Ring main unit partial discharge monitoring method and device

Abstract

The invention relates to the field of ring main unit monitoring technology. In order to solve the technical problem of how to effectively remove interference in a ring main unit partial discharge monitoring scheme using a UHF method, a ring main unit partial discharge monitoring method and device are provided. The method comprises the following steps: acquiring an electromagnetic wave signal collected from a ring main unit and filtering to obtain a partial discharge signal to be processed; decomposing the partial discharge signal to be processed into N sub-signals through empirical mode decomposition; arranging the N sub-signals into a first queue in order from low to high frequency; obtaining a suspected interference signal of the i-th sub-signal through calculation; selecting an interference reference signal; obtaining a plurality of filtering intervals; obtaining a sliding window size of the partial discharge signal to be processed in each filtering interval according to the plurality of filtering intervals; in each filtering interval, sliding filtering the partial discharge signal to be processed with a corresponding sliding window size to obtain a filtered partial discharge signal; and analyzing and judging the partial discharge situation of the ring main unit according to the filtered partial discharge signal.

Description

Technical Field

[0001] The present invention relates to the technical field of ring main unit monitoring, and in particular to a ring main unit partial discharge monitoring method and a ring main unit partial discharge monitoring device. Background Art

[0002] In recent years, the construction of smart grids has received high attention and has made great progress. The intelligence and informatization of power transmission and transformation systems have developed to a certain level. The ring main unit (or distribution transformer) is located at the end of the distribution network and is used to convert the 10kV high voltage electricity transmitted by the substation into 0.4kV lighting and power electricity for residents. Therefore, the importance of ensuring its effective operation is self-evident.

[0003] Partial discharge (PD) is one of the main factors causing ring main unit failures, so determining whether PD occurs in a ring main unit is an important part of the operation and maintenance of the ring main unit. Given the large number of ring main units, the inefficiency of manual inspections and the difficulty of supervision, real-time online monitoring technology for PD in ring main units is gradually becoming popular.

[0004] The partial discharge monitoring of ring main unit depends on effective partial discharge detection and analysis methods. At present, the commonly used partial discharge detection methods mainly include pulse current method, ultrasonic method, ultra-high frequency method and transient voltage to ground method, among which the ultra-high frequency method is relatively widely used. However, a major problem faced by the ultra-high frequency method is the interference of other electromagnetic waves on the detection signal, which can easily cause misjudgment or omission of partial discharge. Therefore, how to effectively remove interference is an important problem to be solved in the partial discharge monitoring scheme of ring main unit using the ultra-high frequency method. Summary of the invention

[0005] In order to solve the above technical problems, the inventors of the present invention focus on the filtering of interference signals accompanying partial discharge signals in the ultra-high frequency method. The inventors of the present invention found in the research process that the filtering of partial discharge signals currently has a good effect on filtering interference signals outside the frequency band of the target partial discharge signal, but the effect of filtering interference signals in the same frequency band as the target partial discharge signal is poor. The use of a sliding filter has a good filtering effect on high-frequency interference, but in view of the fact that the target partial discharge signal belongs to an ultra-high frequency signal, that is, it is at the same high frequency as the interference signal to be filtered out, if it can be filtered through a relatively accurate sliding window size, the filtering effect of the interference signal in the same frequency band as the target partial discharge signal can be significantly improved. In view of this, it is the main purpose of the present invention to apply a sliding filter to the filtering of partial discharge signals and determine the accurate sliding window size.

[0006] To this end, the present invention provides a method and device for monitoring partial discharge of a ring main unit, which can significantly improve the interference filtering effect of partial discharge signals, thereby achieving effective monitoring of partial discharge conditions of the ring main unit.

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

[0008] A method for monitoring partial discharge of a ring main unit comprises the following steps: obtaining an electromagnetic wave signal collected from a ring main unit; performing frequency filtering on the electromagnetic wave signal to obtain a partial discharge signal to be processed; decomposing the partial discharge signal to be processed into N sub-signals by empirical mode decomposition, wherein N is an integer greater than 1;

