JP2013007692A - Grounding resistance measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a grounding resistance of an already installed grounding electrode without installing an auxiliary grounding electrode.SOLUTION: When grounding resistances Ra, Rb and Rc for three arbitrary grounding electrodes 11, 13 and 15 selected from among the respective grounding electrodes 11, 13, 15 and 17 are measured, for three grounding electrode sets (a set of the grounding electrodes 11 and 13, a set of the grounding electrodes 13 and 15, and a set of the grounding electrodes 11 and 15) which are constituted of two grounding electrodes of the three selected grounding electrodes 11, 13 and 15 and do not overlap with each other, synthetic resistances for the grounding resistances between the grounding electrodes consisting of the respective grounding electrode sets are measured, respectively, and solutions for the respective variables of a simultaneous equation consisting of three linear equations using the grounding resistances Ra, Rb and Rc of the three grounding electrodes as variables, respectively, and using the three measured synthetic resistances as constants, respectively are calculated as the grounding resistances Ra, Rb and Rc of the three grounding electrodes 11, 13 and 15.

Description

  The present invention relates to three or more grounding electrodes composed of at least one type of grounding electrode among a class A grounding electrode, a class B grounding electrode, a class C grounding electrode, and a class D grounding electrode (the grounding electrodes that are already installed). ) About the ground resistance measuring method of measuring each ground resistance.

  As a ground resistance measurement method for measuring the ground resistance of the ground electrode, a ground resistance measurement method disclosed as a conventional technique in the following patent document is known as a general ground resistance measurement method. This ground resistance measurement method will be described with reference to FIG. In the figure, the earthing electrode E is a grounding electrode, and the first auxiliary earthing electrode P and the second auxiliary earthing electrode C are temporarily grounded to measure the earthing resistance of the earthing electrode E. It is.

In the ground resistance measuring method using the ground resistance meter 51, the signal generator 52 supplies the second auxiliary voltage while the AC voltage V1 is applied from the signal generator 52 between the ground electrode E and the second auxiliary ground electrode C. An alternating current meter 53 measures the alternating current I1 flowing through the path returning to the signal generation unit 52 through the grounding electrode C, the ground G, and the grounding electrode E. Further, the AC voltage Ve generated between the earth electrode E and the first auxiliary ground electrode P due to the AC current I1 flowing through the ground G is measured by the AC voltmeter 54. In this state, since the alternating current I1 does not flow through the first auxiliary grounding electrode P, the alternating voltage Ve is expressed by the following formula (1) without being affected by the grounding resistance Rp of the first auxiliary grounding electrode P. .
Ve = I1 × Re (1)

The grounding resistance Re of the earth electrode E is expressed by the following formula (2) by modifying the formula (1).
Re = Ve / I1 (2)

  Finally, the grounding resistance Re of the earth electrode E is measured based on the current value of the alternating current I1 measured by the alternating current ammeter 53 and the voltage value of the alternating voltage Ve measured by the alternating current voltmeter 54.

Japanese Patent Application Laid-Open No. 11-118851 (page 2, FIG. 6)

  However, this conventional ground resistance measurement method has the following problems to be improved. That is, in this ground resistance measuring method, as described above, it is necessary to newly ground the first auxiliary grounding pole P and the second auxiliary grounding pole C to the ground. For this reason, this grounding resistance measurement method is, for example, a place where the ground (ground) is covered with concrete or asphalt, such as in the center of a city, or a place where a floor (bottom wall) is present, such as indoors. In addition, in a place where the first auxiliary grounding electrode P and the second auxiliary grounding electrode C cannot be newly installed, there is a problem that it is difficult to measure the grounding resistance of the already installed grounding electrode (earthing electrode E). is doing.

  The present invention has been made to improve such a problem, and it is a main object of the present invention to provide a ground resistance measurement method capable of measuring the ground resistance of an already installed ground electrode without installing an auxiliary ground electrode. To do.

