A mine power supply differential protection data synchronization method based on optical fiber communication

Abstract

The application belongs to the technical field of mine power supply protection communication, and discloses a mine power supply differential protection data synchronization method based on optical fiber communication, two-end differential protection terminals respectively collect currents and generate data frames carrying sampling time and sampling serial numbers, first boundary check frames and second boundary check frames are arranged before and after continuous data frames to form a synchronization check section; an optical fiber communication interface uniformly allocates sending count values to all outbound frames, and records sending hardware time and receiving hardware time of each transmission unit; a time mapping relationship is established according to bidirectional time measurement and positive and negative fixed time delay difference, a first-order time delay change relationship is established by using the first boundary check frame and the data frame, and the second boundary check frame is independently checked. When the section structure, sending continuity, frame check and residual error meet the conditions, the two-end current data are matched according to the estimated transmission time delay, the sampling time and the sampling serial number, and are output to a differential protection calculation unit.

Description

Technical Field

[0001] This invention belongs to the field of communication technology for mine power supply protection, specifically a method for synchronizing differential protection data for mine power supply based on optical fiber communication. Background Technology

[0002] Mine power supply lines typically connect surface substations, underground central substations, and mining area substations, characterized by long line distances, multiple branch levels, and significant load fluctuations. Traditional overcurrent protection, grounding protection, and anti-overcurrent protection mainly rely on the line's own current and preset values ​​for fault judgment. When a remote short circuit or high-resistance fault occurs, the change in the fault current at the line's own end may not be obvious, easily leading to insufficient protection sensitivity, delayed fault clearing, and difficulties in coordinating upper and lower level protection. To improve the ability to distinguish fault currents at both ends of the line, existing mine power supply systems are gradually adopting fiber optic current differential protection, which involves exchanging current sampling data between the differential protection terminals at both ends of the line and performing differential calculations on the currents at the corresponding sampling times.

[0003] Existing current data synchronization methods typically establish the time correspondence between the data at both ends using sampling sequence numbers, communication timestamps, bidirectional timing results, or preset channel delays. However, in addition to transmitting differential protection data frames, fiber optic communication interfaces in mine sites may also transmit equipment status, fault records, and operational information. When other communication frames are inserted between consecutive differential protection data frames, or when the transmission buffer, interface scheduling, or fiber optic communication path status changes, the actual transmission interval and transmission delay of the same set of differential protection data frames may change accordingly. The sampling sequence number or transmission sequence number of the differential protection data frame itself can only reflect the logical order of such data frames, making it difficult to confirm whether adjacent data frames are continuous in the actual transmission sequence of the fiber optic communication interface. Using single timing results or fixed channel delays is also insufficient to accurately reflect short-term delay changes during the transmission of a set of data frames.

[0004] When the aforementioned transmission status and transmission delay cannot be accurately identified, the remote current data may be mismatched with the data from the previous or subsequent sampling time at the local end. In cases of sudden load changes, external faults, or rapid changes in current waveform, sampling mismatch may create additional differential current, causing the normal operating current to be mistakenly identified as the fault differential current, or weakening the actual fault differential current. If the synchronization status is judged solely based on the data involved in the delay calculation, the communication status may have changed by the time a set of data reaches the end, and the existing judgment result may still be used. Therefore, the existing technology still struggles to form a complete verification chain from actual transmission continuity verification, section transmission delay validity confirmation, section end status review to sampling data correspondence check. Data with abnormal communication status may still enter the differential protection calculation, affecting the operational reliability of the differential protection of the mine power supply line. Summary of the Invention

[0005] The purpose of this invention is to provide a data synchronization method for differential protection of mine power supply based on optical fiber communication, so as to solve the problem that when the two ends of the mine power supply line continuously exchange current sampling data, the current data at both ends of the line cannot be accurately matched according to the corresponding sampling time due to the insertion of other communication frames, changes in the transmission order of optical fiber communication interface, inconsistency between forward fixed transmission delay and reverse fixed transmission delay, and delay fluctuations of the same set of differential protection data frames during transmission.

[0006] To achieve the above objectives, differential protection terminals are installed at both ends of the mine power supply line. Each differential protection terminal includes the mine's original protector and a mine-use explosion-proof and intrinsically safe differential protection control box connected to the mine's original protector. The mine-use explosion-proof and intrinsically safe differential protection control box is equipped with an optical fiber communication interface, an RS485 serial communication interface, and an RJ45 Ethernet interface. The two ends of the mine-use explosion-proof and intrinsically safe differential protection control boxes are connected through the optical fiber communication interface, and the transmission distance of the optical fiber communication interface is no more than 10 kilometers.

[0007] The differential protection terminals at both ends collect the current data of the corresponding line end according to their respective local sampling clocks, record the sampling time and sampling sequence number of each set of current data, and encapsulate the current data, sampling time and sampling sequence number into a differential protection data frame.

[0008] For any given transmission direction, a first boundary check frame is sent before at least two consecutively transmitted differential protection data frames, and a second boundary check frame is sent after the at least two differential protection data frames; the first boundary check frame, the differential protection data frame located between the first boundary check frame and the second boundary check frame, and the second boundary check frame together constitute a synchronization check segment.

[0009] The first boundary check frame, differential protection data frame, and second boundary check frame within the synchronization check section are collectively referred to as transmission units. Each transmission unit belonging to the same synchronization check section has the same section identifier and is configured with a continuously increasing transmission sequence number according to the actual transmission order of the optical fiber communication interface.

[0010] The first boundary check frame and the second boundary check frame include a frame type field, a section identifier field, a boundary location field, a transmission sequence number field, a transmission count value field, and a frame check field, respectively; the differential protection data frame includes a section identifier field, a transmission sequence number field, a transmission count value field, a sampling sequence number field, a sampling time field, a current data field, and a frame check field.

[0011] For a synchronization verification section containing m differential protection data frames, the transmission sequence number of the first boundary verification frame is 0, the transmission sequence numbers of the m differential protection data frames are 1 to m respectively, and the transmission sequence number of the second boundary verification frame is m+1, where m is a positive integer not less than 2. The receiving end divides each transmission unit into the corresponding synchronization verification section according to the section identifier, and determines the arrangement order of each transmission unit in the synchronization verification section according to the transmission sequence number.

[0012] The fiber optic communication interface is equipped with a transmit counter. Each time the fiber optic communication interface transmits a frame, the transmit counter increments by one. When a transmission unit in the synchronization check section enters the transmission sequence of the fiber optic communication interface, it writes the current transmit counter value into the transmit counter value field of the corresponding transmission unit. Other outgoing frames that do not belong to the synchronization check section also increment the transmit counter value, but are not written into the current synchronization check section.

[0013] The receiving end compares the transmission count values ​​of any two adjacent transmission units within the synchronization check segment; when the difference between the transmission count values ​​of any two adjacent transmission units is one, it is determined that no other outgoing frames have been inserted between the two transmission units; when the difference between the transmission count values ​​is not one, it is determined that there are other outgoing frames between the two transmission units, and the corresponding synchronization check segment is determined as an invalid synchronization segment.

[0014] The transmission sequence number is used to characterize the logical order of the transmission unit within the current synchronization check segment, and the transmission count value is used to characterize the actual transmission position of the transmission unit in all outgoing frames of the optical fiber communication interface. The transmission sequence number and the transmission count value jointly participate in the segment continuity judgment to distinguish between two transmission states: the loss of the transmission unit itself and the insertion of other communication frames.

[0015] When the first bit of the frame start delimiter of the transmission unit enters the photoelectric conversion transmission path, the transmitting end fiber optic communication interface latches the current timing value of the transmitting end hardware timer and records the timing value as the transmission hardware time of the corresponding transmission unit; when the receiving end fiber optic communication interface detects the first bit of the frame start delimiter of the corresponding transmission unit, it latches the current timing value of the receiving end hardware timer and records the timing value as the receiving hardware time of the corresponding transmission unit.

[0016] The first boundary check frame, the differential protection data frame, and the second boundary check frame all use the first bit of the frame start delimiter as the capture position of the hardware time, so that the transmission and reception hardware time of different types of transmission units have the same physical timing reference, avoiding changes in the start and end points of transmission delay calculation due to different frame lengths or different frame tail check processing times.

[0017] After the sending end completes the transmission of the second boundary check frame, it generates a segment timestamp follow-up frame corresponding to the current synchronization check segment. The segment timestamp follow-up frame includes the segment identifier of the current synchronization check segment, as well as the transmission sequence number, transmission count value and transmission hardware time of each transmission unit in the synchronization check segment.

[0018] After receiving the segment timestamp follow-up frame and completing frame verification, the receiving end matches the transmission hardware time carried by the segment timestamp follow-up frame with the reception hardware time recorded by the receiving end according to the segment identifier and transmission sequence number. When the segment timestamp follow-up frame is not received, the frame verification of the segment timestamp follow-up frame fails, or the segment timestamp follow-up frame lacks the transmission hardware time of any transmission unit in the current synchronization verification segment, the corresponding synchronization verification segment is determined as an invalid synchronization segment.