[0009] Arrange N sub-signals into a first queue in order of frequency from low to high; calculate the difference between the partial discharge signal to be processed and the first to N-1th sub-signals in the first queue in sequence to obtain a second queue consisting of N-1 difference signals, and use the sum of the first to i-th difference signals in the second queue as the suspected interference signal of the i-th sub-signal, where i is an integer and 1≤i≤N-1; calculate the integral of the square of the difference between the first to N-1th sub-signals in the first queue and their suspected interference signals, respectively, to obtain the interference amount evaluation value of the first to N-1th sub-signals in the first queue; select the interference The sub-signal with the smallest disturbance evaluation value is used as the interference reference signal; all minimum value points of the suspected interference signal of the interference reference signal are obtained, and the time interval between every two adjacent minimum value points is used as a filtering interval to obtain multiple filtering intervals; according to the multiple filtering intervals, the sliding window size of the partial discharge signal to be processed in each filtering interval is obtained; in each filtering interval, the partial discharge signal to be processed is sliding filtered with the corresponding sliding window size to obtain the filtered partial discharge signal; according to the filtered partial discharge signal, the partial discharge situation of the ring network cabinet is analyzed and judged.

[0010] According to the plurality of filtering intervals, the sliding window size of the partial discharge signal to be processed in each filtering interval is obtained, specifically comprising: calculating the difference between each maximum value of the partial discharge signal to be processed and the minimum value before the maximum value to obtain a fluctuation range value, and combining the fluctuation range values ​​in each filtering interval to form a fluctuation range set corresponding to the filtering interval; obtaining the derivative function of the upper envelope and the derivative function of the lower envelope of the partial discharge signal to be processed; calculating the derivative of the upper envelope and the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed according to the derivative function of the upper envelope and the derivative of the lower envelope of the partial discharge signal to be processed; calculating the ratio of the derivative of the upper envelope to the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed, and calculating the interference possibility parameter according to the ratio, and combining the interference possibility parameters in each filtering interval to form an interference possibility set corresponding to the filtering interval; calculating the correlation coefficient between the fluctuation range set and the interference possibility set corresponding to each filtering interval; multiplying the absolute value of each filtering interval and its correlation coefficient to obtain the sliding window size in the filtering interval.

[0011] The electromagnetic wave signal is band-pass filtered to obtain a partial discharge signal to be processed with a frequency range of 300 MHz to 1500 MHz.

[0012] The electromagnetic wave signal is subjected to high-pass filtering to obtain a partial discharge signal to be processed with a frequency above 300 MHz.

[0013] The electromagnetic wave signal is collected by an electromagnetic wave receiver arranged in the ring main unit, and the electromagnetic wave signal is transmitted to an external computer through a DTU (Distribution Terminal Unit) in the ring main unit, and the computer executes the ring main unit partial discharge monitoring method.

[0014] A ring main unit partial discharge monitoring device, comprising: a first acquisition module, used to acquire an electromagnetic wave signal collected from a ring main unit; a first filtering module, used to perform frequency filtering on the electromagnetic wave signal to obtain a partial discharge signal to be processed; a decomposition module, used to decompose the partial discharge signal to be processed into N sub-signals by empirical mode decomposition, wherein N is an integer greater than 1; an arrangement module, used to arrange the N sub-signals into a first queue in order of frequency from low to high; a first calculation module, used to sequentially calculate the difference between the partial discharge signal to be processed and the first to N-1th sub-signals in the first queue, to obtain a second queue consisting of N-1 difference signals, and to use the sum of the first to i-th difference signals in the second queue as the suspected interference signal of the i-th sub-signal, wherein i is an integer and 1≤i≤N-1; a second calculation module, used to respectively calculate the difference between the first to N-1th sub-signals in the first queue, wherein ... 1 sub-signal and its suspected interference signal, to obtain the interference evaluation value of the first to N-1th sub-signals in the first queue; a selection module, used to select the sub-signal with the smallest interference evaluation value as the interference reference signal; a second acquisition module, used to obtain all minimum points of the suspected interference signal of the interference reference signal, and take the time interval between every two adjacent minimum points as a filtering interval to obtain multiple filtering intervals; a third acquisition module, used to obtain the sliding window size of the to-be-processed partial discharge signal in each of the filtering intervals according to the multiple filtering intervals; a second filtering module, used to perform sliding filtering on the to-be-processed partial discharge signal with the corresponding sliding window size in each of the filtering intervals to obtain a filtered partial discharge signal; an analysis module, used to analyze and judge the partial discharge situation of the ring network cabinet according to the filtered partial discharge signal.

