Data alignment method, differential protector and differential protection system
By maintaining time synchronization between differential protectors and calculating time deviations, the data alignment problem when differential protectors lose synchronization is solved, achieving accurate data alignment and protection in merging unit and process bus environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SCHNEIDER ELECTRIC IND SAS
- Filing Date
- 2022-01-30
- Publication Date
- 2026-07-28
AI Technical Summary
In power transmission systems, differential protectors fail to achieve proper data alignment due to loss of time synchronization. This is especially true when using merging units and process buses, where delay uncertainty leads to longer response times. Existing asynchronous alignment methods cannot effectively eliminate the delay caused by merging units.
By maintaining time synchronization between differential protectors, using a satellite timing system for synchronization alignment, and calculating and storing time calculation deviations when synchronization is lost, an asynchronous alignment method is adopted, and the transmission delay and time nodes are calculated using formulas to ensure the accuracy of data alignment.
Even when the differential protector loses time synchronization, data alignment can still be achieved, reducing errors and ensuring the correctness and response speed of the differential protection.
Smart Images
Figure CN116560456B_ABST
Abstract
Description
Technical Field
[0001] Embodiments of this disclosure relate to a data alignment method for a differential protector, a differential protector, and a differential protection system. Background Technology
[0002] In power transmission systems, differential protection is typically used to protect equipment and power lines. According to the principle of differential protection, the differential protector needs to acquire current sampling data from various ends (two or more ends) of the differential protection zone, and these current sampling values must be time-aligned. Traditionally, differential protection devices receive current information directly from current transformers, so the time for the differential protector to acquire current information is extremely short and negligible. However, with the development of substation automation systems, this has gradually evolved into a system where the current values collected by the current transformers are first sent to a merging unit, and then the merging unit sends them to the differential protector via network communication methods such as a process bus.
[0003] The delay introduced by the merging unit is uncertain, and the differential protector requires additional time to obtain the delay of the merging unit connected to other differential protectors, thus increasing the response time of subsequent operations. If the merging unit and the differential protector are synchronized with each other, the delay introduced by the merging unit can be eliminated through calculation. However, if the time synchronization of the differential protectors is broken, the delay introduced by the merging unit, combined with the uncertainty of the time information, makes it difficult for differential protection to be implemented correctly in this situation. Summary of the Invention
[0004] At least one embodiment of this disclosure provides a data alignment method, a differential protector, and a differential protection system, which can solve the technical problem that differential protection is difficult to implement correctly when the differential protector loses time synchronization.
[0005] At least one embodiment of this disclosure provides a data alignment method for a first differential protector, comprising: acquiring first sampled current data from a first sampling device at a first time node tA; sending a first message to a second differential protector after a first transmission processing delay ta, the first message including the first sampled current data; receiving a second message from the second differential protector at a first time tA*, the second message including second sampled current data and its sampling time marker, first time information regarding the reception time difference tc of the second differential protector from receiving the first message to the second time node, and second time information regarding the second transmission processing delay td of the second differential protector from the second time node to sending the second message, the second time node being the time point at which the second sampling device acquires the second sampled current data; and, while the first differential protector and the second differential protector maintain time synchronization, aligning the data according to the sampling time marker of the second sampled current data... The system determines the third time node at which the first differential protector acquires the third sampled current data corresponding to the sampling time marker from the first sampling device, and calculates the first calculated value of the second time node at which the second differential protector acquires the second sampled current data from the second sampling device based on the first time node tA, the first moment tA*, the first transmission processing delay ta, the reception time difference tc, and the second transmission processing delay td. It also calculates and stores the time calculation deviation tmem between the third time node and the first calculated value of the second time node. When the first differential protector and the second differential protector lose time synchronization, the system calculates the second calculated value of the second time node based on the first time node tA, the first moment tA*, the first transmission processing delay ta, the acquisition time difference tc, and the second transmission processing delay td. Finally, it determines the third time node based on the second calculated value of the second time node and the stored time calculation deviation tmem.
