KR100587918B1 - Ground resistor analysis system - Google Patents

Abstract

The present invention relates to a method and apparatus for measuring ground resistance for diagnosing grounding performance of a substation grounding system in operation.

The substation ground current classification coefficient measurement and ground resistance analysis system of the present invention for this purpose is an independent power generator that generates a frequency of 50 Hz to minimize external interference and ensure measurement reliability, and output voltage 0-130 V at an input voltage of 100 V. Test current injection power supply which consists of voltage regulator which can control test current and control current, and booster which can maximize test current with rated capacity 2kVA, input voltage 100V and output voltage 440V. ; Current and voltage sensors that can accurately detect classified ground currents using current probes and voltage probes, 8-channel, 16-bit analog / digital, up to 1 MHz sampling to convert analog signals into digital signals Data acquisition system consisting of a multi-channel data acquisition device capable of processing, a data analysis device and an output device capable of outputting the result of the analysis on the window screen in real time through the data analysis program installed in the notebook PC. And an analyzer; And other devices consisting of a grounding rod for the current electrode and a grounding rod for the voltage electrode.

Substation ground resistance, large scale ground network, substation ground current classification coefficient measurement and ground resistance analysis system, potential drop method

Description

Substation ground current classification coefficient measurement and ground resistance analysis system in operation {GROUND RESISTOR ANALYSIS SYSTEM}

1 is a conceptual diagram of the 61.8% law, which is the basic theory of the potential drop method,

2 is a conceptual diagram of reference electrode location (IEEE Std. 81-1983 [3] or IEEE Std 81.2-1991 [4] recommendation);

Figure 3a is a block diagram showing a ground current classification coefficient measurement and ground resistance analysis system according to an embodiment of the present invention,

3B is a conceptual diagram illustrating the multi-channel data acquisition device shown in FIG. 3A;

4 is a potential drop curve analysis model,

5A is a conceptual diagram of a ground resistance estimation algorithm;

5b is an output screen showing ground current and classification coefficient S _f measurement;

5c is a conceptual diagram for performing a potential drop method;

5D is an output screen showing a potential drop curve,

5E is an output screen showing a resistance curve to which a correction coefficient is applied.

-Explanation of symbols for the main parts of the drawings-

1: Independent power generator 2: Voltage regulator

3: booster 4: current and voltage sensor

5: multi-channel data acquisition device 6: data analysis device

7: output device 8: ground rod for voltage electrode

9: ground rod for current electrode

The present invention relates to a substation ground current classification coefficient measurement and ground resistance analysis system in operation, and more particularly, to a method and apparatus for measuring ground resistance for diagnosing the grounding performance of the substation ground system in operation.

In general, ground (ground) means to electrically connect a terminal to the ground, and the ground electrode serves as this electrical terminal. In other words, whether electrical equipment is grounded to the ground through the ground wire and the ground electrode, and easily flows when the current flows into the ground through the ground electrode depends on the ground resistance. For some reason, the potential rises when a fault current flows through the grounding system of the electrical installation. This is expressed as the product of the fault current and the electrical resistance of the grounding system, according to Ohm's Law. In order to suppress the potential rise as much as possible, grounding with low grounding resistance is required. That is, the upper limit of the potential rise without danger to the human body is the most basic for preventing electric shock since it relates to ground resistance.

Therefore, the substation ground is constructed to suppress the voltage rise or stride voltage generated when a large current flows through the grounding system in the ground due to ground fault or lightning strike, and mesh is mainly used as the ground electrode. Therefore, boring electrodes (or deep hole drilling methods) are used in combination, and the role of the mesh grounding is not only to obtain a low grounding resistance but also to reduce the stride voltage of a worker in the premises. By construction.

