KR20000037146A - A new technical method and equipment for the grounding resistance measurement on power service - Google Patents

Abstract

PURPOSE: A device and a method for measuring grounded resistance in active state and a service for measuring grounded resistance in active state are provided to measure accurate grounded resistance from power equipment or the grounded electrodes of communication equipment being operated. CONSTITUTION: A method for measuring grounded resistance in an active state comprises the steps of: designing an independent power supply which hasn't interference with the frequency contained in a grounded potential of grounded electrodes being operated without a grounded potential of the electrodes and the frequency of the grounded potential; applying the power of the power supply to current electrodes(C1,C2); measuring the grounded potentials on potential electrodes(16,17) using an input end having input impedance more than 100 Mohm; and capturing grounded potentials to the frequency applied only to current electrodes to calculate grounded resistances.

Description

Live grounding resistance measurement method and apparatus and live grounding resistance measurement service {A new technical method and equipment for the grounding resistance measurement on power service}

The present invention relates to a method and apparatus for measuring the ground resistance of the grounding equipment, which is the basis for reliability of power equipment and communication equipment, even when the power equipment or communication equipment is in operation. The present invention relates to a method and apparatus having excellent field application capability and reliable, and with the purpose of contributing to the safe operation of a power facility and a communication facility with the practical use of the present invention.

Increasingly industrialized, informatized and urbanized, modern society is characterized by consuming a lot of energy in dense areas, and the stable supply of electric power used as clean energy, which is the most convenient to use, simple to transport, and free of pollution. It is an important factor throughout.

The stable supply of power, which is important energy, must not only be supplied stably from natural disasters such as lightning strikes, but also the quality of electricity must be guaranteed. Of course, it is necessary to secure the quality of power distribution lines that are directly connected to power consumers.

Good grounding is essential for this high-quality, reliable power supply, and grounding not only functions to protect humans from power and lightning, but also provides a reference potential in terms of power business and protects power equipment from lightning strikes. .

In addition, grounding not only plays a very important role as a path for return current in the event of a system failure, and as the information society accelerates, facilities such as facsimile or computer-based image information and the Internet are used. The damage and damage of accidents are growing relatively. Therefore, the management of the ground resistance by measuring the accurate ground resistance is a big national benefit.

Basically, the ground resistance measuring method (FIG. 1) is a potential electrode after applying a current between the ground electrode 10 and the auxiliary current electrode 15 to be measured at a considerable distance (D in FIG. 1) of the current electrodes 15 and 17. P2 (16) is gradually moved from P1 (17) to C2 (15) direction, and the distance measured the potential ratio V14 with respect to the current I13 is made transverse, and the resistance value I / V is vertical axis. The graph 18 obtained can be obtained. At this time, the ground resistance value of the target ground electrode 10 is the value of the portion 19 to be parallel to the ground resistance value.

However, the ground electrode 10 of the power equipment during operation always has a ground potential 21 due to the influence of the leakage current 20 flowing from the power equipment or communication equipment to the ground during operation. In fact, the earth potential measured for the power equipment in operation (Fig. 11) contains not only 60 Hz of fundamental waves but also components of 180 Hz and 3 harmonics, and 300 Hz of 5 harmonics. ) Cannot be measured.

In addition, since the current flowing through the current poles C1 and C2 (15, 17) is generally about a few mA when measuring the ground resistance, the influence of the ground potential caused by such current is caused by the leakage current 20 flowing in the power equipment. Since less is common, a much larger earth resistance value will be obtained if measured by conventional methods than the actual earth resistance value. This phenomenon can be easily understood by comparing the measured waveforms (FIGS. 12 and 13) for actual substations in operation.

Eventually, the application of the existing method to the operating power equipment leads to the conclusion that the measurement value is larger (Fig. 12) and that the accurate measurement is impossible (Fig. 12).

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method and an apparatus capable of measuring an accurate ground resistance value even when a ground electrode of a power equipment or a communication equipment is in operation.

1 is a general grounding resistance measurement method

2 is a view for explaining why the ground resistance of the ground electrode in operation is impossible

3 is a schematic diagram of a measuring method for an operating ground electrode according to the present invention;

4 is a view showing the measuring device of FIG.

5 is a view for explaining the power supply device of FIG.

6 is a view for explaining the current measuring device of FIG.

7 is a view for explaining the potential measuring device of FIG.

8 is a diagram for describing the converter circuit of FIG. 4.

9 is a view for explaining the display device and the control device of FIG.

FIG. 10 is a diagram for explaining a signal generating circuit grounding resistance and a high resistivity calculation algorithm of FIG. 4.

FIG. 11 is a potential waveform in which the potential measured constantly at the ground electrode 10 is measured in the operating state, and this potential is caused, and it is difficult to measure the ground electrode in operation by the conventional measuring method.

