A waveform comparison method for waveform detection of power equipment

Abstract

The present invention discloses a waveform comparison method for waveform detection of power equipment, including the following steps: 1) Obtain the waveform file FD recorded by the device under test and the waveform file FR recorded by the oscillograph; 2) Parse the FD and FR files; 3) Obtain the triggered recording waveform A of the device under test, the triggered recording waveform B of the oscillograph, the device comparison waveform D, and the recording comparison waveform E; 4) Obtain and calculate the relevant data required for the comparison of waveforms A and B from the waveform files; 5) Calculate the rated value of waveform A; 6) Generate the substring waveform C; 7) Use the substring comparison method to find the overlapping part and similarity of the two waveforms; 8) Take the start time and end time corresponding to the minimum value of Error; 9) Generate the substring waveform F once; 10) Directly compare waveform F and waveform G, calculate the error value, and calculate the similarity. The method and system of the present invention based on waveform comparison can calculate the waveform similarity more accurately.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network equipment measurement, and particularly relates to a waveform comparison method for waveform detection of power equipment. Background Art

[0002] At present, with the increasingly wide application range and more advanced technology of distribution network automation, the use of distribution terminals in China is becoming more and more popular. It is becoming increasingly important to judge the on-site operation conditions through distribution terminals. For the fault analysis of on-site closing inrush current, ground fault, short-circuit tripping, etc., from the previous simple on-site inspection and event recording, now through the fault waveforms recorded in the terminal, the situation at the moment of fault occurrence can be more intuitively understood, which is more conducive to fault analysis. By cooperating with the power grid master station system to remotely retrieve the waveforms in the equipment, more abundant power grid operation detail information can be obtained than before, reserve more data for power grid management, establish a rich fault waveform database, and facilitate subsequent on-site fault qualification. Therefore, the verification of the accuracy, authenticity, and reliability of the waveforms inside the terminal has become an important task at present.

[0003] In the "Notice of the State Grid Corporation on Doing a Good Job in the Construction and Application of Distribution Automation", the maximum peak instantaneous error in the transient performance of fault recording should not be greater than 10%, and the basic error of steady-state recorded voltage: 0.05U ≤ 5.0%, 0.1U ≤ 2.5%, 0.5U ≤ 1.0%, 1.0U ≤ 0.5%, 1.5U ≤ 1.0%; the relative error of steady-state recorded current: 0.1I ≤ 5.0%, 0.2I ≤ 2.5%, 0.5I ≤ 1.0%, 1.0I ≤ 0.5%, 5.0I ≤ 1.0%, 10I ≤ 2.5%. The indicators of the basic errors of transient and steady-state recording are clarified.

[0004] For example, the Chinese patent with the publication number CN109001664A discloses a waveform comparison test for a transient recording type fault indicator, including: (1) the steady-state effective value trend before and after the transient fault of the waveform; (2) the amplitude of the first maximum transient characteristic quantity; (3) the amplitude difference between the first maximum transient characteristic quantity and the second maximum transient characteristic quantity; (4) the time difference between the first maximum transient characteristic quantity and the second maximum transient characteristic quantity; (5) the number of times the amplitude exceeds the set value m within two fault cycle periods starting from the fault mutation point. Further, the similarity algorithm judges the recording performance through 5 criteria. If all the criteria are met, it is considered that the recording performance of the fault indicator is qualified, and the 5 criteria judge the recording performance by collecting 5 types of characteristic quantities.

[0005] However, in the main criteria of the above scheme, the ±10% of the amplitude difference and time difference error values, and the number of times the fault exceeds the set value M are all test values, which have a large error from the waveform requirements and cannot meet the waveform similarity comparison in multiple scenarios. Summary of the Invention

[0006] In view of the above problems, the present invention proposes a waveform comparison method for waveform detection of power equipment, which solves the problems that the error values of amplitude difference and time difference in the existing distribution terminal test bench and terminal time scale criteria, and the number of faults exceeding the set value M are both test values, with a large error from the waveform requirements, and it is impossible to meet the waveform similarity comparison in multiple scenarios.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A waveform comparison method for waveform detection of power equipment includes the following steps:

[0009] 1) Obtain the waveform file FD recorded by the device under test and the waveform file FR recorded by the oscillograph;

[0010] 2) Parse the FD and FR files with reference to the waveform standard format;

[0011] 3) Obtain the waveform A triggered by the device under test for recording, the waveform B triggered by the oscillograph for recording, the device comparison waveform D, and the oscillograph comparison waveform E;

