A fault monitoring system and method based on longitudinal differential protection communication link

Abstract

A fault monitoring system and method based on a longitudinal differential protection communication link device, the system includes: a signal conversion and monitoring module, a CPU and a host computer; the signal conversion and monitoring module sends abnormal alarm information and message information of the communication link to the CPU, the host computer reads the abnormal alarm information and message information stored in the CPU, and quickly locates the fault point by analyzing the abnormal alarm information and message information; the signal conversion and monitoring module adopts FPGA+CPU, the optical port transceiver is connected to the protection device via an optical cable, and the electrical port transceiver is connected to the SDH system via a cable. During early debugging, intuitive display and abnormal record can facilitate quick operation on site; in the later link failure, the fault point is preliminarily judged by the panel indicator light, or the abnormal log recorded by the CPU is read to quickly locate the fault, which reduces the complexity of early debugging, improves the accuracy of later fault location, saves costs, and has good economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of power system fault monitoring, and more specifically, to a fault monitoring system and method based on a longitudinal differential protection communication link. Background Art

[0002] Line longitudinal differential protection has been widely used in the field of power system control, and its importance is self-evident. Generally, due to the long distance between stations and different road environments, most longitudinal differential protection systems use multiplexing channels and use the synchronous digital hierarchy (SDH) system for signal transmission, such as Figure 1 As shown, the traditional line longitudinal differential protection system realizes the interconnection between two stations through the SDH system and the communication system. The line protection device transmits the signal to the communication room through the optical fiber, realizes the photoelectric conversion by the power interface communication device, and then connects to the SDH system. The opposite system uses the same method to connect the signal to the protection device.

[0003] The extensive application of longitudinal differential protection systems requires not only the correct and reliable operation of the protection device itself, but also the increasing importance of the channel reliability of this complex link. Timely detection and rapid location of link channel faults are crucial for restoring link communication. The longitudinal differential protection communication link process involves multiple links. Since the power interface communication device information is not currently connected to the fault information system, the link process is like a black box, and it is not convenient to locate problems when there are problems in the on-site link. At the same time, it is not conducive to link debugging during the debugging process.

[0004] In the prior art, for link channel failure, a dedicated person must go to the site to check the optical cable, cable and interface one by one, and a dedicated bit error meter must be used to detect frame loss on the channel, which consumes a lot of manpower and material resources, as well as a lot of time, resulting in extremely low efficiency of conventional diagnosis methods for channel failures in the longitudinal differential protection system. The Chinese invention patent application (CN110768716A) discloses "an online monitoring device and monitoring method for a dedicated optical fiber channel", which is widely used in the signal monitoring of dedicated optical fiber channels for longitudinal differential protection of 110kV and above lines. It supports 103 protocol and 61850 protocol communication within the station, and uses 485 wiring to communicate with line protection with dedicated optical fiber channels and protection information substations. The device is connected in series in the dedicated optical fiber channel, and while realizing lossless forwarding of optical fiber signals, it collects and logically judges the optical fiber signals, thereby locating the fault area; the device needs to use a CPU, and improve the communication board therein, and set more communication interfaces. More importantly, the patented technology only performs online monitoring on the dedicated optical fiber channel for longitudinal differential protection, and cannot cover all communication links. The Chinese invention patent application (CN105846891A) discloses "a short-distance optical fiber network fault monitoring method", which detects short-distance optical fiber network faults based on the back reflection measurement technology of frequency domain analysis. This patent technology is limited by the measurement technology and is not suitable for fault detection of long-distance communication channels. The Chinese utility model patent (CN206135922U) discloses "a fiber channel monitoring system", which installs a monitoring device at one end of the optical fiber channel, combines the monitoring wave emitted by the monitoring device and the working wave emitted by the optical fiber communication device, so that the combined transmission wave is transmitted in the transmission optical fiber to the other end of the optical fiber channel, and decomposes the monitoring wave and the working wave from the transmission wave at the other end, so that the monitoring wave is finally transmitted to the target monitoring device, thereby realizing online monitoring of optical fiber channel faults; this technology requires the emission of monitoring waves of different wavelengths to locate faults.