[0019] During the on-site joint commissioning phase, the hardware timers of the differential protection terminals at both ends receive the same calibration time source and send calibration frames along the two transmission directions respectively. The forward fixed transmission delay is determined based on the hardware time of sending and receiving the forward transmission calibration frame, and the reverse fixed transmission delay is determined based on the hardware time of sending and receiving the reverse transmission calibration frame. The difference between the forward fixed transmission delay and the reverse fixed transmission delay is determined as the forward and reverse fixed delay difference, and the forward and reverse fixed delay difference is stored in the mine explosion-proof and intrinsically safe differential protection control boxes at both ends.

[0020] During the data synchronization operation phase, the differential protection terminals at both ends continuously execute at least three bidirectional timing cycles; each bidirectional timing cycle records the first sending time of the timing request frame sent by the first differential protection terminal, the first receiving time of the timing request frame received by the second differential protection terminal, the second sending time of the timing response frame sent by the second differential protection terminal, and the second receiving time of the timing response frame received by the first differential protection terminal.

[0021] The four moments obtained from each bidirectional timing cycle are corrected based on the fixed time delay difference between the forward and reverse directions, and the time scale ratio and time offset between the hardware timers at both ends are determined based on at least three sets of corrected timing results; a time mapping relationship from the time axis of the transmitting end to the time axis of the receiving end is established based on the time scale ratio and time offset.

[0022] For the same synchronization check segment, the transmission hardware time of the first boundary check frame and each differential protection data frame is converted to the receiving end time scale using the time mapping relationship, and the difference between the receiving hardware time of each transmission unit and the corresponding converted transmission hardware time is determined as the measured transmission delay.

[0023] Subtract the converted transmission hardware time of the first boundary check frame from the converted transmission hardware time of each differential protection data frame to obtain the relative transmission time of the first boundary check frame and each differential protection data frame.

[0024] Using the relative transmission time as the independent variable and the corresponding measured transmission delay as the dependent variable, the initial delay value and delay change rate of the current synchronization check segment are determined by the least squares method, and the first-order delay change relationship of the current synchronization check segment is established by the initial delay value and delay change rate.

[0025] The sending and receiving hardware times of the second boundary check frame do not participate in the establishment of the first-order delay change relationship; the measured transmission delay of the first boundary check frame and each differential protection data frame is compared with the calculated transmission delay output corresponding to the first-order delay change relationship, and the maximum value among the absolute values ​​of each difference is determined as the model fitting residual.

[0026] Substituting the relative transmission time of the second boundary check frame with respect to the first boundary check frame into the first-order delay variation relationship, the predicted transmission delay of the second boundary is obtained; the difference between the receiving hardware time of the second boundary check frame and the transmitting hardware time of the second boundary check frame after time mapping is determined as the measured transmission delay of the second boundary, and the absolute value of the difference between the predicted transmission delay of the second boundary and the measured transmission delay of the second boundary is determined as the boundary check residual.

[0027] The model fitting residual is used to determine whether the transmission delay of the first boundary check frame and each differential protection data frame conforms to the first-order change relationship of the current synchronization check segment; the boundary check residual is used to determine whether the first-order delay change relationship established by the aforementioned transmission unit can continue to the end of the synchronization check segment; the second boundary check frame does not participate in the establishment of the first-order delay change relationship, so that the boundary check residual has a check basis independent of the modeling data.

[0028] During the on-site joint commissioning phase, the mine explosion-proof and intrinsically safe differential protection control box receives the calibration start command and calibration end command, and takes the entire synchronous verification segment formed between the two commands as the calibration segment; the calibration segment should meet the requirements of continuous transmission sequence number, continuous transmission count value, frame verification of each transmission unit passing, and complete segment timestamp following the frame.

[0029] Calculate the model fitting residual and boundary check residual for each calibration segment. The sum of the maximum model fitting residual and the hardware timestamp synthesis error in all calibration segments is determined as the model fitting residual threshold, and the sum of the maximum boundary check residual and the hardware timestamp synthesis error in all calibration segments is determined as the boundary check residual threshold.

[0030] The hardware timestamp synthesis error is determined by adding the hardware timer resolution at the sending end, the hardware timer resolution at the receiving end, the hardware time latching error at the sending end, and the hardware time latching error at the receiving end; the model fitting residual threshold and the boundary check residual threshold are both less than 8 milliseconds.

[0031] A synchronization check segment is determined to be a valid synchronization segment when it simultaneously meets the following conditions: the synchronization check segment has both a first boundary check frame and a second boundary check frame; the segment timestamp follows the complete frame and the frame check passes; the transmission sequence numbers of each transmission unit within the synchronization check segment are consecutive; the difference between the transmission count values ​​of any two adjacent transmission units is one; the frame check of each transmission unit passes; the model fitting residual does not exceed the model fitting residual threshold; and the boundary check residual does not exceed the boundary check residual threshold.

[0032] When the transmitting end detects that the optical fiber communication interface has been reset or has stopped transmitting before the second boundary check frame is sent, it stops adding new differential protection data frames to the current synchronization check segment. If the optical fiber communication interface can still transmit data, it sends a second boundary check frame carrying a segment termination identifier. If the optical fiber communication interface cannot transmit data, it records the segment termination status of the current synchronization check segment, and establishes the next synchronization check segment through a new first boundary check frame after the optical fiber communication interface resumes transmission.

[0033] The receiving end determines the validity of the received synchronization check segment based on the transmission sequence number, transmission count value, frame check result, segment timestamp following frame, and two types of residuals. When the receiving end determines that the synchronization check segment is invalid, it does not require the sending end to retransmit the segment termination flag, so as to avoid confusing the receiving end's post-determination determination with the sending end's real-time termination action into the same process.

[0034] For any differential protection data frame within the effective synchronization segment, substitute the relative transmission time of the differential protection data frame with respect to the first boundary check frame into the first-order delay variation relationship to obtain the corresponding estimated transmission delay; subtract the estimated transmission delay from the receiving hardware time of the differential protection data frame to obtain the estimated transmission hardware time of the differential protection data frame at the receiving end time scale.

[0035] Calculate the time interval between the transmission hardware time of the differential protection data frame and the sampling time it carries, and convert the time interval to the receiving end time scale according to the time scale ratio of the time axes at both ends; subtract the converted time interval from the estimated transmission hardware time to obtain the target sampling time of the transmission end current data at the receiving end time scale.

[0036] For current data sampled at the receiving end with sampling sequence number j, the time interval that is no earlier than half a sampling period before the sampling time of the current data and no earlier than half a sampling period after the sampling time of the current data is determined as the j-th sampling time window; each sampling time window adopts a half-open interval that is included at the front end point and not included at the back end point, so that the same target sampling time corresponds to at most one sampling time window.

[0037] Determine the sampling time window in which the target sampling time of the first differential protection data frame within the effective synchronization segment is located, and determine the difference between the receiving end sampling sequence number corresponding to the sampling time window and the transmitting end sampling sequence number carried by the first differential protection data frame as the segment sampling sequence number offset.

[0038] When the target sampling time of the first differential protection data frame does not belong to any sampling time window, the corresponding synchronization check segment will be determined as an invalid synchronization segment.

[0039] For the remaining differential protection data frames within the synchronization verification section, the sampling time window in which the target sampling time is located is determined respectively. When any target sampling time does not belong to the sampling time window, or when the difference between the receiving end sampling number and the sending end sampling number of the corresponding sampling time window is not equal to the section sampling number offset, the entire synchronization verification section is determined as an invalid synchronization section, and the remote current data in the synchronization verification section is not output to the differential protection calculation unit.

[0040] When all differential protection data frames in the synchronous verification section meet the matching conditions of the sampling time window and the section sampling sequence offset, the transmitting end current data carried by each differential protection data frame and the receiving end current data in the corresponding sampling time window are determined as the matching sampling data at both ends of the line and transmitted to the differential protection calculation unit.

[0041] The mine-use explosion-proof and intrinsically safe differential protection control box only transmits the matching sampling data within the effective synchronization section to the differential protection calculation unit; for the invalid synchronization section, the mine-use explosion-proof and intrinsically safe differential protection control box stops transmitting the remote current data within that section to the differential protection calculation unit, and sends a synchronization invalidity flag to the existing protector in the mine through the RS485 serial communication interface or the RJ45 Ethernet interface.

[0042] When a subsequent synchronization verification section is determined to be a valid synchronization section, and all differential protection data frames within that synchronization verification section have completed the matching of sampling time window and section sampling sequence offset, the time mapping relationship is updated using the bidirectional timing results corresponding to the valid synchronization section, the transmission of synchronization invalid flags is stopped, and the transmission of matching sampling data from both ends of the line to the differential protection calculation unit is resumed.

[0043] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a verifiable basis for determining whether transmission delay data within a segment has continuous transmission conditions by uniformly counting all outgoing frames of the optical fiber communication interface and simultaneously setting transmission sequence numbers within the synchronization verification segment. This allows the receiving end to determine whether a transmission unit is missing based on the transmission sequence number and whether other outgoing frames are inserted between adjacent transmission units based on the transmission count value.

[0044] This invention records the transmission hardware time and the reception hardware time at the first bit of the frame start delimiter of various transmission units, establishes a first-order time delay change relationship with the first boundary check frame and the differential protection data frame, and uses the second boundary check frame, which does not participate in the relationship establishment, as independent check data, so that the model fitting residual reflects the consistency of the time delay data within the segment, and the boundary check residual reflects the applicability of the first-order time delay change relationship at the end of the segment.