[0015] The third acquisition module is specifically used for: calculating the difference between each maximum value of the partial discharge signal to be processed and the minimum value before the maximum value to obtain the fluctuation range value, and combining the fluctuation range values ​​in each of the filtering intervals to form a fluctuation range set corresponding to the filtering interval; obtaining the derivative function of the upper envelope and the derivative function of the lower envelope of the partial discharge signal to be processed; calculating the derivative of the upper envelope and the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed according to the derivative function of the upper envelope and the derivative of the lower envelope of the partial discharge signal to be processed; calculating the ratio of the derivative of the upper envelope to the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed, and calculating the interference possibility parameter according to the ratio, and combining the interference possibility parameters in each of the filtering intervals to form an interference possibility set corresponding to the filtering interval; calculating the correlation coefficient between the fluctuation range set corresponding to each of the filtering intervals and the interference possibility set; multiplying the absolute value of each of the filtering intervals and its correlation coefficient to obtain the sliding window size in the filtering interval.

[0016] The first filtering module performs bandpass filtering on the electromagnetic wave signal to obtain a partial discharge signal to be processed with a frequency range of 300MHz~1500MHz.

[0017] The first filtering module performs high-pass filtering on the electromagnetic wave signal to obtain a partial discharge signal to be processed with a frequency above 300 MHz.

[0018] The electromagnetic wave signal is collected by an electromagnetic wave receiver arranged in the ring main unit, and the electromagnetic wave signal is transmitted to an external computer through a DTU in the ring main unit. The computer includes the partial discharge monitoring device of the ring main unit.

[0019] Beneficial effects of the present invention:

[0020] After the present invention performs frequency filtering on the electromagnetic wave signal in the ring main unit to obtain the partial discharge signal to be processed, the signal is decomposed, sorted, subtracted, and integrated with the square of the difference, and the filtering interval is determined and the corresponding sliding window size is obtained, and the partial discharge signal to be processed is subjected to sliding filtering with the corresponding sliding window size in each filtering interval. Thus, the corresponding appropriate and accurate sliding window size can be determined in sections to perform sliding filtering on the partial discharge signal to be processed, which can significantly improve the interference filtering effect of the partial discharge signal, thereby realizing effective monitoring of the partial discharge situation of the ring main unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flow chart of a method for monitoring partial discharge of a ring main unit according to an embodiment of the present invention;

[0022] Figure 2It is a block diagram of a partial discharge monitoring device for a ring main unit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] like Figure 1 As shown, the ring main unit partial discharge monitoring method according to the embodiment of the present invention includes the following steps S1 to S11.

[0025] S1, obtaining electromagnetic wave signals collected from the ring main unit.

[0026] In one embodiment of the present invention, electromagnetic wave signals can be collected by an electromagnetic wave receiver disposed in the ring main unit, and the electromagnetic wave signals can be transmitted to an external computer through the DTU in the ring main unit, and the computer can execute the ring main unit partial discharge monitoring method of the embodiment of the present invention. In other embodiments of the present invention, when the DTU has redundant and sufficient computing power, or when the computing power of the DTU is generally strong in the future, the ring main unit partial discharge monitoring method of the embodiment of the present invention can also be executed by the DTU, and the partial discharge analysis and judgment results of the ring main unit in which it is located can be transmitted to an external monitoring center.

[0027] The electromagnetic wave signals here generally include target signals and interference signals, wherein the target signal is an ultra-high frequency signal generated purely by partial discharge, while the interference signal comes from other electromagnetic waves in the environment, such as communication electromagnetic waves, and electromagnetic waves generated by other factors other than partial discharge (such as the on and off of switches) in the components of the ring network cabinet.

[0028] S2, frequency filtering the electromagnetic wave signal to obtain a partial discharge signal to be processed.

[0029] In one embodiment of the present invention, the electromagnetic wave signal is frequency filtered to mainly filter out electromagnetic waves of different frequency bands from the target signal. Alternatively, electromagnetic waves with a frequency lower than the lowest frequency of the target signal are filtered out, while electromagnetic waves with a frequency higher than the highest frequency of the target signal can be filtered out by subsequent sliding filtering.

[0030] Therefore, the electromagnetic wave signal can be band-pass filtered to obtain a PD signal to be processed with a frequency range of 300MHz to 1500MHz, which mainly includes the target signal and its interference signal in the same frequency band. Alternatively, the electromagnetic wave signal can be high-pass filtered to obtain a PD signal to be processed with a frequency above 300MHz, which mainly includes the target signal and its interference signal in the same frequency band, and interference signals with a frequency higher than the highest frequency of its frequency band.

[0031] It should also be noted that the signals processed in the embodiments of the present invention are all in the form of time domain signals.

[0032] S3, decomposing the partial discharge signal to be processed into N sub-signals through empirical mode decomposition, where N is an integer greater than 1.

