JP4130908B2 - Equipment monitoring method, equipment monitoring system, equipment monitoring device - Google Patents

Description

  The present invention relates to a facility monitoring method, a facility monitoring system, and a facility monitoring apparatus, and more particularly to a technique for realizing a remote monitoring mechanism with low power consumption and high reliability.

Central monitoring of the state of various facilities that constitute the power transmission system, such as the state of power transmission cables, transformers, circuit breakers, disconnectors, and insulators (oil, gas, etc.) for insulating the power transmission cables from the outside In order to perform remote monitoring from a monitoring site such as a facility, information related to equipment to be monitored is notified from the monitoring site of an electric station such as a substation to the monitoring site (for example, Patent Document 1). See). In such a remote monitoring mechanism, information transmission between a monitoring target site such as an electric station and the monitoring site is generally performed via a metallic cable laid between them.
JP 2003-23732 A

  The metallic cable used for the above information transmission has a large transmission loss in the middle of the route, and is easily affected by noise due to external induction, etc. Recently, as a communication line in a power transmission system, a metallic cable is used as an optical fiber. A cable migration plan is underway. Optical fiber cables have lower transmission loss and better durability than metallic cables, are less susceptible to noise, have a variety of excellent features such as small diameter and light weight, and are more reliable than metallic cables. High information transmission is possible. Therefore, the present inventors have been using a metallic cable by realizing the above-described remote monitoring mechanism using an optical fiber cable under the background of the transition from the metallic cable to the optical fiber cable. Inspired by a remote monitoring mechanism that consumes less power and is more reliable than other methods.

  An object of the present invention is to provide an equipment monitoring method, equipment monitoring system, and equipment monitoring apparatus that can realize a remote monitoring mechanism with low power consumption and high reliability.

The invention according to claim 1 of the present invention for achieving the above object is an equipment monitoring method, wherein the first and second optical communication paths are provided between the monitoring site and the monitoring target site. laid, said in the monitored side site, the first signal light that will be sent via the optical communication path incident on the optical splitter, one signal light of said optical splitter in branches that said signal light Is incident on the photoelectric conversion element, and the other signal light is incident on an optical switch that controls the output light according to the presence or absence of an external input voltage , and the output voltage of the photoelectric conversion element is The input voltage is input to the optical switch as the input voltage via a contact that is turned on and off according to the state, the emitted light of the optical switch is incident on the second optical communication path, and the second site Signal light transmitted through the optical communication path And monitoring the state of the equipment of the monitoring target by viewing.

  In the present invention, the optical branching device, the optical switch, the photoelectric conversion element, etc. provided in the monitoring target site as a mechanism for notifying the monitoring site of information related to the monitoring target facility are all the first from the monitoring site. It operates by the energy of the signal light emitted from the signal light generator sent through the optical fiber cable. That is, since no additional facility for supplying energy such as power supply facilities to the monitoring target site is required, a facility monitoring system with low power consumption and a simple configuration can be constructed. Moreover, since the equipment monitoring system of the present embodiment uses an optical fiber cable, a highly reliable equipment monitoring mechanism can be realized. In addition, due to various advantages of optical fiber cables such as excellent durability, small diameter, and light weight, maintenance costs can be reduced and the amount of cables laid at substations can be reduced.

According to a second aspect of the present invention, in the facility monitoring method according to the first aspect, the optical switch is configured to switch the presence / absence of emitted light according to the presence / absence of an input voltage from the outside .

The invention described in claim 3 is the facility monitoring method according to claim 1, wherein the optical switch is in the fact in accordance with the presence or absence of an input voltage from an external, thereby changing the intensity of the emitted light. In the case of such control, it is possible to distinguish at the monitoring site whether the abnormality is related to the optical communication path such as disconnection of the optical fiber cable or the abnormality related to the monitored equipment.

  The invention according to claim 4 is the equipment monitoring method according to any one of claims 1 to 3, wherein the monitoring target site is a facility in a power transmission system, and the equipment to be monitored constitutes the power transmission system. It is supposed to be a power transmission facility.

