CN113804285A - Method and system for determining low-frequency harmonic noise propagation sound field of power transformer bank - Google Patents
Method and system for determining low-frequency harmonic noise propagation sound field of power transformer bank Download PDFInfo
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Abstract
The invention discloses a method and a system for determining a low-frequency harmonic noise transmission sound field of a power transformer bank, wherein the method comprises the following steps: establishing a geometric model of the power transformer bank, and measuring the total sound power of transformers in the power transformer bank; determining an equivalent point sound source according to the geometric model of the power transformer bank, distributing the total sound power to each point sound source, determining the amplitude and the spatial position of each point sound source, and setting the initial phase of each point sound source according to a phase distribution rule; determining a sound field prediction point, determining effective sound rays of a point sound source influencing the sound field prediction point according to the spatial position of each point sound source, acquiring the three-dimensional length of each sound ray path, and calculating the contribution on each sound ray path; and according to the three-dimensional length of each sound ray path and the initial phase of each point sound source, overlapping the contribution amounts on all the sound ray paths of all the point sound sources having the influence on the sound field prediction point to determine the sound pressure value of the sound field prediction point considering the phase.
Description
Technical Field
The invention relates to the technical field of environmental protection of power grids, in particular to a method and a system for determining a low-frequency harmonic noise propagation sound field of a power transformer bank.
Background
The main noise of the transformer substation is harmonic noise with a fundamental frequency of 100Hz generated by a power transformer, the sound energy of the harmonic noise is mainly concentrated at a harmonic frequency between 100Hz and 500Hz, the noise of the transformer substation is mainly low-frequency harmonic noise from the distribution frequency band of the sound energy, the harmonic noise is not easy to attenuate in the transmission process and has strong penetrability, even if the sound pressure level of the harmonic component is not high, the harmonic component can bring great disturbance to people, in recent years, with the increase of power construction projects, particularly the expansion of extra-high voltage power transmission construction projects, the influence of the transformer substation noise on workers in the substation and the surrounding environment is greater and greater, and the pollution problem of the low-frequency harmonic noise of the transformer substation is more and more emphasized by people.
Harmonic noise of a transformer results from vibrations of the equipment housing, which in turn result from alternating current excitation of the coils and cores in the transformer. The main transformer and the high-impedance equipment of the large-scale transformer substation are mostly divided into A, B, C three phases, and the structures of the electric equipment of each phase are basically identical. Since the input currents of the respective phase devices are 120 degrees out of phase, the ac excitation to the coil and the core, the vibration of the housing, and the harmonic noise radiated from the housing are 120 degrees out of phase as a whole. From this point of view, harmonic noise generated by a three-phase power device inevitably has coherent characteristics.
Therefore, a noise propagation sound field calculation model considering the phase is needed to be researched and established, and a rapid and accurate quantitative evaluation means is provided for the treatment of the transformer substation noise and the evaluation of the sound environment influence.
Disclosure of Invention
The invention provides a method and a system for determining a low-frequency harmonic noise transmission sound field of an electric transformer bank, and aims to solve the problem of how to determine the low-frequency harmonic noise transmission sound field of the electric transformer bank.
In order to solve the above-mentioned problems, according to an aspect of the present invention, there is provided a method of determining a low frequency harmonic noise propagation sound field of a power transformer bank, the method comprising:
establishing a geometric model of the power transformer bank, and measuring the total sound power of transformers in the power transformer bank;
determining an equivalent point sound source according to the geometric model of the power transformer bank, distributing the total sound power to each point sound source, determining the amplitude and the spatial position of each point sound source, and setting the initial phase of each point sound source according to a phase distribution rule;
determining a sound field prediction point, determining effective sound rays of a point sound source having an influence on the sound field prediction point according to the spatial position of each point sound source, acquiring the three-dimensional length of each sound ray path, and calculating the contribution on each sound ray path according to the amplitude of the point sound source having the influence on the sound field prediction point and the three-dimensional length of the sound ray path;
and according to the three-dimensional length of each sound ray path and the initial phase of each point sound source, overlapping the contribution amounts on all the sound ray paths of all the point sound sources having the influence on the sound field prediction point to determine the sound pressure value of the sound field prediction point considering the phase.
Preferably, wherein said distributing said total acoustic power to each point acoustic source comprises:
and distributing the total sound power to each point sound source according to the proportion of the unit area of the grid where each equivalent point sound source is located to the total area of the transformer shell.