[0045] This invention uses the integrity of the segment structure, the actual transmission order of the interface, the frame verification result, the model fitting residual, the boundary verification residual, and the sampling sequence offset as conditions for the remote current data to enter the differential protection calculation unit. When any condition is not met, the output of remote current data is stopped on a synchronous verification segment basis, and a synchronization invalidation flag is sent to the existing protector in the mine.

[0046] The beneficial effects of this invention are as follows: 1. This invention sets a first boundary check frame and a second boundary check frame before and after continuous differential protection data frames, and configures a segment identifier, transmission sequence number, and a transmission count value uniformly allocated by the optical fiber communication interface, respectively. This allows the receiving end to check whether the protection data frames in the synchronization check segment are missing or duplicated based on the transmission sequence number, and to check whether equipment status frames, fault record frames, or other outgoing frames are inserted between adjacent transmission units based on the transmission count value. This achieves the purpose of verifying the actual transmission continuity of differential protection data frames. The sending end and the receiving end record the hardware time when the first bit of the frame start delimiter is sent and received, respectively, so that transmission units with different frame lengths have a consistent timing position, reducing the impact of frame encapsulation length and frame tail processing on the transmission delay calculation results.

[0047] 2. This invention establishes a time mapping relationship between the two ends of the line through bidirectional timing results and pre-calibrated forward and reverse fixed time delay differences. It also establishes a first-order time delay variation relationship using the measured transmission delay of the first boundary check frame and the differential protection data frames in the synchronization check section. This allows each differential protection data frame to obtain an estimated transmission delay according to its actual transmission position in the synchronization check section. The second boundary check frame does not participate in the establishment of the first-order time delay variation relationship but is used to calculate independent boundary check residuals. The model fitting residuals reflect the consistency of transmission delay within the section, and the boundary check residuals reflect the applicability of the time delay variation relationship at the end of the section. This achieves the purpose of identifying abnormal fluctuations within the section and sudden changes in delay at the end of the section, avoiding the need to judge the synchronization status solely based on the fitting results of the modeling data itself.

[0048] 3. This invention restores the target sampling time of the remote current data at the receiving end time scale by estimating the transmission delay, and checks the correspondence between the current data at both ends of the line by combining the sampling time window and the section sampling sequence offset. Only when the section structure is complete, the actual transmission is continuous, the frame verification is passed, the time mapping is effective, the two types of residuals do not exceed the corresponding thresholds, and all current data in the section have completed sampling matching, will the remote current data be sent to the differential protection calculation unit. For synchronization verification sections that do not meet the conditions, the remote current data access is stopped and a synchronization invalidation flag is sent to the original mine protector. At the same time, the original overcurrent protection, grounding protection and backup protection functions are retained to reduce the possibility of sampling mismatch forming additional differential current or weakening the actual fault differential current, and to enable the cause of synchronization anomaly and data access results to be verified by section flag, residual, frame verification result and synchronization invalidation flag. Attached Figure Description

[0049] Figure 1 This is an overall flowchart of the mine power supply differential protection data synchronization method of the present invention; Figure 2 This is a flowchart of the synchronous verification section construction and residual verification process of the present invention; Figure 3 This is a flowchart of the target sampling time matching and remote current data admission process of the present invention; Figure 4 This is a schematic diagram illustrating the overall principle of the mine power supply differential protection data synchronization method of the present invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] like Figures 1 to 4 As shown, this embodiment of the invention provides a method for synchronizing differential protection data in mine power supply based on optical fiber communication. The mine power supply lines described in this embodiment include power supply lines between the underground central substation and the mining area substation, connecting lines between adjacent mining area substations, and power supply lines between the surface substation and the underground substation. The distance between the two ends of such lines is relatively long, and the line operating environment is affected by the concentrated start-up and shutdown of underground electrical equipment, electromagnetic interference, communication equipment buffer occupancy, and concentrated uploading of status information. The differential protection terminals at both ends of the line need to exchange current sampling data, and the same optical fiber communication interface may also send equipment status frames, fault record frames, and operation information frames.

[0052] Differential protection calculation requires that the current data at both ends of the line correspond to the same sampling time. When other outgoing frames are inserted between consecutive differential protection data frames, or when the buffer or scheduling status of the optical fiber communication interface changes during the transmission of a set of differential protection data frames, the use of a fixed communication delay measured once to process the entire set of remote current data may cause misalignment between the remote sampling data and the local sampling data.

[0053] This implementation limits a set of continuously transmitted differential protection data frames to a synchronization verification section. The transmission continuity of this set of data in all outgoing frames is checked by the transmission count value of the fiber optic communication interface. The transmission and reception times of each frame are obtained by a unified hardware timestamp position. The transmission delay of each differential protection data frame is estimated by the first-order delay variation relationship within the section. The first-order delay variation relationship can be checked by a second boundary verification frame that did not participate in the relationship establishment to see if it can continue to the end of the section. Only when the synchronization verification section meets the conditions of structural integrity, actual transmission continuity, valid delay relationship, and consistent sampling sequence number, is the remote current data in the section allowed to enter the differential protection calculation unit.

[0054] Example 1: Differential Protection Terminal and Data Processing Basics The first differential protection terminal is installed at the first end of the mine power supply line, and the second differential protection terminal is installed at the second end; the first differential protection terminal and the second differential protection terminal are connected by an optical fiber communication link.

[0055] Each differential protection terminal includes the mine's original protector and a mine-use explosion-proof and intrinsically safe differential protection control box connected to the mine's original protector. Intrinsically safe refers to intrinsically safe.

[0056] The mine-use explosion-proof and intrinsically safe differential protection control box includes a current acquisition unit, a sampling control unit, a main processor, a programmable logic device, a hardware timer, an optical fiber communication interface, a transmit counter, a storage unit, a differential protection calculation unit, an RS485 serial communication interface, and an RJ45 Ethernet interface.

[0057] The current acquisition unit receives the current signals of each phase output by the current transformer at the line end; the sampling control unit generates a sampling trigger signal according to the local sampling clock, and obtains the current sampling values ​​of each phase of the line at the same sampling trigger time; the current sampling values ​​of each phase obtained by the same sampling trigger signal form a set of current data at the line end.

[0058] When the sampling control unit obtains the line-end current data, it reads the local hardware timer, records the read timing value as the sampling time of the current data set, and configures the sampling sequence number according to the sampling order.

[0059] As the sampling sequence number increments cyclically, the next sampling sequence number is determined according to the following formula: In the formula: Indicates the first The sampling sequence number corresponding to the next sample; Indicates the first The sampling sequence number corresponding to the next sample; The modulus represents the sampling sequence number; mod indicates the modulo operation.

[0060] The main processor encapsulates a set of line-end current data, sampling time, and sampling sequence number into a differential protection data frame.

[0061] In this embodiment, the hardware timer provides a local timing reference to both the sampling control unit and the programmable logic device, so that the sampling time of the current data and the hardware time of the transmission of the optical fiber communication frame adopt the same hardware time axis.

[0062] The transmission distance of the optical fiber communication link is no more than 10 kilometers, and the one-way optical fiber communication delay is no more than 10 milliseconds; the mine explosion-proof and intrinsically safe differential protection control box exchanges synchronization status, protection status and fault records with the mine's original protector through an RS485 serial communication interface or an RJ45 Ethernet interface.

[0063] Example 2: Synchronization Check Section and Frame Structure Taking the transmission of current data from the first differential protection terminal to the second differential protection terminal as an example, the first differential protection terminal is the transmitting end and the second differential protection terminal is the receiving end; when transmitting in reverse, the roles of the transmitting end and the receiving end of the first differential protection terminal and the second differential protection terminal are interchanged, and the processing method is the same.

[0064] The transmitting end sends a first boundary check frame before sending at least two differential protection data frames, and sends a second boundary check frame after the differential protection data frames; the first boundary check frame, the differential protection data frame located between the first boundary check frame and the second boundary check frame, and the second boundary check frame together constitute a synchronization check segment.

[0065] The first boundary check frame, the differential protection data frame, and the second boundary check frame are collectively referred to as a transmission unit.

[0066] Transmission units belonging to the same synchronization check segment have the same segment identifier; the segment identifier increments when a new synchronization check segment is established.

[0067] Both the first and second boundary check frames include a frame type field, a segment identifier field, a boundary location field, a transmission sequence number field, a transmission count value field, and a frame check field.

[0068] The differential protection data frame includes a section identifier field, a transmission sequence number field, a transmission count value field, a sampling sequence number field, a sampling time field, a current data field, and a frame check field.

[0069] When a synchronous verification section contains m differential protection data frames, the transmission sequence number of the first boundary verification frame is 0, the transmission sequence numbers of the differential protection data frames are 1 to m in sequence, and the transmission sequence number of the second boundary verification frame is m+1, where m is a positive integer not less than 2.

[0070] The receiving end divides the received transmission units into corresponding synchronization check segments according to the segment identifier, and determines the logical order of each transmission unit in the synchronization check segment according to the transmission sequence number.