In invention of Claim 5, it is an equipment monitoring system, Comprising: It installs in the 1st and 2nd optical communication path which connects between the monitoring side site and the monitoring object side site, and the said monitoring object side site, an optical branching unit signal light enters that will be sent through the first optical communication paths, a photoelectric conversion element in which one of the signal light is incident of the optical branching device said signal light branched by, The other signal light of the signal light branched by the optical splitter enters and the emitted light enters the second optical communication path according to the presence or absence of an external input voltage. An optical switch for controlling the intensity of the light; a circuit for inputting the output voltage of the photoelectric conversion element to the optical switch as the input voltage via a contact that is turned on / off according to the state of the equipment to be monitored; Installed at the side site and the second optical And further comprising a signal light detection device for detecting the intensity of the signal light transmitted through the road, the.

Invention of Claim 6 is an equipment monitoring system, Comprising: It installs in the 1st and 2nd optical communication path which connects between the monitoring side site and the monitoring object side site, and the said monitoring object side site, an optical branching unit signal light enters that will be sent through the first optical communication paths, a photoelectric conversion element in which one of the signal light is incident of the optical branching device said signal light branched by, The other light of the signal light branched from the optical branching device is incident and the emitted light is incident on the second optical communication path according to the presence or absence of an input voltage from the outside. An optical switch for controlling the intensity of the optical switch, a circuit for inputting the output voltage of the photoelectric conversion element as the input voltage to the optical switch via a contact to be monitored, the second switch installed at the monitoring site, The strength of the signal light transmitted through the optical communication path And that and a signal light detection device for detecting a.

The invention according to claim 7, facilities a monitoring device, a first and a light branching unit signal light that will be sent via the optical communication path is incident, the signal light branched by the optical splitter Among the photoelectric conversion element to which one of the signal light is incident and the other signal light of the signal light branched by the optical splitter are incident and the emitted light is incident on the second optical communication path that, an optical switch that controls the intensity of the emitted light depending on whether the input voltage from the outside, through the contacts to turn on and off depending on the state of the equipment to be monitored, the output voltage of the photoelectric conversion element, wherein And a circuit for inputting the input voltage to the optical switch.

The invention according to claim 8, facilities a monitoring device, a first and a light branching unit signal light that will be sent via the optical communication path is incident, the signal light branched by the optical splitter And one of the signal light branched by the optical branching device and the emitted light are incident on the second optical communication path. An optical switch that controls the intensity of the emitted light according to the presence or absence of an input voltage from the outside, and an output voltage of the photoelectric conversion element is input as the input voltage to the optical switch via a contact to be monitored And a circuit to perform.

  In addition, the problems disclosed by the present application and the solutions thereof will be clarified by the embodiments of the present invention and the drawings.

  According to the present invention, it is possible to provide a facility monitoring method, a facility monitoring system, and a facility monitoring apparatus that can realize a remote monitoring mechanism with low power consumption and high reliability.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the overall configuration of an equipment monitoring system 1 described as an embodiment of the present invention. The equipment monitoring system 1 monitors the state of equipment to be monitored (hereinafter referred to as the monitoring target equipment 4) monitored at the monitoring target site 3 at the monitoring site 2 at a location remote from the monitoring target site 3. Provide a mechanism to Such a facility monitoring system 1 includes, for example, monitoring of power facilities such as power transmission cables and substation facilities constituting a power transmission system, monitoring of railway facilities such as track conditions, monitoring of road facilities, and in these railway facilities and road facilities. It is applied to various purposes such as monitoring of fires in tunnels, monitoring of various facilities in airports, monitoring of stores in franchise chains, etc.

  As shown in FIG. 1, a first optical fiber cable core 5 that provides a first optical communication path and a second optical communication path are provided between the monitoring site 2 and the monitoring target site 3. A second optical fiber cable core 6 to be provided is laid. The optical fiber cable cores 5 and 6 include, for example, the optical fiber cable cores of an optical fiber cable having a structure in which an appropriate number of optical fiber cable cores such as 12 cores, 24 cores, and 48 cores are bundled. One of the lines is used. Further, as the optical fiber cable cores 5 and 6, those having a single-mode (SMF) single-mode optical fiber (SMF) or multi-mode (MMF) core-cladding structure are used.

  The monitoring site 2 shown in FIG. 1 is provided with a signal light generator 21 and a signal light detector 22. The signal light generator 21 generates signal light incident on the first optical fiber cable core wire 5. In the signal light generator 21, as a light emitting element, for example, a semiconductor laser (LD: Laser Diode), a distributed feedback (Distributed Feed-Back) laser, a multi-quantum well LD, a light emitting diode (LED: LED). Light Emitting Diode) etc. are built in. The wavelength of the signal light is determined according to the specifications of the signal light generator 21 (particularly, the type of light emitting element), and is set to about several μm, for example.

