CN108896893B - Positioning system and positioning method for partial discharge source in electrical equipment - Google Patents
Positioning system and positioning method for partial discharge source in electrical equipment Download PDFInfo
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- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/18—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using ultrasonic, sonic, or infrasonic waves
- G01S5/22—Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements
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Abstract
The invention discloses a positioning system and a positioning method for a partial discharge source in electrical equipment. Wherein the method comprises the following steps: establishing a discrete physical model of the electrical equipment, wherein the discrete physical model is a model formed by a plurality of nodes with the same spacing; traversing each node in a plurality of nodes, determining a discharge signal corresponding to each node, and transmitting the discharge signal to the fastest transmission path of the preset sensor position; estimating the arrival time of the discharge signal corresponding to each node according to the fastest propagation path of the discharge signal corresponding to each node to the preset sensor; the position of the partial discharge source in the electrical device is determined from the estimated arrival time and the arrival time actually detected by the preset sensor. The invention solves the technical problem of inaccurate positioning result caused by determining the position of the partial discharge source in the electrical equipment according to the direct wave path of the partial discharge signal in the prior art.
Description
Technical Field
The invention relates to the technical field of electric appliances, in particular to a positioning system and a positioning method of a partial discharge source in electric equipment.
Background
In the field, the insulation of electrical equipment is subject to partial discharges at operating voltages, which can cause the insulation material to undergo corona corrosion, partial overheating, uv radiation and oxidation, the cumulative effect produced being such that the dielectric properties of the insulation are gradually degraded and the local defects are enlarged, eventually leading to a breakdown of the whole insulation and damage to the equipment.
Taking a transformer as an example, partial discharge of the transformer can cause ageing of oil paper insulation, and failure of the whole insulation of the transformer can be caused under the action of a long time. The accurate acquisition of the partial discharge source position plays a very important role in the identification of the type of the partial discharge source and the risk assessment of the defects. When partial discharge occurs, acoustic signals can propagate from the position of the partial discharge source to the whole transformer space, and the ultrasonic sensor can be fixed on the transformer shell through the magnetic bracket to collect signals. Because of the simple sensor arrangement method and the anti-interference property to external electromagnetic noise, the ultrasonic method is widely applied to the field of partial discharge detection and positioning of transformers.
At present, in the prior art, a direct wave path is mainly and directly adopted as a propagation path corresponding to the arrival time, experiments are carried out in an empty box body filled with oil, and in fact, because the ultrasonic sensor is fixedly arranged outside the box body, an acoustic signal generated by partial discharge can be accepted by the sensor after passing through a transformer shell, the signal firstly reaching the sensor is not necessarily a direct wave signal due to the change of the wave speed and complex waveform conversion, and meanwhile, because the transformer consists of an iron core, a winding and the like, a complex structure of the transformer can introduce a large error to the partial discharge positioning result.
Aiming at the problem that the positioning result is inaccurate due to the fact that the position of the local discharge source in the electrical equipment is determined according to the direct wave path of the local discharge signal in the prior art, no effective solution is proposed at present.
Disclosure of Invention
The invention aims to provide a positioning system and a positioning method for a partial discharge source in electrical equipment, so as to solve the problems.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
A positioning system of a partial discharge source in electrical equipment comprises acquisition equipment, a processor, calculation equipment, measurement equipment, a preset sensor and a positioner; the acquisition equipment is connected with the electrical equipment to acquire the size information of the electrical equipment; the processor is connected with the acquisition equipment to establish a discrete physical model of the electrical equipment according to the size information of the electrical equipment; the plurality of preset sensors are fixedly arranged on a shell of the electrical equipment, the computing equipment and the measuring equipment are connected with the processor, and each sensor is connected to the measuring equipment; the computing equipment is used for traversing each node in the discrete physical model, estimating the arrival time of the fastest propagation path of the discharge signal corresponding to each node, and propagating to the preset sensor position; the measuring device is used for measuring the time when each sensor actually detects the discharge signal; the locator is connected to the computing device and the measuring device to determine the location of the partial discharge source within the transformer based on the estimated time of arrival and the time of arrival actually detected by the preset sensor.
Further, the locator comprises a comparator and a selector, wherein the comparator is connected with the computing equipment and the measuring equipment to compare the estimated arrival time of the discharge signal corresponding to each node to the preset sensor and the arrival time of the discharge signal actually detected by the preset sensor to obtain a comparison result of the discharge signal corresponding to each node; and the selector is connected with the comparator and used for selecting a node with the smallest difference from the actual measured arrival time from a plurality of nodes in the discrete physical model according to the comparison result as the position of the local discharge source in the electrical equipment.
Further, the measuring device comprises a timer, a signal amplifier and a laser ranging device, wherein the timer is connected with each sensor arranged on the shell of the electrical equipment and is used for recording the time of each sensor detecting a discharge signal; the laser ranging equipment is connected with the computing equipment and is used for measuring the position of each sensor arranged on the electrical equipment shell and determining the propagation path of the discharge signal corresponding to each node according to the measured position of each sensor; a signal amplifier is provided between the measuring device and each sensor for amplifying the discharge signal detected by each sensor.
Further, the system also comprises an input device connected with the computing device for inputting the propagation speed of the discharge signal; the acquisition equipment is a camera; the sensor is an ultrasonic sensor; the locator is connected with a display for displaying the position of the partial discharge source on the discrete physical model.
