JP7353210B2 - Earth resistance measuring device - Google Patents

Description

The present invention relates to a technique for measuring the ground resistance of a ground electrode connected to an overhead ground wire via a down conductor (down ground wire).

Currently, only the measured value of the grounding resistance of the grounding electrode connected to the down conductor at the time of construction is saved and is not managed thereafter. If the grounding resistance has increased since the time of construction and the potential rise when lightning current flows into the grounding electrode is greater than the expected value, it will have a major impact on surrounding equipment, so it is necessary to always check the accurate grounding resistance. It is extremely important to understand and continuously manage it.

Here, FIG. 4 is a schematic diagram equivalently showing the grounding state of the overhead ground wire, where 10 is the overhead ground wire, 11 to 13 are down conductors, 14 _A , 14 _B , and 14 _C are ground electrodes, and G is the ground, and R _A , R _B , and R _C are the ground resistances of the respective ground electrodes 14 _A , 14 _B , and 14 _C.
In the above configuration, when measuring the grounding resistance _RB of the grounding electrode _14B by the well-known voltage drop method (potential drop method), if the measurement current is directly injected into the point b of the pull-down conductor 12, this measurement current Since it also flows to the grounding electrodes _14A and _14C via _14B , the obtained resistance value becomes the combined resistance of the grounding resistances _RA , _RB , and _RC . Therefore, when measuring the ground resistance _RB , it is necessary to separate the point b and configure the circuit so that the measurement current flows only through the ground electrode _14B .

FIG. 5 shows a conventional method for measuring ground resistance in consideration of the above points. In FIG. 5, point b' is a point separated from point b of the pull-down conductor 12, 40 is a measuring device, E is a measurement terminal, C is a current pole terminal, and P is a voltage pole terminal. The same reference numerals as 4 are given.
According to this prior art, the ground resistance R _B is determined from the voltage between the terminals E and P when a measurement current is passed from the measurement terminal E of the measuring device 40 to point b', the ground electrode 14 _B , and the current pole terminal C. can be found.
However, in this method, it is necessary to separate the pull-down conductor 12 at point b', which is difficult to implement in reality, considering the time and effort involved.

Therefore, a conventional technique that makes it possible to measure ground resistance without disconnecting the pull-down conductor or the ground wire is described in, for example, Patent Document 1 (Japanese Patent No. 4028167).
FIG. 6 is a configuration diagram of a ground resistance measuring device according to Patent Document 1. In FIG. 6, the equipment circuit 43 is connected to the overhead ground wire 10 via the lead wire 15, and to the ground electrode 17 in the earth G via the ground wire 41 and the inductance element 42. Here, the inductance element 42 is made of, for example, a ferromagnetic material, and is fixedly connected to the ground wire 41. A measuring device 40 is connected to the grounding wire 41 between the inductance element 42 and the grounding electrode 17 via a lead wire 44, and a return conducting wire 45 capacitively coupled to the ground G is connected to the other end. It is connected.
Note that 16 is a ground electrode connected to the pull-down conductor 11.

In this prior art, an AC signal is applied between a lead wire 44 and a return conductor 45 by a measuring device 40, and the ground resistance of the ground electrode 17 is measured based on the measured voltage ratio before and after that, and the inductance element 42 has a high impedance near the measurement frequency of the AC signal, and a low impedance at a commercial frequency, so it functions to equivalently separate the grounding electrode 17 from the equipment circuit 43 only when measuring ground resistance.

Furthermore, as another conventional technique, a measuring device for measuring the grounding resistance of a grounding network installed at an electric station or the like is described in Patent Document 2 (Japanese Patent No. 6469740).
FIG. 7 is a configuration diagram of this earth resistance measuring device, where 61 to 63 are steel towers, 50 is a pulse generator that outputs a pulse current of high frequency (several hundred to several thousand times the commercial frequency), and 51 is the ground. 52 is a current auxiliary pole, and Z ₀ to Z ₄ are the impedances of the overhead ground wire 10 functioning as a distributed constant circuit.
In this prior art, the pulse current does not flow to the high-impedance overhead ground wire 10 side, but most of it flows to the ground network 51, so that the ground resistance of the ground network 51 can be measured at a value close to the true value.

Patent No. 4028167 ([0018] to [0021], Fig. 1, Fig. 2, etc.) Patent No. 6469740 ([0037], [0038], Figure 6B, etc.)