[0006] For example, in a method provided in one embodiment of this disclosure, calculating the first calculated value of the second time node at which the second differential protector obtains the second sampled current data from the second sampling device includes: using the first time node tA, the first moment tA*, the first transmission processing delay ta, the reception time difference tc, and the second transmission processing delay td, calculating the calculated value tp of the transmission delay of the data transmitted between the first differential protector and the second differential protector; and using the first moment tA*, the second transmission processing delay td, and the calculated value tp of the transmission delay to calculate the first calculated value; wherein, the calculated value tp of the transmission delay is calculated using the following formula: tp = 1 / 2(tA* - tA - ta - tc - td); and the first calculated value tB' of the second time node is calculated using the following formula: tB' = tA* - td - tp.
[0007] For example, in a method provided in one embodiment of this disclosure, the second calculated value of the second time node is calculated based on the first time node tA, the first moment tA*, the first transmission processing delay ta, the acquisition time difference tc, and the second transmission processing delay td. This includes: calculating the calculated value tp of the transmission delay of the data transmitted between the first differential protector and the second differential protector using the following formula: tp = 1 / 2(tA* - tA - ta - tc - td); and calculating the second calculated value tB” using the following formula: tB” = tA* - td - tp.
[0008] For example, in a method provided in one embodiment of this disclosure, determining a third time node based on a second calculated value of a second time node and a stored time calculation deviation tmem includes: calculating an estimated value of the third time node from the sum of the second calculated value and the time calculation deviation tmem, and taking the time node that is closest to the estimated value of the third time node among multiple time nodes in which the first differential protector obtains the sampled current data from the first sampling device as the third time node; wherein, the estimated value tA' of the third time node is calculated using the following formula: tA'=tA*-td-tp+tmem.
[0009] For example, in a method provided in one embodiment of this disclosure, when the first differential protector and the second differential protector maintain time synchronization, the method further includes: calculating and storing the time calculation deviation tmem whenever a time synchronization signal is received, or calculating and storing the time calculation deviation tmem whenever sampling current data from the first sampling device is received.
[0010] For example, in a method provided in one embodiment of this disclosure, the second message further indicates that the second differential protector has lost or regained time synchronization.
[0011] For example, in a method provided in one embodiment of this disclosure, the first sampling device is a first merging unit, the second sampling device is a second merging unit, and the first merging unit and the second merging unit respectively obtain sampling current values from different locations on the same power line.
[0012] For example, in a method provided in one embodiment of this disclosure, the first differential protector and the second differential protector use satellite timing to maintain time synchronization.
[0013] At least one embodiment of this disclosure provides a differential protector, including a processor and a memory, wherein program code is stored in the memory, and when the program code is executed by the processor, it performs a data alignment method as described in any of the above method embodiments.
[0014] At least one embodiment of this disclosure provides a differential protection system for power lines, comprising: a first sampling device and a second sampling device configured to acquire sampled current values from different locations on the power line, respectively; a first differential protector connected to the first sampling device and configured to receive first sampled current data sent by the first sampling device; and a second differential protector connected to the second sampling device and configured to receive second sampled current data sent by the second sampling device; wherein the first differential protector and the second differential protector are both differential protectors as described in the above-described device embodiments. Attached Figure Description
[0015] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure, and are not intended to limit this disclosure.
[0016] Figure 1 The timing diagram shows the differential protection scheme and data alignment scheme under the condition of no delay in acquiring current data;
[0017] Figure 2 A timing diagram illustrating the data alignment scheme under the condition that there is a delay in acquiring current data is shown.
[0018] Figure 3 A flowchart illustrating a data alignment method provided by an embodiment of this disclosure is shown;
[0019] Figure 4 A timing diagram illustrating the data alignment method provided in an embodiment of this disclosure is shown.
[0020] Figure 5 A schematic diagram of a differential protector provided in an embodiment of this disclosure is shown;
[0021] Figure 6 A schematic diagram of a differential protection system for power lines provided for embodiments of this disclosure;
[0022] Figure 7 A timing diagram of a process bus scenario provided for embodiments of this disclosure. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.
[0024] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “including,” “comprising,” or “containing,” and similar terms mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The terms “connected,” “linked,” or similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.
[0025] Figure 1 This diagram illustrates the timing of a differential protection scheme and data alignment scheme under the condition of no current data transmission processing delay. A and B are denoted as the two ends of the power line. Differential protectors A and B are used at ends A and B, respectively. Both differential protectors A and B can directly sense the current in the power line using current inductance, thus the time when differential protectors A and B acquire current data has almost no delay compared to the actual current. Differential protectors A and B transmit data to each other via a communication link. In the absence of time synchronization between differential protectors A and B, data alignment can be achieved by eliminating communication delay, i.e., asynchronous alignment.
