Distribution network line active protection method based on electrical quantity and non-electrical quantity characteristics and related device

Abstract

The invention discloses a distribution network line active protection method based on electrical quantity and non-electrical quantity characteristics. The method comprises the following steps: acquiring electrical quantity and non-electrical quantity data in real time; performing electrical quantity waveform feature extraction on the collected electrical quantity data; when the electrical quantity waveform characteristics meet the early failure criterion, an electrical quantity device acts, and timing is started; performing non-electrical quantity waveform feature extraction on the non-electrical quantity data after the timing interval; and when the non-electrical quantity waveform characteristics meet the non-electrical quantity criterion, the non-electrical quantity device acts, and the line trips. According to the invention, before the permanent short-circuit grounding fault occurs, each instantaneous arc grounding fault which has occurred in the distribution network line can be diagnosed, monitored and evaluated reliably and quickly, and the line with the instantaneous arc grounding fault which has a relatively large threat is cut off in advance, so that the probability of occurrence of the short-circuit fault is reduced, and the reliability of the distribution network line is improved. And the operation safety and stability of the novel distribution network system are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of instantaneous arc grounding fault diagnosis and active protection of distribution networks, and in particular relates to an active protection method for distribution network lines based on electrical quantity and non-electrical quantity characteristics. Background Art

[0002] With the further development of new energy power grids, the penetration rate of new energy in distribution networks has continued to increase, and its fault characteristics have changed significantly. In today's new distribution networks, some new energy equipment is very sensitive to short-circuit faults, and the reaction time of traditional protection after the fault occurs is difficult to keep up, which often causes equipment damage. In this regard, arc-type instantaneous arc grounding faults are a sign before the system short circuit occurs. In the existing technology, whether it is traditional distribution network current protection or adaptive protection setting technology of new distribution networks, the line is protected after the fault develops into a permanent arc grounding fault; in the existing engineering technology, early fault diagnosis technology has not yet been applied to actively protect the line, especially in the distribution network AC line, because there is a problem of low sensitivity in arc detection, which is easy to misdetect.

[0003] However, by early identification of instantaneous arc grounding fault arcs and tripping, short-circuit faults can be effectively avoided. Therefore, it is of great significance to study the detection method of instantaneous arc grounding faults in new distribution systems. Identifying instantaneous arc grounding faults on distribution lines and taking corresponding active protection measures are important steps to adapt to the development plan of new energy power grids. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned deficiencies in the prior art, thereby providing a distribution network line active protection method and related devices based on electrical quantity and non-electrical quantity characteristics.

[0005] A distribution network line active protection method based on electrical quantity and non-electrical quantity characteristics comprises the following steps:

[0006] Real-time collection of electrical and non-electrical quantity data;

[0007] Extracting electrical quantity waveform features from the collected electrical quantity data;

[0008] When the waveform characteristics of the electrical quantity meet the early fault judgment criteria, the electrical quantity device will be activated and the timing will start;

[0009] After the timing interval, the non-electrical quantity data is subjected to non-electrical quantity waveform feature extraction;

[0010] When the waveform characteristics of non-electrical quantities meet the non-electrical quantity criteria, the non-electrical quantity devices will operate and the line will trip.

[0011] The following steps are also included:

[0012] Construct a dynamic model of arc fault when a transient arc grounding fault occurs and determine the early fault judgment criteria;

[0013] Based on the plane heat transfer theory, a line surface temperature model of the measured line is constructed when an instantaneous arc grounding fault occurs, and the non-electrical quantity judgment criterion is determined.

[0014] Construct a dynamic model of arc fault when a transient arc grounding fault occurs, and determine the early fault judgment criteria, specifically:

[0015] When a transient arc grounding fault occurs, the relationship between the instantaneous arc grounding fault arc resistance and the arc branch VCR is:

[0016]

[0017] u arc =(R g +R arc )i arc

[0018] Where g is the instantaneous conductance of the instantaneous arc ground fault arc, R arc is the instantaneous resistance of the arc; i f Represents the instantaneous current of the arc, u st represents the static arc voltage; τ is the arc time constant, u0 is the arc characteristic voltage, r0 is the arc characteristic resistance, τ, u0 and r0 are three constants that characterize the arc characteristics, which are determined by the type and characteristics of the arc itself; u arc is the instantaneous voltage of the arc branch, i arc is the instantaneous current of the arc branch, R g Set the transition resistance for the arc branch;

[0019] For a line containing an instantaneous arc grounding fault arc branch, the volt-ampere characteristics at the line port should meet the following requirements:

[0020]

[0021] i1=i arc +i R

[0022] In the formula, i arc is the current of the arc branch, i1 is the total current flowing through the measured line, i R is the current in the line that does not flow through the arc fault branch; the capacitance value of the measured line is 1 / sC, and the resistance value is R; the equivalent electromotive force behind the measured line is U s , U s Treated as an independent voltage source;

[0023] From the volt-ampere characteristics at the line port of the line containing the instantaneous arc grounding fault arc branch, it can be known that the waveforms of the voltage and current of the measured line will undergo nonlinear instantaneous mutations;

[0024] The early fault judgment criterion is: when the waveform characteristics of the electrical quantity data undergo nonlinear instantaneous mutation, it is considered that an early fault occurs.