  The signal light detection device 22 receives the signal light emitted from the second optical fiber cable core wire 6. The signal light detection device 22 includes a light receiving element such as a photodiode (PD: Photo Diode) or an avalanche photodiode (APD). The change in the intensity of the signal light detected by the signal light detection device 22 is transmitted to the monitoring computer 23 operating at the monitoring site 2. The operator of the monitoring computer 23 monitors the change in the intensity of the signal light detected by the signal light detection device 22 via the man-machine interface of the monitoring computer 23, so that the monitoring target facility 4 of the monitoring target side site 3 Monitor status.

  The monitoring target site 3 shown in FIG. 1 is provided with an optical branching device 31, an optical switch 32, a photoelectric conversion element 33, and the like as devices for notifying the monitoring site 2 of information related to the monitoring target facility 4. . Among these, the signal light emitted from the first optical fiber cable core 5 is incident on the optical branching device 31, and the incident signal light is branched into two waves by the optical branching device 31 and output. Specific examples of the optical branching device 31 having such an action include a prism, a dielectric multilayer filter, a diffraction grating, an optical fiber having a fusion extending portion, an optical waveguide, an optical waveguide, and a dielectric multilayer filter. And fiber gratings. Each signal light branched into two waves by the optical splitter 31 is incident on the optical switch 32 and the photoelectric conversion element 33, respectively.

  The optical switch 32 has a voltage input terminal 321 to which an external voltage is input. The optical switch 32 controls the emitted light emitted from the optical switch 32 in accordance with a voltage input to the voltage input terminal 321 (hereinafter referred to as input voltage). For example, the optical switch 32 outputs incident signal light as outgoing light when no voltage is input to the voltage input terminal 321, and outputs outgoing light when the voltage is input to the voltage input terminal 321. Operates so as not to output. Specific examples of the optical switch 32 that operates in this way include mechanical optical switches that switch optical paths by mechanically controlling optical elements such as optical fibers and prisms, electrooptic effects, acoustooptic effects, thermooptic effects, and the like. There is a non-mechanical optical switch that switches the optical path by using the. The outgoing light whose output is controlled by the optical switch 32 is incident on the second optical fiber cable core 6.

  The photoelectric conversion element 33 is an element that outputs a voltage corresponding to incident signal light. Specific examples of the photoelectric conversion element 33 include a photodiode (PD), an avalanche photodiode (APD), a silicon-based or compound semiconductor-based solar cell, and the like. A specific product is PPC-9LW manufactured by Photonic Power Systems Incorporated.

  The voltage output terminal 331 of the photoelectric conversion element 33 is connected to the terminal of the alarm contact 7 provided in the monitoring target facility 4 of the monitoring target side site 3 via the wiring 8. The other terminal of the alarm contact 7 is connected to the voltage input terminal 321 of the optical switch 32 via the wiring 9. The alarm contact 7 is turned on / off according to the state of the monitoring target equipment 4.

  For example, the alarm contact 7 is off when the monitoring target equipment 4 is in a normal state, but is on when the monitoring target facility 4 is in an abnormal state. That is, when the alarm contact 7 is off, no voltage is input to the voltage input terminal 321 of the optical switch 32, and when the alarm contact 7 is on, the output voltage of the photoelectric conversion element 33 is changed to the voltage input terminal of the optical switch 32. 321 is input. As described above, the alarm contact 7, the wiring 8, and the wiring 9 perform on / off control of the output voltage of the photoelectric conversion element 33 according to the state of the monitoring target equipment 4, and the output voltage is input to the optical switch 32 as an input voltage. A circuit for doing this is formed.

  FIG. 2 illustrates the relationship between the state of the alarm contact 7, the voltage input to the voltage input terminal 321 of the optical switch 32, and the intensity of light emitted from the optical switch 32. As shown in this figure, before the time t1, when the state of the monitored equipment 4 is normal and the alarm contact 7 is off, no voltage is input to the voltage input terminal 321 of the optical switch 32, and the optical switch From 32, output light having an intensity corresponding to the incident light from the optical branching device 31 is output. On the other hand, when an abnormality occurs in the monitoring target equipment 4 at time t <b> 1 and the alarm contact 7 is turned on, a voltage is input to the voltage input terminal 321 of the optical switch 32 and no signal light is output from the optical switch 32.