12 is a measurement waveform of ground resistance with a conventional ground resistance measuring instrument

Figure 13 is a ground resistance measured waveform measured by the apparatus and method according to the present invention

<Explanation of symbols on main parts of the drawing>

10: Grounding electrode to be measured ground resistance

11: earth surface

12: voltage source for applying the current 13 to the current electrodes 15, 17

13: Current flowing through the current electrodes 15 and 17 by the voltage source 12

14: Voltmeter for measuring the earth potential between the voltage poles (16, 17)

15: one of two current poles

16: one of the two voltage poles

17: One of two current poles or one of two voltage poles

18: A basic ground resistance (R) measurement curve (R = V / I) using the earth resistance calculated as the potential between the current 13 flowing through the current electrodes 15 and 17 and the voltage electrodes 16 and 17.

19: The earth resistance value when the earth resistance is measured by the measured curve, and this value is a curve that has a theoretical basis and is certified and verified worldwide.

20: A system unbalanced current and a leakage current flowing from the power equipment in operation to the ground electrode 10, which causes this current, making it difficult to measure the ground resistance of the power equipment in operation.

21: Potential waveform which always acts on the ground electrode to be measured by (20).

22: distance axis

23: voltage axis indicating earth potential

30: device proposed by the present invention

31: a power supply that is part of the device proposed in the present invention

32: current measuring device which is a part of the device proposed in the present invention

33: Earth potential measuring device which is a part of the device proposed in the present invention

34: Earth resistance and earth resistivity measuring algorithm, which is part of the device proposed by the present invention, and a signal generating circuit

35: converter circuit for converting analog signals to digital signals as part of the device proposed in the present invention

36: Display and control device which is a part of device proposed in the present invention

41: Rechargeable battery used for the power supply which is a part of the device proposed in the present invention

42: rectifier used in the power supply which is part of the device proposed in the present invention

43: insulated circuit used in the power supply which is a part of the device proposed in the present invention

44: DC generator circuit used in the power supply unit which is part of the device proposed in the present invention

45: frequency and voltage magnitude information transmitted from the signal generation circuit 34

51: Current transformer and shunt resistance for measuring the current 13 flowing in the current pole 15 is used in the current measuring device 32 which is part of the device proposed in the present invention

52: Operational amplifier for measuring the accurate current 13 is used in the current measuring device 32 which is part of the device proposed in the present invention

53 is an off-set blocking circuit used in the current measuring device 32 which is a part of the device proposed in the present invention to remove errors and DC components caused by instability of the power supply.

54: Phase correction circuit for accurately measuring the phase difference between the current 13 of the current pole and the voltage 14 of the voltage pole

61: A high input impedance circuit used for the potential measuring device 33, which is a part of the device proposed by the present invention, for measuring accurate potential information.

62: band blocking circuit used in the potential measuring device 33 which is a part of the device proposed in the present invention

63 is used in the potential measuring device 33 which is a part of the device proposed in the present invention, the off-set blocking circuit for removing errors and DC components caused by instability of the power supply

64: A phase correction circuit for measuring the phase difference accurately between the current 13 of the current pole and the voltage 14 of the voltage pole, which is used in the potential measuring device 33 which is a part of the device proposed by the present invention.

71: current conversion circuit included in the converter circuit 35 which is a part of the device proposed in the present invention

72: potential conversion circuit included in converter circuit 35 which is a part of the device proposed in the present invention

73: waveform conversion circuit included in the converter circuit 35 which is a part of the device proposed in the present invention

74: simultaneous conversion system included in the converter circuit 35 which is a part of the device proposed in the present invention

81: LED numeric indicator included in the display device and the control device 36 which is a part of the device proposed in the present invention

82: selection switch included in the display device and the control device 36 which is a part of the device proposed in the present invention

83: selection switch for selecting the current 13 and the frequency included in the display device and the control device 36 which is a part of the device proposed in the present invention

84: frequency increase and decrease button included in the display device and the control device 36 which is a part of the device proposed in the present invention

85: current increase and decrease button included in the display device and the control device 36 which is a part of the device proposed in the present invention

91: Signal generation circuit which is a part of the device proposed by the present invention, and a signal generation algorithm which is included in the software and included in the ground resistance and the large resistivity calculation algorithm 34

92: a phase calculation algorithm, which is a part of the signal generation circuit and ground resistance, the high resistivity calculation algorithm 34, which is part of the device proposed by the invention, and which is written in software.

93: frequency analysis algorithm, which is a part of the signal generation circuit and ground resistance, the high resistivity calculation algorithm 34 which is a part of the device proposed by the invention, and which is written in software.

94: A commercial frequency cancellation algorithm, which is a part of the signal generation circuit, ground resistance, and high resistivity calculation algorithm 34, which is a part of the device proposed by the present invention, and which is written in software.