Therefore, the purpose of grounding is to protect the human body and important equipment by limiting the ground potential rise of the substation and the contact / strength voltage within the allowable value in the event of a ground fault. It is essential to have a system. In addition, in the case of a substation in operation under pressure, the grounding performance may be regarded as good when the grounding failure occurs, and the substation-only grounding network absorbs more fault currents in the substation grounding system. Therefore, the smaller the ground resistance value of the substation single grounding system, the better. Before the substation pressurization, that is, before the distribution grounding system and the transmission grounding system is connected to the substation grounding network, the ground resistance measurement can be measured by the conventional potential drop method, but the substation alone is used to diagnose the substation grounding performance in the operating state. It was very difficult to measure the earth resistance of the earth network.

The substation grounding system in operation forms a large grounding network connected in parallel to the substation grounding network, the distribution grounding system and the transmission grounding system, and in this case, the substation grounding is used to diagnose the grounding performance of the substation grounding system. The earth resistance of the network shall be measured. The distribution ground system and the transmission ground system should be separated after the measurement in the large-scale ground network, but this is impossible for the stable power supply and safety of the system in the case of a pressurized substation, and it is a difficult problem that must be carried out after a truce. Is holding. At present, the ground system diagnosis of a substation in operation is in a difficult position or a practical situation in which the ground resistance of a large ground network connected in parallel to the substation ground network, the distribution ground system, and the transmission ground system is inevitably measured. Therefore, in the conventional method, it is impossible to measure the ground resistance of the substation alone ground network in the operating state.

In the case of measuring the substation grounding resistance by using the conventional potential drop method, when the substation grounding network is connected with the distribution line and the transmission line grounding system to form a large-scale grounding network, as shown in FIG. The ground electrode and the auxiliary electrode are respectively installed. However, since the distance (a) of the ground electrode is not known, the distance (D) between the auxiliary electrode and the ground electrode is also unknown. Therefore, it is impossible to identify the position of the reference potential point by the 61.8% rule. The curve shown in FIG. 1 shows the ground potential when the distance D between the auxiliary electrode and the ground electrode is infinite. Thus, the law of 61.8% results in ΔV 1 = ΔV (x) at the position where x / D is 0.618.

In addition, IEEE Std. 81-1983 [3] or IEEE Std. According to 81.2-1991 [4], it is recommended that the length of the measuring line be located at a distance of at least 6.5 times the diagonal length of the ground pole until the area where the grounding target electrode and the auxiliary electrode are free from interference as shown in FIG. In the case of an operating substation in which the substation ground network is connected to the distribution line and the transmission line ground system to form a large ground network, the size of the ground electrode is not known, so reliable measurement of the ground resistance is impossible. Here, the reference electrode position should be located at a distance of 6.5 times or more of d (L> 6.5d). Reference numeral I denotes a current.

As described above, in order to measure the grounding resistance of the substation grounding network alone, it is almost impossible to isolate all distribution grounding systems and transmission grounding systems connected to the grounding network. Therefore, in the case of measuring substation ground resistance by using the conventional potential drop method, when the substation ground network is connected to the distribution line and the transmission line ground system to form a large ground network, it becomes impossible to identify the position of the reference potential point. In this case, the length of the measuring line should be increased until the area where the grounding target electrode and the auxiliary electrode do not interfere with each other comes out.

Accordingly, the present invention has been invented to solve the conventional problems as described above, it is possible to measure the grounding resistance of the substation grounding network of the substation grounding system in the pressurized and operating state, the ground current classification of the substation grounding system As it is possible to measure coefficients, the current classified after injecting the test current into the grounding system of the substation in operation should be able to detect only pure test current components, and it does not interfere with noise such as commercial frequency and harmonics that appear during operation. The purpose is to provide a substation ground current classification coefficient measurement and ground resistance analysis system that can be eliminated.

Another object of the present invention is to be able to adjust the test current to the maximum because the reliability is low when the test current is small, and to generate an independent power source so that it can be measured even in the absence of power without interference from the surrounding environment. In the case of a large earth electrode such as a substation grounding system, it is necessary to extend the measurement line very far in order to find the reference potential, that is, the zero potential point. By analyzing the measurement result by comprehensively, it provides the algorithm to estimate the ground resistance of the substation ground network alone, and provides the ground current classification coefficient measurement and ground resistance analysis system as a portable weight and structure capable of manpower transportation. Is in.

