CN109299564B - Correction method for temperature factor influence in transformer bias current simulation calculation process - Google Patents
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Abstract
The invention relates to a method for correcting the influence of temperature factors in the process of simulation calculation of bias current of a transformer, which comprises the following steps: building a simulation model, and carrying out modeling assignment according to the collected conductor radius, segment number, conductor type and coating type parameters of the transformer substation grounding grid, main transformer and grounding electrode at the early stage; whether the simulation model is defect-free or not is self-checked through a program, if the simulation model is defect-free, the next step is carried out, and if the simulation model is not defect-free, the model is corrected by reestablishing parameters of a ground grid, a main transformer and a grounding electrode; carrying out magnetic bias current simulation calculation, and comparing whether the error between the calculated value and the measured value is less than 5%; if the error range of 5% is met, the calculation is finished, otherwise, the temperature coefficient is corrected and recalculated. By the invention, the error between the calculated value and the actual value of the direct current magnetic bias current is obviously reduced; the bias magnetic currents under different environmental temperatures are normalized by taking the current at 20 ℃ as a reference, and engineering calculation can be facilitated through temperature coefficient correction.
Description
Technical Field
The invention relates to the technical field of high-voltage direct-current transmission calculation, in particular to a correction method for temperature factor influence in a transformer bias current simulation calculation process.
Background
Under the normal operation state of high-voltage and extra-high voltage direct current transmission, a direct current line works in a bipolar operation mode, direct current forms a loop through a transmission line with two poles, but under the condition of system debugging, maintenance or failure, the high-voltage direct current transmission adopts a single-pole earth loop operation mode. When the single-pole earth loop operates, a current field has a large influence on the environment of a current flowing range, and a huge direct current flows into the earth through a direct current grounding pole, so that the potential of the earth is changed within a large range, and the change of the potential of the earth can influence an alternating current system in an affected area. Especially for an alternating current system with a grounded neutral point, a transformer substation with different direct current potentials forms a direct current loop through a power transmission line and a transformer winding, and direct current can invade the transformer winding through the neutral point of the transformer to cause direct current magnetic biasing of the transformer. The phenomenon of noise increase, vibration aggravation and the like can occur after the transformer has direct current magnetic biasing, overheating can also occur, and harmonic distortion of an alternating current power grid is increased.
For the event that the noise of the transformer increases and the safe operation is threatened due to the phenomenon of ground potential rise when a direct current system operates in a single pole ground, the phenomenon is frequently reported in power systems in China. For the phenomenon, a large amount of manpower is put into research by various domestic relevant institutions for electric power scientific research and colleges, research conditions are focused on two main aspects, and on one hand, the ground surface potential and the current distribution condition of a direct current system during monopolar and ground operation are researched; on the other hand, the influence and suppression method of direct current on coil equipment such as a transformer are studied. It has been found that the effect of ambient temperature on the dc bias current is less of a concern in prior studies. The climate conditions of China are complex, and the climate difference among regions is large, so that the influence of the environmental temperature on the direct-current magnetic bias current of the transformer substation in the power grid needs to be researched, and the calculation result can be conveniently and reasonably evaluated.
Disclosure of Invention
The invention aims to provide a correction method for considering the influence of environmental temperatures in different areas on a direct current bias current, ensuring the accuracy of calculation of the direct current bias current and obviously reducing the error between the calculated value and the actual value of the direct current bias current so as to reduce the influence of temperature factors in the simulation calculation process of the transformer bias current.
In order to achieve the purpose, the invention adopts the following technical scheme: a correction method for temperature factor influence in a transformer bias current simulation calculation process comprises the following sequential steps:
(1) Building a simulation model, and carrying out modeling assignment according to the collected conductor radius, segment number, conductor type and coating type parameters of the transformer substation grounding grid, main transformer and grounding electrode at the early stage;
(2) Whether the simulation model is defect-free or not is self-checked through a program, if the simulation model is defect-free, the next step is carried out, and if the simulation model is not defect-free, the model is corrected by reestablishing parameters of a ground grid, a main transformer and a grounding electrode;
(3) Carrying out magnetic bias current simulation calculation, and comparing whether the error between the calculated value and the measured value is less than 5%;
(4) If the error range of 5% is met, the calculation is finished, otherwise, the temperature coefficient is corrected and the calculation is carried out again.