Preferably, wherein the method further comprises:
and dividing the noise influence area to be predicted into at least one grid according to the preset measurement accuracy, and taking the central point of each grid as a sound field prediction point.
Preferably, the method calculates the contribution amount on each sound ray path according to an ISO9613 model based on the amplitude of the point sound source having an influence on the sound field prediction point and the three-dimensional length of the sound ray path.
Preferably, the superimposing, according to the three-dimensional length of each sound ray path and the initial phase of each point sound source, contributions of all the sound ray paths of all the point sound sources having an influence on the sound field prediction point to determine a sound pressure value of the sound field prediction point considering the phase, includes:
wherein p isjA sound pressure value at a jth sound field prediction point considering the phase; | QijL is the sound pressure amplitude of the ith sound source point transmitted to the jth sound field prediction point, namely the contribution of the sound energy on the sound ray path;
is the phase of the point source; the number of power transformers in the transformer group is L, the phases corresponding to A, B, C three-phase transformers are-2 pi/3, 0 and 2 pi/3 respectively, and the initial phase alpha of each sound source pointPAre respectively as
And
the number of equivalent point sound sources of each phase of equipment is M; the number of prediction points in the sound field is N; the three-dimensional length of the sound ray path from the ith point sound source to the jth sound field prediction point in each phase of the electric power equipment is
k is the wave number corresponding to the harmonic frequency f, k is 2 pi f/c0， c0Is the speed of sound.
According to another aspect of the invention, there is provided a system for determining a low frequency harmonic noise propagation sound field of a power transformer bank, the system comprising:
the modeling unit is used for establishing a geometric model of the power transformer bank and measuring the total sound power of the transformers in the power transformer bank;
the point sound source determining unit is used for determining an equivalent point sound source according to the geometric model of the power transformer bank, distributing the total sound power to each point sound source, determining the amplitude and the spatial position of each point sound source, and setting the initial phase of each point sound source according to a phase distribution rule;
the contribution amount calculation unit is used for determining a sound field prediction point, determining effective sound rays of a point sound source having influence on the sound field prediction point according to the spatial position of each point sound source, acquiring the three-dimensional length of each sound ray path, and calculating the contribution amount on each sound ray path according to the amplitude of the point sound source having influence on the sound field prediction point and the three-dimensional length of the sound ray path;
and a sound pressure value determination unit for superimposing the contribution amounts on all the sound ray paths of all the point sound sources having an influence on the sound field prediction point according to the three-dimensional length of each sound ray path and the initial phase of each point sound source to determine a sound pressure value of the sound field prediction point considering the phase.
Preferably, wherein the point sound source determining unit, which distributes the total sound power to each point sound source, includes:
and distributing the total sound power to each point sound source according to the proportion of the unit area of the grid where each equivalent point sound source is located to the total area of the transformer shell.
Preferably, wherein the system further comprises:
and the sound field prediction point determining unit is used for dividing the noise influence area to be predicted into at least one grid according to the preset measurement precision, and taking the central point of each grid as a sound field prediction point.
Preferably, the contribution amount calculating unit calculates the contribution amount on each sound ray path according to an ISO9613 model based on the amplitude of the point sound source having an influence on the sound field prediction point and the three-dimensional length of the sound ray path.
Preferably, the sound pressure value determination unit, in which contributions of all the sound ray paths of all the point sound sources having an influence on the sound field prediction point are superimposed according to a three-dimensional length of each sound ray path and an initial phase of each point sound source to determine the sound pressure value of the sound field prediction point considering the phase, includes:
wherein p isjA sound pressure value at a jth sound field prediction point considering the phase; | QijL is the sound pressure amplitude of the ith sound source point transmitted to the jth sound field prediction point, namely the contribution of the sound energy on the sound ray path;
is the phase of the point source; the number of power transformers in the transformer group is L, the phases corresponding to A, B, C three-phase transformers are-2 pi/3, 0 and 2 pi/3 respectively, and the initial phase alpha of each sound source pointPAre respectively as
And
the number of equivalent point sound sources of each phase of equipment is M; the number of prediction points in the sound field is N; the three-dimensional length of the sound ray path from the ith point sound source to the jth sound field prediction point in each phase of the electric power equipment is
k is the wave number corresponding to the harmonic frequency f, k is 2 pi f/c0， c0Is the speed of sound.
