KR100734821B1 - Measurement Method of Grounding Resistance of Transmission Towers in an Energized Transmission Line System - Google Patents

Abstract

In the measuring method of the ground resistance of the transmission tower at the tower angle of the transmission system in operation without separating the processing ground wire, measuring equipment configured to flow the induced current (I ₁ ) by generating an induced voltage (E ₁ ) for each of the tower angle. The first step of obtaining the loop resistance measurement (E ₀ / I ₀ ) using the internal low voltage (E ₀ ) and the internal current (I ₀ ) of the transformer circuit, and the current (I ₁ to I ₄ ) measurement classified into the top four angles. And a third step of obtaining a parallel efficiency (η) converted from the distance between the tower angles (D) and a fourth step of calculating the ground resistance of the single transmission tower in steps 1, 2 and 3. have.

Transmission system, transmission tower, grounding resistance

Description

Measurement Method of Grounding Resistance of Transmission Towers in an Energized Transmission Line System

1 is a circuit for measuring the ground resistance of the steel tower after separating the processing ground

2 is a circuit measuring the leakage current of the steel tower as a test current

3 shows the effect of measuring line length on ground electrode potential measurement.

4 is a loop resistance measurement circuit in a distribution line multiple ground system

5 is an equivalent circuit for applying power by inductive coupling.

6 is an equivalent radius calculation of the hemispherical electrode equal to the area of the tower structure.

7 is a hemisphere electrode model when four hemisphere electrodes (top angles) are connected in parallel.

8 shows the parallel efficiency (η) calculation result according to the separation distance between tower angles

9 is an equivalent circuit of a single transmission tower ground electrode in a transmission line in operation;

FIG. 10 is a circuit model approximating the hemisphere electrode model of FIG.

11 is an equivalent circuit diagram of ground measurement in a transmission system in operation

12 is a transmission tower computer model in the transmission system in operation

13 is a result of calculating the current distribution of each part of the steel tower

Fig. 14 is a current calculation value of the top angle to be applied.

Fig. 15 shows the current calculations of the adjacent tower angles of the powered-up tower angles.

Fig. 16 shows the current calculation value of the diagonal tower angle of the power supply tower angle.

The present invention relates to a method for measuring the ground resistance of a transmission tower in a transmission system in operation.

In the conventional measuring method, as shown in FIG. 1, after disconnecting the multi-grounded processing ground wire, a known test current source is injected and the top angle potential is measured to directly measure resistance. In reality, there were many problems.

In addition, in order to solve the problems described above, using the top-angle leakage current as a test current source and measuring the top-angle potential as an indirect measurement method without separating the processing ground wire that can be measured in the operating state as shown in FIG. Although this has been suggested, there was a problem in that work for measuring the potential around the top angle and laying of the measurement line (reference electrode) were required.

The present invention is to solve the problem of the conventional measuring method from the loop resistance measurement of the loop circuit formed by the tower angle grounding of the transmission tower and multiple ground line of the overhead line, the current measurement value divided into four tower angles and the distance between the tower angles We propose an algorithm for estimating the ground resistance of a transmission tower using parallel efficiency (η) between the calculated tower angles. This method applies the test current by the inductive coupling circuit as in the loop resistance measurement method, which is widely used for the electric pole measurement of distribution lines. There is no need for circuits or electrodes, which eliminates measurement errors due to insufficient potential measuring line lengths and makes measurement simple.

The present invention is a method for measuring the ground resistance of a transmission tower at the tower angle of the transmission system in operation without separating the processing ground, it is configured to flow the induced current (I ₁ ) by generating an induced voltage (E ₁ ) for each of the tower angle. The first step of obtaining loop resistance measurement value (E ₀ / I ₀ ) using the internal low voltage (E ₀ ) and internal current (I ₀ ) of the transformer circuit, which is a measuring device, and the current (I ₁ ~ I) ₄ ) a second step of obtaining a measurement value and a third step of calculating parallel efficiency (η) converted from the distance between the tower angles (D) and a fourth step of calculating ground resistance of a single transmission tower in steps 1, 2, and 3; Consists of

1 illustrates a general method of measuring ground resistance (R _T ) in FIGS. 1 and 2.