Further, a positioning method of a positioning system of a partial discharge source in an electrical apparatus, based on any one of the above, includes the following steps:
step 1, establishing a discrete physical model of electrical equipment, and determining a search area;
step 2, selecting a node from the search area as a calculation node, and determining a straight line path between a projection node of the calculation node on a sensor plane and a preset sensor;
Step3, selecting a point on the straight line path as an incident point, and determining the incident angle of the discharge signal corresponding to the calculation node to the incident point;
Step 4, judging the angle range of the incident angle, and if the incident angle is in the first angle range, calculating the propagation time of the discharge signal in the shell at the longitudinal wave speed; if the incident angle is within the second angular range, calculating the propagation time of the discharge signal in the housing at the transverse wave speed; wherein the second angular range is greater than the first angular range;
step 5, selecting an incidence point with the shortest transmission time; different incident points enter the shell, different propagation paths and different propagation speeds exist, and after the propagation path passing through each incident point and corresponding propagation time are determined, the point with the shortest propagation time is selected as the incident point of the computing node;
Step 6, judging whether to traverse the complete straight line path; circularly executing the steps 3 to 5 to guide each point on the linear path to be traversed;
Step 7, judging whether to traverse the whole search area; circularly executing the steps 2 to 6 until each node in the whole search area is traversed, and obtaining the fastest propagation path of each node to a preset sensor;
And 8, selecting a node closest to the measured time difference in the search area as the position of the local discharge source.
Further, in step 1, the discrete physical model is a model formed by a plurality of nodes having the same pitch, each of the plurality of nodes characterizing a potential location of one of the partial discharge sources in the electrical device; traversing each node in a plurality of nodes, determining a discharge signal corresponding to each node, and transmitting the discharge signal to the fastest transmission path of the preset sensor position; the fastest propagation path is the path that propagates the discharge signal fastest; estimating the arrival time of the discharge signal corresponding to each node according to the fastest propagation path of the discharge signal corresponding to each node to the preset sensor; the position of the partial discharge source in the electrical device is determined from the estimated arrival time and the arrival time actually detected by the preset sensor.
Further, in step 3, determining, on the discrete physical model, a position of at least one incident point when the discharge signal corresponding to each of the plurality of nodes is incident on the surface of the discrete physical model when the discharge signal propagates to the preset sensor, includes:
selecting one of a plurality of nodes on the discrete physical model as a computing node;
determining projection nodes of the computing nodes on a plane where the preset sensor is located, and determining a straight line path from the projection nodes to the preset sensor;
The linear path is discretized into a plurality of points with the same distance interval, wherein the position of the incident point is any one point of the plurality of points on the linear path, and the position of each incident point on the linear path corresponds to an incident angle.
Further, in step 5, calculating a propagation time used when the discharge signal corresponding to each node propagates through the propagation path corresponding to the position of each incident point, and determining the propagation path with the shortest propagation time as the fastest propagation path, including:
Determining a corresponding propagation path of a discharge signal corresponding to the calculation node when the discharge signal is incident to the position of each incident point, wherein the propagation path comprises: calculating a first propagation path of the discharge signal corresponding to the node before entering the surface of the discrete physical model and a second propagation path after entering the surface of the discrete physical model; the first propagation path is a linear distance from a calculation node to the position of an incident point, and the second propagation path is a linear distance from the position of the incident point to a preset sensor;
Acquiring a first propagation speed of the discharge signal on a first propagation path and a second propagation speed of the discharge signal on a second propagation path;
traversing the position of each incident point on the straight line path, and calculating the propagation time of the discharge signal corresponding to the calculation node when propagating through the position of each incident point on the straight line path according to the first propagation path, the first propagation speed, the second propagation path and the second propagation speed;
and determining a propagation path corresponding to the position of the incidence point with the shortest propagation time as the fastest propagation path corresponding to the computing node.
Further, in step 5, traversing the position of each incident point on the straight line path, and calculating, according to the first propagation path, the first propagation speed, the second propagation path and the second propagation speed, a propagation time when the discharge signal corresponding to the calculation node propagates through the position of each incident point on the straight line path, where the calculation step includes:
calculating a first propagation time according to the first propagation speed and the first propagation path by the following formula, wherein the first propagation time is the propagation time of the discharge signal corresponding to the calculation node on the first propagation path:
Wherein Vel (i m,jm,km) is the propagation speed of the discharge signal at the node (i m,jm,km) before the discharge signal is incident on the electrical equipment housing, l is the number of nodes on the first propagation path, dl is the spacing between the nodes on the discrete physical model, and m is a positive integer;
Calculating a second propagation time according to the second propagation speed and the second propagation path by the following formula, wherein the second propagation time is the propagation time of the discharge signal corresponding to the calculation node on the second propagation path:
Wherein Vel oil is a propagation speed of the discharge signal when the discharge signal is incident into the electrical equipment housing, l is a number of nodes on the second propagation path, (i 1,j1,k1) is coordinates of a position of an incident point on the second propagation path, (i inc,jinc,kinc) is coordinates of a position where a preset sensor is located, and dl is a distance between nodes on the discrete physical model;
and taking the sum of the first propagation time and the second propagation time as the propagation time when the discharge signal corresponding to the calculation node propagates through the position of each incident point on the straight line path.
Further, in step 8, determining the position of the partial discharge source in the electrical device according to the estimated arrival time and the arrival time actually detected by the preset sensor includes:
According to the arrival time of the discharge signal corresponding to each node to a plurality of preset sensors, calculating the expected arrival time difference of the discharge signal corresponding to each node to the plurality of preset sensors; according to the actual arrival time of the discharge signals corresponding to each node actually detected by the plurality of preset sensors, calculating the actual arrival time difference of the discharge signals corresponding to each node to the plurality of preset sensors; calculating a difference value between the estimated arrival time difference and the actual arrival time difference corresponding to each node; and determining the position corresponding to the node with the smallest difference as the position of the partial discharge source on the electrical equipment.
Compared with the prior art, the invention has the following technical effects:
The invention provides an optimized propagation path searching method by establishing a discrete physical model of electrical equipment, so that any node on the discrete physical model represents a potential partial discharge point, a plurality of propagation paths of each potential partial discharge point when passing through an electrical equipment shell are constructed, and the propagation path which reaches a sensor most quickly is selected from the plurality of propagation paths, thereby realizing the accurate positioning of a partial discharge source.
Drawings
Fig. 1 is a schematic diagram of a transformer according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a method for determining that a discharge signal at a node on a transformer model reaches a sensor with a fastest propagation path, according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the fastest propagation path of an unobstructed local discharge source from a signal source to each sensor, according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of the fastest propagation path of an obstructed partial discharge source from a signal source to various sensors according to an embodiment of the present invention;
Fig. 5 is a flow chart of a method of positioning a partial discharge source in an electrical device according to an embodiment of the present invention.