[0071] When a segment identifier loops around, the receiving end combines the segment identifier, the interface reset status, and the reception time of the previous synchronization check segment to identify the newly established synchronization check segment. After the fiber optic communication interface is reset, the synchronization check segments that were not completed before the reset will not be used.

[0072] Example 3: Determining the number of data frames within the synchronization check segment The number of differential protection data frames within the synchronous verification section is limited by both the section timestamp follow-up frame capacity and the differential protection action time.

[0073] Assume the allowable single-frame payload length of the fiber optic communication protocol is . The segment timestamp follows the fixed frame header, segment identifier, and frame check field in the frame, occupying a length of [length missing]. The length of the timestamp record corresponding to each transmission unit is . Then the total number of transmission units in the synchronization check section should satisfy: In the formula: Indicates the number of differential protection data frames within the synchronous verification section; This indicates the total number of transmission units, including the first boundary check frame and the second boundary check frame. Indicates the payload length allowed for a single segment timestamp following the frame; This represents the transmission sequence number, transmission count value, and record length occupied by the transmission hardware at any given moment for a transmission unit. This indicates rounding down to the nearest integer.

[0074] To avoid affecting the protection action time due to the waiting segment timestamp following the frame, it should also meet the following requirements. In the formula: This indicates the time from the start of sending the first boundary check frame to the end of sending the second boundary check frame; The timestamp of the segment indicates that it follows the generation, transmission, and reception times of the frame; This indicates the processing time required for synchronous verification segment validity determination and sampling matching; This indicates the time required for the differential protection calculation unit to complete the calculations for the differential current and braking current. This indicates the time required from the differential protection calculation result meeting the operating conditions to the differential protection control box outputting an operating signal; When increase If the segment timestamp following the frame cannot be completely transmitted within one communication frame, or if the above time conditions cannot be met, reduce the timetamp. .

[0075] During the on-site joint debugging phase, changes were also made. Determine the maximum duration of the synchronization check segment that is applicable to the first-order time delay variation relationship; only the duration of the segment that satisfies the corresponding threshold for both the model fitting residual and the boundary check residual is allowed as the duration of the synchronization check segment during runtime.

[0076] Example 4: Allocation of transmission count values ​​and check of actual transmission continuity A transmission counter is set at the final outbound scheduling position of the fiber optic communication interface. All frames to be transmitted in each transmission queue pass through this final outbound scheduling position before entering the photoelectric conversion transmission path.

[0077] The transmit counter counts all outgoing frames transmitted through the fiber optic communication interface. All outgoing frames include the first boundary check frame, the second boundary check frame, the differential protection data frame, the segment timestamp follow-up frame, the equipment status frame, the fault record frame, and other service frames.

[0078] After the transmission scheduling unit selects the next frame to be transmitted, it locks the transmission descriptor of that frame. The locked transmission descriptor will not be exchanged with other transmission descriptors until the current transmission is completed.

[0079] The transmission scheduling unit processes frames to be transmitted in the following order: Read the current transmit count value from the transmit counter; Write the current transmit count value into the transmit count field of the frame to be transmitted; Generate a cyclic redundancy check field based on the frame content after writing the transmission counter value; The frame with completed field writing is delivered to the serial transmission unit; After the first bit of the frame start delimiter of the frame is sent, the transmit counter is incremented by 1.

[0080] After the transmission scheduling unit selects a frame to be transmitted, it writes the current transmission count value of the transmission counter into the frame to be transmitted. When the optical fiber communication interface starts transmitting the first bit of the frame start delimiter of the frame to be transmitted, it confirms that the transmission count value has been used and increments the transmission counter by 1. If the transmission scheduling unit cancels the transmission of the frame to be transmitted before the first bit of the frame start delimiter is transmitted, the transmission counter is not incremented, and the current transmission count value continues to be used for subsequent actual transmitted frames. If the transmission is interrupted after the first bit of the frame start delimiter has been transmitted, the transmission count value remains in the used state.

[0081] Let the counting modulus of the transmit counter be... The current send count value is The next send count value is: In the formula: Indicates the first The transmission count value corresponding to each actual outgoing frame; Indicates the first The transmission count value corresponding to each actual outgoing frame; This indicates the counting modulus of the transmit counter; the receiver calculates the transmit count difference between adjacent transmission units using the following formula: In the formula: Indicates the first [number]th [unit] in the synchronous verification section The transmission count value of each transmission unit; Indicates the first [number]th [unit] in the synchronous verification section The transmission count value of each transmission unit; This represents the difference in transmission counts between two adjacent transmission units.

[0082] when When, it is determined that two adjacent transmission units are adjacent in the entire outgoing frame sequence; when When this occurs, it is determined that there are other outgoing frames, duplicate transmission frames, or abnormal transmission count status between two adjacent transmission units.

[0083] In one specific implementation, the transmit counter uses a 32-bit unsigned cyclic counter; when the transmit count value wraps back to 0 from 4294967295, the transmit count difference between adjacent frames is still 1, calculated according to the above modulo method.

[0084] The sequence number check checks whether logical frames within the synchronization check segment are missing or duplicated, while the transmission count check checks whether other outgoing frames not belonging to this segment are inserted between transmission units in the synchronization check segment. The two cannot be substituted for each other.

[0085] Example 5: Sending hardware time, receiving hardware time, and segment timestamp follow the frame Programmable logic devices connect hardware timers and fiber optic communication interfaces.

[0086] When the first bit of the frame start delimiter of the transmission unit enters the photoelectric conversion transmission path, the optical fiber communication interface at the transmitting end sends a latch signal to the hardware timer; the hardware timer latches the timing value at that moment as the corresponding transmission hardware timing of the transmission unit.

[0087] When the receiving end fiber optic communication interface detects the first bit of the frame start delimiter of the corresponding transmission unit, it sends a latch signal to the local hardware timer; the hardware timer latches the timing value at that moment as the receiving hardware time of the corresponding transmission unit.

[0088] Both the sending and receiving ends use the first bit of the frame start delimiter as the timestamp capture position, so that different types of transmission units have the same start and end positions for delay calculation; the total frame lengths of the differential protection data frame and the boundary check frame are different, and the delay calculation benchmark of this embodiment will not be changed due to the different arrival times of the frame tail.

[0089] Since the transmission hardware time is generated only when the frame begins to be transmitted, the transmission hardware time is not written into the original transmission unit that is being transmitted; the sending end establishes a timestamp record table, using the segment identifier and transmission sequence number as a combined index, to record the transmission count value and transmission hardware time of the corresponding transmission unit.

[0090] The receiving end establishes a receiving timestamp record table, using the segment identifier and transmission sequence number as a combined index, to record the receiving hardware time and frame verification results.

[0091] After the sending end completes the transmission of the second boundary check frame, it generates a segment timestamp follow-up frame. The segment timestamp follow-up frame carries: The segment identifier of the current synchronization verification segment; The transmission sequence number of each transmission unit within the current synchronization verification segment; The transmission count value of each transmission unit; The transmission hardware timing of each transmission unit; The segment timestamp follows the frame's own cyclic redundancy check field.

[0092] Before the segment timestamp is sent along with the frame, the next synchronization check segment is not established in the same transmission direction to prevent the segment timestamp from being inserted into the next synchronization check segment along with the frame.

[0093] After receiving the segment timestamp follow-up frame and completing the cyclic redundancy check, the receiving end matches the sending hardware time with the receiving hardware time stored on its own end according to the segment identifier and transmission sequence number.

[0094] The corresponding synchronization check segment is determined to be an invalid synchronization segment when any of the following occurs: No segment timestamp follow-up frame was received before the segment reception waiting time expired; Cyclic redundancy check of the segment timestamp following the frame failed; The segment timestamp follows the hardware moment when any transmission unit of the frame is missing; The segment timestamp is inconsistent with the segment identifier in the follow frame and the segment identifier recorded by the receiver. The segment timestamp cannot correspond one-to-one with the transmission sequence number in the frame and the transmission sequence number recorded by the receiving end.

[0095] The segment reception waiting time is determined according to the following formula: In the formula: Indicates the segment reception waiting time; Indicates the maximum allowed transmission duration for the synchronization check segment; This indicates the upper limit of one-way communication delay in an optical fiber communication link; This indicates the maximum transmission time of the segment timestamp following the frame.

[0096] In this embodiment, The receiving wait time for a specific section is not greater than 10 milliseconds; the specific section receiving wait time is calculated by the equipment configuration values ​​of the above 3 items and written into the mine explosion-proof and intrinsically safe differential protection control box, and fixed empirical values ​​that have not been confirmed by the equipment configuration are not used.

[0097] Example 6: Field calibration of fixed time delay difference in forward and reverse directions The fixed delay difference between forward and reverse directions is calibrated on-site after the fiber optic link is installed.

[0098] The on-site linkage calibration uses the same calibration time source with at least two calibration outputs; the calibration time source sends calibration pulses to the first differential protection terminal and the second differential protection terminal through a temporary calibration channel; the fixed delay of the two calibration output channels is calibrated before use and deducted in the calibration calculation.