[0033] The sub-signal here is IMF (Intrinsic Mode Function). Empirical mode decomposition is a prior art and will not be described in detail here.

[0034] S4, arranging the N sub-signals into a first queue in order of frequency from low to high.

[0035] In a specific embodiment of the present invention, the partial discharge signal to be processed is represented by X(t), and the sub-signals are represented by x1(t), x2(t), ..., x1(t) in descending order of frequency. N (t) indicates.

[0036] S5, sequentially calculate the difference between the partial discharge signal to be processed and the first to N-1th sub-signals in the first queue, obtain a second queue consisting of N-1 difference signals, and use the sum of the first to i-th difference signals in the second queue as the suspected interference signal of the i-th sub-signal, where i is an integer and 1≤i≤N-1.

[0037] The i-th difference signal d in the second queue i (t) is expressed by the following formula:

[0038] d i (t)=X(t)-x i (t)

[0039] It should be understood that higher frequencies mean more jumps, that is, the lower the frequency of the sub-signal, the less interference, and the higher the frequency of the sub-signal, the more interference. After the sub-signals are sorted by frequency, the interference can be gradually revealed by subtracting the sub-signals from the partial discharge signal to be processed in sequence. It should be noted that since the sub-signal with the highest frequency is most similar to the partial discharge signal to be processed, the difference between the two cannot play a role in revealing the interference. Therefore, the sub-signal with the highest frequency is not considered in this step.

[0040] The suspected interference signal ns of the i-th sub-signal i (t) is expressed by the following formula:

[0041]

[0042] S6, respectively calculating the integral of the square of the difference between the first to N-1th sub-signals in the first queue and their suspected interference signals, to obtain the interference amount evaluation values ​​of the first to N-1th sub-signals in the first queue.

[0043] The interference evaluation value eva of the i-th sub-signal in the first queue i The following formula represents:

[0044]

[0045] S7, selecting the sub-signal with the smallest interference evaluation value as the interference reference signal.

[0046] The integral of the square of the difference between the two functions can represent the degree of deviation of the two functions. Therefore, the smaller the interference evaluation value of the sub-signal is, the more similar the sub-signal is to its suspected interference signal, and the more likely the sub-signal is to be the sub-signal with the most interference. Therefore, the embodiment of the present invention selects the sub-signal as the interference reference signal.

[0047] S8, acquiring all minimum value points of the suspected interference signal of the interference reference signal, and taking the time interval between every two adjacent minimum value points as a filtering interval, to obtain a plurality of filtering intervals.

[0048] S9, according to the multiple filtering intervals, obtaining the sliding window size of the partial discharge signal to be processed in each filtering interval.

[0049] In one embodiment of the present invention, step S9 specifically includes steps S91 to S96.

[0050] S91, calculating the difference between each maximum value of the partial discharge signal to be processed and the minimum value before the maximum value to obtain a fluctuation range value, and combining the fluctuation range values ​​in each filtering interval together to form a fluctuation range set corresponding to the filtering interval.

[0051] Here, the "before" of "the minimum value before the maximum value" refers to the time before. In a plane coordinate system with time as the horizontal axis and the right as the positive direction, it refers to the first minimum value to the left of the maximum value.

[0052] S92, obtaining a derivative function of an upper envelope and a derivative function of a lower envelope of the partial discharge signal to be processed.

[0053] S93, calculating the derivative of the upper envelope and the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed according to the derivative function of the upper envelope and the derivative function of the lower envelope of the partial discharge signal to be processed.

[0054] S94, finding the ratio of the derivative of the upper envelope corresponding to each maximum moment of the partial discharge signal to be processed to the derivative of the lower envelope, and calculating the interference possibility parameter according to the ratio, and combining the interference possibility parameters in each filtering interval to form an interference possibility set corresponding to the filtering interval.

[0055] The interference probability parameter p is calculated according to the following formula:

[0056]

[0057] Among them, D up and D down They are respectively the derivative of the upper envelope and the derivative of the lower envelope corresponding to a certain maximum moment of the partial discharge signal to be processed.

[0058] S94, calculating the correlation coefficient between the fluctuation range set and the interference possibility set corresponding to each filtering interval.

[0059] The correlation coefficient ρ is calculated according to the following formula:

[0060]

[0061] Among them, Cov(r,p) represents the covariance of the fluctuation range set and the interference possibility set corresponding to a certain filtering interval, σ r Represents the standard deviation of the fluctuation range set corresponding to the filter interval, σ p Represents the standard deviation of the interference possibility set corresponding to the filtering interval.