Wherein: the device comprises a transformer 1, an acquisition device 6, a processor 7, a computing device 8, a measuring device 9, a positioner 10 and a display 11, an iron core 1-1, windings 1-2, a shell 1-3, a first ultrasonic sensor 2-1, a second ultrasonic sensor 2-2, a third ultrasonic sensor 2-3 and a fourth ultrasonic sensor 2-4.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
referring to fig. 1 to 5, the positioning scheme of the partial discharge source (i.e. the location point of the electrical device where the discharge signal occurs) in the electrical device provided by the embodiment of the invention can be applied to any device that needs to perform partial discharge detection, including but not limited to devices such as a high-voltage switch cabinet and a transformer. As these electrical devices may exhibit partial discharges at the operating voltage, which may lead to breakdown of the insulating material on the electrical device, causing insulation failure. Therefore, the internal partial discharge of the high-voltage electrical equipment is detected and positioned, and the operation reliability of the equipment can be improved.
Partial discharge on electrical equipment mainly releases energy in the form of electromagnetic waves and acoustic waves, and thus electromagnetic wave sensors (e.g., ultra high frequency UHF sensors) or ultrasonic sensors can be generally used to detect the partial discharge signals.
Typically, sensors for partial discharge detection are typically deployed on the surface of an electrical equipment enclosure. Thus, the partial discharge signal is typically detected by the sensor via the housing.
The position of the partial discharge source in the electrical device can be located with four sensors. The scope of the present application is not limited to four, alternatively, more than four sensors (the greater the number of sensors employed, the greater the computational complexity) may be employed to locate the partial discharge sources, which is not limited herein. In the prior art, the positioning of the partial discharge source is performed based on the arrival time difference of the partial discharge signal (i.e., the discharge signal of the electrical device partial discharge source) propagating to the four sensors.
For example, assume that four sensors, sensor a, sensor B, sensor C, and sensor D, respectively, are disposed on the surface of the housing of a certain electrical device. In addition, assuming that there is one partial discharge point (i.e., the position where the partial discharge source is located) X in the electrical apparatus, each sensor can detect the arrival time of the discharge signal at the partial discharge point X at the respective positions, and assuming that T A、TB、TC、TD represents the time at which the partial discharge point X arrives at the sensor a, the sensor B, the sensor C, and the sensor D, respectively.
Further, respectively calculating time difference T AB when the partial discharge point X reaches the sensor A and the sensor B respectively; time difference T AC when partial discharge point X reaches sensor A and sensor C respectively; the time difference that the partial discharge point X reaches the sensor A and the sensor D respectively is T AD; and finally, determining the position of the partial discharge point X according to the three time differences, namely determining the position coordinate of the partial discharge point X as (T AB,TAC,TAD).
In the prior art, a path of a direct wave propagating from a partial discharge point to a sensor is taken as a propagation path corresponding to a arrival time, however, as described above, the sensor is generally fixed on a surface of an electrical device housing, a discharge signal of a partial discharge source can be detected by the sensor after passing through a transformer housing, and a waveform of the discharge signal is complex and a wave speed is changed due to refraction of the discharge signal in the transformer housing, so that a signal reaching the sensor first is not necessarily a direct wave signal, and complex structures (for example, an iron core, a winding and the like inside the transformer) inside the electrical device can make a partial discharge positioning result inaccurate.
The present application will be described below by taking a transformer as an example. Fig. 1 is a schematic diagram of a transformer provided according to an embodiment of the application, the transformer 1 including components that may include: iron core 1-1, winding 1-2 and shell 1-3. The iron core is a magnetic circuit part of the transformer and consists of an iron core column (a winding is sleeved on the column), an iron yoke (a part which only plays a role of a magnetic circuit is not sleeved on the winding, and the iron core is connected to form a closed magnetic circuit); the winding is a circuit part of the transformer and is formed by winding copper wires or aluminum wires, and the primary winding and the secondary winding are concentrically sleeved on the iron core column; the transformer shell is mainly used for safety protection of the operation transformer site.
In detecting the partial discharge point of the transformer (i.e., where the partial discharge source is located), an ultrasonic sensor may be used as an alternative embodiment to locate and detect the partial discharge source on the transformer.
As shown in fig. 1, there are two partial discharge sources in the transformer 1, a first partial discharge source is shown in the diagram 3-1, and a second partial discharge source is shown in the diagram 3-2. Wherein the first partial discharge source is located in transformer oil, without a surrounding obstruction, assuming its coordinates (26, 51, 57); the second partial discharge source is located in the high voltage winding 1-2 with surrounding obstructions and the discharge signal (ultrasonic signal) can propagate through the high voltage winding to the sensor on the transformer housing, assuming its coordinates (75, 50, 138).
In order to locate the position of the partial discharge source (e.g., 3-1 and 3-2 shown in fig. 1) on the transformer, a plurality of sensors (typically, at least four sensors are required if the three-dimensional spatial coordinates of the partial discharge source are located) may be disposed on the transformer housing, and various embodiments of the present application are described with four sensors as an example, assuming that the four sensors disposed on the transformer are the first ultrasonic sensor 2-1, the second ultrasonic sensor 2-2, the third ultrasonic sensor 2-3, and the fourth ultrasonic sensor 2-4, respectively. Table 1 is a list of coordinates of ultrasonic sensors deployed on a transformer.
Table 1 coordinates of ultrasonic sensor deployed on transformer
In consideration of the fact that a discharge signal of a partial discharge source in an electrical apparatus passes through a housing of the electrical apparatus and changes in waveform conversion and wave speed during propagation to a detection sensor (e.g., an ultrasonic sensor), a signal that reaches the sensor first is not necessarily a direct wave signal, a transformer housing and a non-direct propagation path of the discharge signal need to be considered, and a discharge signal that reaches the sensor fastest is selected from a plurality of direct wave signals and non-direct wave signals.