[0099] The hardware timers at both ends continuously receive at least two calibration pulses; based on the timing values ​​recorded by both ends for the same calibration pulse, the initial time mapping relationship between the time axes at both ends during the field calibration phase is first determined: In the formula: This indicates the time on the hardware timer of the first differential protection terminal; Indicates and The corresponding time on the hardware timer of the second differential protection terminal; This indicates the initial timescale ratio of the hardware timers at both ends of the field calibration phase; This indicates the initial time offset of the second differential protection terminal relative to the first differential protection terminal during the field calibration phase.

[0100] The first differential protection terminal sends a positive calibration frame to the second differential protection terminal; the positive calibration frame is recorded at the hardware transmission time of the first differential protection terminal as follows. The receiving hardware time of the second differential protection terminal is recorded as The forward fixed transmission delay is: In the formula: This represents the forward fixed transmission delay from the first differential protection terminal to the second differential protection terminal; Indicates the hardware timing for sending the forward calibration frame; This indicates the hardware timing for receiving the forward calibration frame.

[0101] The second differential protection terminal sends a reverse calibration frame to the first differential protection terminal; the reverse calibration frame is recorded at the hardware transmission time of the second differential protection terminal as follows. The receiving hardware time of the first differential protection terminal is recorded as After converting the transmission hardware time of the second differential protection terminal to the time scale of the first differential protection terminal, the reverse fixed transmission delay is: In the formula: This represents the reverse fixed transmission delay from the second differential protection terminal to the first differential protection terminal; Indicates the hardware timing of the transmission of the reverse calibration frame; This indicates the hardware timing for receiving the reverse calibration frame.

[0102] The fixed time delay difference between forward and reverse directions is: In the formula: Indicates a fixed time delay difference between the forward and reverse directions, when When, it indicates that the forward fixed transmission delay is greater than the reverse fixed transmission delay; when When , it means that the forward fixed transmission delay is less than the reverse fixed transmission delay.

[0103] During on-site joint debugging, multiple sets of forward and reverse calibration frames were repeatedly sent. Only calibration frames that passed the cyclic redundancy check, had continuous transmission counts, and whose fiber optic communication interfaces were not reset were used.

[0104] The forward and reverse fixed time delay difference is associated with the fiber optic link identifier, fiber optic communication interface identifier, fiber optic transceiver module configuration, and the configuration version of the mining explosion-proof and intrinsically safe differential protection control box.

[0105] The original forward and reverse fixed time delay difference will no longer be used to establish the new time mapping relationship, and field calibration will be re-performed if any of the following conditions occur: Replace either end of the fiber optic transceiver module; Change the fiber optic transmission path; Replace either end of the mining explosion-proof and intrinsically safe differential protection control box; The fiber optic communication interface configuration has changed; The boundary check residuals of the continuous synchronous check sections continuously approach the boundary check residual threshold in the same direction.

[0106] Example 7: Two-way timing measurement and time mapping during operation During operation, both the first and second boundary check frames carry a timing request identifier. Upon receiving the boundary check frame, the receiving end returns a boundary timing response frame.

[0107] One bidirectional timing cycle records the following four hardware moments: The first transmission time of the timing request frame sent by the first differential protection terminal. ; The first reception time of the timing request frame received by the second differential protection terminal ; The second transmission moment when the second differential protection terminal sends the timing response frame. ; The second receiving moment of the timing response frame received by the first differential protection terminal. ; in, Indicates the sequential number of the bidirectional time measurement period.

[0108] The first is formed based on the fixed time delay difference between the forward and reverse directions. Group time axis corresponding points , In the formula: Indicates the first differential protection terminal on the time axis. Each corresponding moment; This indicates that after correction for the fixed time delay difference in both directions, the second differential protection terminal on the time axis... Each corresponding moment; This represents the fixed time delay difference between the forward and reverse directions obtained from on-site calibration.

[0109] Continuous achievement After identifying the corresponding points on the effective time axis, the least squares method is used to determine the time scale ratio during operation. and time offset ,in Not less than 3.

[0110] The time offset is determined according to the following formula: In the formula: This indicates the number of valid time axis points involved in the time mapping calculation. and They represent the first Corresponding points on the timeline; Indicates all The arithmetic mean; Indicates all The arithmetic mean; This indicates the time scale ratio of the second differential protection terminal hardware timer relative to the first differential protection terminal hardware timer; This indicates the time offset of the second differential protection terminal hardware timer relative to the first differential protection terminal hardware timer.

[0111] The time mapping relationship from the time axis of the first differential protection terminal to the time axis of the second differential protection terminal is as follows: The reverse time mapping relationship is as follows: The fitting residuals of the time mapping relationship are: In the formula: This represents the maximum fit residual of the time mapping relationship.

[0112] Only bidirectional timing cycles in which both timing request frames and timing response frames are fully received, cyclic redundancy checks pass, all four hardware time points are complete, and the fiber optic communication interface is not reset during the timing process are included in the time mapping calculation.

[0113] After the system starts, an initial time mapping relationship is established through no less than three valid bidirectional time measurement cycles. Before the initial time mapping relationship is established and its fitting residual meets the time mapping residual threshold, remote current data access is not allowed.

[0114] During operation, the update of the time mapping relationship is independent of the first-order delay change relationship of the current synchronization verification segment; invalid bidirectional timing cycles do not update the time mapping relationship, and invalid synchronization verification segments do not use their corresponding timing results to update the time mapping relationship, thereby avoiding a circular dependency between establishing the time mapping relationship and judging the validity of the synchronization verification segment.

[0115] Example 8: First-order time delay variation relationship and applicable scope The first-order delay variation relationship in this embodiment is only used for short-term transmission delay variation within a synchronization check segment, and is not used to describe the state of optical fiber communication for arbitrary duration.

[0116] The synchronous verification section should meet the following conditions: Use the same fiber optic communication interface; Using the same optical fiber communication path; The fiber optic communication interface did not reset within the segment; The transmission count values ​​of adjacent transmission units are continuous; The duration of the section shall not exceed the applicable time of the maximum first-order relationship determined during on-site linkage debugging; All transmission units from the first boundary check frame to the second boundary check frame use the same frame start delimiter first bit timestamp position.

[0117] During on-site joint debugging, the number of differential protection data frames in the synchronous verification section is gradually increased; when the model fitting residual or boundary verification residual of the synchronous verification section under normal communication conditions exceeds the corresponding threshold, the duration of the previous synchronous verification section is recorded as the maximum first-order relation applicable time.

[0118] In this way, the applicability of the first-order delay variation relationship is determined by the actual calibration results of the current equipment, fiber optic link, and communication configuration, rather than by pre-assuming that any communication process satisfies the first-order relationship.

[0119] Example 9: First-order time delay variation relationship, model fitting residuals and boundary check residuals For a synchronization verification interval sent from the first differential protection terminal to the second differential protection terminal, the first boundary verification frame is recorded as the 0th transmission unit. The differential protection data frames are sequentially denoted as the first to the second. The transmission unit records the second boundary check frame as the 1st transmission unit. One transmission unit; The hardware timing for transmitting the i-th transmission unit is denoted as . The receiving hardware time is recorded as .

[0120] The transmitting hardware time is converted to the receiving end time scale using a time mapping relationship: In the formula: This represents the transmission hardware time of the i-th transmission unit at the transmitting end time scale; This represents the transmission hardware time after the i-th transmission unit is converted to the receiving end time scale; Indicates the scale of time; Indicates time offset.

[0121] The first boundary verification frame and each differential protection data frame participate in the establishment of a time delay variation relationship, namely .

[0122] The measured transmission delay of the i-th transmission unit participating in the modeling is: In the formula: This represents the measured transmission delay of the i-th transmission unit; This represents the receiving hardware time of the i-th transmission unit at the receiving end time scale.

[0123] The relative transmission time of the i-th transmission unit with respect to the first boundary check frame is: In the formula: This represents the relative transmission time of the i-th transmission unit with respect to the first boundary check frame; This indicates the transmission hardware time after the first boundary check frame is converted to the receiving end timescale.

[0124] relative transmission time As the independent variable, the measured transmission delay is used. Establish a first-order time delay relationship with the dependent variable as follows: In the formula: Indicates the relative transmission time as The first-order relation of time is used to calculate transmission delay; Indicates the initial value of the delay; Indicates the rate of change of time delay; This indicates the relative transmission time with respect to the first boundary check frame.

[0125] The rate of change of time delay is: The initial delay value is: In the formula: Indicates the 0th to the 1st The arithmetic mean of the transmission units relative to the transmission time; Indicates the 0th to the 1st The arithmetic mean of the measured transmission delay of each transmission unit.

[0126] The model fit residuals are: In the formula: This represents the model fitting residual of the current synchronous verification segment; This represents the first-order time delay variation relative to the transmission time. The computational transmission delay at that location.

[0127] Second boundary verification is not involved. and The calculation.

[0128] The relative transmission time of the second boundary check is: The second boundary predicted transmission delay is: The measured transmission delay at the second boundary is: The boundary check residual is: In the formula: Indicates the relative transmission time of the second boundary check frame; This represents the second boundary transmission delay predicted based on the aforementioned modeling data; This represents the measured transmission delay of the second boundary check frame; This represents the boundary check residual.