[0012] 4) Obtain and calculate the relevant data required for the comparison of waveforms A and B from the waveform files;

[0013] 5) Calculate the rated value of waveform A;

[0014] 6) By the linear interpolation method, solve to make the sampling frequencies of waveforms A and B the same, thereby generating the substring waveform C;

[0015] 7) Use the substring comparison method to find the overlapping part and similarity of the two waveforms;

[0016] 8) Take the start time and end time corresponding to the minimum value of Error;

[0017] 9) Waveforms D and E are processed again according to the methods in the fourth to sixth steps to generate the substring waveform F;

[0018] 10) Waveform F and waveform G are directly compared to calculate the error value Error', and the similarity is calculated. Based on the waveform comparison method and system of the present invention, the waveform similarity is calculated more accurately.

[0019] Optionally, the number of points of waveform C: C.P = A.P * B.N / A.N;

[0020] Linear coefficient: R = (C.i*A.N / B.N) - math.floor(C.i *A.N / B.N);

[0021] C.Y = A[C.i].Y * (1 - R) + A[C.i + 1].Y * R;

[0022] C.T = A[C.i].T * (1 - R) + A[C.i + 1].T * R.

[0023] Optionally, the number of sampling points in each period in step 4) is:

[0024] A.N = A waveform sampling frequency / standard frequency (50Hz);

[0025] B.N = B waveform sampling frequency / standard frequency (50Hz).

[0026] Optionally, in step 7), using the C waveform as the substring waveform, starting from the first point of the B waveform, take the number of points of the C waveform and compare them point by point with the C waveform to calculate the error value; then shift the comparison start position one point to the left and continue the comparison; compare cyclically in this way and record the Error value each time, as well as the start time TStart and end time TEnd of the similar waveform.

[0027] Optionally, the error value calculation formula in step 7) is as follows:

[0028] Error value Error =

[0029] Optionally, the formula for taking the start time and end time corresponding to the minimum Error in step 8) is as follows:

[0030] TStart’ = TStart[Min(Error)];

[0031] TEnd’ = TEnd[Min(Error)].

[0032] Optionally, in step 9), the waveform between the time intervals TStart’ and TEnd’ of the E waveform is taken as G.

[0033] Optionally, the error value calculation formula in step 10) is as follows: Error’ =

[0034] Similarity S = (1 - Error’ / D.R / D.P) * 100%.

[0035] The present invention also discloses a test system that can compare waveforms more accurately, including a host computer PC, a standard clock instrument, a waveform recorder, and a relay protection instrument; one port of the host computer PC is connected to the standard clock instrument through Ethernet, and the other port is connected to a switch and a serial server to communicate and interact with devices such as the waveform recorder, the relay protection instrument, and the device under test.

[0036] The waveform recorder is in the same circuit as the device under test and is used to synchronously collect real-time waveforms on the circuit under test.

[0037] The relay protection instrument is used to transmit analog quantities by playing back waveforms or setting a status sequence.

[0038] The standard clock instrument is used to perform time synchronization with the host computer PC, the waveform recorder, and the relay protection instrument through SNTP and two-way B codes respectively. Among them, the time of the device under test is synchronized by the PC through the protocol / SNTP method to ensure that the times of the PC, the waveform recorder, the standard clock instrument, and the device under test in the test system are consistent.

[0039] (III) Beneficial effects

[0040] 1. The present invention solves the pain points of inconsistent time stamps of the distribution terminal test bench and the terminal and inconsistent waveform sampling frequencies. Based on the waveform comparison method and system, the waveform similarity is calculated more accurately.

[0041] 2. Initiated by the main control software of the host computer PC, according to the test plan, such as waveform playback, analog quantity output, etc., test instructions are sequentially sent to the relay protection instrument, the output module, etc. These intelligent components realize the combined output of various electrical signals. The device under test collects these signals, performs data processing and analysis, executes corresponding alarms / recording waves / actions, etc., and uploads various types of data through the communication protocol, and synchronously collects the waveform files in the waveform recorder for comparison to realize the closed-loop test of related functions and performances such as telemetry, telecontrol, pulses, and recording waves. Based on the standard clock instrument, it is ensured that the waveform comparison method is more reasonable and accurate.

