CN110865286A - Discharge phase calculation method - Google Patents
Discharge phase calculation method Download PDFInfo
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- CN110865286A CN110865286A CN201911165667.6A CN201911165667A CN110865286A CN 110865286 A CN110865286 A CN 110865286A CN 201911165667 A CN201911165667 A CN 201911165667A CN 110865286 A CN110865286 A CN 110865286A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R25/00—Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
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Abstract
The invention relates to the technical field of intelligent power grids, and discloses a discharge phase calculation method, which comprises the following steps: s1: selecting the power frequency sampling rate of a monitoring terminal, and constructing a standard discrete sine sequence y (n) by a central station; s2: the central station collects and records y (N) sampling y (N) of N points in a period, and sends the y (N) sampling to the monitoring terminal; s3: acquiring and intercepting N groups of waveform data from a power frequency sequence w with the field length of m periods, and respectively beginning to intercept the waveform data w of N points in one period for the ith pointi(ii) a S4: respectively calculating the correlation between N groups of waveform data and samples y (N) of one period of standard discrete sine sequence to obtain the maximum correlation wjAnd the corresponding starting point is used as the initial phase of the power frequency sequence. The invention effectively solves the problems that in the prior art, complex trigonometric function transformation is required, the calculation cannot be completed in the monitoring terminal, and the waveform collected by the monitoring terminal is required to be uploaded to a background central station for execution.
Description
Technical Field
The invention relates to the technical field of smart power grids, in particular to a discharge phase calculation method.
Background
Discharge monitoring is a very widely used technical means for discovering and preventing insulation abnormality of power equipment in a power grid, such as the fields of cable joint partial discharge monitoring, GIS partial discharge monitoring, power line defect discharge monitoring and the like.
For the discharge monitoring technology, the phase of the discharge pulse is a very important characteristic quantity, and accurate phase characteristic extraction has important significance for interference suppression and discharge type identification. At present, the phase extraction of the discharge monitoring pulse is realized by acquiring a power frequency waveform with GPS clock information through a monitoring terminal through a power frequency sensor, generally taking a power frequency voltage sensor as a main part, uploading the power frequency waveform to a background central station, calculating a power frequency reference phase through a complex algorithm, and calculating the phase of the pulse by calculating the time difference between the wave head time of the discharge pulse waveform with GPS accurate time uploaded by the monitoring terminal and the power frequency waveform time.
At present, no in-place phase calculation method exists, the monitoring terminal collects power frequency quantity and uploads the power frequency quantity to the background central station for phase calculation, generally, the DFS algorithm, namely Fourier series, is used for phase calculation, complex trigonometric function, inverse trigonometric function and complex number calculation are needed, and the method is only suitable for servers with strong calculation capability and cannot be applied to the monitoring terminal. Under the operation mode, the monitoring terminal needs to collect and upload power frequency waveforms at regular intervals, power consumption and data communication are increased, and adverse factors are brought to long-term operation of the monitoring terminal.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a discharge phase calculation method, which effectively solves the problem that in the prior art, complex trigonometric function transformation is required, the calculation cannot be completed in a monitoring terminal, and the waveform collected by the monitoring terminal is required to be uploaded to a background central station for execution.
In order to achieve the above purposes, the technical scheme adopted by the invention is as follows:
the invention provides a discharge phase calculation method, which comprises the following steps:
s1: selecting a power frequency sampling rate of a monitoring terminal, and constructing a standard discrete sine sequence y (n) by a central station according to the power frequency sampling rate;
s2: the central station collects and records y (N) sampling points y (N) in one period from the initial phase, and sends the sampling points y (N) to the monitoring terminal for storage;
s3: the monitoring terminal collects and stores a power frequency sequence w with the field length of m periods, wherein m is more than or equal to 2, N groups of waveform data are intercepted from the power frequency sequence w, and the N groups of waveform data are waveform data w of N points in one period, which are respectively intercepted from the ith pointiWherein i ∈ [ a, a + N-1 ]]，a∈[1,(m-1)N]；
S4: the monitoring terminal respectively calculates the correlation between the N groups of waveform data and samples y (N) of one period of the standard discrete sine sequence, and uses a group of waveform data w with the maximum correlationjAnd taking the corresponding starting point as the initial phase of the power frequency sequence.