1 is a method of measuring after separating the processing branch is difficult to apply in reality because the measurement method using the leakage current of FIG. 2 has been proposed. In the method of FIG. 2, the current injection circuit is omitted in the method of FIG. 1 since the leakage current I always flows at the top angle, but the top angle potential rise V due to the leakage current should be measured, thereby measuring the potential. The circuit had a problem that remains.

3 is a diagram illustrating the influence of the measuring line length in the measurement of the ground electrode potential, and is a diagram for explaining the accuracy according to the distance measuring line distance (x). In FIG. 3, the ground resistance of the hemispherical electrode having a radius is given by Equation 1. If the ground potential at the point spaced from the electrode center by x is V (x), the resistance measured using the point as the reference potential is as shown in Equation 2, and the ratio between the measured value and the true value of ground resistance (Equation 1) It is represented by Equation 3. It can be seen from Equation 3 that the separation distance x of the potential electrode for securing 90% and 95% accuracy of the measured value is 10 times and 20 times the radius of the hemisphere electrode, respectively. As a result, the accuracy of the measurement is reduced in areas where it is difficult to extend the measurement line.

(식 1)

(Equation 1)

(식 2)

(Equation 2)

(식 3)

(Equation 3)

4 illustrates a loop resistance measuring circuit in a distribution line multi-ground system and an example of a method of calculating ground resistance by measuring loop resistance in a multi-ground circuit will be described. _Assuming that the resistance of the other ground electrode other than the ground resistance (R _g ) to be measured in FIG. 4 is a similar value, the parallel composite resistance (R _Thev ) converges to 0 by Equation 5, so that the loop resistance is measured by Equation 6. Is equal to the ground resistance.

(식 4)

(Equation 4)

(식 5)

(Eq. 5)

(식 6)

(Equation 6)

As shown in the equivalent circuit of applying power by inductive coupling of FIG. 5, when the applied power E of FIG. 4 is generated by an induction voltage and the current I is measured using a non-contact clamp-on current probe. It is possible to measure the ground resistance (R _g ) of a single ground electrode by equation (6) without disconnecting the multiple ground lines. The above description describes the loop resistance measurement method currently widely used for measuring the ground resistance of poles of multi-grounded distribution lines.

In the case of transmission towers, unlike the distribution poles, four parallel composite resistors must be obtained, so the method described above is not applicable. Therefore, a separate algorithm is required to calculate the ground resistance of transmission tower through loop resistance measurement. Here, the ground resistance calculation algorithm of the steel tower is derived from the model where the top angle structure ground is equivalent to the hemispherical electrode for the induction of the equation.

Fig. 6 shows the equivalent radius calculation of the hemispherical electrode equal to the area of the tower structure, and the grounding resistance of the tower angle of the transmission tower in the design of the steel tower grounding is converted to the hemispherical electrode having the same area as the surface area S of the tower structure. In this case, the radius (a) of the hemisphere electrode is the radius of the hemisphere electrode that is the same as the surface area of one column angle, and is obtained by the equation (8).

(식 7)

(Eq. 7)

(식 8)

(Eq. 8)

Since four tower angle grounds are connected in parallel, the transmission tower is the same as the hemisphere electrode model when four hemisphere electrodes in FIG. 7 are connected in parallel. When the current (I) is injected into such an electrode, the potential rise (V) of the electrode is expressed by Equation 9 by adding the potential rise by the remaining three tower angles to the potential rise value of one hemisphere electrode (top angle). Equivalent to the ground resistance at Top Angle 1 assuming the earth as a uniform medium.
The four composite resistors R _T are each divided by Equation 10 since the potential V is divided by the current I.