The invention provides a method and a system for determining a low-frequency harmonic noise propagation sound field of a power transformer bank, which are used for calculating the propagation sound field of low-frequency harmonic noise by considering the initial phase of each equivalent point sound source in the transformer bank and the phase change in the propagation process, and can quickly and accurately calculate the propagation sound field of transformer substation noise.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
FIG. 1 is a flow diagram of a method 100 of determining a low frequency harmonic noise propagation sound field of a power transformer bank in accordance with an embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating phase difference distribution of equivalent point sound sources of phase transformers of a three-phase transformer bank according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the dimensions of a transformer according to an embodiment of the invention; and
FIG. 4 is a diagram illustrating phase-aware propagation model calculations according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating results calculated using a boundary element propagation model according to an embodiment of the present invention;
FIG. 6 is a graph comparing sound pressure values of three model sound receiving points according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a system 700 for determining a low frequency harmonic noise propagation sound field of a power transformer bank according to an embodiment of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Fig. 1 is a flow diagram of a method 100 of determining a low frequency harmonic noise propagation sound field of a power transformer bank according to an embodiment of the invention. As shown in fig. 1, in the method for determining a low-frequency harmonic noise propagation sound field of a power transformer bank provided by the embodiment of the present invention, initial phases of sound sources at equivalent points in the transformer bank and phase changes during propagation are considered, the propagation sound field of the low-frequency harmonic noise is calculated, and the propagation sound field of the transformer substation noise can be quickly and accurately calculated. The method 100 for determining the low-frequency harmonic noise propagation sound field of the power transformer bank provided by the embodiment of the invention starts from step 101, and establishes a geometric model of the power transformer bank in step 101, and measures the total sound power of the transformers in the power transformer bank.
In step 102, an equivalent point sound source is determined according to the geometric model of the power transformer bank, the total sound power is distributed to each point sound source, the amplitude and the spatial position of each point sound source are determined, and the initial phase of each point sound source is set according to the phase distribution rule.
Preferably, wherein said distributing said total acoustic power to each point acoustic source comprises:
and distributing the total sound power to each point sound source according to the proportion of the unit area of the grid where each equivalent point sound source is located to the total area of the transformer shell.
According to the invention, firstly, geometric modeling of the transformer substation is carried out, and a geometric model of the transformer substation is established according to the actual condition of the transformer substation, wherein the geometric model comprises main power equipment and buildings, and the geometric model only needs a main outline and does not contain structural details; then, a sound source model of the power transformer is constructed. Specifically, the method for constructing the sound source model of the power transformer comprises the following steps: measuring according to GB/T1094.10-2003 to obtain the total sound power of the power transformer bank; determining equivalent point sound sources according to the geometric model of the power transformer bank, distributing the total sound power to each point sound source according to the proportion of the unit area of the grid where each equivalent point sound source is located to the total area of the transformer shell, and obtaining the amplitude of each point sound source; and setting the initial phase of the point sound source according to the phase distribution rule.
In the invention, the sound source characteristics of the transformer can be equivalent by a plurality of point sound sources, the parameters of the point sound sources comprise source intensity and spatial position, wherein the source intensity can be obtained by measurement, the source intensity comprises amplitude and initial phase, the spatial position of the point sound sources is known, the spatial position comprises absolute position and relative position, the absolute position is the actual position of the point sound sources with the transformer substation as reference, and the relative position is the relative position of the point sound sources relative to a specific point on the converter transformer. The relative positions of equivalent point sound sources of all transformers in the transformer bank are the same, the amplitude values of the point sound sources in the transformers are the same, and the sum of the sound power of all points is the sound power of the transformers. The phase of each point sound source in the transformer is [ -theta, theta]Uniformly distributed, and the average phase of the point sound source in each phase transformer exists
The phase difference of (1).
As shown in FIG. 2, the phase distribution of the point source in the A-phase transformer is [ - θ, θ [ -]The phases B and C are respectively
And
for harmonic noise above 100Hz, there is θ ═ pi.
In step 103, a sound field prediction point is determined, effective sound rays of a point sound source having an influence on the sound field prediction point are determined according to the spatial position of each point sound source, the three-dimensional length of each sound ray path is obtained, and the contribution on each sound ray path is calculated according to the amplitude of the point sound source having an influence on the sound field prediction point and the three-dimensional length of the sound ray path.
Preferably, wherein the method further comprises:
and dividing the noise influence area to be predicted into at least one grid according to the preset measurement accuracy, and taking the central point of each grid as a sound field prediction point.
