KR101447676B1 - Method and apparatus for measuring isolated ground resistance of power facility of existing powerline - Google Patents

Abstract

The present invention relates to a method and an apparatus for measuring a ground resistance of a support of an existing power line. To this end, the present invention comprises a pulse generator for applying an impulse power between an earth electrode and an auxiliary electrode for current measurement; A current measuring unit for measuring a current between the ground electrode and the auxiliary electrode; A voltage measuring unit for measuring a voltage between the ground electrode and the reference electrode for voltage measurement; And a measurement signal processing unit for converting each of the current and voltage signals measured from the current measuring unit and the voltage measuring unit into digital values to extract the frequency spectrum of the ground impedance and determining whether the frequency spectrum of the ground impedance converges, Device.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for measuring a ground resistance of a support of an existing power line,

More particularly, the present invention relates to a method and an apparatus for measuring a ground resistance of a support of an existing power line, more specifically, The present invention relates to a method and an apparatus for identifying a ground resistance of a support alone by extracting respective frequency spectra, that is, V (jw) and I (jw), and ascertaining a ground impedance convergence characteristic according to an increase in frequency.

In the transmission and distribution system, there is a neutral wire (cable sheath) for safely returning the fault current to the power source in the event of an accident, or a processing branch for protecting the power line from lightning. In addition, it has a grounding facility in the power line support (steel tower, power distribution pole) to safely discharge the fault / lightning current into the earth when it is input. The performance of such grounding equipments is represented by the grounding resistance. The management of the grounding resistance is an important factor in the management of the grounding resistance because the smaller the grounding resistance, the smaller the magnitude of the grounding electrode potential rise due to the lightning stroke and its influence range.

In the case of an existing power line, the most accurate method for measuring the grounding resistance of a support alone is to measure the grounding line after separating the external grounding system including the ground line and the neutral line from the measurement target support. However, this method is troublesome and may be dangerous as it separates the support from the pressurized power line and then measures and reconnects them.

In order to solve this problem, the name of the invention is "Method of Measuring Grounding Resistance of Transmission Tower at Power Transmission Line Connected with Ground Wire ", Korean Patent Publication No. 2010-0036669 published on Apr. 8, 2010, Describes how to measure the grounding resistance of a transmission tower. However, the above-mentioned patent has a problem in that it requires not only an electrode for current measurement but also _four additional measuring instruments for measuring I ₁ , I ₂ , I ₃ , and I ₄ around the transmission tower, resulting in inefficiency.

The object of the present invention is to solve the above-mentioned problems of the related art, and it is an object of the present invention to provide a method and apparatus for measuring the resistance of a power line by using a characteristic that a reactance of a ground wire connected to a support increases as a frequency of a test current injected into an existing power line support increases. And to provide a method and apparatus for measuring a grounding resistance that does not require additional measuring equipment.

According to another aspect of the present invention, there is provided a ground resistance measuring apparatus including: a pulse generator for applying an impulse power between an earth electrode and an auxiliary electrode for current measurement; A current measuring unit for measuring a current between the ground electrode and the auxiliary electrode; A voltage measuring unit for measuring a voltage between the ground electrode and the reference electrode for voltage measurement; And converting the current and voltage signals measured by the current measuring unit and the voltage measuring unit into digital values, extracting a frequency spectrum of the ground impedance based on the digital values of the converted current and voltage, And a measurement signal processing unit for determining whether the convergence occurs.

Also, the measurement signal processing unit may include: an analog-to-digital converter for converting the current and voltage signals measured from the current measuring unit and the voltage measuring unit into digital values; A data operation unit for extracting a frequency spectrum of the current and voltage signals converted into digital signals and extracting a frequency spectrum of the ground impedance based on the frequency spectrum of the extracted current and voltage signals; And a control unit which determines whether the frequency spectrum of the ground impedance converges and regards the frequency value of the ground impedance converging when the frequency spectrum of the ground impedance converges to be a grounding resistance.