[0129] The model fitting residual checks whether the first boundary verification frame and the differential protection data frame involved in the modeling can be described by the same short-term change relationship; the boundary verification residual uses the second boundary verification frame that was not involved in the modeling to check whether the change relationship can continue to the end of the synchronous verification section.

[0130] Example 10: Hardware timestamp error, residual threshold, and total error budget The hardware timestamp synthesis error is determined by the following formula: In the formula: This represents the hardware timestamp synthesis error between the sending and receiving ends; Indicates the time resolution of the hardware timer at the transmitting end; Indicates the time resolution of the receiver's hardware timer; This represents the maximum latch error at the moment of transmission hardware. This represents the maximum latching error at any given moment in the receiving hardware.

[0131] The resolution of the hardware timer is determined by the operating frequency of the hardware timer; the transmission hardware timing latch error and the reception hardware timing latch error are determined through the control box inspection report, logic analysis test or calibration loop test, and the estimated value that has not been inspected is not used.

[0132] During on-site joint commissioning, the mine explosion-proof and intrinsically safe differential protection control box enters the residual calibration state after receiving the calibration start command, and exits the residual calibration state after receiving the calibration end command.

[0133] The calibration section should meet the following requirements: The first and second boundary check frames are complete; The segment timestamp follows the complete frame and the cyclic redundancy check passes. The transmission sequence numbers of each transmission unit are consecutive; The transmission count values ​​of adjacent transmission units are continuous; The fiber optic communication interface did not reset; The time mapping relationship is valid; The residual threshold for model fitting is: The boundary check residual threshold is: In the formula: This represents the threshold of the model fit residual; Indicates the boundary check residual threshold; This represents the model fitting residuals for each calibration segment; This represents the boundary verification residual for each calibration section; This represents the maximum value among the model fitting residuals for all valid calibration sections; This represents the maximum value among all valid calibration section boundary verification residuals.

[0134] The calibration process must cover at least three operating states of the fiber optic communication interface: idle load, normal service load, and maximum allowed service load. The recording time for each state must not be shorter than the maximum transmission period in all periodic state frames of the device, so that the calibration record covers one complete service scheduling cycle.

[0135] The upper limit of the total data synchronization error of the equipment is denoted as In this embodiment, the following conditions are met: The time-mapped residual threshold is denoted as The sampling period at the receiving end is denoted as To ensure that the final data matching error is less than 8 milliseconds, the following conditions must be met simultaneously: ,as well as: In the formula: This represents the maximum allowed residual for the time mapping relationship; This indicates the hardware timestamp synthesis error; This represents the threshold of the model fit residual; Indicates the boundary check residual threshold; Indicates the sampling period at the receiving end; This indicates the maximum allowable sampling window deviation between the target sampling time and the most recent local sampling time; This indicates the upper limit of the data synchronization error set by the device.

[0136] When the above error budget cannot be met, instead of simply increasing the residual threshold to allow access to remote current data, we will take measures such as reducing the sampling period, shortening the synchronization verification section, recalibrating the time mapping relationship, or repairing the fiber optic communication link.

[0137] This avoids the problem that simply specifying the model fitting residual threshold and the boundary check residual threshold to be less than 8 milliseconds can cause the sum of multiple errors to exceed 8 milliseconds.

[0138] Example 11: Validity determination of synchronous verification sections The receiving end checks the synchronization check segment in the following order: Check whether the first boundary check frame, the second boundary check frame, and the segment timestamp follow-up frame are complete; Check whether the cyclic redundancy check of each frame passes; Check whether the transmitted signal is continuous within the synchronization verification section; Check if the transmission count values ​​of adjacent transmission units are continuous; Check if the time mapping relationship is valid; Calculate the model fitting residuals and boundary check residuals; Check whether the two types of residuals exceed the corresponding thresholds.

[0139] A synchronization check segment is determined as a candidate valid synchronization segment when it meets the following conditions: Both the first boundary check frame and the second boundary check frame exist; The segment timestamp follows the complete frame and the cyclic redundancy check passes. The transmission sequence numbers of each transmission unit are consecutive; The difference between the transmission count values ​​of adjacent transmission units is 1; Cyclic redundancy checks of all transmission units passed. The time mapping relationship is in a valid state; The model fit residual does not exceed the model fit residual threshold; The boundary check residual does not exceed the boundary check residual threshold.

[0140] Candidate valid synchronization sections also need to undergo a matching check of the target sampling time and sampling sequence number. Only after all differential protection data frames within the section have been matched will the candidate valid synchronization section be finally determined as a valid synchronization section.

[0141] If any condition is not met, the corresponding synchronization check segment will be determined as an invalid synchronization segment.

[0142] Example 12: Determination of the target sampling time For the i-th differential protection data frame within the candidate valid synchronization segment, its relative transmission time... Substituting the first-order delay variation relationship, we obtain the estimated transmission delay: In the formula: This represents the estimated transmission delay of the i-th differential protection data frame; This represents the initial delay value of the current synchronization check segment; This indicates the rate of change of latency in the current synchronization check segment; This represents the relative transmission time of the i-th differential protection data frame with respect to the first boundary check frame.

[0143] Based on the received hardware time and the estimated transmission delay, the estimated transmission hardware time of the differential protection data frame in the receiving end time scale is obtained: In the formula: This represents the estimated transmission hardware time of the i-th differential protection data frame at the receiving end time scale; This indicates the receiving hardware time of the differential protection data frame.

[0144] The sampling time carried in the differential protection data frame is denoted as Sampling time and sending hardware time Both are within the sending timescale.

[0145] The time interval from sampling to transmission is: In the formula: This represents the time interval between the acquisition of current sampling data and the start of frame transmission for the i-th differential protection data frame; This indicates the hardware timing of the transmission of the differential protection data frame; This indicates the sampling time of the current data carried in the differential protection data frame; the time interval is then converted to the receiving end time scale: In the formula: This represents the sampling-to-transmission time interval after conversion to the receiving end time scale; Indicates the scale of time.

[0146] The target sampling time is: In the formula: This represents the target sampling time of the i-th group of current data at the transmitting end on the receiving end's time scale.

[0147] At the same time, the sampling time at the transmitting end is directly converted to the time scale at the receiving end: In the formula: This represents the sampling time mapping value obtained directly through the time mapping relationship.

[0148] The consistency error between the target sampling time and the direct mapping sampling time is: In the formula: This represents the consistency error of the sampling time of the i-th differential protection data frame; When any Reaching or exceeding the upper limit of data synchronization error When this happens, the corresponding synchronization check segment will be determined as an invalid synchronization segment.

[0149] By estimating the transmission delay and inversely calculating the target sampling time, the actual reception status of the current differential protection data frame can be used to correct short-term deviations that may exist when only time mapping is used; at the same time, the inverse calculation result is checked by directly mapping the sampling time to prevent erroneous corrections when the first-order delay change relationship is abnormal.

[0150] Example 13: Matching Sampling Time Window and Sampling Sequence Number The sampling period of the receiving end is denoted as The sampling time of the current data with sampling sequence number j at the receiving end is denoted as . .

[0151] The j-th sampling time window is: In the formula: This represents the sampling time window corresponding to the j-th group of current data at the receiving end; This indicates the sampling time of the j-th group of current data at the receiving end; Indicates the sampling period at the receiving end; The left square brackets indicate that the time window includes the leading point; The parentheses on the right indicate that the time window does not include the end point.

[0152] A half-open interval is adopted, which includes the front end point but excludes the back end point, so that any target sampling time belongs to at most one sampling time window.

[0153] First, determine the sampling time window in which the target sampling time of the first differential protection data frame in the synchronization verification section is located; if the target sampling time does not belong to any sampling time window, then the entire synchronization verification section is determined as an invalid synchronization section.

[0154] If the target sampling time of the first differential protection data frame belongs to the first... The differential protection data frame carries a sampling time window and a sending end sampling sequence number of [number]. Then the segment sampling sequence offset is: In the formula: This indicates the sampling sequence number offset of the current synchronization verification segment; This indicates the receiver sampling sequence number corresponding to the target sampling time of the first differential protection data frame; This indicates the sending end sampling sequence number carried in the first differential protection data frame; This represents the sampling sequence number and the counting modulus.

[0155] For the remaining differential protection data frames within the synchronous verification section, if the target sampling time of the i-th differential protection data frame belongs to the i-th differential protection data frame... Each sampling time window carries a transmitter sampling sequence number. Then it should satisfy: In the formula: This represents the receiver sampling sequence number corresponding to the target sampling time of the i-th differential protection data frame; This indicates the sampling sequence number of the transmitting end carried in the i-th differential protection data frame.

[0156] When all differential protection data frames in the synchronous verification section have a unique sampling time window and their sampling sequence number difference is equal to the section sampling sequence number offset, the remote current data carried by each differential protection data frame and the local current data in the corresponding sampling time window are determined as the matching sampling data.

[0157] If any differential protection data frame cannot obtain a unique sampling time window, or if the sampling sequence number difference is not equal to the section sampling sequence number offset, the entire synchronization verification section will be determined as an invalid synchronization section. The remaining remote current data of this section will not be used by single-frame completion or by simply discarding abnormal frames.

[0158] Example 14: Differential protection data access and coordination with existing mine protection devices The mine-use explosion-proof and intrinsically safe differential protection control box only transmits the matching sampling data within the final determined effective synchronization section to the differential protection calculation unit.