[0005] In order to solve the problem of channel fault location in the longitudinal differential protection system, a new technical means is urgently needed to facilitate the effective and rapid location of the problem, effectively solve the drawbacks of traditional channel fault location, effectively solve the communication link failure problem, and quickly restore the link channel. Summary of the invention

[0006] In order to solve the deficiencies in the prior art, the purpose of the present invention is to provide a fault monitoring system and method based on a longitudinal differential protection communication link device. In view of the various problems existing in the prior art, it is necessary to improve the existing power interface communication device, add monitoring functions, and turn the existing "black box" process into a "white box", which not only facilitates on-site link debugging, but also greatly improves the progress and accuracy of differential protection link problem positioning. At the same time, the improved method will not affect the on-site operating device and can be fully compatible with the existing device.

[0007] The present invention adopts the following technical solution.

[0008] A fault monitoring system based on a longitudinal differential protection communication link device, the longitudinal differential protection system comprising: a protection device on this side, a power interface communication device on this side, an SDH system on this side, an SDH system on the opposite side, a power interface communication device on the opposite side, a protection device on the opposite side and a communication link, wherein the communication link comprises: an optical cable between the power interface communication device on each side and the corresponding protection device, an electrical cable between the power interface communication device on each side and the corresponding SDH system, and an SDH network between the SDH systems on both sides.

[0009] The fault monitoring system includes: signal conversion and monitoring module, CPU and host computer;

[0010] The signal conversion and monitoring module sends the abnormal alarm information and message information of the communication link to the CPU in real time. The host computer reads the abnormal alarm information and message information stored in the CPU and quickly locates the fault point by analyzing the abnormal alarm information and message information.

[0011] The signal conversion and monitoring module includes an optical port transceiver and an electrical port transceiver; the optical port transceiver is connected to the protection device through an optical cable, and the electrical port transceiver is connected to the SDH system through a cable; wherein the optical port transceiver includes: an optical port receiving end and an optical port transmitting end; the electrical port transceiver includes: a first electrical port receiving end, a second electrical port receiving end, a first electrical port transmitting end, and a second electrical port transmitting end;

[0012] The first electrical port receiving end and the first electrical port sending end are both PCM interfaces that meet the European standard E1, and the second electrical port receiving end and the second electrical port sending end are both PCM interfaces.

[0013] The signal conversion and monitoring module adopts the circuit structure of FPGA and CPU, and FPGA and CPU are connected through an internal bus;

[0014] The FPGA includes: an optical port receiving end, an optical port transmitting end, a first electrical port receiving end, a second electrical port receiving end, a first electrical port transmitting end, a second electrical port transmitting end and an internal bus interface.

[0015] The signal conversion and monitoring module performs signal conversion and signal monitoring simultaneously;

[0016] The signal conversion includes: after the optical signal received by the optical port receiving end is converted into an electrical signal, it is sent to the SDH system by the first electrical port sending end and the second electrical port sending end respectively; after the electrical signal received by the first electrical port receiving end and the second electrical port receiving end is converted into an optical signal, it is sent to the protection device by the optical port sending end;

[0017] Signal monitoring includes: monitoring the optical signal received by the optical port receiving end and recording abnormal alarm information of the optical signal; monitoring the electrical signal received by the first electrical port receiving end and the second electrical port receiving end and recording abnormal alarm information of the electrical signal.

[0018] The FPGA circuit has built-in Manchester code codec, message parser, HDB3 encoder, HDB3 decoder, clock recovery module, PCM drive circuit, PCM receiving circuit and internal bus interface;

[0019] Manchester code codec, which uses Manchester code protocol to realize the conversion between optical signals and electrical signals, and records the abnormal alarm information of optical signals and counts the number of abnormal alarms;

[0020] The HDB3 encoder and the HDB3 decoder modulate the first electrical signal received by the first electrical port receiving end and sent by the first electrical port sending end using the HDB3 protocol, record abnormal alarm information of the first electrical signal, and count the number of abnormal alarms;

[0021] The PCM driving circuit and the PCM receiving circuit use the PCM protocol to modulate the second electrical signal received by the second electrical port receiving end and sent by the second electrical port sending end, record abnormal alarm information of the second electrical signal, and count the number of abnormal alarms;

[0022] Message parser, using HDLC protocol to parse message information;

[0023] Internal bus interface, used to send abnormal alarm information and message information of optical and electrical signals to CPU through the internal bus;

[0024] The clock recovery module uses the Manchester code protocol to recover the link clock from the optical signal for electrical port signal transmission.