=== Operation ===
Next, operation | movement of the equipment monitoring system 1 which consists of a structure demonstrated above is demonstrated. First, as an initial state, the alarm contact 7 is in an off state, and a signal light having a predetermined intensity emitted from the signal light generator 21 is supplied to the first optical fiber cable core wire 5 while the monitoring target equipment 4 is being monitored. It is assumed that it is constantly input. Then, the signal light is transmitted from the monitoring site 2 to the monitoring target site 3 by the first optical fiber cable core 5, and the signal light transmitted to the monitoring target site 3 is steady to the optical branching device 31. Is assumed to be incident.

  In the monitoring target site 3 shown in FIG. 1, the signal light incident on the optical branching device 31 is branched into two waves by the optical branching device 31 as described above, and one of the signal lights (part of the signal light). Is incident on the optical switch 32 and the other signal light (a part of the signal light) is incident on the photoelectric conversion element 33. The photoelectric conversion element 33 outputs a voltage corresponding to the signal light incident from the optical branching device 31, and the output voltage is input to the alarm contact through the wiring. Here, since the alarm contact 8 is in an off state, no voltage is input to the voltage input terminal 321 of the optical switch 32. Accordingly, the signal light incident from the branching device 31 is emitted from the optical switch 32 as it is.

  The signal light emitted from the optical switch 32 enters the second optical fiber cable core 6 and is transmitted from the monitoring target site 3 to the monitoring site 2 by the second optical fiber cable core 6. The signal light transmitted to the monitoring site 2 by the second optical fiber cable core 6 enters the signal light detection device 22. Then, the change in the intensity of the signal light detected by the signal light detection device 22 is transmitted to the monitoring computer 23, and the operator is in the normal state of the monitoring target equipment 4 because the signal light is detected by the signal light detection device 22. I can confirm that. Note that information transmission between the signal light detection device 22 and the monitoring computer 23 can be performed, for example, via a contact provided between them. In this case, for example, the contact ON / OFF state is switched according to the relationship between the intensity of the signal light output from the signal light detection device 22 and a preset threshold value, and the state of the contact is monitored by the monitoring computer 23. To monitor on the side.

  Next, it is assumed that an abnormality or the like occurs in the monitoring target equipment 4 and the alarm contact 7 is turned on. When the alarm contact 7 is turned on, the output voltage of the photoelectric conversion element 33 is input to the voltage input terminal 321 of the optical switch 32, and the emitted light is not output from the optical switch 32. Accordingly, no signal light is incident on the second optical fiber cable core 6 from the optical switch 32, and the signal light from the second optical fiber cable core 6 is detected by the signal light detector 22 at the monitoring site 2. It will not be done. The operator of the monitoring computer 23 recognizes that an abnormality or the like has occurred in the monitoring target equipment 4 when the signal light is no longer detected.

  In the above description, the alarm contact 7 is turned off in a normal state and turned on in an abnormal state. However, the alarm contact 7 may be turned on in a normal state and turned off in an abnormal state. In this case, what is necessary is just to determine that it is normal when signal light is not detected, and is abnormal when detected.

  In the equipment monitoring system 1 described above, the optical branching device 31, the optical switch 32, the photoelectric conversion element 33, and the like provided at the monitoring target site 3 are all from the monitoring site 2 to the first optical fiber cable. It operates only with the energy of the signal light emitted from the signal light generator 21 transmitted through the core wire 5. In other words, the facility monitoring system 1 does not require a facility that serves as an energy supply source such as a power supply facility at the monitoring target site 3. Therefore, an efficient remote monitoring mechanism with low power consumption can be realized. In particular, when there are a plurality of monitoring target facilities, it is not necessary to install a power source facility at the monitoring target side site. Therefore, when implementing the facility monitoring system, the introduction cost and the operation cost can be kept low. Moreover, it can be simply configured using only a general-purpose device, and can be implemented easily and at low cost. In addition, the equipment monitoring system 1 uses a fiber optic cable that has lower loss and less influence on noise such as external guidance than when using a metallic cable, thus realizing a highly reliable remote monitoring mechanism. can do. In addition, due to various advantages of optical fiber cables such as excellent durability, small diameter, and light weight, maintenance costs can be reduced, and the amount of cables installed at substations can be reduced.

