Method for calculating radio interference suffered by a communication device mounted on an electric power tower

Abstract

Disclosed is a method for calculating radio interference suffered by a communication device mounted on an electric power tower. The method includes: establishing a relative position model of the communication device mounted on the electric power tower and transmission lines, calculating interference field strength of the communication device on the electric power tower, and determining whether the radio interference field strength at the mounting point satisfies the requirements.

Claims

1. A method for calculating radio interference suffered by a communication device mounted on an electric power tower, comprising: 1) determining, according to an erection method of electric power towers and electric transmission lines, a radio interference field strength calculation method to be used, calculating an interference value, and calculating a number of charges on a surface of each wire; 2) establishing an approximate cutting model for a sag of a wire between two electric power towers, equating the each wire with the sag as a circular arc, and dividing the circular arc into m segments to make each segment of the circular arc equal to a horizontal straight segment, and linearly allocating a number of charges in each segment according to a segmentation weight; 3) calculating each segment according to the radio interference field strength calculation method, substituting a calculated value into a formula for lateral change of interference field strength, and obtaining an interference field strength component of each segment at an observation point, wherein the observation point is a mounting point prepared for a communication device; 4) geometrically superimposing interference field strength components generated by the segments of the each wire, and then vectorially superimposing interference field strength values obtained from same-name phase wires of different loops; 5) calculating an interference field strength of a corresponding frequency from a radio interference field strength at 0.5 MHz from step 4) by using a formula of field strength changing with frequency; 6) determining whether the radio interference field strength at the mounting point satisfies requirements, wherein when the radio interference field strength does not satisfy the requirements, the mounting point is lowered and the steps are repeated until the requirements are satisfied, and 7) wherein when the radio interference field strength satisfies the requirements, the communication device is mounted at the mounting point.

2. The method for calculating the radio interference suffered by the communication device mounted on the electric power tower of claim 1, wherein the radio interference field strength calculation method in step 1) comprises an empirical formula method and an excitation function method.

3. The method for calculating the radio interference suffered by the communication device mounted on the electric power tower of claim 1, wherein in step 2), the m segments are determined by means of a differential principle making a combination of the segments approach to a line shape of the each wire.

4. The method for calculating the radio interference suffered by the communication device mounted on the electric power tower of claim 1, wherein the formula for lateral change of interference field strength is: $E_x=E+k\lg \frac{400+{\left(H-h\right)}^2}{x^2+{\left(H-h\right)}^2},$ wherein E.sub.x is a radio interference intensity at the lateral distance x of the each wire, H is an altitude of a corresponding segment; h is an altitude of the mounting point of the communication device on the electric power tower; x is a lateral distance between the mounting point and the each wire or a cut section of the each wire; k is a change coefficient, and has a value of 16.5; and E is the interference value calculated by the excitation function method or the empirical formula method.

5. The method for calculating the radio interference suffered by the communication device mounted on the electric power tower of claim 1, wherein the geometrically superimposing in step 4) is: $E_i=20{\lg \left[{\left(10^{\frac{E_{i1}}{20}}\right)}^2+{\left(10^{\frac{E_{i2}}{20}}\right)}^2+\mathrm{.Math.}+{\left(10^{\frac{E_{\mathrm{im}}}{20}}\right)}^2\right]}^{\frac{1}{2}},$ wherein E.sub.i is a radio interference value generated by a i-th wire, E.sub.im is a radio interference value generated by a first segment to a m-th segment of the i-th wire.

6. The method for calculating the radio interference suffered by the communication device mounted on the electric power tower of claim 1, wherein the formula of field strength changing with frequency is:
ΔE.sub.f=5[1−2(1g10f).sup.2], a calculation result of this formula is the difference between an interference field strength under frequency f and an interference field strength at 0.5 MHz.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram of a relative position between a mounting point of a communication device on an electric power tower and electric wires;

(2) FIG. 2 is an approximate cutting model of a wire sag between two electric power towers; and

(3) FIG. 3 is a flowchart of an embodiment of the present disclosure.

DETAILED DESCRIPTION

(4) Regarding the requirements of the related art, the present disclosure provides a method for calculating radio interference suffered by a communication device mounted on an electric power tower, which includes the following steps.

(5) 1) According to an erection method of electric power towers and electric transmission lines, a radio interference field strength calculation method to be used is determined, an interference value is calculated, and the number of charges on a surface of each wire is calculated.

(6) 2) An approximate cutting model for a sag of a wire between two electric power towers is established, the each wire with the sag as a circular arc is equated, and the circular arc is divided into m segments to make each segment of the circular arc equal to a straight segment, and the number of charges in each segment according to a segmentation weight is linearly allocated.

(7) 3) Each segment is calculated according to the radio interference field strength calculation method, a calculated value is substituted into a formula for lateral change of interference field strength, and an interference field strength component of each segment at an observation point is obtained, where the observation point is a mounting point prepared for a communication device.

(8) 4) Interference field strength components generated by the segments of the each wire are geometrically superimposed, and then interference field strength values obtained from same-name phase wires of different loops are vectorially superimposed.

(9) 5) An interference field strength of a corresponding frequency is calculated from a radio interference field strength at 0.5 MHz from step 4) by using a formula of field strength changing with frequency.