[0025] Furthermore, the abnormal alarm information of the optical signal includes abnormal pulse width and non-compliance with the Manchester code rule; the abnormal alarm information of the electrical signal includes abnormal pulse width, all bit stream 0, and all bit stream 1.

[0026] Further, parsing the message information includes: parsing the message frame header, frame tail and frame length, checking CRC, checking overlong frames and undershort frames, abnormal message frame header, and continuous 0 and continuous 1 judgment.

[0027] When the CPU receives the abnormal alarm information, it records the time of the abnormal alarm, and reads the message information cached in the signal conversion and monitoring module through interrupt scanning, and stores both the abnormal alarm information and the message information in the CPU;

[0028] The CPU is connected to the host computer via Ethernet; the host computer has a built-in tool that reads the abnormal alarm information and message information stored in the CPU via the Ethernet protocol, and locates the fault point by analyzing the abnormal alarm information and message information.

[0029] Furthermore, the signal conversion and monitoring module displays abnormal alarm information on the panel of the device by lighting a lamp.

[0030] A fault monitoring method based on a longitudinal differential protection communication link device, comprising:

[0031] Step 1, converting the optical signal or electrical signal of the communication link and monitoring the status of the signal;

[0032] Step 2, when abnormal alarm information appears in the signal during the conversion process, the abnormal alarm information and occurrence time of the signal are recorded;

[0033] Step 3: determine the location of the fault point according to the signal type corresponding to the abnormal alarm information, that is, if the abnormal alarm information comes from an optical signal, the fault point is determined to be an optical cable; if the abnormal alarm information comes from an electrical signal, the fault point is determined to be an electrical cable;

[0034] Step 4, parse the protection message information. If the message information is normal, determine that the fault point is the SDH network; if the message information is abnormal, determine that the fault is due to abnormal protection message.

[0035] The beneficial effect of the present invention lies in that, compared with the prior art, the present invention integrates the signal conversion and monitoring functions into one, and is implemented using an FPGA+CPU circuit. While being compatible with the photoelectric conversion function, the FPGA processes the signal and records the abnormal alarm point, records the abnormal conditions of the optical cable, electrical cable and SDH network in the communication link and sends them to the CPU, and intuitively displays the alarm through the device panel, thereby quickly locating the fault point of the communication link.

[0036] In the early debugging work of the longitudinal differential protection system, the intuitive display function and abnormal recording function of the fault monitoring system proposed in the present invention facilitate the rapid debugging of the communication link on site, thereby improving the debugging efficiency of the longitudinal differential protection system.

[0037] After the longitudinal differential protection system is put into operation, if a communication link fails, the fault point can be preliminarily determined by the indicator light on the device panel in the fault monitoring system proposed by the present invention, or the abnormal log recorded in the CPU can be read through the built-in tool of the host computer to quickly locate the fault point and quickly repair the fault in the communication link.

[0038] In summary, the fault monitoring system proposed in the present invention effectively reduces the complexity of early debugging and improves the rapidity and accuracy of later fault location, greatly reduces labor input, saves device costs, and significantly improves economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1It is a connection diagram of various devices and communication links in a traditional longitudinal differential protection system;

[0040] Figure 2 This is a general architecture diagram of a fault monitoring system based on a longitudinal differential protection communication link device of the present invention;

[0041] Figure 3 A connection diagram of an FPGA circuit in one embodiment of the present invention;

[0042] Figure 4 It is a connection diagram of various devices and communication links in a longitudinal differential protection system in one embodiment of the present invention;

[0043] in, Figures 1 to 4 The reference numerals in the figures are described as follows:

[0044] 1a- protection device on this side; 1b- protection device on the opposite side;

[0045] 2a-power interface communication device on this side; 2b-power interface communication device on the opposite side;