  In the above-described mechanism, the emitted light is not output from the optical switch 32 when the alarm contact 7 is in the on state, that is, the intensity of the emitted light is made zero. It can also be. For example, the intensity of the emitted light may be different between when the state of the monitoring target equipment 4 is normal and when it is abnormal. For example, in conjunction with the alarm contact 7 being turned on. The intensity of the emitted light is controlled to be weaker when the alarm contact 7 is in the on state than when the alarm contact 7 is in the off state. In this case, for example, the signal light detection device 22 recognizes that an abnormality or the like has occurred in the monitoring target equipment 4 due to a change in the intensity of the emitted light. In the case of such control, it is possible to distinguish in the monitoring site 2 whether the abnormality is related to the optical communication path such as the disconnection of the optical fiber cable or the abnormality related to the monitoring target equipment 4. For example, when the signal light is not completely detected, it can be determined that an abnormality has occurred in the optical communication path, and when the intensity of the signal light is attenuated, the monitoring target equipment 4 has an abnormality or the like. It can be determined that it has occurred.

  In addition, the equipment monitoring system 1 of the present embodiment can be easily implemented by configuring the optical branching unit 31, the optical switch 32, and the photoelectric conversion element 33 provided at the monitoring target side site 3 as a unit. It becomes possible.

=== Application Examples ===
FIG. 3 shows an application example in which the equipment monitoring system 1 described above is applied for monitoring the power transmission system. In this example, the monitoring site 2 is, for example, a central monitoring facility that performs overall monitoring of the power transmission system. On the other hand, the monitoring target site 3 is, for example, a substation in a power transmission system. The monitoring target equipment 4 in this example is an oil 43 filled as an insulator in an oil layer 42 provided around a power transmission cable 41 buried in the ground. Gas may be used as an insulator used for insulating the power transmission cable 41.

  A lead-out pipe 44 extending toward the ground is joined to the oil layer 42. The inside of the outlet pipe 44 communicates with the inside of the oil layer 42, and the liquid level in the outlet pipe 44 moves up and down according to the hydraulic pressure of the oil 43. In this case, the alarm contact 7 is provided in the pipe of the lead-out pipe 44. When the liquid level of the oil 43 is higher than a predetermined height, the alarm contact 7 is opened by the buoyancy of the oil 43 and turned off. When the liquid level becomes lower than the predetermined height, the alarm contact 7 is closed and turned on. For this reason, the alarm contact 7 is in an off state when the oil 43 is normally filled in the oil layer 42. However, if the oil 43 in the oil layer 42 decreases due to evaporation or liquid leakage, the alarm contact 7 7 is turned on. Then, the ON / OFF state of the alarm contact 7 is transmitted to the monitoring computer 23 provided in the central monitoring facility that is the monitoring site 2 by the above-described mechanism, so that the oil 43 that is the monitoring target facility 4 is transmitted. The status can be monitored at a central monitoring facility at a remote location. As a mechanism for monitoring the hydraulic pressure of the oil 43, in addition to the mechanism described above, for example, a stretchable container (for example, air inside is filled in the oil layer 42 filled with gas or liquid). It is also possible to insert a filled balloon) and turn the alarm contact 7 on and off by expansion and contraction of the container that changes according to the pressure of the oil layer 42.

  By the way, in recent years, an optical fiber cable is often laid along with a power transmission cable in a power transmission system, and the optical fiber cable core wire in such an optical fiber cable is connected to the first optical fiber cable described above. It can be used as the core wire 5 or the second optical fiber cable core wire 6. Moreover, since the existing metallic cable currently laid for monitoring of such a monitoring object facility can be removed, the amount of cables laid can be reduced. Further, the space for the support of the pipe line and the metallic cable is released. Moreover, the problem of the strength increase by the metallic cable which is a heavy article is eliminated, and the suitable installation formation of a power transmission system is attained.

