zero-phase voltage monitoring circuit is
A voltage detection unit that is connected to the test terminal via the mounting member and detects a zero-phase voltage appearing between the test terminals;
A voltage determination unit that is connected to the voltage detection unit and that compares the detection voltage output from the voltage detection unit with a threshold voltage serving as a determination reference to determine whether or not a zero-phase voltage appears. The zero-phase voltage monitoring device according to claim 1.   The zero-phase voltage monitoring device according to claim 2, further comprising an alarm unit that is connected to the voltage determination unit and generates a ringing sound based on a determination output voltage output from the voltage determination unit.   4. The zero-phase voltage monitoring device according to claim 2, further comprising a display unit that is connected to the voltage determination unit and displays an alarm color based on a determination output voltage output from the voltage determination unit.   The zero-phase voltage monitoring device according to claim 2, wherein the voltage detection unit and the voltage determination unit are sealed with mold resin in the housing. In the mounting member,
The zero-phase voltage monitoring device according to claim 1, wherein a terminal with a claw that can be connected to a test terminal of the test terminal tool is used. A terminal body portion having a terminal block portion and a plate-like portion;
A pair of first terminals provided on the terminal block portion of the terminal main body and connectable to a meter;
A pair of second terminals that are provided in the plate-like portion of the terminal body and connected to the first terminal and connectable to the output terminal connected to the instrument transformer;
The zero-phase voltage monitoring device according to any one of claims 1 to 6 connected to the first or second terminal,
A test terminal device with a zero-phase voltage monitoring function, wherein the zero-phase voltage monitoring device is provided in the terminal main body by sharing a power supply unit and a voltage detection unit . A terminal body portion having a terminal base portion and the plate portion, a first terminal of the instrument together provided the terminal block portion of the terminal body portion is a pair capable of connecting a plate-shaped portion of the terminal body portion A test terminal having a pair of second terminals that are connected to the first terminal and connectable to an output terminal connected to the instrument transformer;
A zero-phase voltage monitoring system comprising: the zero-phase voltage monitoring device according to any one of claims 1 to 6 connectable to a first terminal of the test terminal tool.

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