The prior art according to Patent Document 1 mentioned above is based on the principle of measuring ground resistance by applying an AC signal to a circuit including the return conductor 45 and the ground electrode 17, so the return conductor 45 capacitively couples with the ground G. Moreover, it is difficult to apply the method as is when measuring the ground resistance of concrete, asphalt, etc., instead of burying the ground electrode 17 in the ground G.
Further, the conventional technology according to Patent Document 2 is limited to the use of measuring the grounding resistance of a grounding network 51 installed in an electric station, etc., and requires an extremely high frequency pulse generator 50, which increases the cost of the entire device. There is a problem that the amount is high.

SUMMARY OF THE INVENTION An object of the present invention is to provide a ground resistance measuring device that can measure ground resistance at any measurement location, has a simple circuit configuration, and is inexpensive.

In order to solve the above problem, the invention according to claim 1 provides a grounding resistance measuring device for measuring the grounding resistance of a grounding electrode connected from an overhead grounding wire via a down conductor.
A unipolar transient current is injected into a path including an injection point on the pull-down conductor, the ground electrode, and an external current pole, and a voltage between the injection point and an external voltage pole is measured to determine the voltage. and a measuring device that calculates the grounding resistance by a voltage drop method using the transient current;
a removable lightning inductance core attached to a portion of the down conductor between the injection point and the overhead ground wire;
It is characterized by having the following.

The invention according to claim 2 is the ground resistance measuring device according to claim 1,
The lightning-proof inductance core is characterized in that it has a high impedance with respect to the transient current and does not undergo magnetic saturation with the transient current.

The invention according to claim 3 is the ground resistance measuring device according to claim 1 or 2,
One or both of the current electrode and the voltage electrode is connected by a grounding tool that is made of a gel-like super absorbent polymer that has conductivity and fluidity, and has a built-in grounding resistance reducing material that can seep into concrete or asphalt ground. It is characterized by comprising the following.

The present invention measures ground resistance by a voltage drop method by injecting a single polarity transient current into the down conductor with a lightning inductance core attached to the down conductor.
This makes it possible to simplify the circuit configuration and reduce costs compared to the method of injecting AC signals into the pull-down conductor, and is also suitable for use in concrete, asphalt, and other ground where it is difficult to bury ground electrodes. It is possible to measure ground resistance.

1 is a schematic circuit diagram showing a usage state of a ground resistance measuring device according to an embodiment of the present invention. It is a typical waveform diagram of the measurement current and measurement voltage of the earthing resistance in embodiment. It is a block diagram of the grounding tool in other embodiment of this invention. FIG. 2 is a schematic diagram equivalently showing a grounding state of an overhead ground wire. FIG. 2 is a schematic diagram showing a conventional grounding resistance measuring method. 1 is a configuration diagram of a ground resistance measuring device described in Patent Document 1. FIG. FIG. 2 is a configuration diagram of a ground resistance measuring device described in Patent Document 2.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic circuit diagram showing the usage state of the ground resistance measuring device according to this embodiment, and the same parts as in FIGS. 4 and 5 are given the same reference numerals and explanations are omitted. Let's focus on the different parts.

In FIG. 1, the configurations of the overhead ground wire 10, down conductors 11, 12, 13, ground electrodes _14A , _14B , _14C , etc. are the same as in _FIG . The case of measuring the ground resistance _RB will be explained.
First, reference numeral 20 denotes a measuring device, which includes a current injection terminal A, a voltage measurement terminal V, a current pole terminal C, a voltage pole terminal P, and a display section 21 that displays the ground resistance as a measurement result.

A current transformer 23 for measuring the magnitude of a single polarity transient current to be injected into the down conductor 12, which will be described later, is attached to the lead wire 24a connected to the current injection terminal A, and the lead wire 24a is connected by a clip 24. It can be connected to the down conductor 12. Further, a lead wire 25a connected to the voltage measurement terminal V can be connected to the pull-down conductor 12 by a clip 25.
Furthermore, the current pole terminal C is connected to the current pole _14E , and the voltage pole terminal P is connected to the voltage pole _14D .

A lightning inductance core 30 is detachably attached to the down conductor 12 between the connection point between the down conductor 12 and the overhead ground wire 10 and the clip 24 . As described in Japanese Patent Laid-Open No. 2006-324455, this lightning inductance core 30 is made of, for example, a nanocrystalline soft magnetic material, and is pulled down by opening semicircular split core parts 30a and 30b. It is configured so that it can be attached to the conductor 12.