Further, when it is determined that the frequency spectrum of the ground impedance does not converge, the control unit controls the pulse generator to improve the convergence characteristic of the ground impedance so that at least one of the injection current pulse peak value, the rise time, Thereby further controlling the impulse characteristic included.

According to another aspect of the present invention, there is provided a ground resistance measuring method comprising: applying an impulse power between an earth electrode and an auxiliary electrode for current measurement; Measuring a current between the ground electrode and the auxiliary electrode; Measuring a voltage between a ground electrode and a reference electrode for voltage measurement; And converting the current and voltage signals measured from the current measuring step and the voltage measuring step into digital values, extracting a frequency spectrum of the ground impedance based on the digital values of the converted current and voltage, And a measurement signal processing step of judging whether or not the signal is converged.

The measuring signal processing step may further include: converting the current and voltage signals measured from the current measuring step and the voltage measuring step into digital values; Extracting a frequency spectrum of the current and voltage signals converted to digital and extracting a frequency spectrum of the ground impedance based on the frequency spectrum of the extracted current and voltage signals; And judging and judging whether the frequency spectrum of the ground impedance converges and regards the frequency value of the ground impedance that converges when the frequency spectrum of the ground impedance converges, as a grounding resistance.

Further, the measurement signal processing step is used in the step of applying the impulse power supply to improve the convergence characteristic of the ground impedance if it is determined that the frequency spectrum of the ground impedance does not converge, And adjusting an impulse characteristic including at least one of a magnitude, a magnitude, and a period.

The measuring device and method of the present invention enables accurate measurement of the grounding resistance of the power line support alone with a relatively small number of measurements without requiring additional measuring equipment. Therefore, it is easy to identify the support with a relatively high probability of the occurrence of the flashover fault by lightning with the transmission line.

1 is a block diagram schematically illustrating a ground resistance measurement circuit and apparatus according to an embodiment of the present invention.
2 is a block diagram showing a measurement signal processing unit of the ground resistance measuring apparatus of the present invention.
Fig. 3 is a flowchart showing the ground resistance measuring method of the present invention.
Figs. 4 to 8 are diagrams showing experimental results of measurement using the ground resistance measuring apparatus of the present invention. Fig.

The present invention will now be described in detail with reference to the accompanying drawings. Hereinafter, a repeated description, a known function that may obscure the gist of the present invention, and a detailed description of the configuration will be omitted. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. Accordingly, the shapes and sizes of the elements in the drawings and the like can be exaggerated for clarity.

Hereinafter, a ground resistance measuring apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

1 is a block diagram illustrating a ground resistance measurement circuit and apparatus 100 in accordance with an embodiment of the present invention. 1, a ground resistance measuring apparatus 100 according to an embodiment of the present invention includes a pulse generator 110, a current measuring unit 120, a voltage measuring unit 130, and a measurement signal processing unit 140 do. Each configuration shown in Fig. 1 is described in detail below.

The pulse generator 110 is a high-speed pulse generator whose rise time is in the unit of s. The pulse generator 110 applies an impulse power between the ground electrode E1 of the object to be measured and the auxiliary electrode E2 for pulse power supply circulation and for current measurement . Due to the application of the impulse power source, an impulse current circulates between the earth electrode E1 and the auxiliary electrode E2. A part of the impulse current flows to the ground wire or neutral wire connected to the ground of the object to be measured, and the remaining current flows to the earth electrode E1 of the object to be measured, thereby contributing to the ground potential rise of the earth electrode E1 . Here, there exists a grounding resistance of each of the grounding electrode E1 and the auxiliary electrode E2, and a lead wire connecting E1 and E2. As mentioned earlier, the present invention is due to the fact that as the frequency of the test current injected into the existing power line support increases, the reactance of the ground line connected to the support increases, and the current going out through the ground line decreases. This is due to the fact that as the frequency increases, there is an effect similar to separating the process line from the support to be measured. Therefore, in order to achieve this effect, the impedance of this lead wire must be sufficiently high, and therefore the impedance of the circuit must be high. Therefore, in order to inject a sufficient amount of the impulse current, the output voltage of the pulse generator 110 must be at least 200V or more.