In the step (1), the generation of the grounding grid is to obtain the area of the high-density grounding grid of each station by inputting the soil resistivity and the grounding resistance through GSE software; main transformer modeling, namely sequentially drawing 7 main transformers in the middle of a ground grid in an SESCAD software, simultaneously drawing a high-medium voltage three-phase winding, and connecting the winding with a neutral point of the main transformers; and modeling the grounding electrode, and drawing in the SESCAD by using the original design parameters of the grounding electrode.
In the step (2), after the simulation model is built, checking whether the model has the defects of short sections, conductor overlapping, suspended nodes and network gaps by using a SESCAD program.
In the step (3), after the self-test of the simulation model is completed, the MALZ software is used to calculate the dc bias current, and the calculated value is compared with the measured value to see whether the error is within the range of 5%.
In the step (4), when the error exceeds the range of 5%, correcting the accuracy of the model by modifying the temperature correction coefficients of regions with different resistivities; if the 5% error is satisfied, the calculation is deemed accurate.
According to the technical scheme, the invention has the advantages that: firstly, the error between the calculated value and the actual value of the direct current magnetic bias current is obviously reduced; secondly, the bias current under different environmental temperatures is normalized by taking the current at 20 ℃ as a reference, and engineering calculation can be facilitated through temperature coefficient correction.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a schematic view of an analytical rack according to the present invention;
FIG. 3 is a schematic diagram showing the effect of low resistance region temperature on DC bias current;
FIG. 4 is a schematic diagram illustrating the effect of the middle blocking region temperature on the DC bias current;
FIG. 5 is a diagram illustrating the effect of the temperature of the high resistance region on the DC bias current.
Detailed Description
As shown in fig. 1, a method for correcting the influence of temperature factors in a simulation calculation process of transformer bias current includes the following steps:
(1) Building a simulation model, and carrying out modeling assignment according to the collected conductor radius, segment number, conductor type and coating type parameters of the transformer substation grounding grid, main transformer and grounding electrode at the early stage;
(2) Whether the simulation model is defect-free or not is self-checked through a program, if the simulation model is defect-free, the next step is carried out, and if the simulation model is not defect-free, the model is corrected by reestablishing parameters of a ground grid, a main transformer and a grounding electrode;
(3) Carrying out magnetic bias current simulation calculation, and comparing whether the error between the calculated value and the measured value is less than 5%;
(4) If the error range of 5% is met, the calculation is finished, otherwise, the temperature coefficient is corrected and the calculation is carried out again.
In the step (1), the generation of the grounding grid is to obtain the area of the high-density grounding grid of each station by inputting the soil resistivity and the grounding resistance through GSE software; main transformer modeling, namely sequentially drawing 7 main transformers in the middle of a ground grid in an SESCAD software, simultaneously drawing a high-medium voltage three-phase winding, and connecting the winding with a neutral point of the main transformers; and modeling the grounding electrode, and drawing in the SESCAD by using the original design parameters of the grounding electrode.
In the step (2), after the simulation model is built, checking whether the model has the defects of short sections, conductor overlapping, suspended nodes and network gaps by using an SESCAD program for self-checking.
In the step (3), after the self-test of the simulation model is completed, the MALZ software is used to calculate the dc bias current, and the calculated value is compared with the measured value to see whether the error is within the range of 5%.
In the step (4), when the error exceeds the range of 5%, correcting the accuracy of the model by modifying the temperature correction coefficients of regions with different resistivities; if the 5% error is satisfied, the calculation is deemed accurate.
The invention is further described below with reference to fig. 1, 2, 3, 4 and 5.