[0046] 3a-SDH system on this side; 3b-SDH system on the other side;

[0047] 4-optical cable; 5-electrical cable; 6-SDH network;

[0048] 7a- local fault monitoring system; 7b- opposite side fault monitoring system;

[0049] 8-signal conversion and monitoring module; 9-CPU; 10-host computer;

[0050] 101- optical port receiving end; 102- optical port transmitting end;

[0051] 201-first electrical port receiving end; 202-first electrical port sending end;

[0052] 301-second electrical port receiving end; 302-second electrical port sending end;

[0053] 11-Mann code codec;

[0054] 12- message parser;

[0055] 13-HDB3 encoder;

[0056] 14-HDB3 decoder;

[0057] 15-Clock recovery module;

[0058] 16-PCM driving circuit;

[0059] 17-PCM receiving circuit;

[0060] 18-internal bus interface;

[0061] Figure 5 The present invention is a flowchart of a fault monitoring method based on a longitudinal differential protection communication link device. DETAILED DESCRIPTION

[0062] The present application is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present application.

[0063] like Figure 1 A fault monitoring system based on a longitudinal differential protection communication link device, the longitudinal differential protection system includes: a protection device 1a on this side, a power interface communication device 2a on this side, an SDH system 3a on this side, an SDH system 3b on the opposite side, a power interface communication device 2b on the opposite side, a protection device 1b on the opposite side and a communication link, wherein the communication link includes: an optical cable 4 between the power interface communication device on each side and the corresponding protection device, a cable 5 between the power interface communication device on each side and the corresponding SDH system, and an SDH network 6 between the SDH systems on both sides.

[0064] like Figure 2 , the fault monitoring system includes: a signal conversion and monitoring module 8, a CPU 9 and a host computer 10;

[0065] The signal conversion and monitoring module 8 sends the abnormal alarm information and message information of the communication link to the CPU in real time. The host computer 10 reads the abnormal alarm information and message information stored in the CPU and quickly locates the fault point by analyzing the abnormal alarm information and message information.

[0066] Specifically, the signal conversion and monitoring module 8 includes an optical transceiver and an electrical transceiver. The optical transceiver is connected to the protection device via an optical cable 4 , and the electrical transceiver is connected to the SDH system via an electrical cable 5 .

[0067] Furthermore, the optical port transceiver includes: an optical port receiving end 101 and an optical port transmitting end 102 ; the electrical port transceiver includes: a first electrical port receiving end 201 , a second electrical port receiving end 301 , a first electrical port transmitting end 202 and a second electrical port transmitting end 302 .

[0068] The first electrical port receiving end 201 and the first electrical port transmitting end 202 are both PCM interfaces that meet the European standard E1, and the second electrical port receiving end 301 and the second electrical port transmitting end 302 are both PCM interfaces.

[0069] like Figure 2 and Figure 3The signal conversion and monitoring module 8 adopts the circuit structure of FPGA and CPU, and the FPGA is connected to the CPU through an internal bus; wherein the FPGA includes: an optical port receiving end 101, an optical port transmitting end 102, a first electrical port receiving end 201, a second electrical port receiving end 301, a first electrical port transmitting end 202, a second electrical port transmitting end 302 and an internal bus interface 18.

[0070] In this preferred embodiment, the signal conversion and monitoring module 8 is fully compatible with the photoelectric conversion function and is applicable to the traditional longitudinal differential protection system.

[0071] Specifically, the signal conversion and monitoring module 8 performs signal conversion and signal monitoring simultaneously;

[0072] The signal conversion includes: after the optical signal received by the optical port receiving end 101 is converted into an electrical signal, it is sent to the SDH system by the first electrical port sending end 202 and the second electrical port sending end 302 respectively; after the electrical signals received by the first electrical port receiving end 201 and the second electrical port receiving end 301 are converted into optical signals, they are sent to the protection device by the optical port sending end 102.

[0073] Signal monitoring includes: monitoring the optical signal received by the optical port receiving end 101 and recording abnormal alarm information of the optical signal; monitoring the electrical signal received by the first electrical port receiving end 201 and the second electrical port receiving end 301 and recording abnormal alarm information of the electrical signal.