[0062] S96, multiplying the absolute value of each filtering interval and its correlation coefficient to obtain the sliding window size within the filtering interval.

[0063] S10, in each filtering interval, performing sliding filtering on the partial discharge signal to be processed with a corresponding sliding window size to obtain a filtered partial discharge signal.

[0064] The filtered partial discharge signal is the desired target signal.

[0065] S11, analyzing and judging the partial discharge situation of the ring main unit according to the filtered partial discharge signal.

[0066] According to the partial discharge monitoring method for a ring main unit of an embodiment of the present invention, after frequency filtering is performed on the electromagnetic wave signal in the ring main unit to obtain the partial discharge signal to be processed, operations such as signal decomposition, sorting, difference, and integration of the square of the difference are performed, and the filtering interval is determined and the corresponding sliding window size is obtained, and sliding filtering is performed on the partial discharge signal to be processed with the corresponding sliding window size in each filtering interval. Thus, the corresponding appropriate and accurate sliding window size can be determined in segments to perform sliding filtering on the partial discharge signal to be processed, which can significantly improve the interference filtering effect of the partial discharge signal, thereby realizing effective monitoring of the partial discharge situation of the ring main unit.

[0067] Corresponding to the partial discharge monitoring method of a ring main unit in the above embodiment, the present invention further proposes a partial discharge monitoring device for a ring main unit.

[0068] like Figure 2 As shown, the partial discharge monitoring device of the ring main unit according to the embodiment of the present invention includes a first acquisition module 1, a first filtering module 2, a decomposition module 3, an arrangement module 4, a first calculation module 5, a second calculation module 6, a selection module 7, a second acquisition module 8, a third acquisition module 9, a second filtering module 10 and an analysis module 11. Among them, the first acquisition module 1 is used to obtain the electromagnetic wave signal collected from the ring network cabinet; the first filtering module 2 is used to perform frequency filtering on the electromagnetic wave signal to obtain the partial discharge signal to be processed; the decomposition module 3 is used to decompose the partial discharge signal to be processed into N sub-signals through empirical mode decomposition, wherein N is an integer greater than 1; the arrangement module 4 is used to arrange the N sub-signals into a first queue in order from low to high frequency; the first calculation module 5 is used to sequentially calculate the difference between the partial discharge signal to be processed and the first to N-1th sub-signals in the first queue to obtain a second queue consisting of N-1 difference signals, and use the sum of the first to i-th difference signals in the second queue as the suspected interference signal of the i-th sub-signal, wherein i is an integer and 1≤i≤N-1; the second calculation module 6 is used to respectively calculate the first to N-1th sub-signals in the first queue. The square of the difference between the signal and the suspected interference signal is integrated to obtain the interference evaluation value of the first to N-1th sub-signals in the first queue; the selection module 7 is used to select the sub-signal with the smallest interference evaluation value as the interference reference signal; the second acquisition module 8 is used to obtain all the minimum points of the suspected interference signal of the interference reference signal, and take the time interval between every two adjacent minimum points as a filtering interval to obtain multiple filtering intervals; the third acquisition module 9 is used to obtain the sliding window size of the partial discharge signal to be processed in each filtering interval according to the multiple filtering intervals; the second filtering module 10 is used to perform sliding filtering on the partial discharge signal to be processed with the corresponding sliding window size in each filtering interval to obtain the filtered partial discharge signal; the analysis module 11 is used to analyze and judge the partial discharge situation of the ring network cabinet according to the filtered partial discharge signal.

[0069] In one embodiment of the present invention, electromagnetic wave signals can be collected by an electromagnetic wave receiver arranged in the ring main unit, and the electromagnetic wave signals can be transmitted to an external computer through the DTU in the ring main unit, and the computer includes a partial discharge monitoring device for the ring main unit. In other embodiments of the present invention, when the DTU has redundant and sufficient computing power, or when the computing power of the DTU is generally strong in the future, the partial discharge monitoring device for the ring main unit can also be arranged in the DTU, and the DTU can transmit the partial discharge analysis and judgment results of the ring main unit in which it is located to an external monitoring center.

[0070] The electromagnetic wave signal acquired by the first acquisition module 1 generally includes a target signal and an interference signal, wherein the target signal is an ultra-high frequency signal generated solely by partial discharge, while the interference signal comes from other electromagnetic waves in the environment, such as communication electromagnetic waves, and electromagnetic waves generated by other factors other than partial discharge (such as the on and off of switches) in the components of the ring network cabinet.