[0025] Based on the plane heat transfer theory, a line surface temperature model of the measured line is constructed when a transient arc grounding fault occurs, and the non-electrical quantity criterion is determined, which is specifically:

[0026] According to the plane heat transfer theory, when the instantaneous arc grounding fault occurs, the line surface temperature model of the measured line is constructed as follows:

[0027] The analytical expression of the line surface temperature when a transient arc grounding fault occurs is as follows:

[0028]

[0029] In the formula, the surface heat source is located on the plane x = x', and the heating rate is q s (τ), the excess temperature distribution caused by the surface heat source on the infinite object with uniform initial temperature distribution is recorded as θ(x,τ), and the thickness of the heat source is 2x b ; α is the thermal diffusivity of the line material, also called thermal conductivity; λ is the thermal conductivity or thermal conductivity of the line material, ρ is the density of the line material, and c is the specific heat capacity of the material; τ is the duration of the instantaneous arc grounding fault arc;

[0030] For an initial temperature of T1°C, the temperature distribution function caused by continuous heating of the arc in the line is expressed as:

[0031]

[0032] The quadratic difference quotient method is used to extract the waveform characteristics of the line surface temperature when the instantaneous arc grounding fault occurs. It is found that the waveform characteristics have four obvious peaks, and the peaks are all greater than the threshold M.

[0033] The non-electrical quantity judgment criterion is: when the waveform characteristics of the non-electrical quantity have four obvious peaks, and the peaks are all greater than the threshold M, it is considered that the instantaneous arc grounding fault is relatively serious and may develop into a permanent grounding fault at any time.

[0034] The morphological gradient filtering algorithm is used to extract waveform features from the measured electrical quantity waveform;

[0035] The morphological gradient filtering algorithm is:

[0036] The morphological gradient filtering formula that can distinguish the rising and falling edge features of the sampled waveform is:

[0037]

[0038] Where M T (t) is the processed morphological gradient filtering waveform; f(t) is the sampled electrical quantity waveform signal that needs to be processed, and g(t) is the morphological structural element selected during the calculation; and are dilation and erosion operations, representing a basic morphological operation respectively. The dilation and erosion of the structure element g for the sampled signal f are:

[0039]

[0040] In this formula, f and g are both one-dimensional signals, and their domains are defined in the formula; N is the length of the data signal window, and M is the width of the structure element;

[0041] In the above morphological gradient filtering formula, the flat structure element g + and g - They are used to extract the upper and lower edges of the sampled waveform. The flat structure element refers to a special one-dimensional vector that contains only two elements, 0 and 1. + The 0 elements of g are all on the far right; - The 0 elements are all on the left;

[0042] A flat structure element g with an odd width h + and g - for:

[0043]

[0044] The morphological gradient filtering algorithm is very sensitive to waveforms with sudden changes, which is mainly reflected in the change of the number of peaks in the filtered waveform.

[0045] The quadratic difference quotient method is used to extract the waveform features of non-electrical quantity data after the timing interval.

[0046] The timing interval is 15s to 1min.

[0047] The calculation formula of the quadratic difference quotient method is:

[0048]

[0049] Where, L x It is the N-order difference quotient of the temperature T and the spatial position x on the line, P x is the absolute value waveform of the quadratic difference quotient; N is the number of sampled signals, and the spatial position takes the line port as the coordinate zero point, x k is the spatial coordinate corresponding to the kth sampling value.

[0050] An active protection device for distribution network lines based on electrical quantity and non-electrical quantity characteristics comprises the following steps:

[0051] A data acquisition module, which is used to collect electrical quantity and non-electrical quantity data in real time;

[0052] An electrical quantity waveform extraction module, the electrical quantity waveform extraction module is used to extract electrical quantity waveform features from the collected electrical quantity data;

[0053] An early fault judgment module, wherein when the waveform characteristics of the electrical quantity meet the early fault judgment criteria, the electrical quantity device is activated and timing is started;

[0054] A non-electrical quantity waveform extraction module, wherein the non-electrical quantity waveform extraction module is used to extract non-electrical quantity waveform features from non-electrical quantity data after a timing interval;

[0055] The judgment module is used for actuating the non-electrical quantity device and tripping the line when the waveform characteristics of the non-electrical quantity meet the non-electrical quantity criterion.

[0056] Active protection also includes:

[0057] A fault criterion building module, wherein the fault criterion building module is used to build an arc fault dynamic model when a transient arc grounding fault occurs, and determine an early fault criterion;

[0058] Based on the plane heat transfer theory, a line surface temperature model of the measured line is constructed when an instantaneous arc grounding fault occurs, and the non-electrical quantity judgment criterion is determined.