[0026] exist Figure 1 In the diagram, time nodes tAn and tBn (where n is an integer from 1 to 5) are the moments when differential protectors A and B sample the current from the power line. Figure 1 The proposed scheme assumes that current sampling and transmission of the sampled current data occur at the same time, meaning there is no transmission or processing delay in the circuit data. Communication delay can be determined by the average of the communication times. For example, in... Figure 1In the diagram, differential protector A sends message 1 to differential protector B at time point tA1. Message 1 includes current data sampled at time point tA1. Differential protector B sends message 2 to differential protector A at time point tB3. Message 2 includes current data sampled at time point tB3. tp1 is the transmission delay (also known as propagation delay, communication delay, etc.) from differential protector A to differential protector B, and tp2 is the transmission delay from differential protector B to differential protector A. tc is the duration between the time tB* when differential protector B receives message 1 and time point tB3, and tA* is the time when differential protector A receives message 2. Message 2 may also include tc.
[0027] Therefore, the transmission delay tp1 can be considered equal to the transmission delay tp2, which is 1 / 2(tA* - tA1 - tc). Further, the calculated value of the time node tB3 when differential protector B sends message 2 is tB3* = tA* - tp2. tB3* can be considered an estimate of the time point at which differential protector A acquires the current data that needs to be aligned with the current data sampled by differential protector A at time point tB3. Therefore, the current data acquired at the time node tAn closest to tB3* is the current data aligned with the current data acquired at time point tB3.
[0028] exist Figure 1 In the proposed scheme, since differential protectors A and B can directly use current inductance to sense the current in the power line, and the time required to obtain the sampled current using current inductance sampling is negligible, the data alignment error is relatively small.
[0029] However, in differential protection systems employing process buses, the differential protector does not directly obtain the current value of the power line from the current transformer. Instead, a sampling device, such as a merging unit, samples and performs preliminary processing on the current value collected by the current transformer. The sampling device then sends the processed sampled current data to the differential protector via the process bus. In this process, the presence of the sampling device introduces a delay between sampling and the differential protector receiving the sampled data. This delay can include the delay from sampling to obtaining the sampled current data, as well as the network transmission delay of sending the sampled current data to the differential protector. This delay may exceed the allowable error range and may vary over time. Therefore, Figure 1 The asynchronous alignment method in the code is not suitable for scenarios using process buses.
[0030] In this situation, a synchronously aligned differential protection scheme can be adopted. In this scheme, differential protectors A and B, along with their sampling devices, are time-synchronized using the same satellite positioning system. This allows for the determination of current data sampled at the same time node in different differential protectors based on the same time stamp. However, the synchronously aligned differential protection scheme must ensure that time synchronization is not lost; if time synchronization is lost, data alignment cannot be achieved. In the event of lost time synchronization, only asynchronous alignment can be used. Figure 1 The asynchronous alignment scheme in the code cannot achieve good data alignment in situations where there is a delay in the acquisition and / or transmission of current data (e.g., in scenarios using a process bus).
[0031] Figure 2 This diagram illustrates the timing of a data alignment scheme for current data in the case of transmission and processing delays.
[0032] When terminals A and B are synchronized, the differential protectors and sampling devices at terminals A and B can be actually synchronized via a satellite positioning system, such as GPS. For example, the satellite positioning module periodically generates pulse-per-second (PPS) signals for time calibration. Therefore, the current sampling times at terminals A and B can be based on the PPS signal. For instance, both terminals A and B can sequentially number the current data sampled between two PPS signals, with current data of the same number representing current data collected at the same time. In the case of time synchronization, alignment can be performed based on the current data's number.
[0033] However, when time synchronization is lost at both ends—for example, if either end loses its satellite signal—data with the same label does not represent data acquired at the same time. Therefore, asynchronous alignment is required. For example, differential protector A and differential protector B can use… Figure 1 The proposed solution achieves data alignment, but due to delays in data transmission and processing, alignment errors exist.
