CN112034271B - Method for calculating induction electricity of steel frame under AC power transmission line - Google Patents
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 49
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- 230000005540 biological transmission Effects 0.000 title claims abstract description 47
- 230000006698 induction Effects 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 title claims abstract description 16
- 230000005611 electricity Effects 0.000 title claims abstract description 7
- 239000004020 conductor Substances 0.000 claims abstract description 28
- 239000000725 suspension Substances 0.000 claims description 7
- 230000001133 acceleration Effects 0.000 claims description 3
- 230000005484 gravity Effects 0.000 claims description 3
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- 230000005684 electric field Effects 0.000 description 5
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/12—Measuring electrostatic fields or voltage-potential
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/08—Measuring electromagnetic field characteristics
- G01R29/0807—Measuring electromagnetic field characteristics characterised by the application
- G01R29/0814—Field measurements related to measuring influence on or from apparatus, components or humans, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning
- G01R29/0857—Dosimetry, i.e. measuring the time integral of radiation intensity; Level warning devices for personal safety use
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/08—Measuring electromagnetic field characteristics
- G01R29/0864—Measuring electromagnetic field characteristics characterised by constructional or functional features
- G01R29/0892—Details related to signal analysis or treatment; presenting results, e.g. displays; measuring specific signal features other than field strength, e.g. polarisation, field modes, phase, envelope, maximum value
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Abstract
The invention relates to a method for calculating the induction electricity of an offline steel frame of an alternating current transmission line, which comprises the following steps: s1: step of calculating the equivalent radius of the split sub-conductor, S2: step of calculating sag value of overhead wire, S3: calculating the induced voltage of the initial phase line in the power transmission line on a steel frame, and S4: step of calculating total induction voltage of the steel frame, S5: and calculating the total induced current.
Description
Technical Field
The invention belongs to the technical field of power systems, and particularly relates to a method for calculating the induction electricity of an offline steel frame of an alternating-current transmission line.
Background
The electric energy on the transmission line is transferred by means of moving charges, and the electric field existing around the high-voltage transmission equipment is generated by the moving charges carried on the conductor of the high-voltage transmission equipment, and although the electric field cannot be seen, the electric field does exist, so that the electric field existing around the line and the equipment always exists along with the transfer of the electric energy.
With the continuous expansion of the scale of the power grid and the rapid development of the electric power industry, people gradually increase the awareness of environmental protection and the awareness of power maintenance, power frequency electromagnetic fields generated by power transmission and transformation equipment are also larger and larger, the problem of electromagnetic environment pollution possibly caused by the power transmission and transformation equipment is also more and more concerned by people, and the construction of the power grid is also continuously disturbed by the problems in the aspects of electromagnetic environment protection and the like.
In recent years, the problems of electromagnetic interference and electromagnetic environment of power systems have been increasingly emphasized with the development of power systems and the increase of extra-high voltage power transmission. High voltage transmission lines may cross public activity areas and even enter urban areas, and the electric field intensity caused by the high voltage transmission lines becomes a considerable problem in the technical field of electromagnetic compatibility and environmental protection.
The alternating-current double-circuit transmission line reasonably utilizes the line corridor, improves the transmission capacity, reduces the line construction cost, is a novel transmission mode with more benefits and less disadvantages, and is widely applied to the construction of the transmission line of the power system. According to the practical problems after the ultra-high voltage alternating current transmission line is put into operation in recent years, no relevant literature is available at present for researching the problem of induced electricity when a large number of buildings (such as greenhouse dense areas and the like) with steel frame structures exist in the line, and serious induced electricity overrun conditions exist in the areas, so that the normal work activities and personal safety of people are influenced. This is a disadvantage of the prior art.
In view of the above, the present application provides a method for calculating an induced current of an offline steel frame of an ac power line; it is very necessary to solve the defects existing in the prior art.