(식 9)

(Eq. 9)

(식 10)

(Eq. 10)

 (V: Hemispherical electrode potential [V], ρ: Earth resistivity [Ωm], a: Hemispherical electrode radius [m],

I: injection current [A], D: distance between tower angles [m], R _T : parallel composition resistance of 4 towers [Ω])

Another way of expressing transmission tower grounding resistance is to define and express the parallel efficiency (η) between one tower resistance (R _Leg ) and four tower angles. In other words, the parallel resistance of the four top angles should be 1/4 of the top one resistance (R _Leg ) under ideal conditions, but the actual transmission is the ground resistance when four top angles are connected in parallel by mutual interference between the top angles. The resistance (R _T ) of the tower is greater than this value. Therefore, if the parallel efficiency (η) between the tower angles is defined as Equation 11 and summarized with respect to the pylon resistance R _T , Equation 12 is summarized. By substituting Eq. 12 into Eq. 10 by the parallel efficiency (η), Eq. 13 can be obtained, where a in Equation 13 is the radius of the hemisphere electrode equivalent to the surface area of one tower angle.

(식 11)

(Eq. 11)

(식 12)

(Eq. 12)

(식 13)

(Eq. 13)

For the verification of Equation 13, assuming that the distance (D) between the tower angles is very far away, the potential interference between the tower angles is lost, it can be seen that the parallel efficiency is 1.0 as shown in Equation 14.

(식 14)

(Eq. 14)

In general, the shape of the transmission tower tower angle is standardized, but considering that the distance between tower angles (D) is variable according to the height of the tower, the tower angle and the distance between tower angles (D) of a typical 154 kV pylon are referred to the numerical values of FIG. 6. When the parallel efficiency (η) is calculated in the case of varying from 8 to 12 m, the parallel efficiency (η) according to the separation distance between the tower angles of FIG. 8 can be seen that the parallel efficiency (η) is about 0.5 to 0.6. . For reference, when designing the transmission tower grounding, a parallel coefficient (η) of 0.5 is applied uniformly for conservative design.

9 is an equivalent circuit of a single transmission tower grounding pole in a transmission line in operation and represents a circuit when the induced voltage E ₁ is generated at each tower top of the transmission tower grounding model described above. In FIG. 9, Z _E denotes the impedance of the external circuit multi-grounded through the overhead line, I ₁ ~ I ₄ represents the currents going to the earth through the four tower angles, and I _e represents the current obtained by multiplying all the divided currents of the tower angles.

FIG. 10 is an equivalent circuit model of the hemisphere electrode model of FIG. 9, and when unit current is injected into one hemisphere electrode when the mutual resistance between two electrodes is assumed in FIG. 10. The potential rise of another electrode separated by the distance D is equal to Equation 15, but the single hemispherical electrode ground resistance (R + R _m ) must be equal to R _True of Equation 1 or R _Leg of Equation 12. Is obtained as shown in Eq.

(식 15)

(Eq. 15)

(식 16)

(Eq. 16)

(식 17)

(Eq. 17)

배가 되어 상호저항(R_m)이 상기 식 15보다 작아지게 되므로 상기 도 10의 회로모델은 도 12의 운전 중인 송전계통에서 송전철탑 컴퓨터 모델의 반구모델을 근사화한 것이다. 상기 도 10의 회로모델의 정확성을 검증하기 위하여 반구전극모델에서의 접지저항인 식 12의 R_T와의 비율식인 식 18을 유도하고, 일반적인 154 kV 철탑의 탑각 등가반경(a=2.8m)과 거리(D=8~12m)를 상정했을 때 그 비율을 계산하면 대략 5% 이하의 오차 밖에 나지 않는다. 따라서 상기 도 10의 회로모델은 허용할만한 오차범위 내에서 상기 도 9의 반구전극모델과 등가라고 간주할 수 있다.In the circuit model of FIG. 10, the pylon resistance R _T ′ is obtained as shown in Equation 17, but in the circuit model, when four hemispherical electrodes become four, one of the distances between the electrodes becomes