[0042] 3. The solution of the present invention is easy to build. It is practical, reasonable, and feasible. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a flowchart of the waveform comparison method for power equipment waveform detection in Embodiment 1 of the present invention;

[0044] Figure 2 is the device waveform in the transient waveform comparison in the waveform comparison method for power equipment waveform detection in Embodiment 1 of the present invention;

[0045] Figure 3 is the waveform recorder waveform in the transient waveform comparison in the waveform comparison method for power equipment waveform detection in Embodiment 1 of the present invention;

[0046] Figure 4 It is the result graph of transient waveform comparison in the waveform comparison method for power equipment waveform detection in Embodiment 1 of the present invention;

[0047] Figure 5 It is the terminal waveform of steady-state waveform comparison in the waveform comparison method for power equipment waveform detection in Embodiment 1 of the present invention;

[0048] Figure 6 It is the oscillograph waveform of steady-state waveform comparison in the waveform comparison method for power equipment waveform detection in Embodiment 1 of the present invention;

[0049] Figure 7 It is the result graph of steady-state waveform comparison in the waveform comparison method for power equipment waveform detection in Embodiment 1 of the present invention;

[0050] Figure 8 It is Figure 1 The block diagram of the test system in Embodiment 2 of the present invention; Specific embodiments

[0051] The following combines the accompanying drawings and embodiments to further describe in detail the specific embodiments of the present invention. The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0052] In the description of the present invention, unless otherwise specified, the specific description is as follows:

[0053] Waveform.i: Waveform point number; Waveform.N: Number of sampling points in one period;

[0054] Waveform.P: Number of waveform points;

[0055] Waveform.Y: Waveform point data;

[0056] Waveform.T: Waveform point time;

[0057] Waveform.R: Waveform rated value;

[0058] math.floor: Round down a floating-point number;

[0059] math.Abs: Take the absolute value.

[0060] For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations. Embodiment 1

[0061] The technical solution adopted by the present invention is as follows:

[0062] Such as Figure 1 、 Figure 2 、Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown in Figure 6 and Figure 7 , the present invention discloses a waveform comparison method for power equipment waveform detection, including the following steps:

[0063] 1) Obtain the waveform file FD recorded by the device under test and the waveform file FR recorded by the oscillograph;

[0064] 2) Parse the FD and FR files with reference to the waveform standard Comtrade1999 format;

[0065] 3) Obtain the triggered recording waveform A of the device under test and the triggered recording waveform B of the oscillograph. And the device comparison waveform D and the oscillograph comparison waveform E.

[0066] 4) Obtain and calculate the relevant data required for the comparison of waveforms A and B from the waveform files;

[0067] Number of samples per cycle:

[0068] A.N = Sampling frequency of waveform A / Standard frequency (50Hz);

[0069] B.N = Sampling frequency of waveform B / Standard frequency (50Hz);

[0070] Number of waveform points:

[0071] A.P and B.P;

[0072] 5) Calculate the rated value of waveform A

[0073] A.R = Take the third largest value from the maximum peak values of each cycle of waveform A /

[0074] Taking the third largest value is to filter out possible mutant peaks.

[0075] 6) Solve the problem of inconsistent sampling frequencies of waveforms A and B by the linear interpolation method. Thus generating the substring waveform C.

[0076] Number of points of waveform C: C.P = A.P * B.N / A.N;

[0077] Linear coefficient: R = (C.i * A.N / B.N) - math.floor(C.i * A.N / B.N);

[0078] C.Y = A[C.i].Y * (1 - R) + A[C.i + 1].Y * R;

[0079] C.T = A[C.i].T * (1 - R) + A[C.i + 1].T * R;

[0080] 7) Use the substring comparison method to find the overlapping part and similarity of the two waveforms. Take the C waveform as the substring waveform, starting from the first point of the B waveform, take the number of points of the C waveform and compare it point by point with the C waveform to calculate the error value.

[0081] The error value Error =

[0082] Then compare by shifting one point to the left at the starting position and continue the comparison. Compare cyclically in this way and record the Error value and the start time TStart and end time TEnd of the similar waveform each time.

[0083] 8) Take the start time and end time corresponding to the minimum value of Error;

[0084] TStart’ = TStart[Min(Error)];

[0085] TEnd’ = TEnd[Min(Error)];

[0086] 9) Perform the operations from the fourth step to the sixth step on the D waveform and the E waveform to generate the substring waveform F; Take the waveform between the time intervals TStart’ to TEnd’ of the E waveform as G.

[0087] 10) Directly compare the F waveform and the G waveform to calculate the error value Error’ and calculate the similarity.