The method according to the present invention for achieving the above object completely excludes the frequency of the earth potential and the earth potential present in the ground electrode in operation, and the frequency which does not interfere with the frequency included in the ground potential of the equipment ground electrode in operation. Design an independent power supply with a power source and apply it to current poles C1 and C2 and measure the earth potential captured by potential poles P1 and P2 (16, 17) using an input stage with an input impedance of 100 MΩ or more. By processing 33 and again by software 34, the ground resistance is calculated by capturing only the ground potential for the frequency exactly applied to the current electrode, thereby calculating the ground resistance.

Usage of the present invention is the same method as the conventional method of measuring the ground resistance that the user is familiar with (Fig. 3). This completely eliminates the need to adapt to new devices.

The structure of this invention consists of 6 parts largely.

First, the power supply device 31 that can apply the current 13 to the target ground electrode 10 to be measured may use the power supplied from the power company, it is designed to use a rechargeable battery. At this time, when using the power supplied by the power company includes a function that completely eliminates the electrical relationship with the ground electrode (10) to be measured through a fully insulated design. 5 is a view for explaining the power supply device in detail. When using the power supplied by the power company receives the power is converted into a direct current power supply from the rectifier (42). This completely insulates the relationship with the power supplied by the power company by driving the insulation circuit 42 using the inverter circuit. The insulated circuit is also used to supply the bias voltages of the DC measuring device 32, the potential measuring device 33, the converter circuit 35, the signal generating device 34, and the display device. Using a completely isolated power supply and receiving the frequency and magnitude signals, which are signals from the signal generating circuit, the linear circuit and the amplifying circuit 44 amplify the signals linearly so that they can be used as applied currents of the current poles C1 and C2. An operational amplifier was used.

Second, even if a constant voltage is applied to the current measuring device 32 that measures the current flowing through the current electrodes C1 and C2 (16, 17), the magnitude of the current flowing varies. In this way, the current measured value does not change with respect to the change in current, and in order not to affect the current flowing through the earth, it has the characteristic of using a fully insulated current sensor by an optical element. 6 is a view for explaining the current measuring device in detail. The circuit 51 for detecting the current flowing between the current poles C1 and C2 was composed of a shunt resistor or a current transformer. However, a complete insulation amplifier made of optical elements is constructed so that the current applied from the current pole is not affected in the detection process. The detected current information is amplified by the operational amplifier 52 so as to be less than or equal to ± 10 V, which is the maximum value that can be accepted by the converter circuit 35. Since the signal amplified by hardware is a general phenomenon that the phase is somewhat changed, it is passed through the phase correction circuit 54 composed of the operational amplifier. In addition, the offset phenomenon, which is an electrical phenomenon that may occur due to an unbalance of the bias power supply, is completely compensated by the offset blocking circuit 53 composed of a general operational amplifier, and has a characteristic designed to have accurate current information measured.

Third, the accurate measurement of the ground potential induced in the voltage pole under the influence of the current applied to the earth through the current poles C1 and C2 (16, 17) is a very important factor in determining how accurately the ground resistance can be measured. Potential measuring device 33 having a characteristic of minimizing error in potential measurement by designing the input impedance of earth potential input terminal P1, P2 is 100MΩ or more so that the earth potential can be measured accurately without affecting the applied line Have 7 is an explanatory diagram for accurately measuring the earth potential. The most essential condition for accurate earth potential measurement is, in principle, the input impedance between the measuring terminals P1 and P2 is infinite. In order to meet these conditions, it is designed as a voltage follower circuit using operational amplifier, and designed and manufactured so that the input impedance is over 100MΩ. It is characterized by minimizing the error in measuring earth potential by making it jammed. In addition, the operational amplifier has a band stop circuit 62 that limits the leakage current and noise flowing to the ground electrode from the power equipment in operation. The offset inhibiting circuit 63 and the phase compensating circuit 64 are imposed in the same function as for increasing the accuracy of the current measuring circuit 32.

Fourth, the current information of the current measuring device 32 and the voltage information of the earth potential through the voltage measuring device 33 are converter circuits 35 having a function of digitizing them. The function of this circuit is to minimize the phase difference between the voltage information and the current information by simultaneously processing the voltage information and the current information, which are the ground potentials, in digitizing the current information and the voltage information at the same time (A / D conversion). Another function is to transmit a signal having a magnitude and a frequency generated by the signal generation circuit 34 to the power supply device 31. In this case, D / A conversion is performed to convert the digital signal into an analog signal. 8 is a diagram for describing the converter circuit in detail. In general, when converting information from voltage and current signals into digital signals, the most important thing is the sampling time that determines how much information and how many bits to process once. To this end, the present invention is designed to sample at least 32 times a period of the frequency signal sent from the control device, and designed and manufactured to have a resolution of 1/65536 by performing 16-bit A / D processing once sampling. When calculating the phase difference between the voltage information and the current information by using the voltage information and the current information, it is necessary to sample the voltage information and the current information at the same time so that the accurate phase information can be calculated. It is characterized by having a simultaneous conversion system 74, which is a circuit that uses a technique of simultaneously giving signals to the D converter, converting (71, 72) and accepting them into a 32-bit processor, and simultaneously digitizing the voltage information and the current information without time difference.