  In order to achieve the above object, the ground resistance measuring method according to the present invention includes three methods including at least one kind of grounding electrode selected from the class A grounding electrode, the class B grounding electrode, the class C grounding electrode, and the class D grounding electrode. A grounding resistance measuring method for measuring each grounding resistance for the above grounding electrode, wherein the selected grounding resistance is measured when measuring the grounding resistance for any three grounding electrodes selected from the grounding electrodes. Measuring three combined resistances of the grounding resistance between the grounding poles constituting each grounding pole set for three grounding poles that are constituted by two of the three grounding poles and do not overlap each other; The solution for each variable of the simultaneous equations consisting of three linear equations each having the ground resistance of the three ground poles as a variable and the measured three combined resistances as constants is obtained for the three ground poles. Ground resistance It is calculated as.

  The ground resistance measurement method according to claim 2 is the ground resistance measurement method according to claim 1, wherein the ground electrode other than the selected three ground electrodes has the calculation of the ground resistance completed. The combined resistance is measured, and the ground resistance is calculated by subtracting the ground resistance of the ground electrode for which the calculation of the ground resistance is completed from the measured combined resistance.

  According to the ground resistance measuring method of claim 1, the auxiliary ground electrode is calculated by the above calculation method using any three ground electrodes selected from the three or more ground electrodes already installed. The grounding resistance for these three grounding poles can be calculated without installing.

  According to the ground resistance measuring method of the second aspect, the ground resistance of the ground electrodes other than the three selected ground electrodes can be reliably calculated by a simple method of subtraction.

It is a block diagram of the high voltage power receiving equipment 1 and each grounding electrode 11, 13, 15, 17 in the high voltage power receiving chamber. FIG. 6 is a circuit diagram when measuring a combined resistance between two grounding electrodes 11 and 13. It is explanatory drawing for demonstrating the conventional ground resistance measuring method.

  Hereinafter, an embodiment of a ground resistance measuring method will be described with reference to the accompanying drawings. In addition, as an example, a high voltage (for example, 6.6 kV or 3.3 kV) AC voltage is received from an electric power company, and transformed into a low voltage (100 V or 200 V) AC voltage used in the load facility. An explanation will be given by taking as an example the measurement of ground resistance in a high-voltage power receiving room in which a high-voltage power receiving / transforming facility that outputs to a wire electric circuit is installed.

  First, the configuration of the high-voltage power receiving facility 1 will be described with reference to FIG.

  The high-voltage power receiving facility 1 includes, for example, a section switch (not shown), a disconnect switch (not shown), a circuit breaker (not shown), a transformer 2, a protective relay (not shown), a control device (not shown), equipment 3 and 4 and a single-phase two-wire electric circuit 5 as a low-voltage distribution facility. The transformer 2 receives the high voltage supplied from the high piezoelectric path 6 and transforms it to a low voltage (AC 100 to 200 V), and outputs the transformed low voltage to the single-phase two-wire circuit 5. Further, the housing of the transformer 2 is connected to a ground electrode 11 that passes through the bottom wall 7 of the high-voltage power receiving chamber and is grounded to the ground G via a wiring 12 and is grounded in the A class.

  The electric circuit 1a on the low-voltage side of the single-phase two-wire electric circuit 5 is connected to a ground electrode 13 that passes through the bottom wall 7 and is grounded to the ground G via a wiring 14, and is B-type grounded. The devices 3 and 4 are connected to the single-phase two-wire electric circuit 5 and operate by receiving the supply of the low voltage. Further, since the device 3 is an electric device to be grounded with a resistance value of 100Ω or less with respect to the ground, the casing is connected to the grounding electrode 15 that penetrates the bottom wall 7 and is grounded to the ground G via the wiring 16. Connected and grounded with D type. Since the device 4 is an electrical device to be grounded with a resistance value of 100Ω or less with respect to the ground, the casing is connected to the grounding electrode 17 that passes through the bottom wall 7 and is grounded to the ground G through the wiring 18. D type grounding.

