Clock fault judgment and automatic switching system and method applied to power system

Abstract

The invention provides a clock fault judgment and automatic switching system and method applied to an electric power system, and belongs to the field of time synchronization of the electric power system.The clock fault judgment and automatic switching system comprises a plurality of sites which are annularly connected through an optical fiber link, a GNSS receiver outputs two paths of time signals, one path of time signal TGNSS enters a seamless switching module and is input into electric power equipment, and the other path of time signal TGNSS enters the electric power equipment; the other path of time signal enters the optical fiber time synchronization module to generate a time signal TA, the optical fiber time synchronization module performs time comparison on the time signal TA and the time signals of two adjacent sites to obtain time delays tAB and tAC, and when the two time delays exceed a set threshold value, the optical fiber time synchronization module sends the time signal TA to the optical fiber time synchronization module; the optical fiber time synchronization module regenerates a time signal TB or TC synchronized with one adjacent station; and high-precision time synchronization of the power equipment of the fault site and the adjacent site is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of power system time synchronization, and in particular to a clock fault judgment and automatic switching system and method applied to a power system. Background Art

[0002] Time is one of the seven fundamental physical quantities and is the information cornerstone that affects national economy and people's livelihood, social and national development. Its support for society includes navigation and positioning, communications, electricity, finance, intelligent transportation, digital earth, aerospace, cutting-edge technology and other fields.

[0003] The time synchronization system is a standard configuration for power system applications. It provides accurate time synchronization signals for various production systems and equipment in the power system to meet the requirements of power system time synchronization. The power system time synchronization system consists of time synchronization systems located in rated dispatching organizations, substations, power plants, etc. at all levels of power grids. In modern power management systems, time synchronization is the basis for various monitoring systems to conduct data sampling, fault handling, network supervision, information management, accident recall and analysis, and is an important part of the safe operation of the system. If any node involved in time synchronization has time deviation, it will affect the stable operation of the system.

[0004] In recent years, optical fiber communication technology has made great progress. Optical fiber has the advantages of low loss, little impact from the atmosphere and other environments, and long transmission distance. The use of abundant communication optical fibers to achieve high-precision time and frequency transmission and comparison shows obvious technical advantages. At present, my country has started the construction of a high-precision ground-based timing system. Relying on the existing optical fiber communication network, a networked optical fiber timing system is being built to form a safe and reliable time synchronization network that integrates the earth and the sky. According to Q / GDW11539-2016 "Technical Specifications for Time Synchronization and Monitoring of Power Systems", the time synchronization device of the power system should have multiple clock source options, with space-based timing as the main and ground-based timing as the auxiliary, to establish a complete and reliable time synchronization system.

[0005] At present, the State Grid system widely uses GNSS space-based clocks such as GPS or Beidou as the main clock source. In some cases, Beidou timing is used as the only clock source, and some substations are still using traditional GPS single clock for time synchronization and calibration due to old equipment. At present, the clock systems of some power stations have the ability to select multiple clock sources, but the ground-based timing is basically vacant and not enabled. From the perspective of system application security, relying solely on a clock source for system clock synchronization has certain security risks. Under the current international situation, the GPS system is at risk of unavailability, and the satellite system is also at risk of being unavailable due to weather, environment, etc. In addition, in actual applications, it is not ruled out that malicious attackers use pseudo-satellites near the receiving antenna to suppress the reception of normal signals with the nearby pseudo-satellite signals, causing system clock disorder or failure to obtain convergence solutions for a long time, resulting in clock system failure.

[0006] In the prior art, the Chinese invention patent application with publication number CN110971333A, "A two-way time synchronization system and method based on free-space laser communication", receives the time synchronization signal through the time synchronization terminal to synchronize the sites. This method is based on the free-space laser signal. When the laser is transmitted in the free space, it is easily affected by the atmospheric molecules and other molecules in the atmosphere, causing power attenuation and pulse width broadening, resulting in a decrease in the signal-to-noise ratio and a shortened transmission distance. If the distance between the two sites is far or there are mountains and buildings in the middle to block them, the time synchronization accuracy will decrease or even make it impossible to synchronize the sites. Summary of the invention

[0007] The technical problem to be solved by the present invention is how to achieve time synchronization between sites through an optical fiber network when the space-based system clock in the power system fails.

