JPH073448B2 - Ground fault detector for distribution system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a ground fault detection device for a power distribution system.

B. SUMMARY OF THE INVENTION The present invention differentially detects a current flowing in a ground system that grounds the support in a power distribution system in which the support is insulated and supported by the support and the support is grounded. As a result, a ground fault detection device capable of detecting only the ground fault current and detecting the ground fault only at the relevant ground fault location is obtained.

C. Prior art Fig. 4 shows the support structure of distribution line, 1 is a utility pole,
There is wood, but recently it is mostly made of concrete. Two
Is a braid, 3 is an arm tie, 4, 5 and 6 are insulators, and 7 is a metal band. Reference numeral 8 is an overhead ground wire support which is a metal conductor, and there are various types, but here, an example of a cap type is shown. An overhead ground wire 9 is supported by the overhead ground wire support 8. 10, 11 and 12 are three-phase high-voltage distribution lines, which are supported by the arm 2 through insulators 4, 5 and 6, respectively. 13,14,15 are insulators, 16,17,18 are low-voltage light wires, single-phase three-wire type,
Of these, 16 are grounded and are shared ground lines. 19
Are transformer arms, 20 is an insulator, 21 is a single-phase transformer, the primary winding 22 is connected to two of the high-voltage distribution lines 10 to 12, and the secondary winding 23 has a center tap with a low piezoelectric lamp wire. Others are connected to low-voltage lamp lines 17 and 18. 24 is the case of the single-phase transformer 21. 25a to 25e are grounding wires
It is connected to 26 and is collectively referred to as ground wire 25. The ground impedance of the earth 26 is usually about several tens of ohms.

FIG. 5 is a path diagram of a ground fault current showing an example of a case where a ground fault occurs in the insulator 4, and the capacitance to ground of the high voltage distribution lines 10 to 12 (not shown).
The current flowing through is ignored.

In FIG. 5, 28 is a grounding wire of a utility pole different from the utility pole 1 of FIG. 1 and is connected to the overhead ground wire 9 and the common ground wire 16. Reference numeral 29 indicates a power source of the high voltage distribution line, one end of which is connected to the earth 27 via the neutral point impedance 30. Further, GF in FIG. 5 indicates that a ground fault has occurred. i
₆₁ is a current flowing out of the power supply 29, which is actually a high voltage distribution line 10
Flows to a load (not shown), but since there is no meaning, it will be described as no load.

That is, i ₆₁ may be understood as a current generated by a ground fault. By the way, i _{61 under} normal condition is zero. i ₆₂ is the ground current flowing by the ground fault GF and is equal to i ₆₁ . i _{63 to} i ₇₅ are i
₆₂ shunt current. Although Fig. 5 shows the case where there are two utility poles, the number is actually larger, and the ground fault GF causes ground lines 9, high-voltage distribution lines 10, ground lines 25, 28, and all ground lines (not shown) to be grounded. It can be seen that the junction current is shunted and cannot be easily detected by simply installing a current transformer on the ground line and detecting the ground fault of the insulator.

FIG. 6 shows the flow of the load current of the low-voltage lamp line, and shows the case where there are two electric poles, for ease of explanation.

In FIG. 6, reference numeral 31 is a load between the low-voltage lamp lines 16 and 17. i _{1 to} i ₁₄ show the state of the current flowing through the load 31. From the figure, the following is clear.

i ₁ ＝ i ₂ ＝ i ₃ ＝ i ₄ ＝ i ₅ ＝ i ₁₄ …… (1) i ₆ ＝ i ₈ ＝ i ₁₁ …… (2) i ₇ ＝ i ₁₀ ＝ i ₁₂ …… (3) i ₅ ＝ i ₆ ＋ i ₇ ＋ i ₉ …… (4) i ₁₃ ＝ i ₁₁ ＋ i ₁₂ …… (5) i ₁₄ ＝ i ₉ ＋ i ₁₃ …… (6) As shown in Fig. 6, a ground fault occurs. Even if it is not, there is a possibility that the load current of the low-voltage lamp wire is flowing in each ground wire, and even if a current transformer is installed in each ground wire, as explained in Fig. 5, the ground of the insulator It turns out that the detection of the fault is not easy.

Although not actually used, FIG. 7 shows an example in which a current transformer CT is installed in the insulator 4, for example. In this way, a normal current does not flow between the arms 2 of the high-voltage distribution line 9, but if a ground fault occurs, the current transformer CT detects the ground fault current and the detector (not shown) It is possible to detect a fault. However, the insulator 4 is of the order of about 10 cm in height, and if it covers the current transformer CT, there is a danger of causing a ground fault via the current transformer CT, so it is not realistic and is actually used. This is one of the reasons why it is not done.