[0071] In one embodiment of the present invention, the first filtering module 2 performs frequency filtering on the electromagnetic wave signal, mainly filtering out electromagnetic waves of different frequency bands from the target signal. Alternatively, electromagnetic waves with a frequency lower than the lowest frequency of the target signal are filtered out, while electromagnetic waves with a frequency higher than the highest frequency of the target signal can be filtered out by subsequent sliding filtering.

[0072] Therefore, the first filtering module 2 can perform bandpass filtering on the electromagnetic wave signal to obtain a to-be-processed partial discharge signal with a frequency range of 300MHz to 1500MHz, and the to-be-processed partial discharge signal mainly includes the target signal and its interference signal in the same frequency band. Alternatively, the first filtering module 2 can perform high-pass filtering on the electromagnetic wave signal to obtain a to-be-processed partial discharge signal with a frequency above 300MHz, and the to-be-processed partial discharge signal mainly includes the target signal and its interference signal in the same frequency band, and interference signals with a frequency higher than the highest frequency of the frequency band.

[0073] It should also be noted that the signals processed in the embodiments of the present invention are all in the form of time domain signals.

[0074] The sub-signal decomposed by the decomposition module 3 is an IMF (Intrinsic Mode Function). Empirical mode decomposition is a prior art and will not be described in detail here.

[0075] In a specific embodiment of the present invention, the partial discharge signal to be processed is represented by X(t), and the sub-signals are represented by x1(t), x2(t), ..., x1(t) in descending order of frequency. N (t) indicates.

[0076] The i-th difference signal d in the second queue i (t) is expressed by the following formula:

[0077] d i (t)=X(t)-xi (t)

[0078] It should be understood that a higher frequency means more jumps, that is, the lower the frequency of the sub-signal, the less interference, and the higher the frequency of the sub-signal, the more interference. After the sub-signals are sorted by frequency, the interference can be gradually revealed by subtracting the sub-signals from the partial discharge signal to be processed in sequence. It should be noted that since the sub-signal with the highest frequency is most similar to the partial discharge signal to be processed, the difference between the two cannot play a role in revealing the interference. Therefore, the relevant calculation of the first calculation module 5 does not consider the sub-signal with the highest frequency.

[0079] The suspected interference signal ns of the i-th sub-signal i (t) is expressed by the following formula:

[0080]

[0081] The interference evaluation value eva of the i-th sub-signal in the first queue i The following formula represents:

[0082]

[0083] The integral of the square of the difference between the two functions can represent the degree of deviation of the two functions. Therefore, the smaller the interference evaluation value of the sub-signal is, the more similar the sub-signal is to its suspected interference signal, and the more likely the sub-signal is to be the sub-signal with the most interference. Therefore, the embodiment of the present invention selects the sub-signal as the interference reference signal.

[0084] In one embodiment of the present invention, the third acquisition module 9 is specifically used to: calculate the difference between each maximum value of the partial discharge signal to be processed and the minimum value before the maximum value to obtain the fluctuation range value, and combine the fluctuation range values ​​in each filtering interval to form a fluctuation range set corresponding to the filtering interval; obtain the derivative function of the upper envelope and the derivative function of the lower envelope of the partial discharge signal to be processed; according to the derivative function of the upper envelope and the derivative function of the lower envelope of the partial discharge signal to be processed, calculate the derivative of the upper envelope and the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed; calculate the ratio of the derivative of the upper envelope to the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed, and calculate the interference possibility parameter according to the ratio, and combine the interference possibility parameters in each filtering interval to form an interference possibility set corresponding to the filtering interval; calculate the correlation coefficient between the fluctuation range set corresponding to each filtering interval and the interference possibility set; multiply the absolute value of each filtering interval and its correlation coefficient to obtain the sliding window size in the filtering interval.

[0085] Here, the "before" of "the minimum value before the maximum value" refers to the time before. In a plane coordinate system with time as the horizontal axis and the right as the positive direction, it refers to the first minimum value to the left of the maximum value.

[0086] The interference probability parameter p is calculated according to the following formula:

[0087]

[0088] Among them, D up and D down They are respectively the derivative of the upper envelope and the derivative of the lower envelope corresponding to a certain maximum moment of the partial discharge signal to be processed.

[0089] The correlation coefficient ρ is calculated according to the following formula:

[0090]

[0091] Among them, Cov(r,p) represents the covariance of the fluctuation range set and the interference possibility set corresponding to a certain filtering interval, σ r Represents the standard deviation of the fluctuation range set corresponding to the filter interval, σ p Represents the standard deviation of the interference possibility set corresponding to the filtering interval.