[0008] The present invention solves the above technical problems through the following technical solutions: a clock fault judgment and automatic switching system applied to a power system, comprising a plurality of stations connected in a ring through an optical fiber link, each station comprising a GNSS receiver, a seamless switching module, an optical fiber time synchronization module and a power device, the GNSS receiver outputs two time signals T GNSS , a time signal T GNSS Enter the seamless switching module and input to the power equipment, another time signal T GNSS Enter the optical fiber time synchronization module to generate the time signal T GNSS Synchronous time signal T A , the optical fiber time synchronization module converts the time signal T A The time signal T between two adjacent stations B , T C Perform time comparison respectively to obtain the time delay t between the current site and two adjacent sites. AB ,tAC , when two time delays t AB ,t AC When both exceed the set threshold, the optical fiber time synchronization module regenerates a time signal T synchronized with one of the adjacent sites. B or T C , the seamless switching module switches to the optical fiber time synchronization module and converts the time signal T B or T C Input to the electrical equipment at the current site.

[0009] Preferably, the optical fiber time synchronization module includes a time purification module, a modulation encoder, a laser, a circulator, an optical switching switch, a photoelectric detector, a decoding demodulator, a time difference measurement module, and a time regeneration module. The optical switching switch connects the adjacent site B and site C successively and works in the same way. When the adjacent site B is connected, the laser signal of the adjacent site B is sent to the photoelectric detector through the circulator. The photoelectric detector converts the laser signal into an electrical signal and outputs a coded signal. The decoding demodulator demodulates the time difference value t measured by the adjacent site B from the coded signal. B-A and the time signal T B , time difference t B-A Input to the time regeneration module, the time signal T B Input to the time difference measurement module, one time signal T GNSS Enter the time purification module, the time purification module uses the time signal T GNSS The reference signal T GNSS Synchronous time signal T A and frequency signal f0, time signal T A The frequency signal f0 is input to the modulation encoder, and the time signal T A Input to the time difference measurement module, the time difference measurement module measures the time signal T A and the time signal T B The time difference t A-B The modulation encoder uses the frequency signal f0 as the carrier and converts the time signal T A and the time difference t A-B The coded signal is encoded and input into the laser. The laser modulates the coded signal into the laser signal and inputs it into the circulator. The circulator couples the laser signal to the optical fiber link and connects to an adjacent site through an optical switching switch to receive and send the laser signal. The time difference t A-B The frequency signal f0 is input to the time regeneration module, which measures the time delay t between site A and the adjacent site B. AB , regenerates the time signal T synchronized with the adjacent site B B And input to the seamless switching module.

[0010] Preferably, the time regeneration module measures the time delay t between site A and adjacent site B. AB The time regeneration module measures the time delay t between site A and adjacent site C AC The calculation method is the same as:

[0011] t AB =(t A-B -t B-A ) / 2

[0012] t A-B The time signal T is measured by the time difference measurement module in site A. A and the time signal T B The time difference, t B-A The time signal T is measured by the time difference measurement module in site B. A and the time signal T B The time difference value.

[0013] Preferably, when the two time delays t AB ,t AC When both exceed the set threshold, the time signal T output by the GNSS receiver at the current site is determined GNSS Untrusted, the time purification module in the current site no longer uses the time signal T GNSS For reference, a time signal and a frequency signal are generated autonomously.

[0014] Preferably, the set threshold is 100ns.

[0015] The present invention also provides a clock fault judgment and automatic switching method applied to a power system, comprising:

[0016] Step 1: GNSS receiver outputs two time signals T GNSS , a time signal T GNSS Enter the seamless switching module and input to the power equipment, another time signal T GNSS Enter the fiber optic time synchronization module;

[0017] Step 2: The optical fiber time synchronization module generates the time signal T GNSS Synchronous time signal T A , and the time signal T A The time signal T between two adjacent stations B , T C Perform time comparison respectively to obtain the time delay t between the current site and two adjacent sites. AB ,t AC ;

[0018] Step 3: When the two time delays are t AB ,t ACWhen both exceed the set threshold, the optical fiber time synchronization module regenerates a time signal T synchronized with one of the adjacent sites. B or T C ;

[0019] Step 4: The seamless switching module switches to the optical fiber time synchronization module and transmits the time signal T B or T C Input to the electrical equipment at the current site.