  The above description is intended to facilitate understanding of the present invention and is not intended to limit the present invention. It goes without saying that the present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

1 is a diagram illustrating an overall configuration of a facility monitoring system 1 described as an embodiment of the present invention. It is a figure explaining the relationship between the state of the alarm contact 7 demonstrated as one Example of this invention, the voltage input into the voltage input terminal 321 of the optical switch 32, and the intensity | strength of the emitted light from the optical switch 32. FIG. It is a figure explaining the application example of the equipment monitoring system 1 by one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Equipment monitoring system 2 Monitoring side site 3 Monitoring object side site 4 Monitoring object equipment 5 1st optical fiber cable core wire (1st optical communication path)
6 Second optical fiber cable core (second optical communication path)
7 Alarm contact 8, 9 Wiring 21 Signal light generator 22 Signal light detection device 23 Monitoring computer 31 Optical branching device 32 Optical switch 321 Voltage input terminal 33 Photoelectric conversion element 331 Voltage output terminal 41 Power transmission cable 42 Oil layer 43 Oil 44 Derived tube

Claims (8)

The first and second optical communication paths are laid between the monitoring site and the monitoring target site,
Wherein the monitored side site, the first signal light that will be sent via the optical communication path incident on the optical splitter, the photoelectric conversion of one signal light of the signal light branched by the optical splitter The other signal light is incident on an element and is incident on an optical switch that controls the emitted light according to the presence or absence of an external input voltage , and the output voltage of the photoelectric conversion element is determined according to the state of the equipment to be monitored. The input voltage is input to the optical switch through the contact that is turned on and off, and the emitted light of the optical switch is incident on the second optical communication path,
A facility monitoring method, comprising: monitoring a state of the facility to be monitored by monitoring signal light transmitted through the second optical communication path at the monitoring site. The equipment monitoring method according to claim 1, wherein the optical switch is configured to switch presence / absence of emitted light according to presence / absence of an input voltage from the outside . 2. The facility monitoring method according to claim 1 , wherein the optical switch changes the intensity of emitted light in accordance with the presence or absence of an external input voltage .   The facility monitoring method according to claim 1, wherein the monitoring target site is a facility in a power transmission system, and the monitoring target facility is a power transmission facility constituting the power transmission system. A feature monitoring method. First and second optical communication path connecting between the monitoring side site monitored side site, the installed in the monitored side site, the first optical communication signal light that will be sent via the path An incident light splitter, a photoelectric conversion element to which one of the signal lights branched by the optical splitter is incident, and the other signal of the signal lights branched by the optical splitter An optical switch that controls the intensity of the emitted light according to the presence or absence of an external input voltage , and the state of the equipment to be monitored, in which light is incident and the emitted light is incident on the second optical communication path A circuit that inputs the output voltage of the photoelectric conversion element to the optical switch as the input voltage via a contact that is turned on and off in response to the signal, and is sent to the monitoring site and sent through the second optical communication path. Signal light that detects the intensity of incoming signal light Facility monitoring system comprising: the knowledge device. First and second optical communication path connecting between the monitoring side site monitored side site, the installed in the monitored side site, the first optical communication signal light that will be sent via the path An incident optical splitter, a photoelectric conversion element to which one of the signal lights branched by the optical splitter is incident, and the other of the signal lights branched by the optical splitter And an output voltage of the photoelectric conversion element that controls the intensity of the output light in accordance with the presence or absence of an external input voltage, and the output light of the output light is incident on the second optical communication path. And a signal that detects the intensity of the signal light that is installed at the monitoring site and sent through the second optical communication path. And a light detection device. That facility monitoring system. An optical branching unit signal light enters that will be sent through the first optical communication paths, a photoelectric conversion element in which one of the signal light is incident among branched by the optical branching device said signal light, wherein its emitted light with an optical divider in the other signal light of the branched the signal light is incident is incident on the second optical communication path, the emitted light according to the presence or absence of the input voltage from the outside An optical switch that controls the intensity, and a circuit that inputs the output voltage of the photoelectric conversion element to the optical switch as the input voltage via a contact that is turned on and off according to the state of the equipment to be monitored. A facility monitoring device. An optical branching unit signal light enters that will be sent through the first optical communication paths, a photoelectric conversion element in which one of the signal light is incident among branched by the optical branching device said signal light, wherein One of the signal lights branched by the optical branching unit is incident and the emitted light is incident on the second optical communication path, and the output light depends on the presence or absence of an external input voltage. An equipment monitoring apparatus comprising: an optical switch that controls intensity; and a circuit that inputs an output voltage of the photoelectric conversion element as the input voltage to the optical switch via a contact point to be monitored.

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