[0074] Further, if Figure 3 , the FPGA circuit has a built-in Manchester code codec 11, a message parser 12, an HDB3 encoder 13, an HDB3 decoder 14, a clock recovery module 15, a PCM driving circuit 16, a PCM receiving circuit 17 and an internal bus interface 18;

[0075] Manchester code coder and decoder 11, using Manchester code protocol to realize the conversion between optical signal and electrical signal, and record the abnormal alarm information of optical signal, and count the number of abnormal alarms;

[0076] The HDB3 encoder 13 and the HDB3 decoder 14 modulate the first electrical signal received by the first electrical port receiving end 201 and sent by the first electrical port sending end 202 using the HDB3 protocol, record abnormal alarm information of the first electrical signal, and count the number of abnormal alarms;

[0077] The PCM driving circuit 16 and the PCM receiving circuit 17 use the PCM protocol to modulate the second electrical signal received by the second electrical port receiving end 301 and sent by the second electrical port sending end 302, record the abnormal alarm information of the second electrical signal, and count the number of abnormal alarms;

[0078] A message parser 12, which uses the HDLC protocol to parse message information;

[0079] The internal bus interface 18 is used to send abnormal alarm information of optical signals and electrical signals and message information to the CPU through the internal bus.

[0080] Abnormal alarm information of the optical signal includes but is not limited to abnormal pulse width and non-compliance with Manchester code rules; the selection in this preferred embodiment is a non-restrictive and preferred selection.

[0081] The abnormal alarm information of the electrical signal includes but is not limited to abnormal pulse width, all bit streams 0, and all bit streams 1; the selection in this preferred embodiment is a non-restrictive and preferred selection.

[0082] Parsing message information includes but is not limited to parsing the message frame header, frame tail and frame length, checking CRC, checking overlong frames and overshort frames, abnormal message frame headers, and judging a large number of consecutive 0s and 1s; the selection in this preferred embodiment is a non-restrictive and preferred selection.

[0083] Specifically, when the CPU receives the abnormal alarm information, it records the time of the abnormal alarm, and reads the message information cached in the signal conversion and monitoring module 8 through interrupt scanning, and stores both the abnormal alarm information and the message information in the CPU;

[0084] Specifically, the CPU is connected to the host computer 10 via Ethernet; the host computer 10 has a built-in tool that reads the abnormal alarm information and message information stored in the CPU via the Ethernet protocol, and locates the fault point by analyzing the abnormal alarm information and message information.

[0085] Specifically, the signal conversion and monitoring module 8 displays the abnormal alarm information on the panel of the device by lighting. In this preferred embodiment, the communication link status can be preliminarily judged by the indicator light on the device panel; when the communication link status is normal, the optical port and electrical port signal indicator lights on the panel flash with the data frequency; when the communication link status is abnormal, if the optical signal is abnormal, the optical port signal alarm indicator light on the panel is lit, and if the electrical signal is abnormal, the electrical port signal alarm indicator light on the panel is lit.

[0086] like Figure 4 In this preferred embodiment, after the fault monitoring system is applied, the longitudinal differential protection system includes: a protection device 1a on this side, a power interface communication device 2a on this side, a fault monitoring system 7a on this side, an SDH system 3a on this side, an SDH system 3b on the opposite side, a power interface communication device 2b on the opposite side, a fault monitoring system 7b on the opposite side, a protection device 1b on the opposite side and a communication link; wherein the communication link includes: an optical cable 4 between the power interface communication device on each side and the corresponding protection device, an electrical cable 5 between the power interface communication device on each side and the corresponding SDH system, and an SDH network 6 between the SDH systems on both sides.

[0087] like Figure 5 , a fault monitoring method based on a longitudinal differential protection communication link device comprises:

[0088] Step 1, converting the optical signal or electrical signal of the communication link and monitoring the status of the signal;

[0089] Step 2, when abnormal alarm information appears in the signal during the conversion process, the abnormal alarm information and occurrence time of the signal are recorded;

[0090] Step 3: determine the location of the fault point according to the signal type corresponding to the abnormal alarm information, that is, if the abnormal alarm information comes from an optical signal, the fault point is determined to be an optical cable; if the abnormal alarm information comes from an electrical signal, the fault point is determined to be an electrical cable;

[0091] Step 4, parse the protection message information. If the message information is normal, determine that the fault point is the SDH network; if the message information is abnormal, determine that the fault is due to abnormal protection message.