[0020] Preferably, the step 2 comprises:

[0021] 2.1. The optical switching switch connects to an adjacent station one by one, and sends the laser signal of the adjacent station to the photodetector through the circulator. The photodetector converts the laser signal into an electrical signal and outputs a coded signal. The decoding demodulator demodulates the time difference value t measured by the adjacent station from the coded signal. B-A or C-A , and the time signal T B or T C , time difference t B-A or C-A Input to the time regeneration module, the time signal T B or T C Input to the time difference measurement module;

[0022] 2.2, Time purification module uses time signal T GNSS The reference signal T GNSS Synchronous time signal T A and frequency signal f0, time signal T A The frequency signal f0 is input to the modulation encoder, and the time signal T A Input to the time difference measurement module, the time difference measurement module measures the time signal T A and the time signal T B or T C The time difference t A-B or A-C ;

[0023] 2.3. The modulation encoder uses the frequency signal f0 as the carrier and converts the time signal T A and the time difference t A-B or A-C The coded signal is input into the laser after encoding. The laser modulates the coded signal into the laser signal and inputs it into the circulator. The circulator couples the laser signal to the optical fiber link and connects to an adjacent site through an optical switching switch to receive and send the laser signal.

[0024] 2.4. Time difference value t A-B or A-CThe frequency signal f0 is input to the time regeneration module, which measures the time delay t between site A and the adjacent site. AB ,t AC .

[0025] Preferably, the time regeneration module measures the time delay t between site A and adjacent site B. AB The time regeneration module measures the time delay t between site A and adjacent site C AC The calculation method is the same as:

[0026] t AB =(t A-B -t B-A ) / 2

[0027] t A-B The time signal T is measured by the time difference measurement module in site A. A and the time signal T B The time difference, t B-A The time signal T is measured by the time difference measurement module in site B. A and the time signal T B The time difference value.

[0028] Preferably, in step 3, when the two time delays t AB ,t AC When both exceed the set threshold, the time signal T output by the GNSS receiver at the current site is determined GNSS Untrusted, the time purification module in the current site no longer uses the time signal T GNSS For reference, a time signal and a frequency signal are generated autonomously.

[0029] Preferably, the set threshold is 100ns.

[0030] The advantages provided by the present invention are:

[0031] 1. The present invention sets up multiple sites in the power system in a ring through optical fiber links. When working normally, the system time of the power equipment at each site is provided by the GNSS receiver. At the same time, the time signal T output by the GNSS receiver GNSS The optical fiber time synchronization system is used to compare the time with two adjacent sites respectively to obtain the time delay t between the current site and the two adjacent sites. AB ,t AC , to realize the time signal T GNSS When the GNSS satellite signal of a station is interfered, deceived or otherwise fails, causing the system clock of the station to be unreliable, it will be manifested as two time delays t AB ,t ACWhen both exceed the set threshold, the optical fiber time synchronization module will regenerate a time signal synchronized with one of the adjacent sites and accurately transmit the time signal to the fault site. The seamless switching module will input the accurate time into the power equipment to ensure high-precision synchronization between the power equipment at the fault site and the power equipment at the adjacent site.