[0059] Fault judgment building module, specifically used for:

[0060] When a transient arc grounding fault occurs, the relationship between the instantaneous arc grounding fault arc resistance and the arc branch VCR is:

[0061]

[0062] u arc =(R g +R arc )i arc

[0063] Where g is the instantaneous conductance of the instantaneous arc ground fault arc, R arc is the instantaneous resistance of the arc; i f Represents the instantaneous current of the arc, u strepresents the static arc voltage; τ is the arc time constant, u0 is the arc characteristic voltage, r0 is the arc characteristic resistance, τ, u0 and r0 are three constants that characterize the arc characteristics, which are determined by the type and characteristics of the arc itself; u arc is the instantaneous voltage of the arc branch, i arc is the instantaneous current of the arc branch, R g Set the transition resistance for the arc branch;

[0064] For a line containing an instantaneous arc grounding fault arc branch, the volt-ampere characteristics at the line port should meet the following requirements:

[0065]

[0066] i1=i arc +i R

[0067] In the formula, i arc is the current of the arc branch, i1 is the total current flowing through the measured line, i R is the current in the line that does not flow through the arc fault branch; the capacitance value of the measured line is 1 / sC, and the resistance value is R; the equivalent electromotive force behind the measured line is U s , U s Treated as an independent voltage source;

[0068] From the volt-ampere characteristics at the line port of the line containing the instantaneous arc grounding fault arc branch, it can be known that the waveforms of the voltage and current of the measured line will undergo nonlinear instantaneous mutations;

[0069] The early fault judgment criterion is: when the waveform characteristics of the electrical quantity data undergo a nonlinear instantaneous mutation, an early fault is considered to have occurred.

[0070] Fault judgment building blocks are also used to:

[0071] According to the plane heat transfer theory, when the instantaneous arc grounding fault occurs, the line surface temperature model of the measured line is constructed as follows:

[0072] The analytical expression of the line surface temperature when a transient arc grounding fault occurs is as follows:

[0073]

[0074] In the formula, the surface heat source is located on the plane x = x', and the heating rate is q s (τ), the excess temperature distribution caused by the surface heat source on the infinite object with uniform initial temperature distribution is recorded as θ(x,τ), and the thickness of the heat source is 2x b; α is the thermal diffusivity of the line material, also called thermal conductivity; λ is the thermal conductivity or thermal conductivity of the line material, ρ is the density of the line material, and c is the specific heat capacity of the material; τ is the duration of the instantaneous arc grounding fault arc;

[0075] For an initial temperature of T1°C, the temperature distribution function caused by continuous heating of the arc in the line is expressed as:

[0076]

[0077] The quadratic difference quotient method is used to extract the waveform characteristics of the line surface temperature when the instantaneous arc grounding fault occurs. It is found that the waveform characteristics have four obvious peaks, and the peaks are all greater than the threshold M.

[0078] The non-electrical quantity judgment criterion is: when the waveform characteristics of the non-electrical quantity have four obvious peaks, and the peaks are all greater than the threshold M, it is considered that the instantaneous arc grounding fault is relatively serious and may develop into a permanent grounding fault at any time.

[0079] An electronic device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the active protection method for distribution network lines based on electrical and non-electrical quantity characteristics as described in the above scheme is implemented.

[0080] A non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the active protection method for distribution network lines based on electrical quantity and non-electrical quantity characteristics as described in the above-mentioned solution of claim 1.

[0081] Beneficial effects:

[0082] (1) Dual judgment criteria are given to the instantaneous arc grounding fault of the distribution network line. The active protection will be triggered only when both are activated, thus reducing the false operation rate of the active protection;

[0083] (2) It provides a basis for diagnosing instantaneous arc grounding faults and assessing the degree of danger. When only the electrical quantity element is in operation, it is known that an instantaneous arc occurs and extinguishes itself. When both the electrical quantity and non-electrical quantity elements are in operation, an arc that develops into a permanent grounding fault occurs and continues to develop.

[0084] (3) It is not affected by changes in distribution network line power and line operating conditions, and has high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 It is a flow chart of the active protection method of distribution network lines based on electrical quantity and non-electrical quantity characteristics of the present invention;

[0086] Figure 2A topological diagram of a typical renewable energy distribution network system and possible locations of ground faults.

[0087] Figure 3 This is a schematic diagram of the logical structure of the active protection element. DETAILED DESCRIPTION

[0088] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0089] like Figure 1 The present invention provides a distribution network line active protection method based on electrical quantity and non-electrical quantity characteristics, comprising the following steps:

[0090] Construct a dynamic model of arc fault when a transient arc grounding fault occurs, and determine the early fault judgment criteria, specifically:

[0091] The dynamic model of arc fault is:

[0092] When a transient arc grounding fault occurs in the line, the relationship between the arc resistance and the arc branch VCR is:

[0093]

[0094] u arc =(R g +R arc )i arc

[0095] Where g is the instantaneous conductance of the instantaneous arc ground fault arc, R arc is the instantaneous resistance of the arc; i f Represents the instantaneous current of the arc, u st represents the static arc voltage; τ is the arc time constant, u0 is the arc characteristic voltage, r0 is the arc characteristic resistance, τ, u0 and r0 are three constants that characterize the arc characteristics, which are determined by the type and characteristics of the arc itself; u arc is the instantaneous voltage of the arc branch, i arc is the instantaneous current of the arc branch, R g Set the transition resistance for the arc branch;

[0096] For a line containing an instantaneous arc grounding fault arc branch, the volt-ampere characteristics at the line port should meet the following requirements:

[0097]

[0098] i1=i arc +i R

[0099] In the formula, i arc is the current of the arc branch, i1 is the total current flowing through the measured line, i R is the current in the line that does not flow through the arc fault branch; the capacitance value of the measured line is 1 / sC, and the resistance value is R; the equivalent electromotive force behind the measured line is U s , U s Treated as an independent voltage source.