D. Problems to be Solved by the Invention In the ground fault detection of the insulator of the high voltage distribution line, the ground fault line is first identified by the operation of the ground fault direction relay of the substation. After that, the reclosing relay operates, and the section switches are sequentially thrown in, so that the ground fault range for each section switch is found. However, the number of utility poles in one section of the division switch is small from a little less than 10 places to more than 300 to 400 places, and it takes a very long time to visually detect a ground fault point, and power supply It was a problem from the point of.

Also, even if an insulator ground fault occurs, if the circuit is closed again, the ground fault may have been recovered. In this case, the ground-faulted insulator is in a very unstable state because it cannot know when and when it will be ground-faulted, and it is extremely difficult to determine the ground-faulted current only by identifying the ground-fault line. The reality is that we have no choice but to give up.

The present invention has been made in view of the above problems, and an object thereof is to provide a ground fault detection device for a distribution system capable of immediately determining only a relevant ground fault location and stabilizing power supply. Is.

E. Means and Actions for Solving the Problems In order to achieve the above-mentioned object, the present invention supports an overhead ground wire and a high-voltage distribution line supported through arm wires and arm ties with a utility pole, and further, In a power distribution system in which a low-voltage lamp wire having a wire whose one wire is grounded via a grounding wire shared with an overhead ground wire is arranged on this electric pole, a grounding wire between the overhead ground wire and an arm tie, and a high-voltage distribution wire are provided. A current transformer is provided on each ground line between the low-voltage light lines, and each current transformer is configured to differentially detect a current flowing through the ground line.

In addition, an overhead ground wire and a high-voltage distribution line supported via a armband and an arm tie are supported by a utility pole, and one wire is grounded to this utility pole through a ground wire shared with the overhead ground wire. In a power distribution system in which a low-voltage light wire having the above is arranged, a current transformer is provided on the electric pole, and the current wire penetrates the ground wire between the overhead ground wire and the arm tie and the ground wire between the arm tie and the low-voltage light wire. The current transformer is configured to differentially detect the current flowing through the ground line.

F. Example Hereinafter, an example of the present invention will be described with reference to FIGS.

FIG. 1 shows a ground fault detector for a power distribution system according to an embodiment of the present invention, in which 32a and 32b are current transformers which are differentially arranged in a ground line 25 system wired on a utility pole 1. Specifically, it is arranged as shown in FIG. 2 (A) and is connected to the current detector 34a. Reference numerals 33a and 33b are current transformers that are differentially arranged on a ground line 28 wired to other electric poles, and 34b is a current detector.

i ₁₀₀ and i ₁₀₁ are currents flowing through the ground line 25, which are primary currents of the current transformers 32a and 32b. i ₁₀₂ and i ₁₀₃ are secondary currents of the current transformers 32a and 32b, respectively. i ₁₀₄ and i ₁₀₅ are primary currents of the current transformers 32a and 33b, and i ₁₀₆ and i ₁₀₇ are secondary currents of the current transformers 33a and 33b.
The current detectors 34a and 34b output when the current flowing into the detectors 34a and 34b exceeds a preset value S which is a preset value.

Now, assuming that a ground fault current as shown in FIG. 5 and a load current as shown in FIG. 6 flow, i ₁₀₀ = i ₆₃ −i ₁₁ …… (7) i ₁₀₁ = i ₆₄ + i ₁₁ …… ( 8) Where the current ratio of each current transformer 32a, 32b, 33a, 33b is K
_{Letting CT} be i ₁₀₂ = K _CT (i ₆₃ −i ₁₁ ) …… (9) i ₁₀₃ = K _CT (i ₆₄ + i ₁₁ ) …… (10). The sum of the currents flowing into the current detector 34a is i ₁₀₂ + i ₁₀₃ = K _CT (i ₆₃ + i ₆₄ ) (11). If this value exceeds the set value S, the ground wire 25 of the utility pole that has a ground fault has occurred. A ground fault can be detected. I ₁₀₄ = -i ₇₀ + i ₆ (12) i ₁₀₅ = i ₇₀ -i ₆ (13) i ₁₀₆ = K _CT (-i ₇₀ + i ₆ ) (14) i ₁₀₇ = K _CT (I ₇₀ −i ₆ )… (15) In this case, the sum of the currents flowing into the current detector 34b is i ₁₀₆ + i ₁₀₇ = 0 (16), which means that the occurrence of a ground fault has been detected on the ground wire 28 of the utility pole in which no ground fault has occurred. .

As described above, according to the present device, as is apparent from the equation (11), the ground-fault current detector 34a can detect the ground fault without affecting the low piezoelectric lamp wire and the load current, and As is clear from the equation (16), it is understood that the utility pole current detector 34b in which the ground fault does not occur is not affected by the load currents of the other ground utility poles and the low-voltage lamp lines.