Since the mutual resistance R _m becomes smaller than Equation 15, the circuit model of FIG. 10 is an approximation of the hemisphere model of the transmission tower computer model in the operating transmission system of FIG. In order to verify the accuracy of the circuit model of FIG. 10, Equation 18, which is a ratio with R _T of Equation 12, which is the ground resistance in the hemispherical electrode model, is derived, and a top angle equivalent radius (a = 2.8 m) and distance of a typical 154 kV pylon are derived. Assuming that (D = 8-12m), the ratio is only about 5% or less. Accordingly, the circuit model of FIG. 10 may be considered equivalent to the hemisphere electrode model of FIG. 9 within an acceptable error range.

(식 18)

(Eq. 18)

Now, a model in which the power source E ₁ is replaced with the induction voltage generating circuit of FIG. 5 in the circuit model of FIG. 10 is shown in the ground measurement equivalent circuit diagram of the transmission system in operation in FIG. 11. In FIG. 11, the loop equation between the resistors R may be summarized with respect to E ₁ , and equation 20 may be obtained. Since the applied voltage (E ₁ ) of the circuit under test is derived from the voltage / current relationship according to the transformer turns ratio as shown in Equation 19 without direct measurement, E ₀ , I ₀ , I ₁ that can be directly measured instead of E _{1 in} Equation 20 above. Substitution of Equation 21 results in Equation 21. As shown in FIG. 2, E ₀ and I ₀ are internal to a transformer circuit configured to flow an induced current I ₁ by generating an induced voltage E ₁ at a tower angle of a steel tower. Voltage E ₀ and current I ₀ , and as shown in FIG. 9, I _e is a current leaking to the ground through the entire pylon ground, and is a logarithm of the currents I ₁ to I ₄ flowing through each of the four towers. to be. And in accordance with the tower gakgan definition of parallel efficiency (η) Dun shown above may be represented in the Fig. 10 or circuit type 22 tapgak four parallel resistance (R _T) in Figure 11, if this rearrangement with respect to R _m formula Same as 23. Substituting this back into the left equation of Equation 22, and summed up directly by E ₀ , I ₀ , I ₁ ~ I ₄ and parallel efficiency (η), Equation 24, E ₀ and I ₀ is the tower angle 1 of the tower and groups the induced voltage (E ₁₎ of the induced current (I ₁₎ internal voltage (E ₀₎ of configuring a transformer circuit for shedding and a current (I ₀₎ to generate, R _M is a tapgak four period cross-resistance (mutual resistance) , R is the resistance value (Self Resistance) minus the mutual resistance (R _M ) between the tower angles from the ground resistance (R + R _M ) of one tower angle. For reference, when 1 A unit current flows to one tower angle, the potential rise value of the remaining three tower angles without current injection is R _M , and R is the potential rise value of the tower angle into which the current is injected.

(식 19)

(Eq. 19)

(식 20)

(Eq. 20)

(식 21)

(Eq. 21)

(식 22)

(Eq. 22)

(식 23)

(Eq. 23)

(식 24)

(Eq. 24)

In Equation 24, E ₀ , I ₀ , I ₁ ˜ I ₄ are values directly measured, and the parallel efficiency (η) can be estimated from Equation 13, so that the grounding resistance R _T of the transmission tower can be calculated using the measurement circuit of FIG. 11.

Table 1 shows the simulation results using HIFREQ (Safe Engineering Services, Inc., CANADA), an electromagnetic field analysis program for ground analysis. A computer model for the calculation is shown in FIG. 12 above.

The simulation conditions are summarized as follows. The shape of the tower angle of the steel tower was modeled to have the same specifications as in FIG. 6, the distance between the tower angles is 12 m, the multi-ground resistance of the processed ground wire of Z _E of FIG. 9 is 0.5 Ω, the earth resistivity is 100 Ωm, and the relative dielectric constant of the soil is 30.0 and specific permeability were assumed 1.0.