(10) 6) It is determined whether the radio interference field strength at the mounting point satisfies requirements, when the radio interference field strength satisfies the requirements, the mounting point is capable of mounting the communication device mounted; and when the radio interference field strength does not satisfy the requirements, the mounting point is lowered and the steps are repeated until the requirements are satisfied.

(11) The implementation of the present disclosure will be specifically described below.

(12) There are two calculation methods for radio interference, including an empirical formula method and an excitation function method. The empirical formula method may be used for wires of four or fewer splits, and the excitation function method is used more widely. The method is selected according to the actual erection situation. The formulas are as follows.

(13) The empirical formula method is:

(14) $E=30.3M{\delta }^{\frac{2}{3}}\left(1+\frac{0.3}{\sqrt{r}}\right),$
where M is a linear coefficient, δ is an empirical formula calculation constant, E is a radio interference intensity, and r is a radius of the sub-wire.

(15) The excitation function method is:

(16) $E=3.5g_{\max i}+12r_i-30+33\lg \frac{20}{D_i},$
where g.sub.maxi is a maximum surface electric field strength of wire i, in units of kV/cm; r.sub.i is a radius of wire i, in unites of cm; D.sub.i is a distance from the observation point to wire i, in units of m; a calculation result E is the intensity of radio interference, in units of dB(μV/m). The calculation formula of g.sub.maxi is:

(17) $\{\begin{array}{c}{g}_{\max }=g\left[1+\left(n-1\right)\frac{d}{R}\right]\\ g=\frac{Q}{\pi {\mathrm{.Math.}}_{0}dn}\end{array},$
where g is an average potential gradient on the wire surface, in units of kV/cm; n is the number of sub-wires; d is a diameter of the sub-wire, in units of cm; R is a diameter of the splitting wire, in units of cm; Q is an equivalent total charge of the wire, and the matrix form of the equivalent total charge is calculated as the product of a Maxwell potential inverse matrix and a single-column matrix of the voltage to ground of each wire, namely [Q]=[P].sup.−1[U].

(18) Approximate Sag Model:

(19) The approximate sag model proposed by the present disclosure is shown in FIG. 2. The wire with sag is equivalent to a circular arc, and the idea of differentiation is used to divide the wire into m segments. Since the curvature of each segment is relatively small, each segment of the wire can be equivalent to a horizontal straight segment. Since the sag model of the wire is symmetrical to each other, and the horizontal straight segment of the segment is most conducive to approximate calculation. The radio interference field strength of each segment to the device at the observation point can be calculated by the excitation function method, and then the radio interference field generated by each segment at the observation point is geometrically superimposed to obtain the radio interference field strength generated by the wire at the observation point, this process is repeated for each sub-wire of the power tower, and finally the field strength of respective sub-wires are vectorially superimposed. Regarding the value of the divided m segments, the bending degree of the wire in specific cases needs to be referenced. If the bending degree is large, the number m of divided segments should also be increased appropriately to obtain a more accurate result. The total amount of charges of the wire are distributed to the divided wire segments according to their division weights.

(20) The calculation of the lateral change of interference intensity is:

(21) $E_x=E+k\lg \frac{400+{\left(H-h\right)}^2}{x^2+{\left(H-h\right)}^2},$
where E.sub.x is a radio interference intensity at the lateral distance x of the each wire, H is an altitude of a corresponding segment of the wire; as shown in FIG. 1 and FIG. 2, h is an altitude of the mounting point of the communication device on the electric power tower; x is a lateral distance between the mounting point and the each wire or a cut section of the each wire; k is a change coefficient, and has a value of 16.5; and E is the interference value calculated by the excitation function method or the empirical formula method.

(22) The geometric superimposition formula is:

(23) $E_i=20{\lg \left[{\left(10^{\frac{E_{i1}}{20}}\right)}^2+{\left(10^{\frac{E_{i2}}{20}}\right)}^2+\mathrm{.Math.}+{\left(10^{\frac{E_{\mathrm{im}}}{20}}\right)}^2\right]}^{\frac{1}{2}},$
where E.sub.i is a value of radio interference generated by a i-th wire, E.sub.im is a value of radio interference generated by the first to m-th segments of the i-th wire.

(24) Calculation of relative interference field strength with frequency:
ΔE.sub.f=5[1−2(1g10f).sup.2].

(25) The calculation result of this formula is the difference between an interference field strength at the frequency f and an interference field strength at 0.5 MHz.

EXAMPLES

(26) Assuming that a communication device is to be mounted at a height of 31.5 m on a same four-circuit electric power tower, and the transmission line erection model is known, the radio interference field strength is required. After the excitation function method is selected and the approximate segmentation model is determined, according to the excitation function method, the field strength is obtained as 62.40 dB, according to the lateral change, the field strength at the mounting point on the 0.5 MHz is calculated as 90.35 dB, and according to the spectrum characteristics, the interference field strength at 30 MHz is calculated as 34 dB. Referring to the national standard radio interference peak value (30 dB) at 30 MHz, the interference field strength exceeds the standard, and therefore the mounting point position is lowered and the point-taking calculation is re-executed until the interference field strength drops below the national standard peak value.

(27) As mentioned above, the calculation method for radio interference suffered by the communication device mounted on the electric power towers provided in the proposal of the present disclosure provides an effective method to verify whether the radio interference assignment at the mounting point satisfies the standard. This can improve the efficiency of mounting communication devices on the electric power towers, accelerate the process of 5G construction, and save more social resources during the construction process.