In order to acquire a direct wave propagation path and a non-direct wave propagation path of a partial discharge signal in electrical equipment reaching each sensor, the embodiment of the invention provides a partial discharge source positioning scheme based on an optimized propagation path searching method.
Specifically, taking a transformer as an example, a transformer model including an iron core (iron core limb and iron yoke), windings and a case may be built according to the actual size of the transformer. It is easy to note that it is not practical to build a discrete physical model that corresponds exactly to the actual structure of the transformer, and the necessary simplification can reduce the difficulty and complexity of the positioning method. The transformer model established by the application is discretized into equidistant nodes, and the distance between the nodes can be set as dl. In practical application, the adjustment can be performed according to the specific size of the transformer. Any node in the transformer model can be represented by a new Cartesian coordinate system (i, j, k), and the actual coordinate system of the node is: x=i×dl, y=j×dl, and z=k×dl. Where the values of i, j, k must be positive integers.
In the transformer model, any node can be regarded as a potential partial discharge point (i.e. the position of the partial discharge source), and two parameters, namely a propagation parameter and a speed parameter, are given according to the position of the node. Wherein the propagation parameter may indicate whether the node is located in transformer oil, and when the propagation parameter is equal to 1, it indicates that the discharge signal (e.g., ultrasonic wave) propagates to the node location at a propagation speed in a medium (here, transformer oil) in which the node (e.g., the first partial discharge source 3-1 shown in fig. 1) is located, and when the propagation parameter is equal to 0, it indicates that the node is located in the metal structure (e.g., the second partial discharge source 3-2 shown in fig. 1). Wherein the velocity parameter refers to the propagation velocity of the discharge signal (i.e., ultrasonic wave) at the node position.
Here, it should be noted that the purpose of creating the discrete physical model of the transformer is to find the fastest path of propagation of the acoustic signal corresponding to the arrival time. In fact, the shortest path (direct wave path) is not necessarily the fastest path due to the complex propagation process, but the shortest path method can help find the fastest path.
A straight line path from the projection node (i.e., the projection point of any one node in the discrete physical model on the plane of the sensor) to the ultrasonic sensor can be determined by using the shortest path search method.
Fig. 2 is a schematic diagram of a method for determining that a discharge signal at a node on a transformer model reaches a sensor with a fastest propagation path, as shown in fig. 2, where an icon 1-1 is shown as a housing of the transformer 1, an icon 2 is shown as a sensor (e.g., any one of the first ultrasonic sensor 2-1, the second ultrasonic sensor 2-2, the third ultrasonic sensor 2-3, and the fourth ultrasonic sensor 2-4 in fig. 3) disposed on the transformer housing 1-1, an icon 3 is shown as a potential partial discharge point (i.e., a potential position of the partial discharge source may be any one of the nodes in a discrete physical model), any one of the nodes on the discrete physical model (i.e., the potential partial discharge point, the position of the partial discharge source 3) is selected as a calculation node, and a straight line path of the projection node 4 of the partial discharge source 3 on a plane of the sensor (e.g., the ultrasonic sensor) and the sensor 2 is discretized into a plurality of points equidistant, each of which may be a point when the partial discharge source passes through the transformer housing, e.g., a point of the icon 1-5, 5-5, and a common point 12 shown in the positions of the icon 2-5.
As shown in fig. 2, since any point on the straight path from the projection node 4 to the sensor 2 can be regarded as an oblique incidence point of a non-direct wave, each point on the path (i.e., the position of the incidence point) corresponds to a propagation path, when the discharge signal at each calculation node reaches the expected arrival time of the preset sensor, the propagation time corresponding to the propagation path corresponding to the position of each incidence point can be calculated one by one from the position of the projection node to the position of the ultrasonic sensor, i.e., each point on the straight path from the projection node to the sensor is traversed, so as to obtain a plurality of propagation paths of the discharge signal at the calculation node (which may be any node on the discrete physical model) to the preset sensor, so as to determine the propagation path (i.e., the fastest propagation path) of the sensor that arrives fastest from the plurality of propagation paths.
In addition, it should be further noted that in the prior art, a simple iterative method or a basic intelligent optimization method is generally used to solve the TDOA equation set (TDOA is a time difference of arrival, which is a method for positioning by using a time difference, that is, the time difference of arrival of the discharge signal at different sensors, and the time synchronization requirement can be reduced by using the time difference instead of the absolute time), so as to position the position of the local discharge source in the electrical device. Although these methods have low accuracy, their positioning results can help determine an initial search area. The size of the initial search area may be adjusted according to the size of the transformer. Therefore, the method for optimizing the propagation path provided by the embodiment of the invention can select the optimal partial discharge source position from all nodes in the discrete physical model by combining the measured time difference of the sensor and the fastest propagation path corresponding to each node in the initial search area.
Therefore, as an alternative implementation manner, the application can initially determine a search area by the existing method for positioning the local discharge source, so that only nodes in the area range corresponding to the search area on the discrete physical model of the electrical equipment are required to be further determined, and the calculation steps are greatly reduced.
As shown in fig. 2, for any one node in the discrete physical model, or any one node in the partial discharge source location area (preliminary search area) preliminarily determined according to the existing positioning method in the discrete physical model, the propagation path of the discharge signal corresponding to each node to the sensor is divided into two parts: a first propagation path and a second propagation path, wherein the first propagation path is a straight line distance from a calculation node to a position of an incident point, and the second propagation path is a straight line distance from the position of the incident point to a preset sensor (i.e., any one of four sensors for positioning a partial discharge source).
For the position of any point of incidence, the first part of the propagation path (propagation path before the discharge signal is incident on the envelope, the partial discharge source is located in the transformer oil), i.e. the propagation time of the first propagation path, can be regarded as the sum of the propagation times between adjacent nodes. Specifically, the propagation time of the discharge signal on the first propagation path may be calculated by the formula (1). It is easy to note that the wave speed used for each interval may vary depending on where the node is located.