On the basis of the above technical solution, the step S1 specifically includes the following steps:
selecting power frequency sampling rate f of monitoring terminalsBefore the monitoring terminal starts the collection function of the collected pulse current, the power frequency sampling rate of the monitoring terminal is sent to a central station through a message;
the central station transmits a power frequency sampling rate f according to the monitoring terminalsA standard discrete sine sequence is constructed.
On the basis of the technical scheme, the standard discrete sine sequence is as follows:
wherein N is 1,2,3 … N, and N is 0.02fs+1。
On the basis of the technical scheme, the power frequency period is 0.02s, and the number of sampling points in one period is 0.02fs。
Based on the above technical solution, the initial phase in the step S2 is 0 rad.
On the basis of the technical proposal, the device comprises a shell,by the formula
Calculating a correlation of the N sets of waveform data with a standard discrete sine sequence of one period samples y (N),
wherein R isxFor the correlation of the x-th set of waveform data with one period sample y (N) of the standard discrete sine sequence, wx+N-1For intercepting waveform data of N points in a period from the i + N-1 point, y (N) wx+N-1Representing the arrays y (N) and wx+N-1Multiplication of two by two of the elements of (E), (y), (n) wx+N-1) Is the average value of the multiplication of the two arrays.
On the basis of the technical scheme, the absolute GPS time T of the initial point corresponding to the determined initial phase is calculated by the monitoring terminal according to the GPS clock information of the monitoring terminaljAnd the initial phase of the point and the GPS time TjAnd sending the data to a central station.
On the basis of the technical scheme, the monitoring terminal collects and stores the power frequency sequence w with the field length of three periods.
Compared with the prior art, the invention has the advantages that: according to the power frequency sampling rate of a monitoring terminal, a standard discrete sine sequence y (n) is constructed at a central station at the power frequency sampling rate; the central station collects and records y (N) sampling points y (N) in one period from the initial phase, and sends the sampling points y (N) to the monitoring terminal for storage;
the monitoring terminal collects and stores power frequency sequences w with the field length of m in the period, and intercepts N groups of waveform data from the power frequency sequences w, wherein the N groups of waveform data are waveform data w of N points in one period, which are respectively intercepted from the ith pointi(ii) a The monitoring terminal respectively calculates the correlation between the N groups of waveform data and samples y (N) of one period of the standard discrete sine sequence, and uses a group of waveform data w with the maximum correlationjAnd taking the corresponding starting point as the initial phase of the power frequency sequence. The phase calculation algorithm based on the correlation coefficient only comprises basic operation, has low requirement on operation performance, can be carried out in a monitoring terminal, can obtain a phase value without uploading a waveform, and reduces the number of stepsData communication traffic and power consumption are improved, and the operation reliability of the monitoring terminal is improved. The problem of need carry out complicated trigonometric function transform among the prior art, this kind of calculation can't be accomplished in monitoring terminal, must let monitoring terminal gather the waveform and upload to the backstage central station and just can go on is solved.
Drawings
Fig. 1 is a flowchart of a discharge phase calculation method according to an embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
Fig. 1 is a flowchart of a discharge phase calculation method in an embodiment of the present invention, and as shown in fig. 1, the discharge phase calculation method according to the present invention includes the following steps:
s1: and selecting the power frequency sampling rate of the monitoring terminal, and constructing a standard discrete sine sequence y (n) by the central station according to the power frequency sampling rate.
Preferably, the step of S1 specifically includes the steps of:
selecting power frequency sampling rate f of monitoring terminalsBefore the monitoring terminal starts the pulse current collection function, the power frequency sampling rate is sent to the central station through the message.
The central station transmits a power frequency sampling rate f according to the monitoring terminalsA standard discrete sine sequence is constructed.
In this embodiment, the power frequency period is 0.02s, and when the sampling rate is fsThe number of sampling points in one period is 0.02fs。
Preferably, the standard discrete sine sequence is:
wherein N is 1,2,3 … N, and N is 0.02fs+1。
S2: and the central station collects and records y (N) sampling points y (N) in one period from the initial phase, and sends the sampling points y (N) to the monitoring terminal for storage.