[0034] For example, in Figure 2 In the diagram, differential protector A receives current data at time point tA1 and sends message 1 to differential protector B after a delay of ta. Differential protector B receives message 1 at time tB*. After receiving message 1, differential protector B needs to wait for the next time point tB3 to acquire sampled data, a time interval tc. Similar to differential protector A, differential protector B experiences a transmission processing delay td between acquiring sampled data and actually sending the message. Differential protector B actually sends message 2 at time tB3*, and differential protector A receives message 2 at time tA*. If still based on... Figure 1The asynchronous alignment method used to calculate the estimated value of tB3* and its corresponding current data at terminal A will result in deviations.
[0035] But regardless of the above Figure 1 or Figure 2 In the corresponding scenarios, current sampling is not performed using a merging unit. If time synchronization is not available after using a merging unit, the delay caused by the merging unit cannot be determined and eliminated, and differential protection cannot be performed correctly.
[0036] Embodiments of this disclosure provide a data alignment method, a differential protector, and a differential protection system that can provide correct progressive differential protection when the differential protector loses synchronization.
[0037] Figure 3 A flowchart is shown of a data alignment method for a first differential protector provided according to at least one embodiment of the present disclosure.
[0038] The data alignment method includes the following steps:
[0039] In step S301, at the first time node tA1, the first sampled current data is obtained from the first sampling device.
[0040] Step S302: After the first transmission processing delay ta, a first message is sent to the second differential protector. The first message includes the first sampled current data.
[0041] In step S303, at the first time tA1*, a second message is received from the second differential protector. The second message includes the second sampled current data and its sampling time marker, the first time information about the receiving time difference tc from the second time node to the second differential protector receiving the first message, and the second time information about the second transmission processing delay td from the second time node to the second time node sending the second message. The second time node is the time point at which the second sampling device acquires the second sampled current data.
[0042] Step S304: Based on the sampling time marker of the second sampling current data, determine the third time node at which the first differential protector obtains the third sampling current data corresponding to the sampling time marker from the first sampling device.
[0043] Step S305: Based on the first time node tA1, the first moment tA1*, the first transmission processing delay ta, the reception time difference tc, and the second transmission processing delay td, calculate the first calculated value of the second time node at which the second differential protector obtains the second sampled current data from the second sampling device.
[0044] Step S306: Calculate and store the time calculation deviation tmem between the first calculated value of the third time node and the second time node.
[0045] Step S307: Calculate the second calculated value of the second time node based on the first time node tA1, the first moment tA1*, the first transmission processing delay ta, the acquisition time difference tc, and the second transmission processing delay td.
[0046] Step S308: Determine the third time node based on the second calculated value of the second time node and the stored time calculation deviation tmem.
[0047] Figure 4 A timing diagram of a data alignment method provided in at least one embodiment of the present disclosure is shown.
[0048] To better understand Figure 3 The execution of the data alignment method in [the document] will be explained below. Figure 4 A timing diagram of the data alignment method in the diagram is used to illustrate the process. Figure 3 The method described herein is as follows. In this embodiment, the first message is denoted as message 1, the second message as message 2, the first differential protector as differential protector A, and the second differential protector as differential protector B. The differential protector involved in this disclosure can be, for example, a relay. It is understood that... Figure 4 Although only two differential protectors are shown, in reality, there can be more than three differential protectors communicating with each other and performing actions such as... Figure 3 In the case of data alignment methods, but when more than three differential protectors communicate with each other, the way any two differential protectors perform data alignment with each other is different. Figure 4 The relevant descriptions are the same, so they will not be repeated here.
[0049] Differential protectors A and B, along with their first and second sampling devices, can maintain time synchronization using satellite timing, such as GPS, BeiDou, and Galileo satellites. Satellites can send second pulse signals to differential protectors A and B to achieve time synchronization. Time synchronization can also be achieved through any other periodic time synchronization signal with a fixed interval. In this disclosure, maintaining time synchronization between differential protectors A and B includes maintaining time synchronization between the first and second sampling devices. However, if differential protectors A and B lose time synchronization, the first and second sampling devices also lose time synchronization, making it impossible to ensure that the first and second sampling devices sample the current at the same time, and also making it impossible to know the time corresponding to the current actually sampled by the sampling devices.