[0100] From the arc branch volt-ampere characteristics, it can be seen that the waveforms of the voltage and current of the measured line will undergo nonlinear instantaneous mutations;

[0101] The early fault judgment criterion is: when the waveform characteristics of the electrical quantity data undergo nonlinear instantaneous mutation, it is considered that an early fault occurs.

[0102] Based on the plane heat transfer theory, a line surface temperature model of the measured line is constructed when a transient arc grounding fault occurs, and the non-electrical quantity criterion is determined, which is specifically:

[0103] Based on the plane heat transfer theory, a line surface temperature model of the measured line is constructed when a transient arc grounding fault occurs; specifically:

[0104] The analytical expression of the line surface temperature when a transient arc grounding fault occurs is as follows:

[0105]

[0106] The analytical formula assumes that the instantaneous arc grounding fault arc continues to heat evenly during this process, and the initial temperature is 0℃ (273.15K), which can also be called the one-dimensional temperature distribution formula of the continuous surface heat source. In the formula, the surface heat source is located on the x=x' plane, and the heating rate is q s (τ), the excess temperature distribution caused by the surface heat source on the infinite object with uniform initial temperature distribution is recorded as θ(x,τ). The thickness of the heat source is 2x b ; α is the thermal diffusivity of the line material, also called thermal conductivity; λ is the thermal conductivity or thermal conductivity of the line material, ρ is the density of the line material, c is the specific heat capacity of the material; τ is the duration of the instantaneous arc grounding fault arc. For the case where the initial temperature is T1℃, that is, (273.15+T1)K, the temperature distribution function caused by the continuous heating of the arc in the line is expressed as:

[0107]

[0108] The quadratic difference quotient method is used to extract the waveform characteristics of the line surface temperature when the instantaneous arc grounding fault occurs. It is found that the waveform characteristics have four obvious peaks, and the peaks are all greater than the threshold M.

[0109] The non-electrical quantity judgment criterion is: when the waveform characteristics of the non-electrical quantity have four obvious peaks, and the peaks are all greater than the threshold M, it is considered that the instantaneous arc grounding fault is relatively serious and may develop into a permanent grounding fault at any time.

[0110] Real-time collection of electrical and non-electrical quantity data; electrical quantity data is current and voltage waveform data; electrical quantity data is collected by installing voltage and current transformers at the line entrance, and non-electrical quantity data is collected by installing temperature measuring optical fibers on the line; non-electrical quantity data is collected by temperature measuring optical fibers installed on the line.

[0111] The electrical quantity waveform features are extracted from the collected electrical quantity data; in order to capture the mutation characteristics of the electrical quantity waveform and prevent other disturbances from affecting the instantaneous arc grounding fault detection results, the morphological gradient filtering method is used to process and resolve the waveform.

[0112] The morphological gradient filtering algorithm is:

[0113] The morphological gradient filtering formula that can distinguish the rising and falling edge features of the sampled waveform is:

[0114]

[0115] Where M T (t) is the processed morphological gradient filtering waveform; f(t) is the sampled electrical quantity waveform signal that needs to be processed, and g(t) is the morphological structural element selected during the calculation; and are dilation and erosion operations, representing a basic morphological operation respectively. The dilation and erosion of the structure element g for the sampled signal f are:

[0116]

[0117] In this formula, f and g are both one-dimensional signals, and their domains are defined in the formula; N is the length of the data signal window, and M is the width of the structure element.

[0118] In the above morphological gradient filtering formula, the flat structure element g + and g - They are used to extract the upper and lower edges of the sampled waveform respectively. The flat structure element refers to a special one-dimensional vector that contains only two elements, 0 and 1. + The 0 elements of g are all on the far right; -The 0 elements are all on the left. For example, the flat structure element g with width h (h is an odd number) + and g - for:

[0119]

[0120] The morphological gradient filtering algorithm is very sensitive to waveforms with sudden changes, which is mainly reflected in the change of the number of peaks in the filtered waveform.

[0121] Whether an early fault occurs is determined based on the characteristics of the electrical quantity waveform. If an early fault occurs, the electrical quantity device is activated and timing begins. The basis for judging the occurrence of an early fault is: if the frequency of the electrical quantity waveform extracted by the morphological gradient filtering algorithm changes significantly, it is considered that an instantaneous arc grounding fault arc has occurred in the line.