In this embodiment, the initial phase of the standard discrete sine sequence is 0, unit: and (7) rad. This allows the initial phase of the target sequence to be found in subsequent calculations.
S3: the monitoring terminal collects and stores a power frequency sequence w with the field length of m periods, wherein m is more than or equal to 2, N groups of waveform data are intercepted from the power frequency sequence w, and the N groups of waveform data are waveform data w of N points in one period, which are respectively intercepted from the ith pointiWherein i ∈ [ a, a + N-1 ]]，a∈[1,(m-1)N]。
In this embodiment, wiThe number of the data points is the same as that of one period in the standard discrete sine sequence, and the distance is the same, so that in order to ensure that all the points of the N groups of waveform data correspond to the data points of the whole standard discrete sine sequence, the length of the power frequency sequence w is at least greater than or equal to the period of the two standard discrete sine sequences, namely the initial point of the first group of data in the N groups of waveform data is the first point of the power frequency sequence w, and the last point of the last group of data is the last point of the power frequency sequence w.
In addition, a wider power frequency sequence w can be obtained, and only the last point of the last group of data in the N groups of waveform numbers is required to be in the power frequency sequence w, even if the first point of the last group of data in the N groups of waveform numbers is less than or equal to (m-1) N.
Preferably, the monitoring terminal collects and stores the power frequency sequence w with the length of three periods on site. The value of m then assumes a value of 3. At the moment, the length of the power frequency sequence is within a proper range, so that the calculation time can be saved, and the secondary checking calculation can be carried out.
S4: the monitoring terminal respectively calculates the correlation between the N groups of waveform data and samples y (N) of one period of the standard discrete sine sequence, and uses a group of waveform data w with the maximum correlationjAnd taking the corresponding starting point as the initial phase of the power frequency sequence.
In this embodiment, by continuously calculating the correlation between the waveform data in one continuous period and the samples y (n) in one period of the standard discrete sine sequence, the group most correlated with the samples y (n) is found, and the phase of the group can be determined by the phase of the samples y (n).
The phase of sampling y (N) is waveform data wjThe initial phase of sampling y (N) is 0radThen w isjIs also 0rad。
Preferably by means of a formula
Calculating a correlation of the N sets of waveform data with a standard discrete sine sequence of one period samples y (N),
wherein R isxFor the correlation of the x-th set of waveform data with one period sample y (N) of the standard discrete sine sequence, wx+N-1For intercepting waveform data of N points in a period from the i + N-1 point, y (N) wx+N-1Representing the arrays y (N) and wx+N-1Multiplication of two by two of the elements of (E), (y), (n) wx+N-1) Is the average value of the multiplication of the two arrays. E (y (N)2) The average value of the elements in the array y (N) after being squared is shown.
In this embodiment, the formula is simple to calculate, and the phase of the power frequency sequence w can be calculated, that is, the discharge monitoring of the power line is realized, the waveform data is not required to be transmitted to a background central station, a server with strong calculation capability is applied, the power consumption for transmitting data is large, and the power consumption is large, so that the communication flow and the power consumption of the monitoring terminal can be greatly reduced by adopting the method.
Preferably, according to the GPS clock information of the monitoring terminal, the monitoring terminal calculates the absolute GPS time T of the starting point corresponding to the determined initial phasejAnd the initial phase of the point and the GPS time TjAnd sending the data to a central station.
In this embodiment, after a group of waveform data most relevant to the sampling y (n) is found, the phase of the group can be determined by the phase of the sampling y (n), which is the waveform data wjThe phase of (c). Calculating absolute GPS time T of a starting point corresponding to the determined initial phase by the monitoring terminaljAbsolute GPS time T of other pointsjAnd the calculation can be carried out by the monitoring terminal.