[0032] 2. The present invention connects multiple sites in the power system through optical fiber links. The propagation of laser in the optical fiber is not affected by various factors in the atmosphere, the performance is relatively stable, and the transmission distance can reach 80km-100km. Even if the distance between the two sites is far or there are mountains and buildings in the middle to block it, the present invention can still ensure the accuracy of time synchronization. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of a clock fault judgment and automatic switching system applied to a power system provided by an embodiment of the present invention;

[0034] Figure 2 A flowchart of a clock fault judgment and automatic switching method applied to a power system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the technical solution of the present invention is clearly and completely described below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] like Figure 1 As shown, this embodiment provides a clock fault judgment and automatic switching system for a power system, including multiple sites connected in a ring through an optical fiber link, each site including a GNSS receiver, a seamless switching module, an optical fiber time synchronization module and a power device, and the GNSS receiver outputs two time signals T GNSS , a time signal T GNSS Enter the seamless switching module and input to the power equipment, another time signal T GNSS Enter the optical fiber time synchronization module to generate the time signal T GNSS Synchronous time signal T A , the optical fiber time synchronization module converts the time signal T A The time signal T between two adjacent stations B 、T C Compare the time respectively and get the time delay t between the current site and two adjacent sitesAB ,t AC , when two time delays t AB ,t AC When both exceed the set threshold, the optical fiber time synchronization module regenerates a time signal T synchronized with one of the adjacent sites. B or T C , the seamless switching module switches to the optical fiber time synchronization module and converts the time signal T B or T C Input to the electrical equipment at the current site.

[0038] The present invention sets up multiple sites in the power system in a ring through optical fiber links. When working normally, the system time of the power equipment at each site is provided by the GNSS receiver. At the same time, the time signal T output by the GNSS receiver GNSS The optical fiber time synchronization system is used to compare the time with two adjacent sites respectively to obtain the time delay t between the current site and the two adjacent sites. AB ,t AC , to realize the time signal T GNSS When the GNSS satellite signal of a station is interfered, deceived or otherwise fails, causing the system clock of the station to be unreliable, it will be manifested as two time delays t AB ,t AC When both exceed the set threshold, the optical fiber time synchronization module will regenerate a time signal synchronized with one of the adjacent sites and accurately transmit the time signal to the fault site. The seamless switching module will input the accurate time into the power equipment to ensure high-precision synchronization between the power equipment at the fault site and the power equipment at the adjacent site.

[0039] The propagation of laser in optical fiber is not affected by various factors in the atmosphere, the performance is relatively stable, and the transmission distance can reach 80km-100km. Even if the distance between two sites is far or there are mountains and buildings in between to block it, the present invention can still ensure the accuracy of time synchronization.

[0040] The clock fault judgment and automatic switching system of the present invention is described below using site A and two adjacent sites B and C as examples. Similarly, when clock faults occur at other sites, time synchronization can be performed through the clock fault judgment and automatic switching system of the present invention.

[0041] In each site, the optical fiber time synchronization module includes a time purification module, a modulation encoder, a laser, a circulator, an optical switching switch, a photoelectric detector, a decoding demodulator, a time difference measurement module, and a time regeneration module. When the optical fiber link between site A and site B is connected, the optical switching switch connects to the adjacent site B, and sends the laser signal of the adjacent site B to the photoelectric detector through the circulator. The photoelectric detector converts the laser signal into an electrical signal and outputs a coded signal. The decoding demodulator demodulates the time difference value t measured by the adjacent site B from the coded signal. B-A and the time signal T B , time difference t B-A Input to the time regeneration module, the time signal T B Input to the time difference measurement module, one time signal T GNSS Enter the time purification module, the time purification module uses the time signal T GNSS The reference signal T GNSS Synchronous time signal T A and frequency signal f0, time signal T A The frequency signal f0 is input to the modulation encoder, and the time signal T A Input to the time difference measurement module, the time difference measurement module measures the time signal T A and the time signal T B The time difference t A-B The modulation encoder uses the frequency signal f0 as the carrier and converts the time signal T A and the time difference t A-B The coded signal is encoded and input into the laser. The laser modulates the coded signal into the laser signal and inputs it into the circulator. The circulator couples the laser signal to the optical fiber link and connects to an adjacent site through an optical switching switch to receive and send the laser signal. The time difference t A-B The frequency signal f0 is input to the time regeneration module, which measures the time delay t between site A and the adjacent site B. AB , regenerates the time signal T synchronized with the adjacent site B B And input to the seamless switching module.