[0122] After 15-1min of timing, the non-electrical quantity waveform feature extraction is performed on the non-electrical quantity data at the current moment, specifically:

[0123] The quadratic difference quotient method is used to filter the non-electrical quantity data measured after the timing interval, specifically:

[0124] The calculation formulas for the first and second difference quotients are as follows:

[0125]

[0126] Where, L x It is the N-order difference quotient of the temperature T and the spatial position x on the line, P x is the absolute value waveform of the quadratic difference quotient; N is the number of sampled signals, and the spatial position takes the line port as the coordinate zero point, x k is the spatial coordinate corresponding to the kth sampling value.

[0127] When the waveform characteristics of non-electrical quantities meet the non-electrical quantity criterion, the non-electrical quantity device operates and the line trips, specifically:

[0128] The absolute value waveform of the quadratic difference quotient P x Compared with the set threshold M, if P xIf there are four obvious peaks, and the peaks are all greater than the threshold value M, it is considered that the instantaneous arc grounding fault is serious and may develop into a permanent grounding fault at any time. At this time, the non-electrical quantity element also takes action, and issues a command to start active protection, so that the line protection can take action in advance; after the protection action, the continuous arc type instantaneous arc grounding fault is recorded once, and the electrical quantity and non-electrical quantity element states are reset. If the above requirements are not met, it is considered that the instantaneous arc grounding fault is good, the arc is only generated instantaneously, and it has been self-extinguished; at this time, the protection will not take action, and the non-electrical quantity information verification and reset electrical quantity action elements will be closed.

[0129] Figure 2 The distribution network topology diagram is built with reference to a typical high-proportion renewable energy access distribution network system. The voltage level of the distribution system is 10kV, the system neutral point is resonantly grounded, and overcompensation is adopted. The line length of each section is 3km, and there is a 4MW distributed renewable energy distribution network. The simulation step is 50μs, the sampling frequency is 1kHz, and the line spacing is 30mm. The distribution network line model is YJV22-10kV. In addition to current and voltage transformers, temperature measuring optical fibers are used to collect the surface temperature of the line. The maximum measurement distance of the temperature measuring optical fiber equipment can reach 100km, the temperature measurement accuracy is ±0.5~1.5℃, and the spatial resolution is within 1m, which can meet the temperature information collection requirements of the proposed active protection. The instantaneous arc grounding fault occurs on a selected branch in the distribution network. According to Figure 2 The transient and steady-state operation models of the distribution network are built in COMSOL and PSCAD / EMTDC based on the topological structure and the corresponding line model of the distribution network, and the temperature field model is used to verify the instantaneous arc grounding fault diagnosis and active protection action method proposed in the present invention.

[0130] In order to further verify the effectiveness of the instantaneous arc grounding fault severity assessment and active protection method proposed in the present invention, simulation verification was carried out. Table 1 shows the correct action rate of active protection obtained by multiple instantaneous arc grounding fault tests at different fault locations. It can be seen that the proposed algorithm can accurately diagnose instantaneous arc grounding faults and identify their degree of danger.

[0131] Table 1

[0132]

[0133] Figure 3The protection logic diagram of the active protection method for distribution network lines based on the characteristics of electrical and non-electrical quantities is shown in the figure. The three-phase current and voltage waveform data of the line port are placed in the real-time filtering calculation module. When the filtering algorithm detects the transient and steady-state waveform changes of the electrical quantity, the non-electrical quantity data verification is started. The temporary storage device reads the line temperature data for 20 seconds from this moment and puts it into the calculation device for non-electrical quantity data verification. When the calculation result of the non-electrical quantity waveform meets the threshold condition, it is considered that a permanent ground fault may occur, and the non-electrical quantity element issues a command to the trip coil for active protection; at the same time, the electrical quantity and non-electrical quantity element states are reset.

[0134] Another aspect of the present invention provides a distribution network line active protection device based on electrical quantity and non-electrical quantity characteristics, comprising the following steps:

[0135] A data acquisition module, which is used to collect electrical quantity and non-electrical quantity data in real time;

[0136] An electrical quantity waveform extraction module, the electrical quantity waveform extraction module is used to extract electrical quantity waveform features from the collected electrical quantity data;

[0137] An early fault judgment module, wherein when the waveform characteristics of the electrical quantity meet the early fault judgment criteria, the electrical quantity device is activated and timing is started;

[0138] A non-electrical quantity waveform extraction module, wherein the non-electrical quantity waveform extraction module is used to extract non-electrical quantity waveform features from non-electrical quantity data after a timing interval;

[0139] The judgment module is used for actuating the non-electrical quantity device and tripping the line when the waveform characteristics of the non-electrical quantity meet the non-electrical quantity criterion.

[0140] Active protection also includes:

[0141] A fault criterion building module, wherein the fault criterion building module is used to build an arc fault dynamic model when a transient arc grounding fault occurs, and determine an early fault criterion;

[0142] Based on the plane heat transfer theory, a line surface temperature model of the measured line is constructed when an instantaneous arc grounding fault occurs, and the non-electrical quantity criterion is determined.