The current measuring unit 120 measures a current flowing between the ground electrode E1 and the auxiliary electrode E2 of the measurement target support. The current measured by the current measuring unit 120 is used to extract the ground impedance from the measurement signal processing unit 140, as described below. Here, the current measuring unit 120 is constituted by at least one of a meter current transformer (CT) having a bandwidth of at least 10 MHz or more from DC and a shunt resistor. Here, the term shunt resistor is a type of shunt resistor used to sense current and measure the amount of current.

The voltage measuring unit 130 measures the potential difference between the ground electrode E1 of the supporter to be measured and the reference electrode E3 for voltage measurement, that is, the voltage. The voltage measured by the voltage measuring unit 130 is used for extracting the ground impedance from the measurement signal processing unit 140, as in the previously described measured current. The voltage measuring unit 130 is constituted by a meter transformer PT. Here, the bandwidth of the voltage measuring unit 130 is larger than the bandwidth of the current measuring unit 120, and the input terminal resistance of the voltage measuring unit 130 is 100 MΩ or more.

Although current measuring instrument CT and shunt resistors are used and voltage measuring instrument power transformer (PT) is used throughout the specification, the equipment used for these measurements is not limited to these, It is to be understood that the measurement equipment to be developed and the measurement equipment to be developed in the future may be used.

The measurement signal processing unit 140 converts the current and voltage signals measured from the current measuring unit 120 and the voltage measuring unit 130 into digital values to extract the frequency spectrum of the ground impedance, And determines whether the frequency spectrum converges. The functions included in the measurement signal processing unit 140 and the respective configurations will be described in detail below with reference to FIG.

2 shows each configuration of the measurement signal processing unit 140 included in the ground resistance measurement apparatus 100 of the present invention described above. The measurement signal processing unit 140 includes an analog-to-digital converter 141, a data operation unit 142, a control unit 143, and a display unit 144.

The analog-to-digital converter 141 digitally converts the current and voltage signals measured in the current measuring unit 120 and the voltage measuring unit 130, that is, i (t) and v (t) . Also, although not shown in the figure, the measurement signal processing unit 140 may include an amplifier or a voltage divider to adjust the measured current and voltage signals, and then receive the adjusted signal in the analog-to-digital converter 141. [

In one embodiment, the data computing unit 142 functions to extract the frequency spectrum of the current and voltage that have been previously converted to digital in the analog-to-digital converter 141. It should be understood that, in extracting such a spectrum, Fast Fourier Transform (FFT) or Discrete Fourier Transform (DFT) may be used. After extracting the frequency spectrum of the current and voltage, the data operation unit 142 also extracts the spectrum of the ground impedance using the frequency spectrum of the extracted current and voltage. This spectrum extraction of the ground impedance can be done by dividing the voltage by the current in the frequency spectrum of the extracted current and voltage.

Further, in another embodiment, the data operation unit 142 calculates the time-dependent resistance, i.e., R (t), by dividing the voltage measured in each time period by the current, that is, dividing v (t) by i (E.g., t = 1, 2, 3, 5, 10, 30 μs) may be derived.

The control unit 143 determines whether the frequency spectrum of the ground impedance extracted by the data operation unit 142 converges according to the frequency increase. Here, if it is determined that the frequency spectrum of the ground impedance converges with increasing frequency, the convergent impedance value is regarded as the ground resistance of the support, and this value is transmitted to the display unit 144. However, if not, by adjusting the impulse waveform of the pulse generator 110, that is, the rise time, the magnitude and the cycle, etc., by increasing the injection current pulse peak value or shortening the rise time so that the power of the high frequency band is amplified, Improves the convergence characteristic of the impedance.

The display unit 144 functions to display the converged impedance value when the control unit 143 determines that the frequency spectrum of the ground impedance converges as the frequency increases. The display unit 144 may be formed of at least one of currently known displays, that is, a CRT, a PDP, an LCD, and an LED, and may be a display to be developed in the future.

Hereinafter, a ground resistance measuring method will be described in detail with reference to FIG.

3 shows a flow chart of the ground resistance measuring method of the present invention.