[0092] The filtered partial discharge signal is the desired target signal.

[0093] According to the partial discharge monitoring device of the ring main unit of the embodiment of the present invention, after frequency filtering the electromagnetic wave signal in the ring main unit to obtain the partial discharge signal to be processed, through the decomposition, sorting, difference, integration of the square of the difference and other operations of the signal, and by determining the filtering interval and obtaining the corresponding sliding window size, and sliding filtering the partial discharge signal to be processed with the corresponding sliding window size in each filtering interval, it is possible to determine the corresponding appropriate and accurate sliding window size in sections to slide filter the partial discharge signal to be processed, which can significantly improve the interference filtering effect of the partial discharge signal, thereby realizing effective monitoring of the partial discharge situation of the ring main unit.

[0094] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0095] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0096] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0097] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0098] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0099] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0100] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0101] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0102] In addition, each functional unit in each embodiment of the present invention may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0103] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for monitoring partial discharge of a ring main unit, characterized in that: The following steps are involved: Obtain electromagnetic wave signals collected from the ring main unit; Performing frequency filtering on the electromagnetic wave signal to obtain a partial discharge signal to be processed; Decomposing the partial discharge signal to be processed into N sub-signals by empirical mode decomposition, wherein N is an integer greater than 1; Arrange the N sub-signals into a first queue in order of frequency from low to high; Sequentially calculating the difference between the partial discharge signal to be processed and the first to N-1th sub-signals in the first queue to obtain a second queue consisting of N-1 difference signals, and taking the sum of the first to i-th difference signals in the second queue as the suspected interference signal of the i-th sub-signal, where i is an integer and 1≤i≤N-1; Respectively calculating the integral of the square of the difference between the first to N-1th sub-signals in the first queue and their suspected interference signals to obtain interference amount evaluation values ​​of the first to N-1th sub-signals in the first queue; Selecting the sub-signal with the smallest interference evaluation value as the interference reference signal; Acquire all minimum value points of the suspected interference signal of the interference reference signal, and take the time interval between every two adjacent minimum value points as a filtering interval to obtain multiple filtering intervals; According to the plurality of filtering intervals, obtaining a sliding window size of the partial discharge signal to be processed in each filtering interval; In each filtering interval, sliding filtering is performed on the partial discharge signal to be processed with a corresponding sliding window size to obtain a filtered partial discharge signal; Analyze and judge the partial discharge situation of the ring main unit according to the filtered partial discharge signal, According to the plurality of filtering intervals, the sliding window size of the partial discharge signal to be processed in each filtering interval is obtained, specifically including: calculating the difference between each maximum value of the partial discharge signal to be processed and the minimum value before the maximum value to obtain the fluctuation range value, and combining the fluctuation range values ​​in each filtering interval together to form a fluctuation range set corresponding to the filtering interval; obtaining the derivative function of the upper envelope and the derivative function of the lower envelope of the partial discharge signal to be processed; calculating the derivative of the upper envelope and the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed according to the derivative function of the upper envelope and the derivative of the lower envelope of the partial discharge signal to be processed; calculating the ratio of the derivative of the upper envelope to the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed, and calculating the interference possibility parameter according to the ratio, and combining the interference possibility parameters in each filtering interval together to form an interference possibility set corresponding to the filtering interval; calculating the correlation coefficient between the fluctuation range set and the interference possibility set corresponding to each filtering interval; multiplying the absolute value of each filtering interval and its correlation coefficient to obtain the sliding window size in the filtering interval, The interference possibility parameter p is calculated according to the following formula: ; Among them, D up and D down are the derivative of the upper envelope and the derivative of the lower envelope corresponding to a certain maximum moment of the partial discharge signal to be processed, The correlation coefficient ρ is calculated according to the following formula: ; Among them, Cov(r,p) represents the covariance of the fluctuation range set and the interference possibility set corresponding to a certain filtering interval, σ r Represents the standard deviation of the fluctuation range set corresponding to the filter interval, σ p Represents the standard deviation of the interference possibility set corresponding to the filtering interval.

2. The method for monitoring partial discharge of a ring main unit according to claim 1, characterized in that: The electromagnetic wave signal is band-pass filtered to obtain a partial discharge signal to be processed with a frequency range of 300 MHz to 1500 MHz.

3. The method for monitoring partial discharge of a ring main unit according to claim 1, characterized in that: The electromagnetic wave signal is subjected to high-pass filtering to obtain a partial discharge signal to be processed with a frequency above 300 MHz.