Disclosure of Invention
The present invention aims to provide a method for calculating the induced current of the steel frame under the line of the ac power transmission line, so as to solve the above technical problems.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for calculating the induction power of an offline steel frame of an AC power transmission line comprises the following steps:
s1: the step of calculating the equivalent radius of the split sub-conductor specifically comprises the following steps:
defining the equivalent radius of the split conductor as Req，
Req＝(nrRn-1)1/n
Wherein n is the number of the split sub-conductors, R is the radius of the split conductor, namely the split distance, and is unit millimeter, and R is the radius of the split sub-conductors, and is unit millimeter;
s2: the method comprises the following steps of calculating the sag value of the overhead line, and specifically comprises the following steps:
the equation of the catenary at the maximum span inner sag is as follows:
wherein L represents span, unit m; h represents the height from the ground at the maximum sag in m; s represents the maximum sag of the overhead line in a unit of m; alpha represents the stress coefficient of the horizontal direction of the lead, and the technical formula of the alpha is as follows:
α＝γL/σ0
wherein gamma represents the lead dead weight ratio and the unit N/(m.mm)2)；σ0Representing the stress of the wire in the horizontal direction in units of N/mm2(ii) a The calculation formula of the dead weight of the wire is as follows:
wherein g represents the acceleration of gravity, and is 9.8m/s2；m0Represents the mass of a unit wire in kg/km; s0Represents the cross-sectional area of the wire in mm2；
The general equation of the catenary of the power transmission line during equal-height suspension is as follows:
the sag calculation formula of the overhead line is as follows:
s3: the method comprises the following steps of calculating the induced voltage generated by a primary phase line in the power transmission line on a steel frame, and specifically comprises the following steps:
calculating the average height ha of the wire from the ground:
wherein H represents the height of the suspension point of the wire in m; s represents the sag parameter of the wire in m;
calculating the equivalent length of each steel frame leq:
wherein a represents the height of the steel frame in m; b represents the width of the steel frame in m;
calculating the induced voltage ua:
wherein, mu0Represents the vacuum permeability; i is0Representing the highest operating current of the alternating current transmission line in unit A; ω is 2 pi f, f is the system frequency; d represents the distance between each steel frame in m; ha represents the average height of the wire from the ground; d0Representing the horizontal distance between the steel frame and the lead in m; req represents the equivalent radius of each phase conductor, in m; leq denotes the equivalent length of each steel frame; ω t represents an initial phase angle of the transmission line;
s4: the step of calculating the total induction voltage of the steel frame specifically comprises the following steps:
obtaining initial phase induction voltage ua according to the step S3, converting relevant parameters according to the spatial position, sequentially reducing the phase angle by 120 degrees and 240 degrees, and calculating induction voltages generated by the other two phases of circuits on the steel frame; the induced voltages of the three-phase line are superposed to obtain a total induced voltage ui；
S5: the step of calculating the total induced current specifically comprises the following steps:
wherein s isiRepresents the cross-sectional area of each steel frame in m2；ρ0Representing the resistivity of the steel frame.
The method has the beneficial effect that the induced voltage and the induced current obtained by calculation by the method in the technical scheme can provide theoretical reference data for the advanced design work and related scientific research work of the power transmission line. The designer of the power transmission line and related scientific researchers can determine whether the designed line meets the specification according to the induction voltage and induction current limit value specified internationally, if the induction current exceeding the limit value is light, symptoms such as human body pain are caused, and if the induction current exceeding the limit value is serious, the personal safety of people is harmed. The method has important significance for planning the power transmission line of the power system, stabilizing and safety the power system and personal safety of agricultural production workers.
In addition, the invention has reliable design principle, simple structure and very wide application prospect.
Therefore, compared with the prior art, the invention has prominent substantive features and remarkable progress, and the beneficial effects of the implementation are also obvious.
Drawings
Figure 1 is a schematic diagram of a quad-split conductor.
Fig. 2 is a schematic diagram of a line catenary calculation.
Fig. 3 is a schematic view of a greenhouse steel frame.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings by way of specific examples, which are illustrative of the present invention and are not limited to the following embodiments.