[0050] For example, differential protector A and differential protector B both use GPS second pulse signals for synchronization. tAn is the time node when differential protector A receives the sampled current data sent by the first sampling device, and tBn is the time node when differential protector B receives the sampled current data sent by the second sampling device, where n is a positive integer.
[0051] The first sampling device can be a first merging unit MU1, and the second sampling device can be a second merging unit MU2. Alternatively, the sampling device can also include a merging unit and a current transformer. The first sampled current data is denoted as sampled current data 1, and the second sampled current data is denoted as sampled current data 2.
[0052] The first merging unit and the second merging unit respectively acquire sampled currents from different locations on the same power line, process the sampled currents, and send them to differential protector A and differential protector B respectively via the process bus. tacq1 is the delay from when the first sampling device samples the first sampled current to when differential protector A acquires the first sampled current data, and tacq2 is the time delay when differential protector B receives another sampled current data sampled at the same time as the first sampled current data. For example, Figure 4 The 1PPS occurs at time T0. At time T0, there is current in the power line. Both the first and second sampling devices sample this current. The first sampling device samples current 1 at terminal A, and the second sampling device samples current 2 at terminal B. At time tA1, after a delay of tacq1 at time T0, differential protector A receives the sampled current data of current 1. At time tB1, after a delay of tacq2 at time T0, differential protector B receives the sampled current data of current 1. The values of tacq1 and tacq2 can be equal to 0. That is, the data alignment method involved in this disclosure is applicable to combinations where all sampling devices are merging units or where the sampling devices include merging units and current transformers.
[0053] Figure 4 This involves various time-related parameters. For ease of distinction, the time point when the differential protector receives the sampled current data is called the "time node," while the time points when differential protectors send and receive messages are called "moments." Each delay should be understood as a period of time, and the time difference also refers to a period of time. Furthermore, it should be understood that... Figure 4 All time points and message reception times in the document are for illustrative purposes only. Sending message 1 at time point tA1 does not necessarily mean it will be received between tB2 and tB3. The length between time points, the message sending and receiving times, and the sending, receiving, and transmission delays are all adaptively varied depending on the actual application. The specific labels such as "tB3" and "tA3" used in this document are for illustrative purposes only and not as limitations.
[0054] Execute step S301. At time node tA1, differential protector A obtains sampled current data 1 from MU1. This sampled current data 1 may carry a sampling time stamp of MU1, which reflects the sampling time of sampled current data 1, for example, indicating which sampling data is sampled by MU1 since its satellite positioning module generates the PPS signal.
[0055] Execute step S302. After a transmission processing delay ta, differential protector A sends message 1 to differential protector B. Message 1 includes sampled current data 1. Optionally, message 1 may also carry the identifier of time node tA1 and the transmission processing delay ta. Correspondingly, message 2 also carries the identifier of time node tA1, so that after receiving message 2, differential protector A can determine the time node tA1 corresponding to time tA1*.
[0056] Execute step S303. At time tA1*, differential protector A receives message 2 from differential protector B. Message 2 includes sampled current data 2 and its sampling timestamp, first time information about the reception time difference tc between the differential protector B receiving message 1 and time node tB3, and second time information about the transmission processing delay td between the differential protector B and time node tB3, where time node tB3 is the time point at which MU2 acquires sampled current data 2. The sampling timestamp of sampled current data 2 reflects the sampling time of sampled current data 1, for example, indicating which sampling data 2 is from the time MU2 generates the PPS signal from its satellite positioning module.
[0057] The first time information may include the time node tB3 and the time when the differential protector B receives message 1, or the time difference tc between the two. The second time information may include the transmission processing delay td.
[0058] It should be noted that steps S301-S303 will be executed regardless of whether differential protector A and differential protector B are in time synchronization or have lost time synchronization.
[0059] Differential protector A is always aware of its connection status with the GPS. After receiving message 2, differential protector A can determine whether differential protector B is still maintaining time synchronization. Optionally, message 2 also indicates whether differential protector B has lost or regained time synchronization. For example, message 2 carries a flag indicating whether differential protector B is maintaining time synchronization with the GPS.
[0060] When it is determined that time synchronization is maintained, differential protector A continues to execute steps S404 to S406.