Preferably, the method calculates the contribution amount on each sound ray path according to an ISO9613 model based on the amplitude of the point sound source having an influence on the sound field prediction point and the three-dimensional length of the sound ray path.
The method disclosed by the invention is used for completing sound propagation calculation by applying a coherent propagation model, a noise influence area needing to be predicted is divided into grids in a transformer substation, the size of each grid is determined according to the solving precision, and the central point of each grid is used as a sound field prediction point. And aiming at a specific sound field prediction point, obtaining effective sound rays of all sound source points influencing the sound field prediction point, obtaining the three-dimensional length of each sound ray path, and calculating the contribution amount of sound energy on each sound ray path according to ISO 9613.
In step 104, according to the three-dimensional length of each sound ray path and the initial phase of each point sound source, the contribution amounts on all the sound ray paths of all the point sound sources having influence on the sound field prediction point are superposed to determine the sound pressure value of the sound field prediction point considering the phase.
Preferably, the superimposing, according to the three-dimensional length of each sound ray path and the initial phase of each point sound source, contributions of all the sound ray paths of all the point sound sources having an influence on the sound field prediction point to determine a sound pressure value of the sound field prediction point considering the phase, includes:
wherein p isjA sound pressure value at a jth sound field prediction point considering the phase; | QijL is the sound pressure amplitude of the ith sound source point transmitted to the jth sound field prediction point, namely the contribution of the sound energy on the sound ray path;
is the phase of the point source; the number of power transformers in the transformer group is L, the phases corresponding to A, B, C three-phase transformers are-2 pi/3, 0 and 2 pi/3 respectively, and the initial phase alpha of each sound source pointPAre respectively as
And
the number of equivalent point sound sources of each phase of equipment is M; the number of prediction points in the sound field is N; the three-dimensional length of the sound ray path from the ith point sound source to the jth sound field prediction point in each phase of the electric power equipment is
k is the wave number corresponding to the harmonic frequency f, k is 2 pi f/c0， c0Is the speed of sound.
In the present invention, at each sound field prediction point, the contribution amounts on all the sound ray paths contributed by all the sound source points are superimposed in a sound pressure manner in consideration of the phase to obtain a sound pressure value at the sound field prediction point in consideration of the phase. The calculation result is related to the sound wave frequency, the distance between the sound source point and the sound field prediction point, the initial phase of the sound source and the sound line contribution amount.
Generally, the structure, operation condition and firewall of each phase of equipment in three-phase power equipment are basically the same, so that point source groups corresponding to each phase of equipment have the same number and spatial distribution, and the amplitude of equivalent point sound sources at the same position of each phase transformer is equal, but the phase difference is 2 pi/3.
In the present invention, let | QiI is the amplitude of the point sound source on the transformer, QijL is the sound pressure amplitude transmitted from the ith sound source point to the jth sound field prediction point, namely the contribution of the sound energy of the given sound ray path, and the magnitude of the contribution is calculated according to an ISO9613 model;
is the phase angle of the point sound source; the number of power transformers in the transformer group is L, and the phases corresponding to A, B, C three-phase transformers are-2 pi/3, 0 and 2 pi/3 respectively, so the initial phase alpha of each sound source pointPAre respectively as
And
and setting the number of equivalent point sound sources of each phase of equipment as M. The number of prediction points in the sound field is N. The distances from the ith point sound source to the jth sound field prediction point in each phase of electric power equipment are respectively
I.e. the path length of the sound, according to ISO 9613; k is the wave number corresponding to the harmonic frequency, k is 2 pi f/c0， c0For the sound velocity, the sound pressure at the sound field prediction point can be found to be pj：
After all sound ray paths between the sound source point and the sound field prediction point are obtained, the three-dimensional length of each sound ray path, the contribution amount on the path and other information are respectively calculated, then phase superposition calculation is carried out according to different frequencies by combining the initial phase of the sound source point corresponding to each sound ray path, and the sound pressure value of the sound field prediction point considering the phase is solved.
Compared with the boundary element method, the method has the advantages that the calculation results are basically consistent, the calculation efficiency is greatly improved, and the transmission sound field of the noise of the transformer substation can be quickly and accurately calculated; compared with an ISO9613 calculation model, the method not only considers the energy of noise, but also considers the phase factor in the sound transmission process, and can accurately predict the transmission sound field of the coherent noise of the transformer substation.