[0042] The time regeneration module measures the time delay t between site A and adjacent site B. AB The calculation method is:

[0043] t AB =(t A-B -t B-A ) / 2

[0044] t A-B The time signal T is measured by the time difference measurement module in site A. A and the time signal T B The time difference, tB-A The time signal T is measured by the time difference measurement module in site B. A and the time signal T B The time difference value.

[0045] Similarly, when the optical fiber link between site A and site C is connected, the optical switch connects to the adjacent site C, and sends the laser signal of the adjacent site C to the photodetector through the circulator. The photodetector converts the laser signal into an electrical signal and outputs a coded signal. The decoder demodulates the time difference value t measured by the adjacent site C from the coded signal. C-A and the time signal T C , time difference t C-A Input to the time regeneration module, the time signal T C Input to the time difference measurement module, one time signal T GNSS Enter the time purification module, the time purification module uses the time signal T GNSS The reference signal T GNSS Synchronous time signal T A and frequency signal f0, time signal T A The frequency signal f0 is input to the modulation encoder, and the time signal T A Input to the time difference measurement module, the time difference measurement module measures the time signal T A and the time signal T C The time difference t A-C The modulation encoder uses the frequency signal f0 as the carrier and converts the time signal T A and the time difference t A-C The coded signal is encoded and input into the laser. The laser modulates the coded signal into the laser signal and inputs it into the circulator. The circulator couples the laser signal to the optical fiber link and connects to an adjacent site through an optical switching switch to receive and send the laser signal. The time difference t A-C The frequency signal f0 is input to the time regeneration module, which measures the time delay t between site A and the adjacent site C. AC , regenerates the time signal T synchronized with the adjacent site C C And input to the seamless switching module.

[0046] The time regeneration module measures the time delay t between site A and the adjacent site C. AC The calculation method is:

[0047] t AC =(t A-C -t C-A ) / 2

[0048] t A-C The time signal T is measured by the time difference measurement module in site A. A and the time signal TC The time difference, t C-A The time signal T is measured by the time difference measurement module in site C. A and the time signal T C The time difference value.

[0049] The setting threshold can be set to 100ns.

[0050] Similarly, when the time signal output by the GNSS receiver at site B is unreliable, the time signal T A (or T N ) to site B.

[0051] Example 2

[0052] like Figure 2 As shown, this embodiment provides a clock fault judgment and automatic switching method applied to a power system, including:

[0053] Step 1: GNSS receiver outputs two time signals T GNSS , a time signal T GNSS Enter the seamless switching module and input to the power equipment, another time signal T GNSS Enter the fiber optic time synchronization module;

[0054] Step 2: The optical fiber time synchronization module generates the time signal T GNSS Synchronous time signal T A , and the time signal T A The time signal T between two adjacent stations B , T C Perform time comparison respectively to obtain the time delay t between the current site and two adjacent sites. AB ,t AC ;

[0055] Step 2 includes:

[0056] 2.1. The optical switching switch connects to an adjacent station one by one, and sends the laser signal of the adjacent station to the photodetector through the circulator. The photodetector converts the laser signal into an electrical signal and outputs a coded signal. The decoding demodulator demodulates the time difference value t measured by the adjacent station from the coded signal. B-A or C-A , and the time signal T B or T C , time difference t B-A or C-A Input to the time regeneration module, the time signal T B or T C Input to the time difference measurement module;

[0057] 2.2, Time purification module uses time signal T GNSS The reference signal T GNSS Synchronous time signal T A and frequency signal f0, time signal T A The frequency signal f0 is input to the modulation encoder, and the time signal T A Input to the time difference measurement module, the time difference measurement module measures the time signal T A and the time signal T B or T C The time difference t A-B or A-C ;

[0058] 2.3. The modulation encoder uses the frequency signal f0 as the carrier and converts the time signal T A and the time difference t A-B or A-C The coded signal is input into the laser after encoding. The laser modulates the coded signal into the laser signal and inputs it into the circulator. The circulator couples the laser signal to the optical fiber link and connects to an adjacent site through an optical switching switch to receive and send the laser signal.