[0061] In step S304, the differential protector A determines the time node at which it acquired the sampling current data 3 corresponding to the sampling time marker from MU1, based on the sampling time marker of the sampling current data 2. For example, if the sampling time marker indicates that the sampling current data 2 is the third sampling result since the current PPS signal, and the differential protector A determines that the third sampling result since the current PPS signal was acquired at time node tA3, then the differential protector A determines that time node tA3 is the time node corresponding to time node tB3, and the data acquired at time node tA3 is aligned with the data acquired at time node tB3.
[0062] In step S305, based on time node tA1, time tA1*, transmission processing delay ta, reception time difference tc, and transmission processing delay td, the first calculated value tB3' of the time node tB3 when the differential protector B obtains the sampled current data 2 from MU2 is calculated.
[0063] For example, using time node tA1, time tA1*, transmission processing delay ta, reception time difference tc, and transmission processing delay td, the calculated value tp of the transmission delay for data transmission between differential protector A and differential protector B can be calculated. For example, tp = 1 / 2(tA1* - tA1 - ta - tc - td).
[0064] Then, using time tA1*, transmission processing delay td, and transmission delay tp, the first calculated value (shown as tB3' in the diagram) is calculated. The transmission delay tp1 from differential protector A to differential protector B and the transmission delay tp2 from differential protector B to differential protector A can be considered equal during calculation, i.e., tp = tp1 = tp2. The first calculated value tB3' = tA1* - td – tp.
[0065] In step S306, the time calculation deviation tmem between time node tA3 and the first calculated value tB3' is calculated and stored. For example, tmem = tA3 - tB3'. This tmem comprehensively considers tacq1, tacq2, tp1, and tp2, so that data alignment can be accurately achieved when time synchronization is lost.
[0066] Upon determining that time synchronization has been lost, differential protector A continues to execute steps S407 and S408. It should be noted that if any one of the differential protectors in the communication connection loses time synchronization, the remaining differential protectors also enter a state of time synchronization loss.
[0067] In step S307, the differential protector A calculates the second calculated value tB3” for time node tB3 based on time node tA1, time tA1*, transmission processing delay ta, acquisition time difference tc, and transmission processing delay td. For example, tB3” = tA1* - td - tp. The calculated value tp for the transmission delay can be pre-stored or calculated during step S307. The calculation method can be found in the relevant description of step S305, and will not be repeated here.
[0068] Continue executing step S308, where differential protector A determines the third time node tA3 based on the second calculated value tB3” of time node tB3 and the stored time calculation deviation tmem.
[0069] For example, the estimated value tA3' of the third time node is calculated by summing the second calculated value tB3" and the time calculation deviation tmem, such as tA3' = tA1*-td-tp+tmem. The third time node is the time node at which the second time node needs to be aligned in the differential protector A, therefore the estimated value of the third time node depends on the information related to the second time node.
[0070] Then, the time node that is closest to the estimated value tA3' of the third time node among the multiple time nodes tAn in which the differential protector A receives the sampled current data from MU1 is taken as the third time node.
[0071] The data alignment method provided in this embodiment calculates and records the delay compensation in advance when the differential protector is synchronized with the satellite, so that the differential protector can maintain normal differential protection when synchronization is lost by using the pre-obtained delay compensation.
[0072] In some embodiments, whenever a time synchronization signal is received, the differential protector A calculates and stores the time calculation deviation tmem. That is, the differential protector continuously updates the time calculation deviation tmem while maintaining time synchronization, so that the stored time calculation deviation tmem is always up-to-date and best reflects the sampling delay changes of the sampling device when time synchronization is lost, in order to further reduce errors.
[0073] See also Figure 4 It should be noted that, in Figure 4 At each time point tAn, differential protector A can execute the data alignment method described above. Similarly, this data alignment method can also be executed by differential protector B.
[0074] Figure 5 A schematic diagram of a differential protector provided in an embodiment of this disclosure is shown.
[0075] exist Figure 5In this differential protector 500, a processor 510 and a memory 520 are included. The memory 520 stores program code, which, when executed by the processor 510, performs the data alignment method as described in the above embodiments. The manner in which the processor 510 executes this data alignment method is described in the above embodiments and will not be elaborated here. By executing this data alignment method, the differential protector 500 can be adapted to differential protection in situations where the differential protector loses time synchronization and there is a large delay or uncertain delay in acquiring current data.
[0076] Figure 6 A schematic diagram of a differential protection system for power lines provided by an embodiment of the present disclosure is shown.