The following specifically exemplifies embodiments of the present invention
The example originates from an actual substation, and a coherent propagation model (i.e. a propagation model corresponding to the method of the present invention) is first applied to calculate a propagation sound field of 100Hz harmonic noise. Calculating the same object under the same frequency by using a boundary meta-model, and verifying a coherent propagation model by using a calculation result of the boundary meta-model; and finally, calculating the same object by using an ISO9613 model, and comparing the difference with a coherent propagation model.
(1) Description of computational models
As shown in fig. 4, the transformer substation model is composed of three A, B, C three-phase transformers and four partition walls, the transformers have the same size, the height of the transformer box is 4.5 m, the length of the transformer box is 3.8 m, the width of the transformer box is 7.39 m, the three transformers are separated by 4 partition walls with the height of 9.5m, and the phases of the sound sources of the three transformers are different by 120 °.
(a) Calculation model taking phase into account
The total acoustic power of each transformer is set to 110 dB. According to the sound source decomposition and phase distribution principle, the phase-A transformer sound source is dispersed into 101 point sound sources with the phases of +/-180-120 degrees, the phase-B transformer sound source is dispersed into 101 point sound sources with the phases of +/-180 degrees, and the phase-C transformer sound source is dispersed into 101 point sound sources with the phases of +/-180-120 degrees. The sound energy is distributed according to the area of each surface of the transformer shell, the sound power of each point sound source in front of and behind each transformer is 80.44dB, the sound power of each point sound source on the left surface and the right surface is 79.65dB, and the sound power of each point sound source on the top surface is 71 dB.
Setting the isolation wall as a sound barrier; the sound field grid is set at 1.5m height, and the grid density is 0.5m multiplied by 0.5 m. Setting the ground reflection coefficient to be 1 in the calculation process, namely setting the ground as a reflection surface; setting the sound propagation environment temperature at 10 ℃; relative humidity is 70%; the sound pressure level of the background noise is 25 dB; consider barrier attenuation, atmospheric attenuation, geometric attenuation, ground effects.
(b) Boundary meta-model
And establishing a geometric model of the transformer substation through grid division software, and dividing grids. The transformer model is divided according to the size of each grid being 100mm, and 225768 surface grids are divided in total. And importing the grid-divided transformer substation model into boundary element calculation software.
In the boundary element method calculation, a substation model is first set as an acoustic grid, and a partition wall is set as a rigid reflecting surface. The model z is set to 0 plane, that is, the ground plane is set as a reflection plane. The sound propagation environment was set at room temperature, i.e., the sound velocity was 340m/s and the density was 1.225kg/m 3. A site grid is set in the boundary element method calculation, and a square area with the height of 1.5m and the grid size of 4m × 4m is calculated to be 100m × 100m and comprises the substation 1/4.
The transformer substation model is large in size and cannot be processed into a single point sound source. Respectively dispersing A, B, C transformers into 26 point sound sources which are uniformly distributed according to the decomposition and phase distribution principle of a single transformer sound source, wherein the total sound power of each transformer is 110dB, and the amplitude of each point sound source in the front and the rear is set to be 0.047kg/s 2; the amplitude distribution of each point sound source on the left and right surfaces is set to be 0.053kg/s 2; the amplitude value of each point sound source is set to be 0.049kg/s2, and the phase value of each point sound source on the transformer is set to be randomly distributed between [ -pi, pi ].
(c) ISO9613 model
According to an ISO9613 calculation model, the sound field grid is at the height of 1.5m, and the grid density is 0.5m multiplied by 0.5 m; setting the ground reflection coefficient to be 1 in software, namely setting the ground as a reflection surface; setting the 4-sided firewall as a reflecting surface; setting the sound propagation environment to a relative humidity of 70% at 10 ℃; the sound pressure level of the background noise is 25 dB; and calculating and opening the barrier attenuation, the atmospheric attenuation, the geometric attenuation and the ground effect.
And considering the simulated actual transformer substation noise, setting the total sound power of each transformer to be 110dB in transformer substation noise estimation software added with a new calculation model. Since ISO9613 is not considering coherent phase, all the point sound source phases are set to 0 ° when the transformer is discretized into a set of point sound sources. The sound power of the point sound source in front of and behind the transformer is 80.44dB, the sound power of the point sound source on the left and right sides is 79.65dB, and the sound power of the point sound source on the top surface is 71 dB.
(2) Calculation results and comparison
(a) Calculation results
The sound field cloud images calculated by the coherent propagation model and the boundary element model are respectively shown in fig. 4 and 5.