The theoretical rack in fig. 2 is composed of 9 substations, respectively S 1 -S 9 The distance between the geographical positions of all the stations is 30km, the stations are connected with connecting lines, the whole transformer substation is distributed in a square shape with the side length of 60km, and g is a direct current grounding electrode and is positioned at a distance S 8 Station level 30 km. Geographical range of the model and associated proceduresAre in agreement; and dividing a geographical area in a research range into a high-resistance area, a medium-resistance area and a low-resistance area by taking the soil resistivity of the constant-temperature layer at 20 ℃ as a reference. Wherein, the region with shallow soil resistivity below 60 Ω · m is called low-resistance region; the region with the shallow soil resistivity of 60-300 omega-m is called a middle-resistance region; the region where the shallow soil resistivity is 300 Ω · m or more is called a high resistance region. In consideration of the climate conditions of China, five environmental temperatures are set in the simulation respectively as follows: the magnitudes of the bias currents in the regions with different resistivities at the five temperatures are respectively calculated at 0 ℃, 10 ℃, 20 ℃, 30 ℃ and 40 ℃, the data are normalized by taking the current at the temperature of 20 ℃ as a reference, and the bias current temperature characteristic curves of all the stations are shown in figures 3, 4 and 5. As can be seen from fig. 3, 4 and 5, temperature has an influence on the bias current; during correction, the calculated value of the bias current at 20 ℃ can be corrected by taking the actual environmental temperature as a reference, so that the calculated value is closer to the actual value. The stations are sorted into S according to the degree of temperature influence according to FIGS. 3, 4, 5 9 >S 7 ≈S 5 >S 8 >S 6 >S 1 ≈S 3 >S 2 ≈S 4 . It can be seen that S 8 The temperature characteristic of the station is in the central position and the station is most affected by the bias current in the rack closest to the earth, so according to S in fig. 4, 5 8 The temperature characteristic curve of the station is used for selecting the corresponding correction coefficient, which has the most reliability and the most significance. The curve discrete degree of each station in the medium resistance region and the high resistance region is low, the error of the medium resistance region is +/-4% according to the correction method, the error of the high resistance region is +/-2%, and the discrete degree of the low resistance region is high, so that large errors can be caused, therefore, the transformer substation in the low resistance region is recommended to be classified according to the distance between the transformer substation and the grounding electrode, and correction coefficients in different temperature ranges are provided for each station.
The invention considers the influence of the environmental temperature of different areas on the direct current magnetic bias current, ensures the accuracy of the calculation of the direct current magnetic bias current and provides a temperature correction method for different soil resistivity areas. The correction method is verified by using the field measurement data of the bias current, and the result shows that the error between the calculated value and the actual value of the direct current bias current is obviously reduced after the temperature correction method provided by the invention is used.
Claims (4)
1. A correction method for temperature factor influence in a transformer bias current simulation calculation process is characterized by comprising the following steps: the method comprises the following steps in sequence:
(1) Building a simulation model, and carrying out modeling assignment according to the parameters of conductor radiuses, section numbers, conductor types and coating types of the transformer substation grounding grid, the main transformer and the grounding electrode which are collected in the earlier stage; the generation of the grounding grid is to obtain the area of the high-density grounding grid of each station by inputting the resistivity and the grounding resistance of the soil through GSE software; main transformer modeling, namely sequentially drawing 7 main transformers in the middle of a ground grid in an SESCAD software, simultaneously drawing a high-medium voltage three-phase winding, and connecting the winding with a neutral point of the main transformers; modeling the grounding electrode, and drawing the grounding electrode in the SESCAD by using the original design parameters of the grounding electrode;
(2) Whether the simulation model is defect-free or not is self-checked through a program, if the simulation model is defect-free, the next step is carried out, and if the simulation model is not defect-free, the model is corrected by reestablishing parameters of a ground grid, a main transformer and a grounding electrode;
(3) Carrying out magnetic bias current simulation calculation, and comparing whether the error between the calculated value and the measured value is less than 5%;
(4) If the error range of 5% is met, the calculation is finished, otherwise, the temperature coefficient is corrected and recalculated.
2. The method for correcting the influence of the temperature factor in the simulation calculation process of the bias current of the transformer according to claim 1, wherein the method comprises the following steps: in the step (2), after the simulation model is built, checking whether the model has the defects of short sections, conductor overlapping, suspended nodes and network gaps by using an SESCAD program for self-checking.
3. The method for correcting the influence of the temperature factor in the simulation calculation process of the bias current of the transformer according to claim 1, wherein the method comprises the following steps: in the step (3), after the self-test of the simulation model is completed, the MALZ software is used to calculate the dc bias current, and the calculated value is compared with the measured value to see whether the error is within the range of 5%.
4. The method for correcting the influence of the temperature factor in the simulation calculation process of the bias current of the transformer according to claim 1, wherein the method comprises the following steps: in the step (4), when the error exceeds the range of 5%, correcting the accuracy of the model by modifying the temperature correction coefficients of regions with different resistivities; if the 5% error is satisfied, the calculation is deemed accurate.
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| CN113673083B (en) * | 2021-07-16 | 2023-08-18 | 国网浙江省电力有限公司杭州供电公司 | Transformer direct-current magnetic bias risk assessment method |
| CN114184876B (en) * | 2022-02-16 | 2022-05-10 | 国网江西省电力有限公司电力科学研究院 | DC magnetic bias monitoring, evaluation and earth model correction platform |
| CN117113733B (en) * | 2023-10-24 | 2024-02-02 | 国家电网有限公司西北分部 | Method and device for acquiring bias current of direct current near zone of power grid |
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