[0143] Fault judgment building module, specifically used for:

[0144] When a transient arc grounding fault occurs, the relationship between the instantaneous arc grounding fault arc resistance and the arc branch VCR is:

[0145]

[0146] uarc =(R g +R arc )i arc

[0147] Where g is the instantaneous conductance of the instantaneous arc ground fault arc, R arc is the instantaneous resistance of the arc; i f Represents the instantaneous current of the arc, u st represents the static arc voltage; τ is the arc time constant, u0 is the arc characteristic voltage, r0 is the arc characteristic resistance, τ, u0 and r0 are three constants that characterize the arc characteristics, which are determined by the type and characteristics of the arc itself; u arc is the instantaneous voltage of the arc branch, i arc is the instantaneous current of the arc branch, R g Set the transition resistance for the arc branch;

[0148] For a line containing an instantaneous arc grounding fault arc branch, the volt-ampere characteristics at the line port should meet the following requirements:

[0149]

[0150] i1=i arc +i R

[0151] In the formula, i arc is the current of the arc branch, i1 is the total current flowing through the measured line, i R is the current in the line that does not flow through the arc fault branch; the capacitance value of the measured line is 1 / sC, and the resistance value is R; the equivalent electromotive force behind the measured line is U s , U s Treated as an independent voltage source;

[0152] From the volt-ampere characteristics at the line port of the line containing the instantaneous arc grounding fault arc branch, it can be known that the waveforms of the voltage and current of the measured line will undergo nonlinear instantaneous mutations;

[0153] The early fault judgment criterion is: when the waveform characteristics of the electrical quantity data undergo a nonlinear instantaneous mutation, an early fault is considered to have occurred.

[0154] Fault judgment building blocks are also used to:

[0155] According to the plane heat transfer theory, when the instantaneous arc grounding fault occurs, the line surface temperature model of the measured line is constructed as follows:

[0156] The analytical expression of the line surface temperature when a transient arc grounding fault occurs is as follows:

[0157]

[0158] In the formula, the surface heat source is located on the plane x = x', and the heating rate is q s (τ), the excess temperature distribution caused by the surface heat source on the infinite object with uniform initial temperature distribution is recorded as θ(x,τ), and the thickness of the heat source is 2x b ; α is the thermal diffusivity of the line material, also called thermal conductivity; λ is the thermal conductivity or thermal conductivity of the line material, ρ is the density of the line material, and c is the specific heat capacity of the material; τ is the duration of the instantaneous arc grounding fault arc;

[0159] For an initial temperature of T1°C, the temperature distribution function caused by continuous heating of the arc in the line is expressed as:

[0160]

[0161] The quadratic difference quotient method is used to extract the waveform characteristics of the line surface temperature when the instantaneous arc grounding fault occurs. It is found that the waveform characteristics have four obvious peaks, and the peaks are all greater than the threshold M.

[0162] The non-electrical quantity judgment criterion is: when the waveform characteristics of the non-electrical quantity have four obvious peaks, and the peaks are all greater than the threshold M, it is considered that the instantaneous arc grounding fault is relatively serious and may develop into a permanent grounding fault at any time.

[0163] The calculation formula of the quadratic difference quotient method is:

[0164]

[0165] Where, L x It is the N-order difference quotient of the temperature T and the spatial position x on the line, P x is the absolute value waveform of the quadratic difference quotient; N is the number of sampled signals, and the spatial position takes the line port as the coordinate zero point, x k is the spatial coordinate corresponding to the kth sampling value.

[0166] On the other hand, the present invention provides an electronic device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the processor executes the computer program, the active protection method for distribution network lines based on electrical and non-electrical quantity characteristics described in the above scheme is implemented.

[0167] On the other hand, the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the active protection method for distribution network lines based on electrical and non-electrical quantity characteristics as described in the above-mentioned solution of claim 1.

[0168] In view of the analysis basis and conditions of the present method, the method of the present invention is applied to perform partial judgment using the electrical quantities and temperature quantities of the distribution network line, which can provide accurate diagnosis of instantaneous arc grounding faults in the distribution system and active protection action instructions, thereby solving the engineering problem that the existing technology is difficult to reliably and timely detect instantaneous arc grounding faults in the distribution network and active protection.

[0169] It can be provided as a method, system, or computer program product. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0170] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0171] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0172] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A distribution network line active protection method based on electrical quantity and non-electrical quantity characteristics, characterized in that: The following steps are involved: Real-time collection of electrical and non-electrical quantity data; Extracting electrical quantity waveform features from the collected electrical quantity data; When the waveform characteristics of the electrical quantity meet the early fault judgment criteria, the electrical quantity device will be activated and the timing will start; After the timing interval, the non-electrical quantity data is subjected to non-electrical quantity waveform feature extraction; When the waveform characteristics of non-electrical quantities meet the non-electrical quantity criteria, the non-electrical quantity devices will operate and the line will trip.

2. The method for active protection of distribution network lines based on electrical quantity and non-electrical quantity characteristics according to claim 1 is characterized in that: The following steps are also included: Construct a dynamic model of arc fault when a transient arc grounding fault occurs and determine the early fault judgment criteria; Based on the plane heat transfer theory, a line surface temperature model of the measured line is constructed when an instantaneous arc grounding fault occurs, and the non-electrical quantity judgment criterion is determined.