[0059] 2.4. Time difference value t A-B or A-C The frequency signal f0 is input to the time regeneration module, which measures the time delay t between site A and the adjacent site. AB ,t AC .

[0060] The time regeneration module measures the time delay t between site A and adjacent site B. AB The time regeneration module measures the time delay t between site A and adjacent site C AC The calculation method is the same as:

[0061] t AB =(t A-B -t B-A ) / 2

[0062] t A-B The time signal T is measured by the time difference measurement module in site A. A and the time signal T B The time difference, t B-A The time signal T is measured by the time difference measurement module in site B. A and the time signal T B The time difference value.

[0063] Step 3: When the two time delays are t AB ,t ACWhen both exceed the set threshold, the optical fiber time synchronization module regenerates a time signal T synchronized with one of the adjacent sites. B or T C ;

[0064] In step 3, when the two time delays t AB ,t AC When both exceed the set threshold, the time signal T output by the GNSS receiver at the current site is determined GNSS Untrusted, the time purification module in the current site no longer uses the time signal T GNSS For reference, a time signal and a frequency signal are generated autonomously. The threshold can be set to 100ns.

[0065] Step 4: The seamless switching module switches to the optical fiber time synchronization module and transmits the time signal T B or T C Input to the electrical equipment at the current site.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A clock fault judgment and automatic switching system applied to a power system, characterized in that: It includes multiple sites connected in a ring through optical fiber links. Each site includes a GNSS receiver, a seamless switching module, an optical fiber time synchronization module and power equipment. The GNSS receiver outputs two time signals T GNSS , a time signal T GNSS Enter the seamless switching module and input to the power equipment, another time signal T GNSS Enter the optical fiber time synchronization module to generate the time signal T GNSS Synchronous time signal T A , the optical fiber time synchronization module converts the time signal T A The time signal T between two adjacent stations B , T C Perform time comparison respectively to obtain the time delay t between the current site and two adjacent sites. AB ,t AC , when two time delays t AB ,t AC When both exceed the set threshold, the optical fiber time synchronization module regenerates a time signal T synchronized with one of the adjacent sites. B or T C , the seamless switching module switches to the optical fiber time synchronization module and converts the time signal T B or T C Input to the electrical equipment at the current site.

2. The clock fault judgment and automatic switching system applied to the power system according to claim 1 is characterized in that: The optical fiber time synchronization module includes a time purification module, a modulation encoder, a laser, a circulator, an optical switching switch, a photoelectric detector, a decoding demodulator, a time difference measurement module, and a time regeneration module. The optical switching switch connects the adjacent site B and site C successively and works in the same way. When the adjacent site B is connected, the laser signal of the adjacent site B is sent to the photoelectric detector through the circulator. The photoelectric detector converts the laser signal into an electrical signal and outputs a coded signal. The decoding demodulator demodulates the time difference value t measured by the adjacent site B from the coded signal. B-A and the time signal T B , time difference t B-A Input to the time regeneration module, the time signal T B Input to the time difference measurement module, one time signal T GNSS Enter the time purification module, the time purification module uses the time signal T GNSS The reference signal T GNSS Synchronous time signal T A and frequency signal f0, time signal T A The frequency signal f0 is input to the modulation encoder, and the time signal T A Input to the time difference measurement module, the time difference measurement module measures the time signal T A and the time signal T B The time difference t A-B The modulation encoder uses the frequency signal f0 as the carrier and converts the time signal T A and the time difference t A-B The coded signal is encoded and input into the laser. The laser modulates the coded signal into the laser signal and inputs it into the circulator. The circulator couples the laser signal to the optical fiber link and connects to an adjacent site through an optical switching switch to receive and send the laser signal. The time difference t A-B The frequency signal f0 is input to the time regeneration module, which measures the time delay t between site A and the adjacent site B. AB , regenerates the time signal T synchronized with the adjacent site B B And input to the seamless switching module.