In the above configuration, from the current injection terminal A of the measuring device 20, the measurement current of the grounding resistor _RB is a single polarity transient current that reaches its peak in 0.2 [μs] as shown in FIG. 2(a), for example. i is injected into the pull-down conductor 12. This injected current i is large enough to prevent the lightning inductance core 30 from being magnetically saturated. If the lightning-proof inductance core 30 is made of a single nanocrystalline soft magnetic material, the residual magnetic flux density can be reduced and it can be used repeatedly without being magnetized even by a single-polarity transient current.

With respect to the above injection current i, since the lightning inductance core 30 operates as a high impedance element, most of the injection current i flows to the ground electrode _14B side and does not flow to the overhead ground wire 10 side. The measuring device 20 measures the voltage v (see FIG. 2(b)) between the voltage measurement terminal V and the voltage terminal P at this time and divides it by the injection current i, thereby calculating the ground resistance R _B. It can be calculated. Specifically, for example, by dividing the difference between the maximum value of the voltage v up to 1 [μs] and the maximum value after 10 [μs] by the injection current i, the transient ground resistance R _B It is possible to determine the grounding characteristics for lightning countermeasures.

Note that if the ground you want to measure ground resistance is not soil but concrete, asphalt, etc., instead of excavating it and burying a grounding electrode etc. in the soil, use the grounding tool 100 as shown in Fig. 3. can be used to respond.
The grounding device 100 shown in FIG. 3 is disclosed in Patent No. 5839430 by the present applicant, and has an electrode network 102 disposed inside a casing 101 that is open at the bottom, and a conductive It is filled with a ground resistance reducing material 103 such as a gel-like super absorbent polymer having elasticity and fluidity, and is used by being placed on the surface of the target concrete ground 200 or the like.

According to this grounding tool 100, the grounding resistance reducing material 103 inside the casing 101 flows down to the concrete ground 200 side via the electrode network 102, thereby forming the reducing material permeation region 201, and from the grounding wire 105 to the lead wire. 104, an electrode network 102, and a grounding path via the reducing material permeation region 201.
Therefore, if the above-mentioned grounding tool 100 is applied as the current pole _14E and voltage pole _14D in FIG. 1 as needed, it is possible to measure the ground resistance even in the ground such as concrete or asphalt where it is difficult to bury the ground electrode etc. becomes possible.

10: Overhead ground wire 11, 12, 13: Down conductor 14 _A , 14 _B , 14 _C : Earth electrode 14 _E : Current electrode 14 _D : Voltage electrode 20: Measuring device A: Current injection terminal V: Voltage measurement terminal C: Current pole terminal P: Voltage pole terminal 21: Display section 23: Current transformers 24, 25: Clips 24a, 25a: Lead wire 30: Lightning inductance cores 30a, 30b: Split core section 100: Grounding tool 101: Housing 102 : Electrode network 103 : Grounding resistance reducing material 104 : Lead wire 105 : Grounding wire 200 : Concrete ground 201 : Reducing material seepage area G : Earth _RA , _RB , _RC : Grounding resistance

Claims (3)

In a grounding resistance measuring device that measures the grounding resistance of a grounding electrode connected from an overhead grounding wire via a down conductor,
A unipolar transient current is injected into a path including an injection point on the pull-down conductor, the ground electrode, and an external current pole, and a voltage between the injection point and an external voltage pole is measured to determine the voltage. and a measuring device that calculates the grounding resistance by a voltage drop method using the transient current;
a removable lightning inductance core attached to a portion of the down conductor between the injection point and the overhead ground wire;
A grounding resistance measuring device characterized by comprising: In the ground resistance measuring device according to claim 1,
A grounding resistance measuring device characterized in that the lightning inductance core has a property of having a high impedance with respect to the transient current and not being magnetically saturated with the transient current. The earth resistance measuring device according to claim 1 or 2,
One or both of the current electrode and the voltage electrode is connected by a grounding tool that is made of a gel-like super absorbent polymer that has conductivity and fluidity, and has a built-in grounding resistance reducing material that can seep into concrete or asphalt ground. A grounding resistance measuring device characterized by comprising:

Images