  Moreover, each said wiring 12, 14, 16, 18 is connected to each corresponding grounding electrode 11, 13, 15, 17 via the terminal block 19 arrange | positioned in a high voltage | pressure receiving chamber as an example. . With this configuration, each of the wirings 12, 14, 16, 18 is connected to the low potential side (ground G side) wirings 12a, 14a, 16a, 18a and the high potential side wirings 12b, 14b, 16b, It can be divided into 18b.

  Next, in the high-voltage power receiving chamber in which the high-voltage power receiving facility 1 is installed, the grounding electrode (class A grounding electrode) 11, the grounding electrode (class B grounding electrode) 13, the grounding electrode (class D grounding electrode) 15, and the grounding electrode (D A method of measuring each grounding resistance Ra, Rb, Rc, Rd of the seed grounding electrode 17 without installing an auxiliary grounding electrode will be described.

  First, the ground resistances of any three ground electrodes selected from the ground electrode 11, the ground electrode 13, the ground electrode 15, and the ground electrode 17 are measured. In this example, as an example, the grounding resistances Ra, Rb, and Rc for the three grounding poles of the grounding pole 11, the grounding pole 13, and the grounding pole 15 are measured.

  When measuring the ground resistances Ra, Rb, and Rc, first, the low-potential-side wirings 12 a, 14 a, and 16 a constituting the wirings 12, 14, and 16 are removed from the terminal block 19. Next, three sets of grounding poles (that is, two pairs of grounding poles 11, 14 a and 16 a connected to the wirings 12 a, 14 a, and 16 a, which are composed of two grounding poles out of the three grounding poles 11, 13, and 15) A group of grounding electrodes that do not share one grounding electrode, in other words, a grouping of grounding electrodes that differ in one or more grounding electrodes, in this example, a group of grounding electrodes 11 and 13, a group of grounding electrodes 13 and 15, and a grounding For the pair of poles 11 and 15, the combined resistance of the ground resistance between the ground poles constituting each ground pole pair is measured.

  Specifically, as shown in FIG. 2, a resistance measuring instrument 21 is connected to each of the removed ends of the wirings 12a and 14a for the pair of grounding electrodes 11 and 13, and the combined resistance between the wirings 12a and 14a. R1 (= Ra + Rb) is measured. Similarly, a resistance measuring device 21 is connected to each of the removed ends of the wirings 14a and 16a for the set of the ground electrodes 13 and 15, and the combined resistance R2 (= Rb + Rc) between the wirings 14a and 16a is measured. . Further, with respect to the pair of ground electrodes 11 and 15, a resistance measuring device 21 is connected to each of the removed ends of the wirings 12a and 16a, and a combined resistance R3 (= Ra + Rc) between the wirings 12a and 16a is measured.

As a result, the following three linear equations (3), (4), (5) are used with the ground resistances Ra, Rb, Rc as variables and the measured combined resistances R1, R2, R3 as constants. The simultaneous equations are obtained.
Ra + Rb = R1 (3)
Rb + Rc = R2 (4)
Ra + Rc = R3 (5)

Therefore, by obtaining a solution for each variable Ra, Rb, Rc of the simultaneous equations, the ground resistances Ra, Rb, Rc are calculated (measured) by the following equations (6), (7), (8). .
Ra = (R1-R2 + R3) / 2 (6)
Rb = (R1 + R2-R3) / 2 (7)
Rc = (− R1 + R2 + R3) / 2 (8)

  Subsequently, the ground poles other than the three selected ground poles 11, 13, and 15 (that is, the remaining ground resistance) Rd are calculated (measured) as follows.