First, an impulse power source is applied between the grounding electrode E1 and the auxiliary electrode E2 for current measurement (S210). As described above, the impulse current is circulated between the ground electrode E1 and the auxiliary electrode E2 through power application in this step S210. A part of the impulse current flows to the ground wire or neutral wire connected to the ground of the object to be measured, and the remaining current flows to the earth electrode E1 of the object to be measured, thereby contributing to the ground potential rise of the earth electrode E1 . Further, as mentioned above, in order to inject a sufficient amount of the impulse current, the output voltage of the pulse generator 110 must be at least 200V or more.

Thereafter, the current between the grounding electrode E1 and the auxiliary electrode E2 is measured and a step S220 of measuring the potential difference between the grounding electrode E1 and the reference electrode E3 installed for voltage measurement, . Here, the current measurement may be performed through at least one of the meter current transformer (CT) and the shunt resistor. In addition, the voltage measurement can be made via a meter transformer (PT). In Figure 3 and in the detailed description, it is to be understood that although the voltage measurement is described as being performed after the current measurement is made, the voltage measurement may be made first, and then the current measurement may be performed.

After the current and voltage measurement step S220 is performed, the measured current and voltage signals are converted into digital values (S230). Although not shown in the figure, it is possible to amplify or divide the measured current and voltage signals before converting them to digital values, so that a more accurate conversion can be performed.

After the digital conversion step S230, a step S240 of extracting the frequency spectrum of the digital current and voltage is performed. For extracting such a spectrum, a well-known extraction method, such as a fast Fourier transform (FFT) or a discrete Fourier transform (DFT), can be used.

Thereafter, a frequency spectrum of the ground impedance is extracted (S250) by using the frequency spectrum of the extracted current and voltage. The extraction of the frequency spectrum of the ground impedance can be made by dividing the voltage by the current in the frequency spectrum of this current and voltage.

Then, a step (S260) of judging whether the frequency spectrum of this ground impedance converges appropriately is performed. If it is determined in step S260 that the frequency spectrum of the ground impedance converges with increasing frequency, the converged impedance value is regarded as the ground resistance of the support (S270), and the step of displaying this value (S280) do.

Otherwise, the impulse waveform of the pulse generator 110, that is, the rise time, the magnitude, and the cycle of the impulse may be adjusted by increasing the injection current pulse peak value or shortening the rise time so that the power of the high frequency band is amplified, A step S290 of improving the convergence characteristic of the ground impedance is performed.

Hereinafter, an experiment for confirming the reliability of measurement using the grounding resistance measuring apparatus 100 of the present invention will be described with reference to FIGS. 4 to 8. FIG.

Figs. 4 to 8 show an example of calculating the grounding resistance of a single tower of a 154 kV transmission line.

For comparison with this measurement method, the support current measurement method is performed in the conventional measurement technique. This support current measurement method is a method of measuring the grounding resistance of a pressurized power line support, in which a low-frequency test current is used and a ring CT is installed on the tower of the transmission tower. This measurement method is advantageous in that it produces an accurate result as compared with other conventional measurement methods. However, measurement methods that measure only the injection current, for example, current measurements are performed for each tower angle unlike the impulse current method and the high frequency current method , And a current measurement point is added.

First, the measurement using the support current measurement method will be described. According to the present embodiment, the four tower-top ground resistances of the 154-kV power transmission tower were measured to be 209 ?, 191?, 157 ?, and 144?, Respectively. Therefore, their combined resistance becomes 43?.

4 and 5 illustrate waveforms of impulse current injected into an existing 154 kV transmission tower using the method proposed by the present invention and measuring the potential of the tower and the applied current when an impulse current is applied using a portable oscilloscope. Here, FIG. 4 shows the current waveform measured with time, and FIG. 5 shows the voltage waveform measured with time. FIG. 6 shows the ground resistance for each time period obtained by using the acquired waveforms, that is, dividing the voltage value by the current value for each time period. The ground impedance for each frequency based on the result of the frequency spectrum analysis of each of the ground resistance and the current / voltage is shown in Figs. 7 and 8. Fig. Here, FIG. 7 shows the magnitude of the ground impedance, and FIG. 8 shows the phase value of the ground impedance. As shown in Fig. 7, it can be seen that the ground impedance converges at about 40 [Omega].