[0077] exist Figure 6 In this system, the differential protection system 600 is used to protect the power line 610. The differential protection system 600 may include sampling devices 621 and 622, differential protector 631, and differential protector 632.
[0078] Sampling devices 621 and 622 are connected to power line 610. Sampling devices 621 and 622 are configured to obtain and process sampling current from power line 610.
[0079] Differential protector 630 is connected to sampling device 621 and configured to receive first sampled current data sent by sampling device 621. Differential protector 632 is connected to sampling device 622 and configured to receive second sampled current data sent by sampling device 622.
[0080] Differential protectors 631 and 632 can both be the differential protectors described in the above embodiments. Sampling devices 621 and 622 can be merging units.
[0081] Both differential protectors 631 and 632 can perform the data alignment method described in the above method embodiments, thereby compensating for the delay caused by the sampling device, effectively aligning the sampled current data when time synchronization is lost, and properly protecting the power line to avoid erroneous operation.
[0082] The embodiments disclosed above illustrate a data alignment method when there is a delay in the acquisition and processing of current data, using a merging unit and a process bus as examples. Various delay scenarios in the process bus context are further described below.
[0083] Figure 7 A timing diagram of a process bus scenario provided for at least one embodiment of this disclosure.
[0084] exist Figure 7In this system, current sampling is performed by merging units MU1, MU2, and MU3. For example, MU1, MU2, and MU3 sample the current of power lines at different locations. MU1, MU2, and MU3 utilize GPS second pulses for synchronized sampling. The different locations of the power lines can be different positions of the power lines or different power lines themselves. Differential protector A is used at end A, and differential protector B is used at end B. MU1 is connected to differential protector A via a network, and MU2 and MU3 are connected to differential protector B via a network. Differential protector B receives data from MU2 and MU3, and performs data alignment on the data from MU2 and MU3.
[0085] In the process bus scheme, differential protector A and differential protector B obtain sampled current data from MU1 and MU2 (MU2 represents MU2 and MU3), respectively.
[0086] For differential protector A, from the time MU1 samples the current to the time differential protector A sends the sampled current data to differential protector B, there are MU1 sampling delay, network transmission delay, differential protector A decoding delay of the data sent by MU1, and transmission delay caused by differential protector A sending the data.
[0087] For differential protector B, there are MU sampling delays for MU2 and MU3, network transmission delays, alignment delays, decoding delays of data sent by differential protector B to MU2, and transmission delays caused by data transmission by differential protector B.
[0088] Among them, the sampling delay and network transmission delay of MU1, MU2, and MU3 are uncontrollable by differential protectors A and B, while the decoding delay and transmission delay are relatively stable for differential protectors A and B and can be considered as fixed values. The alignment delay is a delay that only occurs when there is more than one MU at the B end. Multiple MUs need to first combine multiple sampled currents into one sampled current, for example, by performing vector addition.
[0089] for Figure 7 In the process bus scenario, the data alignment method, differential protector and differential protection system in the above embodiments can be sampled. For details, please refer to the description above, which will not be repeated here.
[0090] It should be noted that the above embodiments of this disclosure are illustrated using merging units and process buses as examples, but this disclosure is also applicable to other application scenarios with corresponding delays.
[0091] According to embodiments of this disclosure, the processes described above can also be implemented as computer software programs. For example, embodiments of this disclosure include a computer program product comprising a computer program containing program code for performing the processes described above.
[0092] The method flowcharts and device block diagrams disclosed herein are merely illustrative examples and are not intended to require or imply that connections or arrangements must be made in the manner shown in the flowcharts and block diagrams. As those skilled in the art will recognize, these devices and equipment can be connected and arranged in any manner that achieves the desired purpose.
[0093] The scope of protection of this disclosure is not limited to the specific embodiments thereof, but should be determined by the scope of the claims. The accompanying drawings of the embodiments of this disclosure only relate to the structures involved in the embodiments; other structures can be referred to with common designs. Where there is no conflict, the embodiments of this disclosure and the features within them can be combined to obtain new embodiments.