3. The method for active protection of distribution network lines based on electrical quantity and non-electrical quantity characteristics according to claim 2 is characterized in that: Construct a dynamic model of arc fault when a transient arc grounding fault occurs, and determine the early fault judgment criteria, specifically: When a transient arc grounding fault occurs, the relationship between the instantaneous arc grounding fault arc resistance and the arc branch VCR is: u arc =(R g +R arc )i arc Where g is the instantaneous conductance of the instantaneous arc ground fault arc, R arc is the instantaneous resistance of the arc; i f Represents the instantaneous current of the arc, u st represents the static arc voltage; τ is the arc time constant, u0 is the arc characteristic voltage, r0 is the arc characteristic resistance, τ, u0 and r0 are three constants that characterize the arc characteristics, which are determined by the type and characteristics of the arc itself; u arc is the instantaneous voltage of the arc branch, i arc is the instantaneous current of the arc branch, R g Set the transition resistance for the arc branch; For a line containing an instantaneous arc grounding fault arc branch, the volt-ampere characteristics at the line port should meet the following requirements: i1=i arc +i R In the formula, i arc is the current of the arc branch, i1 is the total current flowing through the measured line, i R is the current in the line that does not flow through the arc fault branch; the capacitance value of the measured line is 1 / sC, and the resistance value is R; the equivalent electromotive force behind the measured line is U s , U s Treated as an independent voltage source; From the volt-ampere characteristics at the line port of the line containing the instantaneous arc grounding fault arc branch, it can be known that the waveforms of the voltage and current of the measured line will undergo nonlinear instantaneous mutations; The early fault judgment criterion is: when the waveform characteristics of the electrical quantity data undergo nonlinear instantaneous mutation, it is considered that an early fault occurs.

4. The method for active protection of distribution network lines based on electrical quantity and non-electrical quantity characteristics according to claim 2 is characterized in that: Based on the plane heat transfer theory, a line surface temperature model of the measured line is constructed when a transient arc grounding fault occurs, and the non-electrical quantity criterion is determined, which is specifically: According to the plane heat transfer theory, when the instantaneous arc grounding fault occurs, the line surface temperature model of the measured line is constructed as follows: The analytical expression of the line surface temperature when a transient arc grounding fault occurs is as follows: In the formula, the surface heat source is located on the plane x = x', and the heating rate is q s (τ), the excess temperature distribution caused by the surface heat source on the infinite object with uniform initial temperature distribution is recorded as θ(x,τ), and the thickness of the heat source is 2x b ; α is the thermal diffusivity of the circuit material, also called thermal conductivity; λ is the thermal conductivity or thermal conductivity of the line material, ρ is the line material density, c is the specific heat capacity of the material; τ is the time duration of the instantaneous arc grounding fault arc; For an initial temperature of T1°C, the temperature distribution function caused by continuous heating of the arc in the line is expressed as: The quadratic difference quotient method is used to extract the waveform characteristics of the line surface temperature when the instantaneous arc grounding fault occurs. It is found that the waveform characteristics have four obvious peaks, and the peaks are all greater than the threshold M. The non-electrical quantity judgment criterion is: when the waveform characteristics of the non-electrical quantity have four obvious peaks, and the peaks are all greater than the threshold M, it is considered that the instantaneous arc grounding fault is relatively serious and may develop into a permanent grounding fault at any time.

5. The active protection method for distribution network lines based on electrical quantity and non-electrical quantity characteristics according to claim 1 is characterized in that: The morphological gradient filtering algorithm is used to extract waveform features from the measured electrical quantity waveform; The morphological gradient filtering algorithm is: The morphological gradient filtering formula that can distinguish the rising and falling edge features of the sampled waveform is: Where M T (t) is the processed morphological gradient filtering waveform; f(t) is the sampled electrical quantity waveform signal that needs to be processed, and g(t) is the morphological structural element selected during the calculation; and are dilation and erosion operations, representing a basic morphological operation respectively. The dilation and erosion of the structure element g for the sampled signal f are: In this formula, f and g are both one-dimensional signals, and their domains are defined in the formula; N is the length of the data signal window, and M is the width of the structure element; In the above morphological gradient filtering formula, the flat structure element g + and g - They are used to extract the upper and lower edges of the sampled waveform. The flat structure element refers to a special one-dimensional vector that contains only two elements, 0 and 1. + The 0 elements of g are all on the far right; - The 0 elements are all on the left; A flat structure element g with an odd width h + and g - for: The morphological gradient filtering algorithm is very sensitive to waveforms with sudden changes, which is mainly reflected in the change of the number of peaks in the filtered waveform.

6. The method for active protection of distribution network lines based on electrical quantity and non-electrical quantity characteristics according to claim 1, characterized in that: The quadratic difference quotient method is used to extract the waveform features of non-electrical quantity data after the timing interval.

7. The active protection method for distribution network lines based on electrical quantity and non-electrical quantity characteristics according to claim 1 or 6, characterized in that: The timing interval is 15s to 1min.