The present invention for achieving the above object, the independent power generator 1 for generating a frequency of 50Hz in order to minimize external interference and ensure measurement reliability, the input voltage 100V to the output voltage can be varied from 0 to 130V test current Voltage regulator (2) to control the voltage, voltage regulator (2), rated voltage of 2kVA, input voltage of 100V and output voltage of 440V, and booster (3) to maximize the test current. Current and voltage sensor (4) capable of accurately detecting ground currents, 8-channel, 16-bit analog / digital, multi-channel data acquisition device capable of processing analog data into digital signals with up to 1 MHz sampling and processing in data analysis programs (5) Each outputted data signal can be output in real time on the window screen through the data analysis program installed in the notebook PC. It is characterized by consisting of a data analysis device 6 and an output device 7, and ground rods 9 and 8 for current and voltage electrodes.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3A is a block diagram showing a ground current classification coefficient measurement and analysis system according to an embodiment of the present invention, and FIG. 3B is a conceptual diagram showing the multi-channel data acquisition device 5 shown in FIG. 3A. Components of the substation ground current classification coefficient measurement and ground resistance analysis system of the present invention are as shown in FIG. 3A, a power supply device for test current injection (1 to 3), a data acquisition and analysis device (4 to 7), and And other devices 8 and 9.

The test current injection power supply device is composed of an independent power generator (1), a voltage regulator (2), and a booster (3), the independent power generator 1 is a small and lightweight portable By adopting the capacity of 1.6kVA, output voltage 100V and output frequency 50Hz, it does not interfere with the commercial frequency of 60Hz. The voltage adjusting device (2) has a structure that can be changed to the input voltage 100V, the output voltage 0 ~ 130V to be able to adjust the test current in consideration of the generator capacity. The boosting device 3 can improve the measurement reliability by allowing the test current to be maximized by setting the capacitance 2kVA, the input voltage as 100V, and the output voltage as 440V. In the power supply device for test current injection, the independent power generator 1, the voltage regulator 2, and the booster 3 are sequentially connected.

The data acquisition and analysis device comprises a current and voltage sensor (4), a multi-channel data acquisition device (5), a data analysis device (6) and an output device (7), and is connected to the boosting device (3). The current and voltage sensor 4 can accurately detect the classified ground current using the current probe CT and the voltage probe PT, and the current probe is composed of a combination of a clamp type and a flexible type. The measurement can be performed according to the shape of the voltage probe, and the voltage probe can measure the voltage during the potential drop curve measurement using the potential drop method.

The boosting device 3 and the current and voltage sensor 4 are connected to a substation ground grid, and the substation ground grid is connected to an external ground system through each current sensor. have. The multi-channel data acquisition device 5 converts an analog signal into a digital signal with 8-channel, 16-bit analog / digital, and up to 1 MHz sampling so that it can be processed in a data analysis program, and the resolution is good for easy analysis. do.

The data analysis device 6 and the output device 7 convert the analog signal into a digital signal by the multi-channel data acquisition device 5 through the data analysis program mounted on the notebook PC. The user's convenience is provided by displaying the result of analysis on the window screen in real time.

Other devices include a ground electrode 8 for a voltage electrode and a ground electrode 9 for a current electrode connected to the current and voltage sensor 4. A plurality of current sensors and voltage sensors 4 are respectively connected to the multi-channel data acquisition device 5 as analog / digital converters.

As shown in FIG. 3B, the multi-channel data acquisition device 5 uses differential amplifiers through buffers 11 and 12 in multi-channels CH # 1 to CH # 8, respectively, for inputting bayonet neil concealers (BNCs). Input to (13) is supplied to the buffer 16 through each anti-alias filter (ANTI-ALIAS FILTER 14) and summer 15. In addition, the buffers 11 and 12 of the CH # 1 are connected to the analog trigger 20 while the buffer 16 is connected to the 1 MHz 16-bit analog / digital converter 17.