[0092] In this preferred embodiment, the tool of the host computer 10 calls the signal conversion and monitoring module 8 and the abnormal alarm information and alarm time stored in the CPU to determine whether the fault point is in the optical cable or the electrical cable; further, the message information stored in the CPU is called to check whether the message is normal, so as to locate whether the fault occurs in the SDH network.

[0093] The beneficial effect of the present invention lies in that, compared with the prior art, the present invention integrates the signal conversion and monitoring functions into one, and is implemented using an FPGA+CPU circuit. While being compatible with the photoelectric conversion function, the FPGA processes the signal and records the abnormal alarm point, records the abnormal conditions of the optical cable, electrical cable and SDH network in the communication link and sends them to the CPU, and intuitively displays the alarm through the device panel, thereby quickly locating the fault point of the communication link.

[0094] In the early debugging work of the longitudinal differential protection system, the intuitive display function and abnormal recording function of the fault monitoring system proposed in the present invention facilitate the rapid debugging of the communication link on site, thereby improving the debugging efficiency of the longitudinal differential protection system.

[0095] After the longitudinal differential protection system is put into operation, if a communication link fails, the fault point can be preliminarily determined by the indicator light on the device panel in the fault monitoring system proposed by the present invention, or the abnormal log recorded in the CPU can be read through the built-in tool of the host computer to quickly locate the fault point and quickly repair the fault in the communication link.

[0096] In summary, the fault monitoring system proposed in the present invention effectively reduces the complexity of early debugging and improves the rapidity and accuracy of later fault location, greatly reduces labor input, saves device costs, and significantly improves economic benefits.

[0097] The applicant of the present invention has made a detailed explanation and description of the implementation examples of the present invention in conjunction with the drawings in the specification. However, those skilled in the art should understand that the above implementation examples are only preferred implementation schemes of the present invention, and the detailed description is only to help readers better understand the spirit of the present invention, but not to limit the scope of protection of the present invention. On the contrary, any improvements or modifications based on the inventive spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A fault monitoring system based on a longitudinal differential protection communication link device, the longitudinal differential protection system comprising: The protection device on this side, the power interface communication device on this side, the SDH system on this side, the SDH system on the opposite side, the power interface communication device on the opposite side, the protection device on the opposite side and the communication link, wherein the communication link includes: an optical cable between the power interface communication device on each side and the corresponding protection device, an electric cable between the power interface communication device on each side and the corresponding SDH system, and an SDH network between the SDH systems on both sides, characterized in that: The fault monitoring system comprises: a signal conversion and monitoring module, a CPU and a host computer; The signal conversion and monitoring module sends the abnormal alarm information and message information of the communication link to the CPU in real time, and the host computer reads the abnormal alarm information and message information stored in the CPU, and quickly locates the fault point by analyzing the abnormal alarm information and message information; wherein, the signal conversion and monitoring module adopts the circuit structure of FPGA and CPU, and the FPGA is connected to the CPU through an internal bus; the FPGA circuit has a built-in Manchester code codec, a message parser, an HDB3 encoder, an HDB3 decoder, a clock recovery module, a PCM driving circuit, a PCM receiving circuit and an internal bus interface; the Manchester code codec uses the Manchester code protocol to realize the conversion between optical signals and electrical signals, and records the abnormal alarm information of the optical signal, and counts the number of abnormal alarms; the The HDB3 encoder and the HDB3 decoder use the HDB3 protocol to modulate the first electrical signal received by the first electrical port receiving end and sent by the first electrical port sending end, record the abnormal alarm information of the first electrical signal, and count the number of abnormal alarms; the PCM driving circuit and the PCM receiving circuit use the PCM protocol to modulate the second electrical signal received by the second electrical port receiving end and sent by the second electrical port sending end, record the abnormal alarm information of the second electrical signal, and count the number of abnormal alarms; the message parser uses the HDLC protocol to parse the message information; the internal bus interface is used to send the abnormal alarm information of the optical signal and the electrical signal and the message information to the CPU through the internal bus; the clock recovery module uses the Manchester code protocol to recover the link clock from the optical signal for electrical port signal transmission; Among them, the abnormal alarm information of the optical signal includes abnormal pulse width and non-compliance with Manchester code rules; the abnormal alarm information of the electrical signal includes abnormal pulse width, bit stream all 0, and bit stream all 1.