The coherent propagation model takes about half an hour to calculate, and a sound pressure cloud picture of a 100Hz harmonic sound field of the transformer substation is obtained and shown in figure 4. It can be seen that there are significant interference fringes in their calculated sound pressure cloud images, which are the result of coherent noise interaction. The related propagation model not only considers the sound pressure amplitude of the low-frequency coherent noise, but also considers the phase factor of the low-frequency coherent noise, and accords with the physical essence of coherent noise propagation.
The boundary element model calculation takes 170 hours, and a sound pressure cloud chart of the 100Hz harmonic sound field of the transformer substation is obtained and is shown in FIG. 5. Compared with the calculation result shown in fig. 4, the distribution of the acoustic pressure cloud image interference fringes is basically consistent with the distribution of the acoustic pressure cloud image interference fringes. Because the boundary element model is based on the wave equation and is a numerical solution closest to the physical nature of coherent noise propagation attenuation, the boundary element method can accurately predict the attenuation propagation of the low-frequency coherent noise. However, in the process of calculating the low-frequency coherent sound propagation sound field of such a large area of the substation, it takes 170 hours to calculate only one frequency point of 100Hz, and the efficiency is extremely low. If the method is applied to the calculation of the sound propagation of the actual transformer substation, the calculation range needs to be larger, and the calculation frequency points need to be more, so that the method is difficult to be applied to the prediction of the sound propagation of the actual transformer substation. But since the model most reflects the physical nature of coherent noise, it can be used to validate other types of propagation attenuation models under certain conditions.
The ISO9613 model has no obvious interference fringes in the sound pressure cloud chart, because the ISO9613 model does not consider the phase calculation term in the wave equation and only superposes the sound energy.
(b) Comparison and verification
The calculation result of the boundary meta-model is used as a verification standard, and the calculation result of the coherent propagation model is basically consistent with the overall trend of the result of the boundary meta-model and the position of the coherent fringe; and the results of the ISO9613 model are greatly different from the results of the boundary meta model calculation. In order to further quantitatively compare the difference of the three models, sound receiving point groups are respectively arranged in the propagation sound fields of the three models, the point groups are distributed on a straight line with the starting point being the center point of the transformer bank and forming an included angle of 45 degrees with the symmetric center line of the transformer bank, and the distance between the point groups is 1 m.
Fig. 6 is a comparison of sound pressure values of the three models at 25 sound receiving points. It can be seen from the figure that the calculation results of the boundary meta-model and the coherent propagation model are closer, the sound pressure values of most sound receiving points are different by less than 3dB except the sound receiving points of individual near-field positions.
The ISO9613 model in fig. 6 has a higher calculated sound pressure value than the other two algorithms, and the reason for this phenomenon can be explained by the attenuation characteristics of the line array sound source. Let r be the distance from the sound receiving point to the linear array, and for the incoherent linear array, the sound pressure and
is in direct proportion; for coherent arrays, the sound pressure at the sound receiving point is proportional to r, so that the incoherent arrays decay more slowly than the coherent arrays. Therefore, for the transformer bank, the sound pressure obtained by the ISO9613 model without considering the coherence characteristic is higher than the sound pressure values of the boundary meta model and the coherence propagation model with considering the coherence effect at the same sound receiving point.
TABLE 1 comparison of Performance of three computational models
Table 1 shows the performance comparison of three acoustic propagation attenuation calculation models. Compared with the boundary element method, the coherent propagation model considering the phase has basically consistent calculation results, greatly improves the calculation efficiency and can quickly and accurately calculate the propagation sound field of the noise of the transformer substation; compared with an ISO9613 calculation model, the correlation propagation model not only considers the energy of noise, but also considers the phase factor in the sound propagation process, and can accurately predict the propagation sound field of the coherent noise of the transformer substation. In conclusion, the coherent propagation model applying the method can accurately, quickly and effectively calculate the noise propagation sound field of the transformer substation.
Fig. 7 is a schematic diagram of a system 700 for determining a low frequency harmonic noise propagation sound field of a power transformer bank according to an embodiment of the present invention. As shown in fig. 7, a system 700 for determining a low-frequency harmonic noise propagation sound field of a power transformer bank according to an embodiment of the present invention includes: a modeling unit 701, a point sound source determination unit 702, a contribution amount calculation unit 703, and a sound pressure value determination unit 704.