FIG. 3 shows a ground fault detecting device for a power distribution system according to another embodiment of the present invention, which is a first-order differential detecting device. Specifically, as shown in FIG. 2 (B). It is installed in. That is, the ground wire 25 is bent, and the induced magnetic flux due to the current flowing through the ground wire 25 is made differential to make one current transformer.
One current detector by differentially detecting two currents at 32
In addition to detecting the ground fault with, the other ground line 28 is also bent, and the induced magnetic flux due to the current flowing through this ground line 28 is made differential, and the two currents are differentiated by one current transformer 33. To detect the secondary current of this current transformer by one current detector 36
It is designed to be detected by.

According to the method of FIG. 3, i ₁₀₈ and i ₁₀₉ are secondary currents of the current transformer, i ₁₀₈ = K _CT (i ₁₀₀ + i ₁₀₁ ) = K _CT (i ₆₃ −i ₁₁ + i ₆₄ + i ₁₁ ). ＝ K _CT (i ₆₃ ＋ i ₆₄ ) …… (17) i ₁₀₉ ＝ K _CT (i ₁₁₀ ＋ i ₁₁₁ ) ＝ K _CT (−i ₇₀ ＋ i ₆ ＋ i ₇₀ −i ₆ ) = 0 …… (18) The same effect as that of FIG. 1 is obtained. Note that the pole and the ground may be electrically connected to the utility pole by means other than the ground wire (leakage resistance due to leakage current during electricity). In such a case, the apparatus of FIG. 1 is not affected, but in the apparatus of FIG. 3, the current flowing into the current detectors 35 and 36 as an error is different from that in the case of FIG. Even in this case, the same effect as that of FIG. 1 can be obtained by appropriately selecting the set value S.

G. Effect of the Invention The present invention is as described above, and since it is possible to individually detect only the ground fault accident of the ground system of the support body that insulates and supports the distribution line and the overhead ground wire, the power failure section It is possible to obtain a highly reliable ground fault detection device for a power distribution system that can minimize the range and shorten the power outage time.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a ground fault detection device of a power distribution system according to an embodiment of the present invention, FIG. 2 (A) is a schematic view showing an example of mounting a current transformer in the device of FIG. 1, and FIG. B) is a schematic view showing an example of mounting a current transformer in the device of FIG. 3, FIG. 3 is a circuit diagram showing a ground fault detection device of a power distribution system according to another embodiment of the present invention, and FIG. 4 is a support. 5 is an explanatory view showing a connection example of a utility pole, FIG. 5 is a ground fault current route diagram, FIG. 6 is a load current route diagram, and FIG. 7 is a schematic diagram showing a grounding example of a current transformer. 1 ... Support pole, 2 ... Armor, 3 ... Arm tie, 4-6 ... Insulator, 8 ... Aerial ground wire support, 9 ... Aerial ground fault, 10-12 ... High voltage distribution Electric wire, 13 to 15 ... Insulator, 16 to
18 ...... Low-voltage light wire, 25,28 ...... Ground wire, 32a, 32b, 33a, 33b
...... Current transformers, 34a, 34b, 35, 36 …… Current detectors.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroshi Haga 1-1-1 Kokubuncho, Hitachi City, Ibaraki Prefecture 1-1-1 Kokubun Plant, Hitachi, Ltd. (72) Tadashi Miyano 2-1-17-1 Osaki, Shinagawa-ku, Tokyo Stock company Shameidensha (72) Inventor Toshihiro Nakamura 2-17 Osaki, Shinagawa-ku, Tokyo Stockholder Shashadensha

Claims (2)

[Claims] 1. An aerial ground wire and a high-voltage distribution line supported via armbands and arm ties are supported by a utility pole, and one wire is grounded to the utility pole via a ground wire shared with the aerial ground wire. In a power distribution system in which a low-voltage light wire having an electric wire is arranged, a ground wire between the overhead ground wire and the arm tie and a ground wire between the high-voltage power wire and the low-voltage light wire are differentially provided to each other. The current that detects the current flowing through the ground wire by the current transformer and each current transformer differentially, and detects the ground fault of the distribution system on condition that the difference between the detected currents exceeds a predetermined set value. A ground fault detection device for a power distribution system, which is configured by a detector. 2. An aerial ground wire and a high-voltage distribution line supported through a arm and a tie are supported by a utility pole, and one wire is grounded to the utility pole through a ground wire shared with the aerial ground wire. In a power distribution system in which a low-voltage light wire having an electric wire is arranged, a current transformer provided on the utility pole and penetrating a ground wire between the overhead ground wire and the arm tie and a ground wire between the arm tie and the low-voltage light wire. And a current detection that differentially detects the current flowing in the ground wire detected by the current transformer, and detects the ground fault of the distribution system on condition that the difference becomes a predetermined set value or more. A ground fault detection device for a power distribution system, which is configured by a power supply device.