3. The clock fault judgment and automatic switching system applied to the power system according to claim 2 is characterized in that: The time regeneration module measures the time delay t between site A and adjacent site B. AB The time regeneration module measures the time delay t between site A and adjacent site C AC The calculation method is the same as: t AB =(t A-B -t B-A ) / 2 t A-B The time signal T is measured by the time difference measurement module in site A. A and the time signal T B The time difference, t B-A The time signal T is measured by the time difference measurement module in site B. A and the time signal T B The time difference value.

4. The clock fault judgment and automatic switching system for electric power system according to claim 1, characterized in that: When two time delays t AB ,t AC When both exceed the set threshold, the time signal T output by the GNSS receiver at the current site is determined GNSS Untrusted, the time purification module in the current site no longer uses the time signal T GNSS For reference, a time signal and a frequency signal are generated autonomously.

5. The clock fault judgment and automatic switching system for electric power system according to claim 1, characterized in that: The set threshold is 100ns.

6. A clock fault judgment and automatic switching method applied to a power system, characterized in that: include: Step 1: GNSS receiver outputs two time signals T GNSS , a time signal T GNSS Enter the seamless switching module and input to the power equipment, another time signal T GNSS Enter the fiber optic time synchronization module; Step 2: The optical fiber time synchronization module generates the time signal T GNSS Synchronous time signal T A , and the time signal T A The time signal T between two adjacent stations B , T C Perform time comparison respectively to obtain the time delay t between the current site and two adjacent sites. AB ,t AC ; Step 3: When the two time delays are t AB ,t AC When both exceed the set threshold, the optical fiber time synchronization module regenerates a time signal T synchronized with one of the adjacent sites. B or T C ; Step 4: The seamless switching module switches to the optical fiber time synchronization module and transmits the time signal T B or T C Input to the electrical equipment at the current site.

7. The clock fault judgment and automatic switching method applied to the power system according to claim 6 is characterized in that: The second step comprises: 2.

1. The optical switching switch connects to an adjacent station one by one, and sends the laser signal of the adjacent station to the photodetector through the circulator. The photodetector converts the laser signal into an electrical signal and outputs a coded signal. The decoding demodulator demodulates the time difference value t measured by the adjacent station from the coded signal. B-A or C-A , and the time signal T B or T C , time difference t B-A or C-A Input to the time regeneration module, the time signal T B or T C Input to the time difference measurement module; 2.2, Time purification module uses time signal T GNSS The reference signal T GNSS Synchronous time signal T A and frequency signal f0, time signal T A The frequency signal f0 is input to the modulation encoder, and the time signal T A Input to the time difference measurement module, the time difference measurement module measures the time signal T A and the time signal T B or T C The time difference t A-B or A-C ; 2.

3. The modulation encoder uses the frequency signal f0 as the carrier and converts the time signal T A and the time difference t A-B or A-C The coded signal is input into the laser after encoding. The laser modulates the coded signal into the laser signal and inputs it into the circulator. The circulator couples the laser signal to the optical fiber link and connects to an adjacent site through an optical switching switch to receive and send the laser signal. 2.

4. Time difference value t A-B or A-C The frequency signal f0 is input to the time regeneration module, which measures the time delay t between site A and the adjacent site. AB ,t AC .

8. The clock fault judgment and automatic switching method applied to the power system according to claim 7 is characterized in that: The time regeneration module measures the time delay t between site A and adjacent site B. AB The time regeneration module measures the time delay t between site A and adjacent site C AC The calculation method is the same as: t AB =(t A-B -t B-A ) / 2 t A-B The time signal T is measured by the time difference measurement module in site A. A and the time signal T B The time difference, t B-A The time signal T is measured by the time difference measurement module in site B. A and the time signal T B The time difference value.

9. The clock fault judgment and automatic switching method applied to the power system according to claim 6, characterized in that: In step 3, when the two time delays t AB ,t AC When both exceed the set threshold, the time signal T output by the GNSS receiver at the current site is determined GNSS Untrusted, the time purification module in the current site no longer uses the time signal T GNSS For reference, a time signal and a frequency signal are generated autonomously.

10. The clock fault judgment and automatic switching method applied to the power system according to claim 6, characterized in that: The set threshold is 100ns.

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