Preferably, the modeling unit 701 is configured to establish a geometric model of the power transformer bank and measure the total acoustic power of the transformers in the power transformer bank.
Preferably, the point sound source determining unit 702 is configured to determine an equivalent point sound source according to a geometric model of the power transformer bank, distribute the total sound power to each point sound source, determine the amplitude and the spatial position of each point sound source, and set the initial phase of each point sound source according to a phase distribution rule.
Preferably, the point sound source determining unit 702, which distributes the total sound power to each point sound source, includes:
and distributing the total sound power to each point sound source according to the proportion of the unit area of the grid where each equivalent point sound source is located to the total area of the transformer shell.
Preferably, the contribution amount calculating unit 703 is configured to determine a sound field prediction point, determine an effective sound ray of a point sound source having an influence on the sound field prediction point according to a spatial position of each point sound source, acquire a three-dimensional length of each sound ray path, and calculate a contribution amount on each sound ray path according to an amplitude of the point sound source having an influence on the sound field prediction point and the three-dimensional length of the sound ray path.
Preferably, wherein the system further comprises:
and the sound field prediction point determining unit is used for dividing the noise influence area to be predicted into at least one grid according to the preset measurement precision, and taking the central point of each grid as a sound field prediction point.
Preferably, the contribution amount calculating unit 703 calculates the contribution amount on each sound ray path according to an ISO9613 model, based on the amplitude of the point sound source having an influence on the sound field prediction point and the three-dimensional length of the sound ray path.
Preferably, the sound pressure value determining unit 704 is configured to superimpose the contribution amounts on all the sound ray paths of all the point sound sources having an influence on the sound field prediction point according to the three-dimensional length of each sound ray path and the initial phase of each point sound source to determine the sound pressure value of the sound field prediction point considering the phase.
Preferably, the determining unit 704 of sound pressure values, which superimposes the contributions of all the sound ray paths of all the point sound sources having an influence on the sound field prediction point according to the three-dimensional length of each sound ray path and the initial phase of each point sound source, to determine the sound pressure value of the sound field prediction point considering the phase, includes:
wherein p isjA sound pressure value at a jth sound field prediction point considering the phase; | QijL is the sound pressure amplitude of the ith sound source point transmitted to the jth sound field prediction point, namely the contribution of the sound energy on the sound ray path;
is the phase of the point source; the number of power transformers in the transformer group is L, the phases corresponding to A, B, C three-phase transformers are-2 pi/3, 0 and 2 pi/3 respectively, and the initial phase alpha of each sound source pointPAre respectively as
And
the number of equivalent point sound sources of each phase of equipment is M; the number of prediction points in the sound field is N; the three-dimensional length of the sound ray path from the ith point sound source to the jth sound field prediction point in each phase of the electric power equipment is
k is the wave number corresponding to the harmonic frequency f, k is 2 pi f/c0， c0Is the speed of sound.
The system 700 for determining the low-frequency harmonic noise propagation sound field of the power transformer bank according to the embodiment of the present invention corresponds to the method 100 for determining the low-frequency harmonic noise propagation sound field of the power transformer bank according to another embodiment of the present invention, and is not described herein again.
The invention has been described with reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ device, component, etc ]" are to be interpreted openly as referring to at least one instance of said device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (10)
1. A method of determining a power transformer bank low frequency harmonic noise propagation sound field, the method comprising:
establishing a geometric model of the power transformer bank, and measuring the total sound power of transformers in the power transformer bank;
determining an equivalent point sound source according to the geometric model of the power transformer bank, distributing the total sound power to each point sound source, determining the amplitude and the spatial position of each point sound source, and setting the initial phase of each point sound source according to a phase distribution rule;
determining a sound field prediction point, determining effective sound rays of a point sound source having an influence on the sound field prediction point according to the spatial position of each point sound source, acquiring the three-dimensional length of each sound ray path, and calculating the contribution on each sound ray path according to the amplitude of the point sound source having the influence on the sound field prediction point and the three-dimensional length of the sound ray path;
and according to the three-dimensional length of each sound ray path and the initial phase of each point sound source, overlapping the contribution amounts on all the sound ray paths of all the point sound sources having the influence on the sound field prediction point to determine the sound pressure value of the sound field prediction point considering the phase.
2. The method of claim 1, wherein said distributing said total acoustic power to each point source comprises:
and distributing the total sound power to each point sound source according to the proportion of the unit area of the grid where each equivalent point sound source is located to the total area of the transformer shell.