The 100 MHz timebase 18 connected to the analog / digital converter 17 is connected to the digital signal processor 19, the analog trigger 20, and the control and timing section 22, respectively. The control and timing unit 22 to which the analog trigger 20 is connected is connected to an EEPROM 23 and a high-speed EEP interface 24, respectively, and a FIFO (First In First Out) through the digital signal processor 19. The data buffer 21 is connected to the high speed EEP interface 24. The high speed EEP interface 24 is interconnected with the portable computer 25, for example, as a notebook PC.

The present invention configured as described above can measure the ground resistance of the substation ground network alone without disconnecting the distribution grounding system and the transmission grounding system after completion of the operation of the substation, that is, the completion of the operation, and injects the test current into the substation being operated under pressure. In this case, the error caused by the interference can be minimized by injecting a test current with a frequency of 50 Hz by an independent power source to eliminate the interference on the commercial frequency 60 Hz and harmonics and to increase the measurement reliability.

In addition, the present invention performs both the measurement of the ground current classification coefficient and the potential drop method, and by analyzing each measurement result comprehensively, the algorithm that can estimate the ground resistance of the ground network alone is very far to find the zero potential point. It is possible to solve the problem of unfolding the measuring line, and by adjusting the test current to the maximum by applying the combination of the voltage adjusting device and the boosting device, it is possible to improve the reliability and provide convenience to the user with the portable structure. have.

In the analysis algorithm for estimating the ground resistance of the ground network alone, V (x) is the ground potential at x point, Va is the potential of electrode a, and R (x) is x in the potential drop curve analysis model shown in FIG. Assuming that the apparent resistance of the point and Rg is the true value of the ground resistance of the ground electrode, m (x), which is equation (4), can be derived by the following equations (1) to (3). Where Zexternal stands for external impedance.

(1)

(One)

(2)

(2)

(3)

(3)

(4)

(4)

Therefore, by multiplying the apparent resistance measured by the potential drop method with the value of m (x), a curve in which the true value of Rg, which is the true value of the ground resistance of the ground electrode, can be obtained regardless of x.

5A is a conceptual diagram of the grounding resistance estimation algorithm, FIG. 5B is an output screen of the ground current and classification coefficient measurement, FIG. 5C is a conceptual diagram of the potential drop method, FIG. 5D is an output screen of the potential drop curve, and FIG. 5E is a correction. Output screen of resistance curve applying coefficients. 5B, 5D, and 5E display the ground resistance analysis output screen by the ground resistance estimation algorithm on the portable computer, which can solve the problem of extending the measurement line very far in order to find the zero potential point. .

The ground resistance estimation algorithm shown in FIG. 5A measures the ground network classification coefficient in a portable computer, that is, the ground network classification coefficient S _f can be obtained as (II _D -I _T ) / I. Here, I is the test current injected into the ground system (frequency 50Hz), I _D is the current detected by being classified as the distribution neutral wire (frequency 50Hz), and I _T is the current detected by being classified as the overhead line of the transmission line (frequency 50 Hz). )to be.

The potential drop curve can then be measured from a portable computer. At this time, input the measurement result and ground network information. Then, the voltage drop (FOP (Fall of Potential)) curve x correction coefficient is obtained. Accordingly, as shown in FIG. 5E, the resistance curve may be analyzed and the grounding resistance alone may be calculated (the grounding resistance of the grounding network alone, which is the apparent resistance in the section where the flat portion appears between the grounding network and the current feedback electrode). True value).

In other words, in the ground resistance analysis method using the ground resistance estimation algorithm, the analysis of the potential drop curve is performed after the ground current and the potential drop method have been measured, and the analysis of the potential drop method curve (potential drop curve) based on the measurement result. In this case, the ground resistance of the ground network alone can be estimated.