Where Vel (i m,jm,km) is the propagation velocity (i.e., first propagation velocity) of the discharge signal at the node (i m,jm,km) before the discharge signal is incident on the electrical equipment enclosure, l is the number of nodes on the first propagation path, dl is the spacing between the nodes on the discrete physical model, and m is a positive integer.
Alternatively, when the propagation time of the second part of the propagation path (propagation path of the discharge signal incident into the housing), i.e., the second propagation path of the oblique incidence point to the sensor, can be determined by the oblique incidence point coordinates and the sensor position coordinates, specifically, the propagation time of the discharge signal on the second propagation path can be calculated by the formula (2).
Wherein Vel oil is a propagation speed of the discharge signal when the discharge signal is incident into the electrical equipment housing, l is a number of nodes on the second propagation path, (i 1,j1,k1) is coordinates of a position of an incident point on the second propagation path, (i inc,jinc,kinc) is coordinates of a position of a preset sensor, and dl is a distance between the nodes on the discrete physical model.
It is to be noted that, in the case where there is no obstacle on the first propagation path, for example, the first partial discharge source shown in fig. 1, calculation of the propagation time using the formula (1) introduces a dispersion error, and in order to avoid discretizing the first propagation path without an obstacle, the calculation method of the propagation time can be calculated by the formula (2).
After the first propagation time and the second propagation time are calculated, the sum of the first propagation time and the second propagation time can be used as the propagation time when the discharge signal corresponding to the calculation node propagates through the position of each incident point on the straight line path.
In addition, it should be further noted that, since the first propagation speed of the partial discharge signal on the first propagation path is the propagation speed in the medium in which the partial discharge point is located (for example, the propagation speed of the partial discharge point inside the transformer in transformer oil), the first propagation speed is related to the medium, that is, the propagation speed of the discharge signal in the corresponding medium may be adopted.
Whereas the propagation velocity of the discharge signal in the second propagation path, i.e. in the electrical equipment enclosure, is related to the angle of incidence of the discharge signal to the enclosure, it is possible to use the longitudinal wave velocity as well as the transverse wave velocity. Thus, how to select an accurate propagation velocity requires a relatively complex calculation. Wherein the oblique incidence angle is the angle between the normal vector of the sensor plane and the vector from the start node to the position of the incidence point.
Thus, as an alternative embodiment, the second propagation speed may be determined from the angular range in which the angle of incidence lies. For example, if the incident angle is within the first angle range, that is, a transverse wave velocity of the discharge signal in the electrical equipment enclosure is adopted as a propagation velocity of the discharge signal when it propagates into the electrical equipment enclosure; if the incident angle is within the second angle range, that is, the longitudinal wave velocity of the discharge signal in the electrical equipment enclosure is used as the propagation velocity of the discharge signal when it propagates into the electrical equipment enclosure.
The first angle range and the second angle range may be preset angle ranges set according to specific application scenes, the second angle range is greater than the first angle range, optionally, the first angle range may be less than 14 °, and the second angle range may be between 14 ° and 26 °. Still taking a transformer as an example, when the incident angle is smaller than 14 °, the sound velocity in the tank wall should use the longitudinal wave sound velocity in steel, for example, the position of 4 incident points shown by the icon 5-1 in fig. 2 adopts the longitudinal wave sound velocity; when the oblique incidence angle is between 14 ° and 26 °, the sound velocity at this time should be selected as that of a transverse wave in steel, for example, the positions of 4 incidence points shown by the icon 5-2 in fig. 2 employ longitudinal wave sound velocities; when the angle of incidence is further increased beyond 26 deg., i.e. the position of the 4 points of incidence shown by the icons 5-3 in fig. 2, the ultrasonic sensor will not receive any signal from the direct wave, directly jumping out of the cycle. When this occurs or the positions of all the incident points have been traversed, the current cycle is ended and the path with the shortest propagation time is selected as the fastest path.
For any node in the discrete physical model or any node in the preliminary search area preliminarily determined according to the existing positioning method in the discrete physical model, different incident points enter the shell to form different propagation paths, and the propagation time of the propagation paths corresponding to all the incident points is traversed and calculated to obtain the propagation path which reaches the sensor fastest, namely the fastest propagation path. By traversing each node, the fastest propagation path for each node to reach a preset sensor (any one of a plurality of sensors deployed on the electrical device) can be obtained.
After the fastest propagation paths between each node and the different sensors, and the corresponding propagation times, the expected arrival time differences between each node and the respective sensors may be calculated to locate the position of the partial discharge source in the electrical device by time difference locating techniques (time difference locating techniques are techniques that utilize the difference in time required for the ultrasonic signals generated by the partial discharge to propagate to the sensors at different locations).
After determining the time difference of each node (i.e. the potential partial discharge point) reaching each sensor device, the time difference between the node and each sensor can be obtained by the method, in order to select the optimal node from the search area, specifically, the difference between the estimated time difference and the actually measured time difference of each node is compared by the formula (3), and finally, the position corresponding to the node with the smallest difference is determined as the position of the local power supply in the electrical equipment.
Where N i represents the i-th potential partial discharge node, Δt m 12 is the measured value of the signal arrival time difference detected by sensor 1 (e.g., first ultrasonic sensor 2-1) and sensor 2 (e.g., second ultrasonic sensor 2-2). ΔT Ni 12 is the estimated time difference of arrival between the first sensor and the second sensor obtained by the optimized propagation path search method described above. When the node N i approaches the partial discharge source, the value of Δt Ni gradually approaches Δt m, and the value of the evaluation function F (N i) decreases accordingly. When all nodes in the search area have been traversed, the node position with the minimum value of F (N i) can be selected as the optimal partial discharge source position.
As a preferred implementation, taking the transformer shown in fig. 1 as an example, fig. 3 is a schematic diagram of a fastest propagation path of an unobstructed local discharge source (for example, a local discharge source shown by an icon 3-1 in fig. 1) from a signal source to each sensor according to an embodiment of the present invention, and fig. 4 is a schematic diagram of a fastest propagation path of an obstructed local discharge source (for example, a local discharge source shown by an icon 3-2 in fig. 1) from a signal source to each sensor according to an embodiment of the present invention. Wherein, table 2 is the positioning result using the positioning method of the present invention.