As shown in fig. 1 to 3, the method for calculating the induction power of the steel frame under the ac power line provided by this embodiment includes the following steps:
s1: the step of calculating the equivalent radius of the split sub-conductor specifically comprises the following steps:
for an overhead transmission line with the voltage of more than 110kV, in order to enable current to flow in the cross section of a lead as uniformly as possible, reduce the potential gradient on the surface of the lead, reduce the resistance of the line and avoid generating large corona loss, audible noise and the like, the power transmission is carried out by adopting the erection mode of split leads. The conductor erection height and tower span of the overhead transmission line are far larger than the split distance of the split conductors, so when analyzing and calculating the electromagnetic field environment around the overhead transmission line, n split sub-conductors of each phase are generally equivalently replaced by one conductor. Taking a four-split conductor commonly used in a high-voltage transmission line as an example, assuming that each split sub-conductor is uniformly distributed, as shown in fig. 1, the equivalent radius of the split conductor is calculated by the following formula, unit mm,
Req＝(nrRn-1)1/n
wherein n is the number of the split sub-conductors, R is the radius of the split conductor, namely the split distance, and is unit millimeter, and R is the radius of the split sub-conductors, and is unit millimeter;
s2: the method comprises the following steps of calculating the sag value of the overhead line, and specifically comprises the following steps:
the transmission lines in the span are distributed in a catenary manner, as shown in fig. 2, two ends of each phase of transmission line are positioned at the horizontal equal height of a suspension point on a tower, and the center of the span is the maximum sag value of the transmission line. By establishing a three-dimensional coordinate system as shown in FIG. 2 for the overhead line, the line can be obtained within a span
And the overhead line catenary equation at the maximum sag value is as follows:
wherein L represents span, unit m; h represents the height from the ground at the maximum sag in m; s represents the maximum sag of the overhead line in a unit of m; alpha represents the stress coefficient of the horizontal direction of the lead, and the technical formula of the alpha is as follows:
α＝γL/σ0
wherein gamma represents the lead dead weight ratio and the unit N/(m.mm)2)；σ0Representing the stress of the wire in the horizontal direction in units of N/mm2(ii) a The calculation formula of the dead weight of the wire is as follows:
wherein g represents the acceleration of gravity, and is 9.8m/s2；m0Represents the mass of a unit wire in kg/km; s0Represents the cross-sectional area of the wire in mm2；
If the distances between the empty lines are equal, the general equation of the catenary of the power transmission line during equal-height suspension is as follows:
the sag calculation formula of the overhead line is as follows:
s3: the method comprises the following steps of calculating the induced voltage generated by a primary phase line in the power transmission line on a steel frame, and specifically comprises the following steps:
calculating the average height ha of the wire from the ground:
wherein H represents the height of the suspension point of the wire in m; s represents the sag parameter of the wire in m;
calculating the equivalent length of each steel frame leq:
wherein a represents the height of the steel frame in m; b represents the width of the steel frame in m; the schematic view of the steel frame is shown in FIG. 3;
calculating the induced voltage ua:
the system formed by two adjacent steel frames and the ground is equivalent to a closed conductor, the induced voltage generated on the steel frames by the initial phase line in the alternating current transmission line is calculated by the following formula,
wherein, mu0Represents the vacuum permeability; i is0Representing the highest operating current of the alternating current transmission line in unit A; ω is 2 pi f, f is the system frequency;d represents the distance between each steel frame in m; ha represents the average height of the wire from the ground; d0Representing the horizontal distance between the steel frame and the lead in m; req represents the equivalent radius of each phase conductor, in m; leq denotes the equivalent length of each steel frame; ω t represents an initial phase angle of the transmission line; since the power transmission system is a dual-back-alternating current power transmission, each phase differs by 120 °.