[0159] The differential protection calculation unit calculates the differential current and braking current based on the current data at both ends of the line corresponding to the same target sampling time, and judges the line fault based on the differential operating current setting value and proportional braking coefficient in the original protection setting scheme.

[0160] When a synchronization verification section is determined to be an invalid synchronization section, only the remote current data within that synchronization verification section is stopped from entering the differential protection calculation unit; the overcurrent protection, grounding protection, backup protection, and anti-overcurrent protection functions of the original mine protector are not stopped.

[0161] The mine explosion-proof and intrinsically safe differential protection control box sends a synchronization invalidation flag to the existing protector in the mine via an RS485 serial communication interface or an RJ45 Ethernet interface.

[0162] Synchronization invalidation flags include at least: Section identification; The moment when synchronization failure occurs; Reasons for synchronization failure; Current status of the fiber optic communication interface.

[0163] Reasons for synchronization failure include missing first boundary check frame, missing second boundary check frame, missing segment timestamp follow-up frame, discontinuous transmission sequence number, discontinuous transmission count value, failure of cyclic redundancy check, failure of time mapping relationship, excessive model fitting residual, excessive boundary check residual, excessive target sampling time consistency error, and failure of sampling sequence number matching.

[0164] The current transformer disconnection detection is performed by the original current transformer disconnection logic of the mine's existing protector or the mine explosion-proof and intrinsically safe differential protection control box; the synchronization invalidation flag and the current transformer disconnection flag are generated separately, and the synchronization invalidation flag is not used to replace the current transformer disconnection detection.

[0165] Example 15: Insertion of other outbound frames Within a synchronization verification segment, the transmitting end sequentially sends the first boundary verification frame, the first differential protection data frame, the second differential protection data frame, and the second boundary verification frame.

[0166] If a device status frame is inserted between the first differential protection data frame and the second differential protection data frame, the device status frame increments the transmit counter by 1.

[0167] The transmission sequence numbers of the first differential protection data frame and the second differential protection data frame are still consecutive, but the difference between their transmission count values ​​is 2.

[0168] The receiving end confirms that the differential protection data frame itself has not been lost based on the transmission sequence number, and confirms that there are other outgoing frames between them based on the transmission count value, and determines the corresponding synchronization check segment as an invalid synchronization segment.

[0169] The receiving end does not need to identify the specific service content of the inserted frame; it can determine whether the actual transmission continuity is maintained within the synchronization check segment based solely on the unified counting result of all outgoing frames.

[0170] Example 16: A sudden change in delay occurs before the second boundary check frame. Within a synchronous verification section, the measured transmission delays of the first boundary verification frame and each differential protection data frame satisfy the first-order delay variation relationship, and the model fitting residual does not exceed the model fitting residual threshold.

[0171] Before the second boundary check frame is sent, the buffer state or communication path state of the optical fiber communication equipment changes, causing the measured transmission delay of the second boundary check frame to deviate from the aforementioned first-order delay change relationship.

[0172] Since the second boundary check frame is not involved in the calculation of the initial delay value and the delay change rate, any sudden change in transmission delay that occurs in it will not reverse the established first-order delay change relationship.

[0173] If the boundary check residual calculated by the receiver exceeds the boundary check residual threshold, the current synchronization check segment is determined to be an invalid synchronization segment.

[0174] This embodiment is used to handle situations where the data involved in the modeling fits normally internally, but the communication status at the end of the synchronous verification segment has changed.

[0175] Example 17: Transmission unit loss, duplication, and segment timestamp missing following frame When a differential protection data frame is lost, the receiving end detects that the difference between adjacent transmission sequence numbers is not 1 and determines the current synchronization check segment as an invalid synchronization segment.

[0176] When a differential protection data frame is repeatedly transmitted, the receiving end detects that the same transmission sequence number appears repeatedly, or that adjacent transmission sequence numbers cannot be incremented in the predetermined order, and determines the current synchronization check segment as an invalid synchronization segment.

[0177] When the segment timestamp is lost along with the frame, the receiving end determines the current synchronization check segment as an invalid synchronization segment after the segment reception waiting time expires, and does not use the received data frames to infer the transmission hardware time.

[0178] When a segment timestamp exists following a frame but any transmission unit record is missing, the entire synchronization check segment is also determined to be an invalid synchronization segment.

[0179] Example 18: Fiber Optic Communication Interface Reset If the transmitting end detects that the optical fiber communication interface has been reset or stopped transmitting when the first boundary check frame has been sent but the second boundary check frame has not yet been sent, it immediately stops adding new differential protection data frames to the current synchronization check segment.

[0180] When the fiber optic communication interface is still able to send data, the sending end sends a second boundary check frame carrying a segment termination identifier; after the receiving end identifies the segment termination identifier, it determines the current synchronization check segment as an invalid synchronization segment.

[0181] When the fiber optic communication interface can no longer send data, the sending end records the segment termination status in the local storage unit; after the segment reception waiting time expires, the receiving end determines the current synchronization check segment as an invalid synchronization segment due to the lack of a second boundary check frame or a segment timestamp follow-up frame.

[0182] After the fiber optic communication interface is restored, the transmitting end reinitializes the transmission count state and the synchronization check segment state, and establishes the next synchronization check segment through a new first boundary check frame; the synchronization check segment established after the reset does not continue to use the transmission sequence number of the synchronization check segment before the reset.

[0183] Example 19: Sampling sequence number wrapping When the sampling sequence number wraps back to 0 from the maximum value of the counting modulus, the receiving end calculates the sampling sequence number offset according to the modulus taking method.

[0184] For example, if the sampling sequence number counting modulus is 65536, and the sending end continuously samples the sequence numbers 65534, 65535, 0 and 1, the receiving end calculates the relationship between adjacent sampling sequence numbers according to the modulus of 65536, and does not consider the change from 65535 to 0 as an interruption of the sampling sequence number.

[0185] This embodiment is only used to illustrate the processing method of the cyclic sampling sequence number and does not constitute a limitation on the number of digits of the sampling sequence number.

[0186] Example 20: Synchronization State Restoration After the synchronization verification section is determined to be an invalid synchronization section, the mine explosion-proof and intrinsically safe differential protection control box retains the last valid time mapping relationship, but does not use the invalid synchronization verification section or invalid bidirectional timing cycle to update the time mapping relationship.

[0187] Subsequent new synchronization verification segments are re-checked in the following order: segment integrity, cyclic redundancy check, transmission sequence number, transmission count value, time mapping relationship, model fitting residual, boundary check residual, and sampling sequence number matching.

[0188] When the subsequent synchronization verification section is finally determined to be a valid synchronization section, and the time mapping relationship updated using the corresponding bidirectional timing results still meets the time mapping residual threshold, the mine explosion-proof and intrinsically safe differential protection control box stops sending synchronization invalid flags and resumes transmitting matching sampling data from both ends of the line to the differential protection calculation unit.

[0189] Synchronous recovery only restores remote current data access, without modifying differential operating current settings, proportional braking coefficients, current transformer disconnection blocking thresholds, or other protection settings of existing mine protectors.

[0190] Example 21: Field Test and Data Recording The field tests in this embodiment include normal communication, insertion of other outgoing frames, loss of differential protection data frames, loss of segment timestamp following frames, sudden change in delay before the second boundary check frame, reset of fiber optic communication interface, replacement of fiber optic transceiver module, fault within the zone, fault outside the zone, and current transformer disconnection scenarios.

[0191] Field test records should include at least the following data: Fiber optic link identifier and actual fiber length; The equipment configuration versions of the first differential protection terminal and the second differential protection terminal; Fiber optic transceiver module configuration; Equipment operating temperature and relative humidity; Hardware timer resolution; Maximum latching error at the time of transmission hardware and maximum latching error at the time of reception hardware; Sampling period and sampling sequence number counting modulus; Transmit counter modulus; The section identifier and the number of differential protection data frames for each synchronous verification section; The transmission sequence number, transmission count value, transmission hardware time, and reception hardware time of each transmission unit; Time scale ratio, time offset, and time mapping residual; Initial delay value, rate of change of delay, model fitting residual, and boundary check residual; Consistency error between target sampling time, corresponding local sampling time, and sampling time; Synchronously verify the validity judgment results of the section and the reasons for invalidity; Whether the differential protection calculation should include remote current data; Fiber optic communication delay, bit error rate, and differential protection action time.

[0192] The bit error rate is determined by the following formula: In the formula: This represents the bit error rate in fiber optic communication. Indicates the number of error bits detected during the test. This indicates the total number of bits transmitted during the test.

[0193] During on-site acceptance, the fiber optic communication delay should not exceed 10 milliseconds, and the bit error rate should not exceed [missing value]. The data synchronization error should be less than 8 milliseconds, the differential protection action time should not exceed 40 milliseconds, and the equipment working environment, action setting, proportional braking coefficient and current transformer disconnection test should be carried out in accordance with the project technical specifications and the complete test procedure.