Table 2 optimization of propagation path method positioning results
According to the embodiment of the invention, a positioning method of the partial discharge source in the electrical equipment is also provided. The method may be applied to any type of test device for partial discharge signal detection (e.g., the test device shown by the icon 6 in fig. 1), where the test device 6 includes a computing device 6-1 and a plurality of measuring devices 6-2 for precisely locating the position of the partial discharge source in the electrical device to be tested (e.g., the transformer shown by the icon 1 in fig. 1). Wherein the computing device may include a processor, an input device, a display, a signal amplifier, a timer, etc., where the input device is configured to input or collect one or more of the following configuration parameters, such as size information of the electrical device, a transverse wave velocity and a longitudinal wave velocity of the discharge signal propagating in the electrical device housing, the signal amplifier is connected between the processor and each sensor for amplifying the discharge signal detected by each sensor, and the timer is connected to the plurality of sensors and the processor, respectively, for recording the time at which the discharge signal corresponding to each node on the discrete physical model reaches each sensor.
Fig. 5 is a flowchart of a positioning method of a partial discharge source in an electrical apparatus according to an embodiment of the present invention, as shown in fig. 5, the method includes the steps of:
step S501, a discrete physical model of the electrical device is built, and a search area is determined.
Specifically, in detecting partial discharge signals in an electrical device (e.g., a transformer), detection sensors (e.g., ultrasonic sensors) may be disposed at a plurality of fixed positions on the housing 1-1 of the electrical device 1 to be tested to detect discharge signals on the electrical device 1, for example, four sensors are shown in fig. 1, as shown in icons 2-1, 2-2, 2-3, and 2-4, respectively. The test device 6 may establish a discrete physical model composed of a plurality of nodes with the same pitch according to the actual size information of the electrical device, and it should be noted that each node of the plurality of nodes on the discrete physical model may represent a potential position of a partial discharge source in the electrical device. In addition, the search area may be the entire area of the discrete physical model. In order to improve the calculation efficiency, the above search area may also be a preliminary search area determined according to the existing partial discharge positioning method, which is not described herein.
In practical application, a tester may input size information of an electrical device into the computing device through an input device (e.g., a keyboard, a touch screen, etc.) of the computing device, and the computing device may automatically collect the size information of the electrical device through various collecting devices.
After the computing device obtains the size information of the electrical device through the input device or the acquisition device, a discrete physical model of the electrical device can be established through a processor of the computing device, and the discrete physical model of the electrical device is displayed through a display of the computing device so as to display the position of the local discharge source positioned by the computing device on the discrete physical model.
In step S502, a node is selected from the search area as a calculation node, and a straight line path between a projection node of the calculation node on the sensor plane and a preset sensor is determined.
Specifically, after a search area is determined on the discrete physical model, a node may be determined in the search area as a calculation node to reach the fastest propagation path of the discharge signal at the calculation node to the preset sensor according to the shortest path method. Specifically, in the discrete physical model, a projection node of the computing node on the sensor plane and a straight line path between the projection node and a certain preset sensor are determined, and it is to be noted that each point on the straight line path may be an incident point when the computing node is incident on the electrical equipment housing. As an alternative implementation manner, as shown in fig. 2, the straight path may be discretized into a plurality of equidistant points, so as to calculate the propagation time of each point as an incident point, and further find the incident point with the shortest propagation time, where the propagation path corresponding to the incident point is the fastest propagation path of the calculation node.
In step S503, a point is selected as an incident point on the straight path, and an incident angle of the discharge signal corresponding to the calculation node to the incident point is determined.
Since the incident angles of the discharge signals when they are incident on the housing are different, the propagation speeds when they propagate in the housing are also different, so that in order to correspond to the propagation speeds when they propagate in the housing on the straight path, the incident angle when the calculation node is incident on the housing through each incident point on the straight path can be determined by step S503.
Step S504, the angle range of the incident angle is judged.
Specifically, if the incident angle is within the first angle range, step S505 is performed; if the incident angle is within the second angle range, step S506 is performed. Wherein the second angular range is greater than the first angular range. If the angle of incidence exceeds the second angular range, the sensor will not receive any signal from the direct wave, directly jumping out of the cycle.
In step S505, the propagation time of the discharge signal in the casing is calculated at the longitudinal wave velocity.
Specifically, if the incident angle of the discharge signal at the calculation node to the electrical equipment enclosure is relatively small, i.e., the incident angle is within the first angular range, the longitudinal wave velocity of the acoustic wave in the enclosure is used to calculate the corresponding travel time.
Step S506, calculating propagation time of the discharge signal in the housing at longitudinal wave speed.
Specifically, if the angle of incidence of the discharge signal at the computation node to the electrical equipment enclosure is large, but does not exceed a certain range, i.e., the angle of incidence is within a second angular range, the longitudinal wave velocity of the acoustic wave in the enclosure is used to calculate the corresponding travel time.
In step S507, the incidence point of the shortest propagation time is selected.
Specifically, entering the enclosure at different points of incidence, there are different propagation paths, and different propagation speeds, and after determining the propagation path through each point of incidence and the corresponding propagation time, the point of shortest propagation time is selected as the point of incidence of the computing node.
Step S508, judging whether to traverse the complete straight-line path.
The above-described schemes disclosed in steps S503 to S507 are circularly executed to guide the traversal of each point on the straight-line path.
Step S509, determining whether to traverse the entire search area.
And circularly executing the schemes disclosed in the steps S502 to S508 until each node in the whole search area is traversed, and obtaining the fastest propagation path of each node to the preset sensor.
In step S510, a node closest to the measured time difference in the search area is selected as the position of the partial discharge source.
After the fastest propagation path of the discharge signal corresponding to each node in the search area to the preset sensor is determined, the arrival time difference of the discharge signal corresponding to each node reaching each preset sensor can be estimated, the arrival time difference actually detected by each preset sensor is combined, and the node closest to the actual measurement time difference in each node is used as the position of the local discharge source, so that the purpose of determining the position of the local discharge source according to the fastest arrival time difference is achieved, and the positioning accuracy of the position of the local discharge source is improved.