As described above, an optimal embodiment has been disclosed in the drawings and specification. Although specific terms have been employed herein, they are used for purposes of illustration only and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

100: ground resistance measuring device 110: pulse generator
120: current measuring unit 130: voltage measuring unit
140: measurement signal processor 141: analog-to-digital converter
142: data operation unit 143:
144:

Claims (12)

A pulse generator for applying an impulse power between an earth electrode and an auxiliary electrode for current measurement;
A current measuring unit for measuring a current between the ground electrode and the auxiliary electrode;
A voltage measuring unit for measuring a voltage between the ground electrode and a reference electrode for voltage measurement; And
Converts the current and voltage signals measured from the current measuring unit and the voltage measuring unit into digital values, extracts a frequency spectrum of the ground impedance based on the digital values of the converted current and voltage, And a measurement signal processor for determining whether the frequency spectrum is converged. The method according to claim 1,
Wherein the measurement signal processing unit comprises:
An analog-to-digital converter for converting each of the current and voltage signals measured by the current measuring unit and the voltage measuring unit into digital values;
A data operation unit for extracting a frequency spectrum of the current and voltage signals converted into digital signals and extracting a frequency spectrum of a ground impedance based on a frequency spectrum of the extracted current and voltage signals; And
Further comprising a controller for determining whether the frequency spectrum of the ground impedance converges and regards the frequency value of the ground impedance to be converged as a ground resistance when the frequency spectrum of the ground impedance converges. The method according to claim 1,
Wherein the measurement signal processing unit comprises:
And controlling the pulse generator to improve the convergence characteristic of the ground impedance when it is determined that the frequency spectrum of the ground impedance does not converge, thereby generating an impulse including at least one of an injection current pulse peak value, a rise time, And further adjusting the characteristic of the ground resistance. The method according to claim 1,
Wherein an output voltage of the pulse generator is 200V or more. The method according to claim 1,
Wherein the current measuring unit comprises at least one of a current transformer (CT) and a shunt resistor. The method according to claim 1,
Wherein the voltage measuring unit comprises a meter transformer (PT). Applying an impulse power between an earth electrode and an auxiliary electrode for current measurement;
Measuring a current between the ground electrode and the auxiliary electrode;
Measuring a voltage between the ground electrode and a reference electrode for voltage measurement; And
Converting each of the current and voltage signals measured from the current measuring step and the voltage measuring step into digital values, extracting a frequency spectrum of the ground impedance based on the digital values of the converted current and voltage, And a measurement signal processing step of determining whether the frequency spectrum converges. 8. The method of claim 7,
Wherein the measurement signal processing step comprises:
Converting each of the current and voltage signals measured from the current measuring step and the voltage measuring step into digital values;
Extracting a frequency spectrum of the digital converted current and voltage signals and extracting a frequency spectrum of the ground impedance based on the frequency spectrum of the extracted current and voltage signals; And
Further comprising the step of determining whether the frequency spectrum of the ground impedance converges and considering the convergent frequency value of the ground impedance as the ground resistance when the frequency spectrum of the ground impedance converges. 8. The method of claim 7,
Wherein the measurement signal processing step comprises:
Wherein the step of applying the impulse power comprises the step of applying the impulse power to at least one of the peak value of the injection current pulse, the rise time of the pulse, the magnitude and the period of the pulse to improve the convergence characteristic of the ground impedance when it is determined that the frequency spectrum of the ground impedance does not converge. And adjusting the impulse characteristic including the impulse characteristic. 8. The method of claim 7,
Wherein the voltage output from the step of applying the impulse power is 200 V or more. 8. The method of claim 7,
Wherein the current measuring step is performed through at least one of a current transformer (CT) and a shunt resistor. 8. The method of claim 7,
Wherein the voltage measuring step is performed through a meter transformer (PT).

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