S4: the step of calculating the total induction voltage of the steel frame specifically comprises the following steps:
obtaining initial phase induction voltage ua according to the step S3, converting relevant parameters according to the spatial position, sequentially reducing the phase angle by 120 degrees and 240 degrees, and calculating induction voltages generated by the other two phases of circuits on the steel frame; the induced voltages of the three-phase line are superposed to obtain a total induced voltage ui；
S5: the step of calculating the total induced current specifically comprises the following steps:
wherein s isiRepresents the cross-sectional area of each steel frame in m2；ρ0Representing the resistivity of the steel frame.
The above disclosure is only for the preferred embodiments of the present invention, but the present invention is not limited thereto, and any non-inventive changes that can be made by those skilled in the art and several modifications and amendments made without departing from the principle of the present invention shall fall within the protection scope of the present invention.
Claims (1)
1. A method for calculating the induction electricity of an offline steel frame of an AC power transmission line is characterized by comprising the following steps:
s1: a step of calculating an equivalent radius of the split sub-conductor,
s2: calculating the sag value of the overhead line,
s3: calculating the induced voltage of the initial phase line in the power transmission line on the steel frame,
s4: calculating the total induction voltage of the steel frame,
s5: calculating the total induced current;
the step S1 specifically includes:
defining the equivalent radius of the split conductor as Req，
Req＝(nrRn-1)1/n
Wherein n is the number of the split sub-conductors, R is the radius of the split conductor, namely the split distance, and is unit millimeter, and R is the radius of the split sub-conductors, and is unit millimeter;
the step S2 specifically includes:
the equation of the catenary at the maximum span inner sag is as follows:
wherein L represents span, unit m; h represents the height from the ground at the maximum sag in m; s represents the maximum sag of the overhead line in a unit of m; alpha represents the stress coefficient of the horizontal direction of the lead, and the technical formula of the alpha is as follows:
α＝γL/σ0
wherein gamma represents the lead dead weight ratio and the unit N/(m.mm)2)；σ0Representing the stress of the wire in the horizontal direction in units of N/mm2(ii) a The calculation formula of the dead weight of the wire is as follows:
wherein g represents the acceleration of gravity, and is 9.8m/s2；m0Represents the mass of a unit wire in kg/km; s0Represents the cross-sectional area of the wire in mm2；
The general equation of the catenary of the power transmission line during equal-height suspension is as follows:
the sag calculation formula of the overhead line is as follows:
the step S3 specifically includes:
calculating the average height ha of the wire from the ground:
wherein H represents the height of the suspension point of the wire in m; s represents the sag parameter of the wire in m;
calculating the equivalent length of each steel frame leq:
wherein a represents the height of the steel frame in m; b represents the width of the steel frame in m;
calculating the induced voltage ua:
wherein, mu0Represents the vacuum permeability; i is0Representing the highest operating current of the alternating current transmission line in unit A; ω is 2 pi f, f is the system frequency; d represents the distance between each steel frame in m; ha represents the average height of the wire from the ground; d0Representing the horizontal distance between the steel frame and the lead in m; req represents the equivalent radius of each phase conductor, in m; leq denotes the equivalent length of each steel frame; ω t represents an initial phase angle of the transmission line;
the step S4 specifically includes:
the initial phase induced voltage ua is obtained according to the step S3, the related parameters are transformed according to the spatial position, and the parameters are sequentially transformedReducing the phase angle by 120 degrees and 240 degrees, and calculating the induction voltage generated on the steel frame by the other two phases of lines; the induced voltages of the three-phase line are superposed to obtain a total induced voltage ui；
The step S5 specifically includes:
wherein s isiRepresents the cross-sectional area of each steel frame in m2；ρ0Representing the resistivity of the steel frame.
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| CN109002648A (en) * | 2018-08-20 | 2018-12-14 | 国网安徽省电力有限公司 | The emulated computation method of construction line inductive voltage and current based on CDEGS |
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| 1000kV/500kV同塔四回输电线路电磁场分布及走廊优化研究;石超群;《中国优秀硕士学位论文全文数据库工程科技Ⅱ辑》;20140915;全文特别是第8-13页 * |
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