2. A fault monitoring system based on a longitudinal differential protection communication link device according to claim 1, characterized in that: The signal conversion and monitoring module includes an optical port transceiver and an electrical port transceiver; The optical port transceiver is connected to the protection device through an optical cable, and the electrical port transceiver is connected to the SDH system through a cable; wherein the optical port transceiver includes: an optical port receiving end and an optical port transmitting end; the electrical port transceiver includes: a first electrical port receiving end, a second electrical port receiving end, a first electrical port transmitting end and a second electrical port transmitting end; The first electrical port receiving end and the first electrical port sending end are both PCM interfaces that meet the European standard E1, and the second electrical port receiving end and the second electrical port sending end are both PCM interfaces.

3. A fault monitoring system based on a longitudinal differential protection communication link device according to claim 1, characterized in that: in, The FPGA comprises: an optical port receiving end, an optical port transmitting end, a first electrical port receiving end, a second electrical port receiving end, a first electrical port transmitting end, a second electrical port transmitting end and an internal bus interface.

4. A fault monitoring system based on a longitudinal differential protection communication link device according to any one of claims 1 to 3, characterized in that: The signal conversion and monitoring module performs signal conversion and signal monitoring simultaneously; The signal conversion includes: after the optical signal received by the optical port receiving end is converted into an electrical signal, it is sent to the SDH system by the first electrical port sending end and the second electrical port sending end respectively; after the electrical signal received by the first electrical port receiving end and the second electrical port receiving end is converted into an optical signal, it is sent to the protection device by the optical port sending end; The signal monitoring includes: monitoring the optical signal received by the optical port receiving end, and recording abnormal alarm information of the optical signal; monitoring the electrical signal received by the first electrical port receiving end and the second electrical port receiving end, and recording abnormal alarm information of the electrical signal.

5. A fault monitoring system based on a longitudinal differential protection communication link device according to claim 1, characterized in that: The parsing of message information includes: parsing the message frame header, frame tail and frame length, checking CRC, checking overlong frames and overshort frames, abnormal message frame header, and continuous 0 and continuous 1 judgment.

6. A fault monitoring system based on a longitudinal differential protection communication link device according to claim 1, characterized in that: When the CPU receives the abnormal alarm information, it records the time of the abnormal alarm, reads the message information cached in the signal conversion and monitoring module through interrupt scanning, and stores both the abnormal alarm information and the message information in the CPU; The CPU is connected to the host computer via Ethernet; the host computer has a built-in tool that reads the abnormal alarm information and message information stored in the CPU via the Ethernet protocol, and locates the fault point by analyzing the abnormal alarm information and message information.

7. A fault monitoring system based on a longitudinal differential protection communication link device according to any one of claims 1 to 3, characterized in that: The signal conversion and monitoring module displays abnormal alarm information on the panel of the device by lighting up the lamp.

8. A fault monitoring method implemented by a fault monitoring system based on a longitudinal differential protection communication link device according to any one of claims 1 to 7, characterized in that: The method comprises: Step 1, converting the optical signal or electrical signal of the communication link and monitoring the status of the signal; Step 2, when abnormal alarm information appears in the signal during the conversion process, the abnormal alarm information and occurrence time of the signal are recorded; Step 3: determine the location of the fault point according to the signal type corresponding to the abnormal alarm information, that is, if the abnormal alarm information comes from an optical signal, the fault point is determined to be an optical cable; if the abnormal alarm information comes from an electrical signal, the fault point is determined to be an electrical cable; Step 4, parse the protection message information. If the message information is normal, determine that the fault point is the SDH network; if the message information is abnormal, determine that the fault is due to abnormal protection message.

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