Table 1. Summary of calculation results

The calculation results of I ₁ , I _2, and I ₃ , I ₄ are shown in FIGS. 14 to 16, and as shown in Table 1, the error from the true value of ground resistance when using the method of calculating the ground resistance of the present patent is about 5.5%. (= 1-2.387 / 2.263) confirmed good levels.

As described above, preferred embodiments of the present invention have been described, but the present invention is not limited to the above-described embodiments, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the following claims. Anyone with ordinary knowledge will have the technical spirit of the present invention to the extent that various modifications can be made.

As described above, using the ground resistance calculation principle of the present invention, it is possible to measure the ground resistance of a single transmission tower without spreading a long distance voltage (current) measurement line in an operating transmission system that does not separate the processing ground.

In the existing method using the leakage current of the steel tower as a test current source, the measurement resistance should be expanded while extending the measurement line of sufficient length and moving the electrode on the measurement line, but using the principle of the present invention, a separate measurement line (electrode ), So the measurement work is simplified.

Claims (7)

In the measuring method of the ground resistance of the transmission tower at the top angle of the transmission system in operation without separating the processing ground wire, Loop resistance measurement value using the internal low voltage (E ₀ ) and the internal current (I ₀ ) of the transformer circuit, which is a measuring device configured to generate an induced voltage (I ₁ ) to flow the induced current (I ₁ ) by generating an induced voltage (E ₁ ) for each of the top angles. A first step of obtaining E ₀ / I ₀ ); A second step of obtaining current (I ₁ to I ₄ ) measurement values classified into four tower angles; A third step of obtaining a parallel efficiency η converted from the distance between the tower angles D; A fourth step of calculating ground resistance of the single transmission tower in steps 1, 2, and 3; Method of measuring ground resistance of transmission tower in transmission system in operation. The method of claim 1, Synthetic resistance (R _T ) of the four tower angles is

Where p is the earth resistivity equivalent to the grounding resistance of one tower angle assuming the earth as a uniform medium.          a: Radius of the hemisphere electrode equal to the surface area of one tower angle.) Method for measuring the ground resistance of the transmission tower in the transmission system in operation. The method of claim 2, The synthesis resistance (R _T ) is a method for measuring the ground resistance of a transmission tower in a transmission system in operation, characterized in that to calculate the ground resistance of the steel tower from the model equivalent to the top angle structure ground as a hemisphere electrode. The method of claim 1, The parallel efficiency (η) is By mutual interference between the tower angles

(Where R _LEG : 1 grounding resistor R _T : Ground resistance when 4 towers are connected in parallel) Method for measuring the ground resistance of the transmission tower in the transmission system in operation. The method of claim 4, wherein The parallel efficiency (η) is

(Where a is the radius of the hemispherical electrode equal to the surface area of one tower angle) Method for measuring the ground resistance of the transmission tower in the transmission system in operation. The method of claim 1, Resistor R to obtain the ground resistance (R _T ) can be measured directly E ₀ , Using I ₀ , I ₁

Where E _O is the internal voltage of the transformer circuit. I _O : Internal current of the transformer circuit. E ₁ : Induction voltage of one tower angle. I _e : The current leaking to the ground through the entire ground of the pylon, which is the logarithm of the current (I ₁ ~ I ₄ ) flowing through each of the four towers.) Method for measuring the ground resistance of the transmission tower in the transmission system in operation. The method of claim 1, The ground resistance (R _T ) is

Where E _O is the internal voltage of the transformer circuit. I _O : Internal current of the transformer circuit. R _m : Mutual resistance between 4 towers R: Resistance value obtained by subtracting mutual resistance (R _m ) from the ground resistances (R + R _m ) of two tower angles. Method for measuring the ground resistance of the transmission tower in the transmission system in operation.

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