3. The method of claim 1, further comprising:
and dividing the noise influence area to be predicted into at least one grid according to the preset measurement accuracy, and taking the central point of each grid as a sound field prediction point.
4. The method according to claim 1, wherein the method calculates the contribution on each sound ray path according to an ISO9613 model based on the amplitude of the point sound source having an influence on the sound field prediction point and the three-dimensional length of the sound ray path.
5. The method according to claim 1, wherein the determining the sound pressure value of the sound field prediction point considering the phase by adding contributions of all sound ray paths of all point sound sources having an influence on the sound field prediction point according to the three-dimensional length of each sound ray path and the initial phase of each point sound source comprises:
wherein p isjA sound pressure value at a jth sound field prediction point considering the phase; | QijL is the sound pressure amplitude of the ith sound source point transmitted to the jth sound field prediction point, namely the contribution of the sound energy on the sound ray path;
is the phase of the point source; the number of power transformers in the transformer group is L, the phases corresponding to A, B, C three-phase transformers are-2 pi/3, 0 and 2 pi/3 respectively, and the initial phase alpha of each sound source pointPAre respectively as
And
equivalent point sound source of each phase equipmentThe number of (3) is M; the number of prediction points in the sound field is N; the three-dimensional length of the sound ray path from the ith point sound source to the jth sound field prediction point in each phase of the electric power equipment is
k is the wave number corresponding to the harmonic frequency f, k is 2 pi f/c0，c0Is the speed of sound.
6. A system for determining a low frequency harmonic noise propagation sound field of a power transformer bank, the system comprising:
the modeling unit is used for establishing a geometric model of the power transformer bank and measuring the total sound power of the transformers in the power transformer bank;
the point sound source determining unit is used for determining an equivalent point sound source according to the geometric model of the power transformer bank, distributing the total sound power to each point sound source, determining the amplitude and the spatial position of each point sound source, and setting the initial phase of each point sound source according to a phase distribution rule;
the contribution amount calculation unit is used for determining a sound field prediction point, determining effective sound rays of a point sound source having influence on the sound field prediction point according to the spatial position of each point sound source, acquiring the three-dimensional length of each sound ray path, and calculating the contribution amount on each sound ray path according to the amplitude of the point sound source having influence on the sound field prediction point and the three-dimensional length of the sound ray path;
and a sound pressure value determination unit for superimposing the contribution amounts on all the sound ray paths of all the point sound sources having an influence on the sound field prediction point according to the three-dimensional length of each sound ray path and the initial phase of each point sound source to determine a sound pressure value of the sound field prediction point considering the phase.
7. The system according to claim 6, wherein the point sound source determining unit distributes the total sound power to each point sound source, including:
and distributing the total sound power to each point sound source according to the proportion of the unit area of the grid where each equivalent point sound source is located to the total area of the transformer shell.
8. The system of claim 6, further comprising:
and the sound field prediction point determining unit is used for dividing the noise influence area to be predicted into at least one grid according to the preset measurement precision, and taking the central point of each grid as a sound field prediction point.
9. The system according to claim 6, wherein the contribution amount calculating unit calculates the contribution amount on each sound ray path according to an ISO9613 model from the amplitude of the point sound source having an influence on the sound field prediction point and the three-dimensional length of the sound ray path.
10. The system according to claim 6, wherein the sound pressure value determination unit adds the contribution amounts on all the ray paths of all the point sound sources having an influence on the sound field prediction point according to the three-dimensional length of each ray path and the initial phase of each point sound source to determine the sound pressure value of the sound field prediction point considering the phase, includes:
wherein p isjA sound pressure value at a jth sound field prediction point considering the phase; | QijL is the sound pressure amplitude of the ith sound source point transmitted to the jth sound field prediction point, namely the contribution of the sound energy on the sound ray path;
is the phase of the point source; the number of power transformers in the transformer group is L, the phases corresponding to A, B, C three-phase transformers are-2 pi/3, 0 and 2 pi/3 respectively, and the initial phase alpha of each sound source pointPAre respectively as
And
the number of equivalent point sound sources of each phase of equipment is M; the number of prediction points in the sound field is N; the three-dimensional length of the sound ray path from the ith point sound source to the jth sound field prediction point in each phase of the electric power equipment is
k is the wave number corresponding to the harmonic frequency f, k is 2 pi f/c0，c0Is the speed of sound.
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