By the scheme provided by the embodiment, a transformer model (any node in the model represents the potential position of a partial discharge source) is established according to the actual transformer size, and on the basis of the model, the application provides a shortest path searching method for searching the shortest path between two nodes. Due to the complex propagation process of the acoustic signal, the shortest path is not necessarily the fastest path of the acoustic wave propagation, but the fastest path is the key of performing partial discharge positioning according to the time difference. Therefore, the application provides an optimized propagation path searching method, which can reduce the propagation process of acoustic waves and calculate the shortest path from a potential partial discharge point to the position of a sensor so as to realize the accurate positioning of a partial discharge source.
According to an embodiment of the present invention, there is also provided an embodiment of an apparatus for implementing the positioning method of a partial discharge source in an electrical apparatus, including: the device comprises a building unit, a first determining unit, an estimating unit and a second determining unit.
The system comprises a building unit, a storage unit and a control unit, wherein the building unit is used for building a discrete physical model of the electrical equipment, the discrete physical model is a model formed by a plurality of nodes with the same distance, and each node in the plurality of nodes represents the potential position of one partial discharge source in the electrical equipment;
The first determining unit is used for traversing each node in the plurality of nodes, determining a discharge signal corresponding to each node and transmitting the discharge signal to the fastest transmission path of the preset sensor position; the preset sensors are sensors deployed at fixed positions on the surface of the electrical equipment shell, a plurality of fixed positions are arranged on the electrical equipment shell, and one sensor is arranged at one fixed position;
The estimating unit is used for estimating the arrival time of the discharge signal corresponding to each node according to the fastest propagation path of the discharge signal corresponding to each node to the preset sensor;
And a second determining unit for determining the position of the partial discharge source in the electrical apparatus based on the estimated arrival time and the arrival time actually detected by the preset sensor.
According to the scheme disclosed by the embodiment of the device disclosed by the application, the purpose of determining the position of the partial discharge source by considering the fastest propagation path of the partial discharge signal when the partial discharge signal propagates through the outer shell of the electrical equipment is achieved, so that the technical effect of accurately positioning the position of the partial discharge source in the electrical equipment is realized, and the technical problem of inaccurate positioning result caused by determining the position of the partial discharge source in the electrical equipment according to the direct wave path of the partial discharge signal in the prior art is solved.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, where functionally equivalent elements and algorithm steps are disclosed in the foregoing description
The components and steps of each example are generally described. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be disposed in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The foregoing detailed description of the invention has been presented for purposes of illustration and description, and it should be understood that the invention is not limited to the particular embodiments disclosed, but is intended to cover all modifications, equivalents, alternatives, and improvements within the spirit and principles of the invention.
Claims (5)
1. A method of positioning a positioning system for a partial discharge source in an electrical apparatus, the system comprising:
The device comprises an acquisition device (6), a processor (7), a computing device (8), a measuring device (9), a preset sensor and a positioner (10); the acquisition device (6) is connected with the electrical equipment to acquire the size information of the electrical equipment; the processor (7) is connected with the acquisition equipment to establish a discrete physical model of the electrical equipment according to the size information of the electrical equipment; a plurality of preset sensors are fixedly arranged on a shell of the electrical equipment, a computing device (8) and a measuring device (9) are connected with a processor (7), and each sensor is connected to the measuring device (9); the computing equipment (8) is used for traversing each node in the discrete physical model, estimating the arrival time of the fastest propagation path of the discharge signal corresponding to each node, and propagating to the preset sensor position; a measuring device (9) for measuring the time at which each sensor actually detects the discharge signal; the locator (10) is connected with the computing device (8) and the measuring device (9) to determine the position of the partial discharge source in the transformer according to the estimated arrival time and the arrival time actually detected by the preset sensor;
The locator comprises a comparator and a selector, wherein the comparator is connected with the computing equipment and the measuring equipment to compare the estimated arrival time of the discharge signal corresponding to each node to the preset sensor and the arrival time of the discharge signal actually detected by the preset sensor to obtain a comparison result of the discharge signal corresponding to each node; the selector is connected with the comparator and used for selecting a node with the smallest difference value with the actual measured arrival time from a plurality of nodes in the discrete physical model as the position of the local discharge source in the electrical equipment according to the comparison result;
The measuring equipment comprises a timer, a signal amplifier and a laser ranging equipment, wherein the timer is connected with each sensor arranged on the shell of the electrical equipment and is used for recording the time of each sensor detecting a discharge signal; the laser ranging equipment is connected with the computing equipment and is used for measuring the position of each sensor arranged on the electrical equipment shell and determining the propagation path of the discharge signal corresponding to each node according to the measured position of each sensor; the signal amplifier is arranged between the measuring equipment and each sensor and is used for amplifying the discharge signal detected by each sensor;
The system also comprises an input device connected with the computing device for inputting the propagation speed of the discharge signal; the acquisition equipment (6) is a camera; the sensor is an ultrasonic sensor; the locator is connected with a display (11) for displaying the position of the partial discharge source on the discrete physical model;
the method comprises the following steps:
step 1, establishing a discrete physical model of electrical equipment, and determining a search area;
step 2, selecting a node from the search area as a calculation node, and determining a straight line path between a projection node of the calculation node on a sensor plane and a preset sensor;
Step3, selecting a point on the straight line path as an incident point, and determining the incident angle of the discharge signal corresponding to the calculation node to the incident point;
Step 4, judging the angle range of the incident angle, and if the incident angle is in the first angle range, calculating the propagation time of the discharge signal in the shell at the longitudinal wave speed; if the incident angle is within the second angular range, calculating the propagation time of the discharge signal in the housing at the transverse wave speed; wherein the second angular range is greater than the first angular range;
step 5, selecting an incidence point with the shortest transmission time; different incident points enter the shell, different propagation paths and different propagation speeds exist, and after the propagation path passing through each incident point and corresponding propagation time are determined, the point with the shortest propagation time is selected as the incident point of the computing node;
Step 6, judging whether to traverse the complete straight line path; circularly executing the steps 3 to 5 to guide each point on the linear path to be traversed;
Step 7, judging whether to traverse the whole search area; circularly executing the steps 2 to 6 until each node in the whole search area is traversed, and obtaining the fastest propagation path of each node to a preset sensor;
step 8, selecting a node closest to the measurement time difference in the search area as the position of the partial discharge source;
In step 1, the discrete physical model is a model formed by a plurality of nodes with the same distance, and each node in the plurality of nodes represents the potential position of one partial discharge source in the electrical equipment; traversing each node in a plurality of nodes, determining a discharge signal corresponding to each node, and transmitting the discharge signal to the fastest transmission path of the preset sensor position; the fastest propagation path is the path that propagates the discharge signal fastest; estimating the arrival time of the discharge signal corresponding to each node according to the fastest propagation path of the discharge signal corresponding to each node to the preset sensor; the position of the partial discharge source in the electrical device is determined from the estimated arrival time and the arrival time actually detected by the preset sensor.