5D shows a screen configuration of the potential drop curve analysis program. First, the potential drop measurement result, that is, the position of the voltage electrode and the apparent resistance values measured at the position are input. After inputting, press the "FOP curve" button to check the measured value and input the data of earth current classification rate. Enter the ground network area, and enter the distance from the approximate center of the ground network to the location (outside of the substation) where the potential drop measurement was started.

Enter the total length of the potential drop measurement line, that is, the distance from the outside of the ground network to the remote current feedback electrode, and finally, the ground network classification coefficient. The ground network classification coefficient is a current flowing out of the ground network among the total currents injected by the ground current measurement. After inputting all the data, press the "Draw resistance curve" button of FIG. 5E to multiply the correction coefficient for each measurement position. Under ideal conditions, the same value would be calculated at all locations, but this condition would be difficult to be established near the substation ground network in operation and near the remote current feedback electrode.

However, a flat portion always appears between the ground network and the current feedback electrode. That is, the apparent resistance value in this section where the flat portion appears as shown in Figure 5e can be seen as the true value of the ground resistance of the ground network alone.

Here, the principle of the algorithm applying the correction factor that shows the flat portion of FIG. 5E, which can be determined as the true value, is that the apparent resistance R (x) at distance x is the ground resistance R of the hemisphere electrode in the potential drop curve analysis model of FIG. x equal to _g becomes 61.8% of the distance D between electrodes as shown in the 61.8% law conceptual diagram shown in FIG. 1. In other words, x, where x / D is 0.618, becomes the position where the zero potential is artificially created.

However, this 61.8% rule is based on the assumption that 100% of the test current is injected into the ground electrode, so it is not applicable if the ground electrode to be measured is connected to an external ground system such as a distribution ground system or a transmission ground system. Because of the dividing effect, the apparent resistance curve itself along the distance x is lowered so that the position itself equal to the ground resistance of the grounding electrode to be measured is eliminated.

Therefore, the ratio of the current (m) of the earth resistance Rg of the ground electrode and the apparent resistance R (x) of the distance x to which the ratio of the current classified into the substation ground network, which is the earth to be measured, among the test currents, is further taken into account. By deriving the equation, by multiplying this value by the apparent resistance at distance x, a curve in which the ground resistance Rg of the ground electrode is converted regardless of the distance x, that is, a curve in which the flat portion of FIG. 5E appears can be obtained.

As described above, the substation ground current classification coefficient measurement and ground resistance analysis system in operation according to the present invention includes all distribution grounding systems and transmission grounding systems connected to the grounding network in order to measure the grounding resistance of the substation grounding network alone. It is possible to measure the grounding resistance of substation grounding networks alone without disconnecting the distribution substations, transmission grids, and transmission grids after the construction of the substations in operation, i.e., those that are practically impossible.

In addition, the present invention injects the test current of the frequency of 50Hz by the independent power supply to remove the interference to the commercial frequency 60Hz and harmonics and to increase the measurement reliability when injecting the test current into the substation under pressure to operate the error caused by interference It can be minimized.

In addition, the present invention performs both the measurement of the ground current classification coefficient and the potential drop method, and by analyzing each measurement result comprehensively, the algorithm that can estimate the ground resistance of the ground network alone is very far to find the zero potential point. The problem of unfolding the measuring line can be solved.

In addition, the present invention can adjust the test current to the maximum by applying a combination of the voltage adjusting device and the boosting device to improve the reliability, it can provide convenience to the user in a portable structure.