Fifth, the display device and the control device 36 are provided. The display function displays the phase difference and ground resistance of the applied frequency, voltage information, and current information. The control function consists of a switch that selects the current and frequency flowing through the current poles C1 and C2. 9 is an explanatory diagram for describing the display device and the control device in detail. The display function is a portion of the LED 81 which shows the resistance value and phase processed by the frequency and calculation algorithm 34 applied to the current poles C1 and C2, and a selection switch 82 which can select and display the frequency, phase and resistance value. Each time the selector switch 82 is pressed, the lamp indicating the frequency, phase, and resistance is turned on, and the value is displayed on the LED 81. The control portion is composed of switches 84 and 85 for determining the magnitude of the frequency and current to be applied, and a selection switch 83 for setting the frequency and the current magnitude. The frequency setting switch 84 and the current magnitude setting switch 85 You can press up and down to press the upper part to increase continuously, and press the lower part to keep decreasing function.

Sixth, the signal generation circuit, the ground resistance, and the high resistivity calculation algorithm 34, which are parts of the most important digital processors, are used. This device receives the frequency and current selected by the control device 36 and generates a signal generating portion corresponding to the sinusoidal wave, current information from the current poles C1 and C2, and voltage information from the voltage poles from the voltage poles P1 and P2. Processing through (35) calculates the phase difference between ground resistance, voltage information and current information, and transmits the information when required by the display device. 10 is a part for explaining in detail the algorithm for calculating the signal generation circuit, the ground resistance, the large resistivity. All of these functions are written in software, and the present invention uses DSP32, a 32-bit processor. Receiving the frequency and current magnitude information from the control device 36 generates a sine wave signal, and processes it continuously and transfers it to the converter circuit 35 to reach the current pole through the power supply device 31. The feedback is compared with the current information transmitted from the current measuring circuit 32 to the converter circuit 36 for accurate processing. In order to accurately measure the phase between the voltage information which is the exact ground potential and the current information which is the applied current, the voltage information and the current information are passed through a free transform 93. The voltage and current information passed in this way is divided into real and imaginary parts corresponding to respective frequencies, and when processed as a relative concept, an error free phase can be calculated. The present invention has a function 94 for processing phases having an error of 0.1 degree or less. The result of passing the phase calculation algorithm 91 and the frequency analysis algorithm 93, the voltage information and the current information of the applied frequency portion is processed to calculate the impedance (94) in a space configured as a memory to be delivered to the display device. Save it. By doing so, the software 95 performs a function 95 to completely remove the influence on the commercial frequency.

The effects of the present invention are as follows.

First, by measuring the ground resistance of the power equipment or communication equipment in operation in the same manner as the conventional ground resistance measuring method (Fig. 3) can also be used to users familiar with the conventional ground resistance measuring instrument (Fig. 1), In the case of the installation, all the functions of the existing earth resistance meter are included.

Second, in the case of the ground electrode in operation, it is difficult to measure the actual ground resistance value due to the unbalanced current and leakage current generated in the installed equipment, and the ground resistance value is large when the conventional method is measured (FIG. 12) and the phenomenon that cannot be measured. 12 can be completely removed to measure the correct ground resistance (FIG. 13).

Third, the present invention basically adopts a method of completely removing the potential generated in the equipment.

Fourth, it is possible to measure the ground resistance of commercial frequency by making power of completely different frequency.

Fifth, the principle is a simple principle of applying the principle of superposition, or by applying it to the ground electrode can obtain a result consistent with the principle was demonstrated (Fig. 13).

Claims (4)

In measuring the ground resistance in the live state, it is necessary to target the ground poles of the power equipment and the communication equipment in operation and to overcome the ground potential generated by the influence of the power equipment and the communication equipment in operation. Grounding resistance measuring system and method for measuring the grounding resistance by completely removing the frequency and the influence of the 2, 3, 5 harmonics of the frequency. In implementing the above 1, by applying the principle of superposition grounding resistance measurement system and method for forming a current pole with a separate power source having a frequency different from the commercial frequency (60Hz) of the power equipment and the frequency of the communication equipment. The ground resistance measuring system and method for implementing the above-mentioned 1 to measure the ground resistance by completely removing the influence of the ground potential by the existing power equipment through hardware and software filters. A service for providing live ground resistance measurement by the method and apparatus of 1