2. The positioning method of a positioning system of a partial discharge source in an electrical apparatus according to claim 1, wherein in step 3, determining, on a discrete physical model, a position of at least one incident point of a discharge signal corresponding to each of a plurality of nodes when propagating to a preset sensor, the discharge signal being incident on a surface of the discrete physical model, comprises:
selecting one of a plurality of nodes on the discrete physical model as a computing node;
determining projection nodes of the computing nodes on a plane where the preset sensor is located, and determining a straight line path from the projection nodes to the preset sensor;
The linear path is discretized into a plurality of points with the same distance interval, wherein the position of the incident point is any one point of the plurality of points on the linear path, and the position of each incident point on the linear path corresponds to an incident angle.
3. The positioning method of a positioning system of a partial discharge source in an electrical apparatus according to claim 1, wherein in step 5, a discharge signal corresponding to each node is calculated, a propagation time used when propagation is performed through a propagation path corresponding to a position of each incident point, and a propagation path having a shortest propagation time is determined as a fastest propagation path, comprising:
Determining a corresponding propagation path of a discharge signal corresponding to the calculation node when the discharge signal is incident to the position of each incident point, wherein the propagation path comprises: calculating a first propagation path of the discharge signal corresponding to the node before entering the surface of the discrete physical model and a second propagation path after entering the surface of the discrete physical model; the first propagation path is a linear distance from a calculation node to the position of an incident point, and the second propagation path is a linear distance from the position of the incident point to a preset sensor;
Acquiring a first propagation speed of the discharge signal on a first propagation path and a second propagation speed of the discharge signal on a second propagation path;
traversing the position of each incident point on the straight line path, and calculating the propagation time of the discharge signal corresponding to the calculation node when propagating through the position of each incident point on the straight line path according to the first propagation path, the first propagation speed, the second propagation path and the second propagation speed;
and determining a propagation path corresponding to the position of the incidence point with the shortest propagation time as the fastest propagation path corresponding to the computing node.
4. The positioning method of a positioning system of a partial discharge source in an electrical apparatus according to claim 1, wherein in step 5, traversing a position of each incident point on a straight path, calculating a propagation time when a discharge signal corresponding to a calculation node propagates through the position of each incident point on the straight path according to a first propagation path, a first propagation speed, a second propagation path, and a second propagation speed, includes:
calculating a first propagation time according to the first propagation speed and the first propagation path by the following formula, wherein the first propagation time is the propagation time of the discharge signal corresponding to the calculation node on the first propagation path:
Wherein Vel (i m,jm,km) is the propagation speed of the discharge signal at the node (i m,jm,km) before the discharge signal is incident on the electrical equipment housing, l is the number of nodes on the first propagation path, dl is the spacing between the nodes on the discrete physical model, and m is a positive integer;
Calculating a second propagation time according to the second propagation speed and the second propagation path by the following formula, wherein the second propagation time is the propagation time of the discharge signal corresponding to the calculation node on the second propagation path:
Wherein Vel oil is a propagation speed of the discharge signal when the discharge signal is incident into the electrical equipment housing, l is a number of nodes on the second propagation path, (i 1,j1,k1) is coordinates of a position of an incident point on the second propagation path, (i inc,jinc,kinc) is coordinates of a position where a preset sensor is located, and dl is a distance between nodes on the discrete physical model;
and taking the sum of the first propagation time and the second propagation time as the propagation time when the discharge signal corresponding to the calculation node propagates through the position of each incident point on the straight line path.
5. A positioning method of a positioning system of a partial discharge source in an electrical apparatus according to claim 1, wherein in step 8, determining the position of the partial discharge source in the electrical apparatus based on the estimated arrival time and the arrival time actually detected by the preset sensor comprises:
According to the arrival time of the discharge signal corresponding to each node to a plurality of preset sensors, calculating the expected arrival time difference of the discharge signal corresponding to each node to the plurality of preset sensors; according to the actual arrival time of the discharge signals corresponding to each node actually detected by the plurality of preset sensors, calculating the actual arrival time difference of the discharge signals corresponding to each node to the plurality of preset sensors; calculating a difference value between the estimated arrival time difference and the actual arrival time difference corresponding to each node; and determining the position corresponding to the node with the smallest difference as the position of the partial discharge source on the electrical equipment.
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| CN111308287B (en) * | 2020-03-06 | 2021-04-20 | 西南交通大学 | Ultrasonic positioning method for partial discharge fault point of traction transformer |
| CN111983398B (en) * | 2020-08-05 | 2024-01-30 | 国网江苏省电力有限公司电力科学研究院 | Method and system for positioning power transformer partial discharge TDOA under NLOS (non-linear optical system) condition |
| CN112834849B (en) * | 2021-01-05 | 2022-07-19 | 国网浙江省电力有限公司电力科学研究院 | Ultrasonic positioning method and device for partial discharge source of transformer |
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