Claims
1. A data alignment method for a first differential protector, comprising: At the first time point tA, the first sampled current data is obtained from the first sampling device; After a first transmission processing delay ta, a first message is sent to the second differential protector, the first message including the first sampled current data; At the first moment tA The second message is received from the second differential protector. The second message includes second sampled current data and its sampling time stamp, first time information about the receiving time difference tc of the second differential protector from receiving the first message to the second time node, and second time information about the second transmission processing delay td of the second differential protector from the second time node to sending the second message. The second time node is the time point at which the second sampling device acquires the second sampled current data. When the first differential protector and the second differential protector maintain time synchronization Based on the sampling time marker of the second sampled current data, determine the third time node at which the first differential protector obtains the third sampled current data corresponding to the sampling time marker from the first sampling device, and Based on the first time node tA and the first moment tA The first transmission processing delay ta, the receiving time difference tc, and the second transmission processing delay td are used to calculate the first calculated value of the second time node at which the second differential protector obtains the second sampled current data from the second sampling device, and to calculate and store the time calculation deviation tmem between the third time node and the first calculated value of the second time node; When the first differential protector and the second differential protector lose time synchronization Based on the first time node tA and the first moment tA The first transmission processing delay ta, the receiving time difference tc, and the second transmission processing delay td are used to calculate the second calculated value of the second time node, and The third time node is determined based on the second calculated value of the second time node and the stored time calculation deviation tmem.
2. The data alignment method as described in claim 1, wherein, The calculation of the first calculated value at the second time node when the second differential protector obtains the second sampled current data from the second sampling device includes: Using the first time node tA and the first time point tA Calculate the transmission delay tp between the first differential protector and the second differential protector, using the first transmission processing delay ta, the receiving time difference tc, and the second transmission processing delay td; and Using the first time tA The second transmission processing delay td and the calculated value of the transmission delay tp are used to calculate the first calculated value; wherein, The calculated value of the transmission delay tp is calculated using the following formula: tp = 1⁄2(tA - tA - ta - tc - td): The first calculated value tB' of the second time node is calculated using the following formula: tB' = tA - td - tp。 3. The data alignment method as described in claim 1, wherein, The first time node tA, the first moment tA The calculation of the second calculated value at the second time node is based on the first transmission processing delay ta, the receiving time difference tc, and the second transmission processing delay td, including: The transmission delay tp between the first differential protector and the second differential protector is calculated using the following formula: tp = 1⁄2(tA - tA - ta - tc - td): The second calculated value tB'' is calculated using the following formula: tB'' = tA - td - tp。 4. The data alignment method according to any one of claims 1 to 3, wherein, The third time node is determined based on the second calculated value of the second time node and the stored time calculation deviation tmem, including: The estimated value of the third time node is calculated by the sum of the second calculated value and the time calculation deviation tmem, and the time node that is closest to the estimated value of the third time node among the multiple time nodes when the first differential protector obtains the sampled current data from the first sampling device is taken as the third time node; The estimated value tA' of the third time node is calculated using the following formula: tA = tA - td - tp + sleep。 5. The data alignment method according to any one of claims 1 to 3, wherein, When the first differential protector and the second differential protector maintain time synchronization, the method further includes: Whenever a time synchronization signal is received, the time calculation deviation tmem is calculated and stored, or whenever sampling current data from the first sampling device is received, the time calculation deviation tmem is calculated and stored.
6. The data alignment method according to any one of claims 1 to 3, wherein, The second message also indicates whether the second differential protector loses or regains time synchronization.
7. The data alignment method as described in any one of claims 1-3, wherein, The first sampling device is a first merging unit, and the second sampling device is a second merging unit. The first merging unit and the second merging unit respectively obtain the sampling current value from different locations on the same power line.
8. The data alignment method as described in any one of claims 1-3, wherein, The first differential protector and the second differential protector use satellite time synchronization to maintain time synchronization.
9. A differential protector, comprising a processor and a memory, wherein program code is stored in the memory, and when executed by the processor, the program code performs a data alignment method as described in any one of claims 1-8.
10. A differential protection system for power lines, comprising: The first sampling device and the second sampling device are configured to obtain sampling current values from different locations on the power line, respectively; The first differential protector is connected to the first sampling device and is configured to receive the first sampling current data sent by the first sampling device; as well as The second differential protector, connected to the second sampling device, is configured to receive the second sampled current data sent by the second sampling device. Wherein, both the first differential protector and the second differential protector are differential protectors as described in claim 9.