First, a combined resistance with a ground electrode (ground electrode 11 as an example in this example) for which the calculation of the ground resistance has been completed is measured. Specifically, the low-potential-side wiring 18a constituting the wiring 18 is removed from the terminal block 19 in the same manner as the other wirings 12, 14, and 16 described above. Next, the resistance measuring instrument 21 is connected to the removed end of one of the wirings 12a, 14a, and 16a (in this example, the end of the wiring 12a as an example) and the removed end of the wiring 18a. Then, the combined resistance R4 (= Ra + Rd) between the wirings 12a and 18a is measured. Therefore, based on the ground resistance Ra already calculated and the measured combined resistance R4, the remaining ground is expressed by the following equation (9) (by subtracting the ground resistance Ra from the combined resistance R4). The ground resistance Rd for the pole 17 is calculated (measured). Thereby, the calculation (measurement) of the ground resistances Ra, Rb, Rc, and Rd for all the ground electrodes 11, 13, 15, and 17 is completed.
Rd = R4-Ra (9)

  Thus, according to this ground resistance measurement method, any three grounding electrodes selected from the installed grounding electrodes 11, 13, 15, and 17 (in the above example, the grounding electrodes 11, 13, and 15) are selected. To calculate the ground resistance (ground resistances Ra, Rb, Rc in the above example) for these three ground poles without installing an auxiliary ground pole. )can do.

  Further, in this ground resistance measurement method, for the ground poles other than the three selected ground poles (the ground pole 17 in the above example), the ground poles for which the ground resistance has been calculated (in the above example, the ground pole 11 is used). ) (In the above example, the combined resistance R4 (= Ra + Rd)) is measured, and the ground resistance of the ground electrode for which the ground resistance has been calculated is subtracted from the measured combined resistance (in the above example, The ground resistance is calculated by subtracting the ground resistance Ra of the ground electrode 11 from the combined resistance R4). Therefore, according to this ground resistance measurement method, the ground resistance of the ground electrodes other than the three selected ground electrodes can be reliably calculated (measured) by a simple method of subtraction.

  In addition, although the earth resistance measuring method for calculating (measuring) the earth resistance of the three kinds of earth electrodes, ie, the class A ground electrode, the class B ground electrode, and the class D ground electrode has been described above, the present invention is not limited to this. The ground resistance measuring method of the present application is applied to three or more grounding poles composed of at least one kind of grounding poles of class A grounding poles, class B grounding poles, class C grounding poles and class D grounding poles. The present invention can also be applied to the case where contact resistance is calculated (measured). Moreover, although the example applied to the measurement of the ground resistance in the high-voltage power receiving chamber has been described above, the ground resistance measuring method of the present application is limited to the high-voltage power receiving chamber as long as three or more grounding electrodes are installed. Instead, it can be applied to the measurement of the grounding resistance for each grounding pole at various locations.

  The resistance measuring instrument 2 used when calculating the combined resistances R1, R2, R3, R4 between the ground electrodes 11, 13, 15, 17 is a clamp type resistance measuring instrument (clamp type for voltage injection). A sensor (current transformer) and a resistance measuring instrument including a clamp-type sensor (current transformer) for current detection can also be used.

  In addition, a single-phase two-wire circuit has been described as an example, but the present invention is also applicable to a high-voltage power receiving room in which high-voltage receiving and transforming equipment that outputs to a single-phase three-wire circuit or a three-phase circuit is installed. Can do.

11, 13, 15, 17 Grounding electrode Ra, Rb, Rc, Rd Grounding resistance

Claims (2)

A ground resistance measuring method for measuring each ground resistance of three or more grounding poles composed of at least one kind of grounding poles of class A grounding pole, class B grounding pole, class C grounding pole and class D grounding pole. Because
When measuring the ground resistance for any three ground poles selected from the ground poles,
For the three grounding electrode sets that are constituted by two of the selected three grounding poles and do not overlap each other, a combined resistance for the grounding resistance between the grounding poles constituting each grounding electrode set is obtained. Measure each
The solution for each variable of the simultaneous equations consisting of three linear equations each having the ground resistance of the three ground poles as a variable and the measured three combined resistances as constants is obtained for the three ground poles. Ground resistance measurement method to calculate as ground resistance. For the grounding poles other than the selected three grounding poles,
Measure the combined resistance with the ground electrode for which the calculation of the ground resistance is completed,
The ground resistance measuring method according to claim 1, wherein the ground resistance is calculated by subtracting the ground resistance of the ground electrode for which the calculation of the ground resistance has been completed from the measured combined resistance.

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