On the other hand, the present invention has been described on the basis of the drawings the technical idea of the substation ground current classification coefficient measurement and ground resistance analysis system in operation, which is illustrative of the best embodiment of the present invention by claim Without limiting the scope, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (6)

An independent power generator 1 for generating a frequency of 50 Hz to minimize external interference and to ensure measurement reliability; A voltage regulator (2) connected to the independent power generator (1) and capable of varying the output voltage from 0 to 130 V to an input voltage of 100 V according to the voltage input of the independent power generator (1) (2). ); It is connected to the voltage regulating device (2), and is composed of a boosting device (3) which can improve the test reliability by maximizing the test current by using a rated capacity of 2kVA, input voltage 100V and output voltage 440V as an isolation transformer Test current injection power supply, A plurality of current and voltage sensors 4 connected to the boosting device 3 to accurately detect ground currents classified by the current probe CT and the voltage probe PT; The plurality of current and voltage sensors 4 are connected to each other, and multi-channel data which can be processed in a data analysis program by converting an analog signal into a digital signal with 8-channel, 16-bit analog / digital and up to 1 MHz sampling. Acquisition device 5; Each data signal connected to the multi-channel data acquisition device 5 and converted and output by the multi-channel data acquisition device 5 into a digital signal is analyzed on a window screen through a data analysis program mounted in a notebook PC. A data acquisition and analysis device comprising a data analysis device 6 and an output device 7 capable of outputting a result in real time; Substation ground current classification coefficient measurement and ground resistance analysis of a substation in operation comprising the other device consisting of a grounding electrode (9) and a grounding electrode (8) for the current electrode connected to the current and voltage sensor (4) system. The method of claim 1, The data acquisition and analysis apparatus performs both the measurement of the ground current and the potential drop method, and comprehensively analyzes each measurement result by a ground resistance estimation algorithm to estimate the ground resistance of the ground network alone. Substation ground current classification coefficient measurement and ground resistance analysis system in operation. The method of claim 1, The multi-channel data acquisition device is input to the differential amplifier 13 through the respective buffers 11 and 12 in the multi-channels CH # 1 to CH # 8 for inputting the BNCs, respectively, and then to each anti-array filter 14. And buffer 15 are supplied to buffer 16 via a summer 15, and the buffer 16 is connected to an analog trigger 20 from buffers 11 and 12 of CH # 1 while the buffer 16 is a 1MHz 16-bit analog / Connected to the digital converter 17; The 100 MHz timebase 18 connected to the analog / digital converter 17 is connected to the digital signal processor 19, the analog trigger 20, and the control and timing unit 22, respectively, and the analog trigger 20 is connected. The control and timing unit 22 is connected to the memory EEPROM 23 and the high speed EEP interface 24, respectively, and the FIFO data buffer 21 through the digital signal processor 19 is connected to the high speed EEP interface 24. Substation ground current classification coefficient measurement and ground resistance analysis system in operation characterized in that it is connected to and interconnected with the portable computer (25). The method of claim 3, In the portable computer, the ground resistance estimation measures the ground network classification coefficient, performs the potential drop method to measure the potential drop curve, inputs the measurement result and the information of the ground network, and obtains the voltage drop curve × correction coefficient. The substation ground-current classification in operation characterized by analyzing the resistance curve and estimating the grounding resistance of the grounding network alone to obtain the true value of the grounding resistance of the grounding network alone, the apparent resistance in the section where the flat portion appears between the grounding network and the current feedback electrode. Coefficient measurement and ground resistance analysis system. The method of claim 4, wherein The ground substation ground current classification coefficient measurement and ground resistance analysis system according to claim 1 , wherein the ground network classification coefficient S _f is obtained from the equation (II _D -I _T ) / I. However, in the above formula, I is a test current (frequency 50Hz) injected into the ground system, I _D is a current detected by being classified as a distribution neutral wire (frequency 50Hz), and I _T is a current classified and detected as a overhead line of transmission line ( Frequency 50 Hz). The method of claim 4, wherein The ratio of the earth resistance Rg of the ground electrode and the apparent resistance R (x) of the distance x, which considers the current ratio classified as the substation ground network, which is the earth to be measured, among the test currents, by considering the variable of the classification coefficient b.

And multiply this m (x) by the apparent resistance R (x) at distance x to find the curve at which the ground resistance true value Rg of the ground electrode is converted, i.e. Substation ground current classification coefficient measurement and ground resistance analysis system, characterized in that can be obtained.

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