4. The method for monitoring partial discharge of a ring main unit according to claim 1, characterized in that: The electromagnetic wave signal is collected by an electromagnetic wave receiver arranged in the ring main unit, and the electromagnetic wave signal is transmitted to an external computer through the DTU in the ring main unit, and the computer executes the partial discharge monitoring method of the ring main unit.

5. A ring main unit partial discharge monitoring device, characterized in that: include: The first acquisition module is used to acquire the electromagnetic wave signal collected from the ring main unit; A first filtering module, used for performing frequency filtering on the electromagnetic wave signal to obtain a partial discharge signal to be processed; A decomposition module, used for decomposing the partial discharge signal to be processed into N sub-signals through empirical mode decomposition, wherein N is an integer greater than 1; An arranging module, used for arranging the N sub-signals into a first queue in order of frequency from low to high; A first calculation module is used to sequentially calculate the difference between the partial discharge signal to be processed and the first to N-1th sub-signals in the first queue to obtain a second queue consisting of N-1 difference signals, and take the sum of the first to i-th difference signals in the second queue as the suspected interference signal of the i-th sub-signal, where i is an integer and 1≤i≤N-1; A second calculation module, used to calculate the integral of the square of the difference between the first to N-1th sub-signals in the first queue and their suspected interference signals, to obtain the interference amount evaluation value of the first to N-1th sub-signals in the first queue; A selection module is used to select a sub-signal with a minimum interference evaluation value as an interference reference signal; A second acquisition module is used to acquire all minimum value points of the suspected interference signal of the interference reference signal, and take the time interval between every two adjacent minimum value points as a filtering interval to obtain multiple filtering intervals; A third acquisition module is used to acquire the sliding window size of the partial discharge signal to be processed in each filtering interval according to the multiple filtering intervals; A second filtering module is used to perform sliding filtering on the partial discharge signal to be processed with a corresponding sliding window size in each filtering interval to obtain a filtered partial discharge signal; An analysis module is used to analyze and judge the partial discharge situation of the ring main unit according to the filtered partial discharge signal. The third acquisition module is specifically used for: calculating the difference between each maximum value of the partial discharge signal to be processed and the minimum value before the maximum value to obtain the fluctuation range value, and combining the fluctuation range values ​​in each of the filtering intervals to form a fluctuation range set corresponding to the filtering interval; obtaining the derivative function of the upper envelope and the derivative function of the lower envelope of the partial discharge signal to be processed; calculating the derivative of the upper envelope and the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed according to the derivative function of the upper envelope and the derivative of the lower envelope of the partial discharge signal to be processed; calculating the ratio of the derivative of the upper envelope to the derivative of the lower envelope corresponding to each maximum moment of the partial discharge signal to be processed, and calculating the interference possibility parameter according to the ratio, and combining the interference possibility parameters in each of the filtering intervals to form an interference possibility set corresponding to the filtering interval; calculating the correlation coefficient between the fluctuation range set corresponding to each of the filtering intervals and the interference possibility set; multiplying the absolute value of each of the filtering intervals and its correlation coefficient to obtain the sliding window size in the filtering interval, The interference possibility parameter p is calculated according to the following formula: ; Among them, D up and D down are the derivative of the upper envelope and the derivative of the lower envelope corresponding to a certain maximum moment of the partial discharge signal to be processed, The correlation coefficient ρ is calculated according to the following formula: ; Among them, Cov(r,p) represents the covariance of the fluctuation range set and the interference possibility set corresponding to a certain filtering interval, σ r Represents the standard deviation of the fluctuation range set corresponding to the filter interval, σ p Represents the standard deviation of the interference possibility set corresponding to the filtering interval.

6. The ring main unit partial discharge monitoring device according to claim 5, characterized in that: The first filtering module performs bandpass filtering on the electromagnetic wave signal to obtain a partial discharge signal to be processed with a frequency range of 300MHz~1500MHz.

7. The ring main unit partial discharge monitoring device according to claim 5, characterized in that: The first filtering module performs high-pass filtering on the electromagnetic wave signal to obtain a partial discharge signal to be processed with a frequency above 300 MHz.

8. The ring main unit partial discharge monitoring device according to claim 5, characterized in that: The electromagnetic wave signal is collected by an electromagnetic wave receiver arranged in the ring main unit, and the electromagnetic wave signal is transmitted to an external computer through a DTU in the ring main unit. The computer includes the partial discharge monitoring device of the ring main unit.

Images