In summary, the central station is constructed at the power frequency sampling rate according to the power frequency sampling rate of the monitoring terminalCreating a standard discrete sine sequence y (n); the central station collects and records y (N) sampling points y (N) in one period from the initial phase, and sends the sampling points y (N) to the monitoring terminal for storage; the monitoring terminal collects and stores power frequency sequences w with the field length of m in the period, and intercepts N groups of waveform data from the power frequency sequences w, wherein the N groups of waveform data are waveform data w of N points in one period, which are respectively intercepted from the ith pointi(ii) a The monitoring terminal respectively calculates the correlation between the N groups of waveform data and samples y (N) of one period of the standard discrete sine sequence, and uses a group of waveform data w with the maximum correlationjAnd taking the corresponding starting point as the initial phase of the power frequency sequence. The phase calculation algorithm based on the correlation coefficient only comprises basic operation, has low requirement on operation performance, can be carried out in the monitoring terminal, can obtain a phase value without uploading waveforms, reduces data traffic and power consumption, and is beneficial to improving the operation reliability of the monitoring terminal. The problem of need carry out complicated trigonometric function transform among the prior art, this kind of calculation can't be accomplished in monitoring terminal, must let monitoring terminal gather the waveform and upload to the backstage central station and just can go on is solved.
The present invention is not limited to the above-mentioned preferred embodiments, and any other products in various forms can be obtained by anyone with the teaching of the present invention, but any changes in the shape or structure thereof, which have the same or similar technical solutions as the present invention, are within the protection scope.
Claims (8)
1. A discharge phase calculation method, comprising the steps of:
s1: selecting a power frequency sampling rate of a monitoring terminal, and constructing a standard discrete sine sequence y (n) by a central station according to the power frequency sampling rate;
s2: the central station collects and records y (N) sampling points y (N) in one period from the initial phase, and sends the sampling points y (N) to the monitoring terminal for storage;
s3: the monitoring terminal collects and stores power frequency sequences w with the field length of m periods, wherein m is more than or equal to 2, and N groups of waveform data are intercepted from the power frequency sequences w, and the N groups of waveform data are respectively the ith waveformThe waveform data w of N points in one period is intercepted from the beginning of the pointiWherein i ∈ [ a, a + N-1 ]]，a∈[1,(m-1)N]；
S4: the monitoring terminal respectively calculates the correlation between the N groups of waveform data and samples y (N) of one period of the standard discrete sine sequence, and uses a group of waveform data w with the maximum correlationjAnd taking the corresponding starting point as the initial phase of the power frequency sequence.
2. The discharge phase calculation method according to claim 1, wherein the step of S1 specifically includes the steps of:
selecting power frequency sampling rate f of monitoring terminalsBefore the monitoring terminal starts the collection function of the collected pulse current, the power frequency sampling rate of the monitoring terminal is sent to a central station through a message;
the central station transmits a power frequency sampling rate f according to the monitoring terminalsA standard discrete sine sequence is constructed.
3. The discharge phase calculation method according to claim 2, wherein the standard discrete sine sequence is:
wherein N is 1,2,3 … N, and N is 0.02fs+1。
4. The discharge phase calculation method according to claim 1, wherein the power frequency period is 0.02s, and the number of sampling points in one period is 0.02fs。
5. The discharge phase calculation method according to claim 1, wherein the initial phase in the step of S2 is 0 rad.
6. The discharge phase calculation method according to claim 1, characterized in that: by the formula
Calculating a correlation of the N sets of waveform data with a standard discrete sine sequence of one period samples y (N),
wherein R isxFor the correlation of the x-th set of waveform data with one period sample y (N) of the standard discrete sine sequence, wx+N-1For intercepting waveform data of N points in a period from the i + N-1 point, y (N) wx+N-1Representing the arrays y (N) and wx+N-1Multiplication of two by two of the elements of (E), (y), (n) wx+N-1) Is the average value of the multiplication of the two arrays.
7. The discharge phase calculation method according to claim 1, characterized in that: according to the GPS clock information of the monitoring terminal, calculating the absolute GPS time T of the initial point corresponding to the determined initial phase by the monitoring terminaljAnd the initial phase of the point and the GPS time TjAnd sending the data to a central station.
8. The discharge phase calculation method according to claim 1, wherein the monitoring terminal collects and stores a power frequency sequence w having a field length of three periods.
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