[0194] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0195] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A data synchronization method for differential protection of mine power supply based on optical fiber communication, applied to differential protection terminals at both ends of a mine power supply line, characterized in that, include: The two terminals respectively collect the line end current, record the sampling time and sampling sequence number, and generate differential protection data frames; First boundary check frames and second boundary check frames are sent before and after at least two consecutive differential protection data frames in the same transmission direction to form a synchronization check segment. Each frame in the segment is used as a transmission unit, and a segment identifier and a consecutive transmission sequence number are configured for each transmission unit. The fiber optic communication interface assigns a transmission count value to all outgoing frames and records the transmission hardware time and reception hardware time when the frame start delimiter is sent and received in the transmission unit, respectively, forming a timestamp record associated with the segment identifier and transmission sequence number and exchanging it between the two terminals; the time mapping relationship between the two terminals is established based on bidirectional boundary timing and forward and reverse fixed delay difference; The first-order time delay variation relationship within the segment is established using the hardware timing of the first boundary check frame and the differential protection data frame. The second boundary check frame does not participate in the establishment of the relationship. The model fitting residual and the boundary check residual of the second boundary check frame are determined based on the relationship. A valid synchronization segment is determined when the transmission sequence numbers are consecutive, the transmission count values ​​of adjacent transmission units are consecutive, the frame verification passes, and both types of residuals do not exceed the corresponding thresholds. The current data at both ends of the line is matched based on the estimated transmission delay, sampling time, and sampling sequence number of the differential protection data frame within the effective synchronization section and output to the differential protection calculation unit. The output of current data for the invalid synchronization section is stopped.

2. The method for synchronizing differential protection data in mine power supply based on optical fiber communication according to claim 1, characterized in that: Both the first boundary check frame and the second boundary check frame include a frame type field, a segment identifier field, a boundary location field, a transmission sequence number field, a transmission count value field, and a frame check field; The differential protection data frame includes a section identifier field, a transmission sequence number field, a transmission count value field, a sampling sequence number field, a sampling time field, a current data field, and a frame check field; The transmission sequence number of the first boundary check frame is 0, the transmission sequence numbers of the differential protection data frames are 1 to m in sequence, and the transmission sequence number of the second boundary check frame is m+1, where m is a positive integer not less than 2. For each frame sent, the optical fiber communication interface increments the current transmission count by one. The transmission count is allocated to transmission units within the synchronization check segment and other outgoing frames that do not belong to the synchronization check segment.

3. The method for synchronizing differential protection data in mine power supply based on optical fiber communication according to claim 2, characterized in that: The transmitting end fiber optic communication interface latches the transmission hardware moment when the first bit of the frame start delimiter of the transmission unit enters the photoelectric conversion transmission path, and the receiving end fiber optic communication interface latches the receiving hardware moment when it detects the first bit of the frame start delimiter. After the sending end completes the second boundary check frame, it generates a segment timestamp follow-up frame. The segment timestamp follow-up frame carries the segment identifier, transmission sequence number, transmission count value and transmission hardware time of each transmission unit in the same segment. The receiving end, based on the segment identifier and transmission sequence number, maps the segment timestamp to the sending hardware time in the follow frame and matches it with the receiving hardware time recorded by the receiving end.

4. The method for synchronizing differential protection data in mine power supply based on optical fiber communication according to claim 3, characterized in that: The fixed time delay difference between the forward and reverse directions is determined in the following manner: During the on-site joint debugging phase, the hardware timers of the two differential protection terminals are made to receive the same calibration time source and send calibration frames in two transmission directions respectively. The forward fixed transmission delay and the reverse fixed transmission delay are determined based on the hardware time of sending and receiving the calibration frame, respectively. The difference between the two is determined as the forward and reverse fixed delay difference and stored in the two differential protection terminals. During the data synchronization operation phase, the corresponding times of the two terminals are obtained through no less than three bidirectional timing cycles. The corresponding times of each set are corrected according to the fixed time delay difference between the forward and reverse directions, and the time scale ratio and time offset between the time axes of the two terminals are determined by the corrected corresponding times.

5. The method for data synchronization of differential protection in mine power supply based on optical fiber communication according to claim 4, characterized in that: The first-order time delay variation relationship is established as follows: The time mapping relationship is used to convert the transmission hardware time of the first boundary check frame and each differential protection data frame to the receiving end time scale, and the difference between the receiving hardware time of each transmission unit and the corresponding converted transmission hardware time is determined as the measured transmission delay. Subtract the converted transmission time of the first boundary check frame from the converted transmission time of each differential protection data frame to obtain the relative transmission time. Using the relative transmission time as the independent variable and the measured transmission delay as the dependent variable, the initial value of the delay and the rate of change of the delay are determined by the least squares method. The maximum value among the absolute values ​​of the difference between the measured transmission delay and the corresponding calculated value of the first boundary check frame and each differential protection data frame is determined as the model fitting residual.

6. The method for synchronizing differential protection data in mine power supply based on optical fiber communication according to claim 5, characterized in that: Substituting the relative transmission time of the second boundary check frame into the first-order delay change relationship, the second boundary predicted transmission delay is obtained; The difference between the receiving hardware time of the second boundary verification frame and the transmitting hardware time after conversion by the time mapping relationship is determined as the second boundary measured transmission delay. The absolute value of the difference between the predicted transmission delay of the second boundary and the measured transmission delay of the second boundary is determined as the boundary verification residual. During the on-site joint debugging phase, the model fitting residual and boundary check residual are calculated using calibration segments with continuous transmission counts, continuous transmission sequence numbers, and passed frame verification. The sum of the maximum model fitting residual and the hardware timestamp synthesis error in all calibration segments is determined as the model fitting residual threshold, and the sum of the maximum boundary check residual and the hardware timestamp synthesis error in all calibration segments is determined as the boundary check residual threshold. Both residual thresholds are less than 8ms.

7. A method for synchronizing differential protection data in mine power supply based on optical fiber communication according to claim 6, characterized in that: When the difference between the transmission count values ​​of any two adjacent transmission units within the synchronization check segment is one, it is determined that no other outgoing frames have been inserted between the two adjacent transmission units. When the difference between the transmission count values ​​of any two adjacent transmission units is not one, the difference between the transmission sequence numbers is not one, the frame verification of any transmission unit fails, or the optical fiber communication interface is reset before the second boundary verification frame is sent, the corresponding synchronization verification segment is determined as an invalid synchronization segment. When the fiber optic communication interface is still able to send data, the transmitting end sends a second boundary check frame carrying a segment termination identifier; when the fiber optic communication interface is unable to send data, the transmitting end records the segment termination status and establishes the next synchronization check segment through a new first boundary check frame after the interface is restored.

8. A method for synchronizing differential protection data in mine power supply based on optical fiber communication according to claim 7, characterized in that: The target sampling time is determined in the following manner: Substituting the relative transmission time of the differential protection data frame into the first-order delay variation relationship, the corresponding estimated transmission delay is obtained; Subtract the estimated transmission delay from the received hardware time of the differential protection data frame to obtain the estimated transmission hardware time of the differential protection data frame at the receiving end time scale. Calculate the time interval between the transmission hardware time and the sampling time of the differential protection data frame, and convert the time interval to the receiving end time scale according to the time scale ratio; Subtracting the converted time interval from the estimated transmission hardware time yields the target sampling time of the transmitter current data on the receiver time scale.

9. A method for synchronizing differential protection data in mine power supply based on optical fiber communication according to claim 8, characterized in that: For current data sampled at the receiving end with sampling sequence number j, the time interval that is no earlier than half a sampling period before the sampling time of the current data and no earlier than half a sampling period after the sampling time is determined as the j-th sampling time window. Determine the sampling time window in which the target sampling time of the first differential protection data frame in the effective synchronization section is located, and determine the difference between the receiving end sampling sequence number corresponding to the window and the transmitting end sampling sequence number carried by the first differential protection data frame as the section sampling sequence number offset. When the target sampling time of the first differential protection data frame does not belong to any sampling time window, the corresponding synchronization verification segment will be determined as an invalid synchronization segment. For the remaining differential protection data frames within the effective synchronization section, when their target sampling time belongs to a sampling time window, and the difference between the receiving end sampling sequence number and the transmitting end sampling sequence number corresponding to the window is equal to the sampling sequence number offset of the section, the receiving end current data corresponding to the window is determined as the matching sampling data.

10. A method for synchronizing differential protection data in mine power supply based on optical fiber communication according to claim 9, characterized in that: Both differential protection terminals include the original mine protector and a mine explosion-proof and intrinsically safe differential protection control box connected to the original mine protector. The mine explosion-proof and intrinsically safe differential protection control box is equipped with an optical fiber communication interface, an RS485 interface and an RJ45 interface. The transmission distance of the optical fiber communication interface is no more than 10km. When the synchronization verification section is determined to be an invalid synchronization section, the mine explosion-proof and intrinsically safe differential protection control box stops transmitting the remote current data of that section to the differential protection calculation unit, and sends a synchronization invalidation flag to the mine's original protector through the RS485 interface or RJ45 interface. When the subsequent synchronization verification section is determined to be a valid synchronization section, and the target sampling time determined after updating the time mapping relationship using this section meets the matching condition described in claim 9, the transmission of the synchronization invalid flag is stopped, and the transmission of matching sampling data at both ends of the line to the differential protection calculation unit is resumed.

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