8. The active protection method for distribution network lines based on electrical quantity and non-electrical quantity characteristics according to claim 4 or 6, characterized in that: The calculation formula of the quadratic difference quotient method is: Where, L x It is the N-order difference quotient of the temperature T and the spatial position x on the line, P x is the absolute value waveform of the quadratic difference quotient; N is the number of sampled signals, and the spatial position takes the line port as the coordinate zero point, x k is the spatial coordinate corresponding to the kth sampling value.

9. An active protection device for distribution network lines based on electrical and non-electrical quantity characteristics, characterized in that: The following steps are involved: A data acquisition module, which is used to collect electrical quantity and non-electrical quantity data in real time; An electrical quantity waveform extraction module, the electrical quantity waveform extraction module is used to extract electrical quantity waveform features from the collected electrical quantity data; An early fault judgment module, wherein when the waveform characteristics of the electrical quantity meet the early fault judgment criteria, the electrical quantity device is activated and timing is started; A non-electrical quantity waveform extraction module, wherein the non-electrical quantity waveform extraction module is used to extract non-electrical quantity waveform features from non-electrical quantity data after a timing interval; The judgment module is used for actuating the non-electrical quantity device and tripping the line when the waveform characteristics of the non-electrical quantity meet the non-electrical quantity criterion.

10. The active protection device for distribution network lines based on electrical quantity and non-electrical quantity characteristics according to claim 9, characterized in that: Also includes: A fault criterion building module, wherein the fault criterion building module is used to build an arc fault dynamic model when a transient arc grounding fault occurs, and determine an early fault criterion; Based on the plane heat transfer theory, a line surface temperature model of the measured line is constructed when an instantaneous arc grounding fault occurs, and the non-electrical quantity judgment criterion is determined.

11. The method for active protection of distribution network lines based on electrical quantity and non-electrical quantity characteristics according to claim 10, characterized in that: Fault judgment building module, specifically used for: When a transient arc grounding fault occurs, the relationship between the instantaneous arc grounding fault arc resistance and the arc branch VCR is: u arc =(R g +R arc )i arc Where g is the instantaneous conductance of the instantaneous arc ground fault arc, R arc is the instantaneous resistance of the arc; i f Represents the instantaneous current of the arc, u st represents the static arc voltage; τ is the arc time constant, u0 is the arc characteristic voltage, r0 is the arc characteristic resistance, τ, u0 and r0 are three constants that characterize the arc characteristics, which are determined by the type and characteristics of the arc itself; u arc is the instantaneous voltage of the arc branch, i arc is the instantaneous current of the arc branch, R g Set the transition resistance for the arc branch; For a line containing an instantaneous arc grounding fault arc branch, the volt-ampere characteristics at the line port should meet the following requirements: i1=i arc +i R In the formula, i arc is the current of the arc branch, i1 is the total current flowing through the measured line, i R is the current in the line that does not flow through the arc fault branch; the capacitance value of the measured line is 1 / sC, and the resistance value is R; the equivalent electromotive force behind the measured line is U s , U s Treated as an independent voltage source; From the volt-ampere characteristics at the line port of the line containing the instantaneous arc grounding fault arc branch, it can be known that the waveforms of the voltage and current of the measured line will undergo nonlinear instantaneous mutations; The early fault judgment criterion is: when the waveform characteristics of the electrical quantity data undergo a nonlinear instantaneous mutation, an early fault is considered to have occurred.

12. The active protection device for distribution network lines based on electrical quantity and non-electrical quantity characteristics according to claim 10, characterized in that: Fault judgment building blocks are also used to: According to the plane heat transfer theory, when the instantaneous arc grounding fault occurs, the line surface temperature model of the measured line is constructed as follows: The analytical expression of the line surface temperature when a transient arc grounding fault occurs is as follows: In the formula, the surface heat source is located on the plane x = x', and the heating rate is q s (τ), the excess temperature distribution caused by the surface heat source on the infinite object with uniform initial temperature distribution is recorded as θ(x,τ), and the thickness of the heat source is 2x b ; α is the thermal diffusivity of the circuit material, also called thermal conductivity; λ is the thermal conductivity or thermal conductivity of the line material, ρ is the line material density, c is the specific heat capacity of the material; τ is the time duration of the instantaneous arc grounding fault arc; For an initial temperature of T1°C, the temperature distribution function caused by continuous heating of the arc in the line is expressed as: The quadratic difference quotient method is used to extract the waveform characteristics of the line surface temperature when the instantaneous arc grounding fault occurs. It is found that the waveform characteristics have four obvious peaks, and the peaks are all greater than the threshold M. The non-electrical quantity judgment criterion is: when the waveform characteristics of the non-electrical quantity have four obvious peaks, and the peaks are all greater than the threshold M, it is considered that the instantaneous arc grounding fault is relatively serious and may develop into a permanent grounding fault at any time.

13. An electronic device, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the active protection method for distribution network lines based on electrical quantity and non-electrical quantity characteristics as described in any one of claims 1 to 8 is implemented.

14. A non-transitory computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method for actively protecting distribution network lines based on electrical quantity and non-electrical quantity characteristics as described in any one of claims 1 to 8 is implemented.

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