[0088] Among them, Error’ =

[0089] The similarity S = (1 - Error’ / D.R / D.P) * 100%. Embodiment 2

[0090] As Figure 8 shown, the present invention also discloses a test system that can more accurately compare waveforms, including a host computer PC, a standard clock instrument, a waveform recorder, and a relay protection instrument; One port of the host computer PC is connected to the standard clock instrument through Ethernet, and the other port is connected to a switch and a serial server to communicate and interact with devices such as the waveform recorder, the relay protection instrument, and the device under test.

[0091] The waveform recorder is in the same circuit as the device under test and is used to synchronously collect the real-time waveforms on the circuit under test.

[0092] The relay protection instrument is used to transmit analog quantities by playing back waveforms or setting status sequences.

[0093] The described standard clock instrument is used for time synchronization with the upper computer PC, oscillograph, and relay protection instrument through SNTP and two-way B code respectively. Among them, the time of the measured terminal is synchronized by the PC through the protocol / SNTP method to ensure that the times of the PC, oscillograph, standard clock instrument, and measured terminal in the test system are consistent.

[0094] The above are only the preferred embodiments of the present invention, and thus do not limit the patent protection scope of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention, directly or indirectly applied in other related technical fields, shall be equally included in the protection scope of the present invention.

Claims

1. A waveform comparison method for waveform detection of power equipment, characterized in that: The following steps are involved: 1) Obtain the waveform file FD recorded by the device under test and the waveform file FR recorded by the oscilloscope; 2) Refer to the standard waveform format and parse FD and FR files; 3) Obtain the waveform A triggered by the device under test, the waveform B triggered by the recorder, the waveform D for device comparison, and the waveform E for recording comparison; 4) Obtain and calculate the relevant data required for the comparison of waveforms A and B from the waveform file; specifically, the number of sampling points per cycle, which is: AN = A waveform sampling frequency / standard frequency (50Hz); BN = B waveform sampling frequency / standard frequency (50Hz); 5) Calculate the rated value of waveform A, AR = the third largest value of the maximum peak value of each cycle of waveform A / ; 6) Through linear interpolation, the sampling frequencies of waveforms A and B are made consistent, thereby generating substring waveform C; C waveform points: CP = AP * BN / AN; Linear coefficient: R = (Ci*AN / BN) - math.floor(Ci *AN / BN); CY = A[Ci].Y * (1-R) ​​+ A[Ci + 1].Y * R; CT = A[Ci].T * (1-R) ​​+ A[Ci + 1].T* R; 7) Use the substring comparison method to find the overlap and similarity of the two waveforms; the specific error value calculation formula is as follows: Error valueError = ; Take the C waveform as the substring waveform, start from the first point of the B waveform and compare the C waveform point by point to calculate the error value; then move the comparison start position one point to the left and continue the comparison; repeat the comparison in this way and record the Error value and the start time TStart and end time TEnd of the similar waveform each time; 8) Take the start time and end time corresponding to the minimum Error value; the formula for taking the start time and end time corresponding to the minimum Error value is as follows: TStart' = TStart[Min(Error)]; TEnd' = TEnd[Min(Error)]; 9) Repeat steps 4 to 6 for waveforms D and E to generate substring waveform F; 10) The F waveform and the G waveform are directly compared to calculate the error value Error' and the similarity. The specific error value calculation formula is as follows: Error’ = ; Similarity S = (1-Error' / DR / DP) * 100%.

2. A waveform comparison method for waveform detection of power equipment according to claim 1, characterized in that: The waveform between the time interval TStart' and TEnd' of the E waveform taken out in step 9) is G.

3. A test system capable of more accurately comparing waveforms, characterized in that: The waveform comparison method for waveform detection of power equipment as described in any one of claims 1 to 2 above comprises: a host computer PC, a standard clock, a recorder and a relay protection instrument; one port of the host computer PC is connected to the standard clock instrument via Ethernet, and the other port is connected to a switch and a serial port server to communicate and interact with the recorder, the relay protection instrument, the terminal under test and other equipment; The waveform recorder is in the same circuit as the terminal under test and is used to synchronously collect the real-time waveform on the circuit under test; The relay protection instrument is used to transmit analog quantity by playing back waveforms or setting state sequences; The standard clock instrument is used to synchronize the time with the host computer PC, the recorder, and the relay through SNTP and two B codes, wherein the time of the terminal under test is synchronized by the PC through the protocol / SNTP method to ensure that the time of the PC, the recorder, the standard clock instrument, and the terminal under test in the test system is consistent.

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