JP2007209173A - Equipment for protecting lightning and surge damage of overhead electric line, and its construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide equipment for protecting lightning and surge damage that allows an overhead ground wire to be installed without service interruption while preventing burning of lightning arrester, and to provide a construction method of an overhead electric line. <P>SOLUTION: In the equipment for protecting the lightning and surge damage of an overhead electric line in which an insulated conductor 2 serving as power line is laid among the tops of supports, an overhead ground wire 3 is laid with a spacing along the insulated conductor, and a lightning arrester 4 is provided at intervals of at least two or more supports, wherein the overhead ground wire is arranged below the insulated conductor, the overhead ground wire is earthed by an individual earthing conductor, or is earthed via an earth cable 5 for the lightning arrester directly earthed. There is provided a construction method of an overhead ground wire comprising laying the overhead ground wire below the insulated conductor, while supplying electric power to the insulated conductor, as well as earthing the overhead ground wire, for the overhead electric line provided with the insulated conductor 2 serving as power line and the lightning arrester on the supports. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention mainly relates to lightning damage protection equipment for overhead electric lines of 3.3 to 33 kV, and a construction method thereof.

  The overhead electric line of 3.3 to 33 kV is composed of electric wires, insulators, and supports (electric poles, arms, etc.). In addition, lightning overvoltage generated by direct lightning strike or induced lightning is applied to the overhead electric line, and thus lightning damage such as insulation of insulators is broken.

As a countermeasure against lightning damage, methods of attaching a lightning arrester to a support or attaching an overhead ground wire (grounded wire) to the top of the support are used alone or in combination (Patent Document 1). The term “lightning arrester” refers to all devices intended to suppress lightning overvoltage, and is intended to protect the entire overhead power line in accordance with JEC-203-1978 “lightning arrester” and JEC-217-1984 “zinc oxide type lightning arrester”. Lightning protection equipment for the purpose of protecting not only lightning arresters but also individual installation equipment such as wire breaks and transformers (those that use lightning protection elements compliant with the above standards and represented by zinc oxide elements (hereinafter referred to as lightning protection) Also referred to as equipment)).
JP-A-2004-266900 (conventional technology)

  When the lightning arrester is used alone, the lightning current flowing through the lightning arrester increases and the lightning arrester may burn out. Therefore, it is considered effective to reduce the current flowing through the lightning arrester by distributing the lightning current to the lightning arrester and the overhead ground wire by using the lightning arrester and the overhead ground wire in combination.

  Since overhead ground wires receive direct strikes in addition to dispersing lightning current and suppressing lightning passing voltage, it is common technical knowledge to place them above the wires, and usually on top of the support. It is attached. However, when an overhead ground wire is attached to the top of an existing support, the surroundings must be blacked out in consideration of safety, and it is necessary to negotiate with customers or for those who cannot Since it is necessary to prepare a power source, it is difficult to realize it. In addition, since the exclusive fastener was used when attaching to the top part of a support body, the cost of the fastener also became high.

  The present invention was created in consideration of the above circumstances, and the object of the present invention is to provide a lightning damage protection facility capable of attaching an overhead ground wire without a power failure while preventing the lightning arrester from being burnt out, and a method for constructing the same. Is to provide.

  Since the insulated wire used for the power line is usually covered and insulated with a synthetic resin, the present inventor has paid attention to the feature that it is harder to strike than an uncovered bare wire. Therefore, it was speculated that even if no overhead ground wire was attached, the top of the support would be a lightning shield, preventing or reducing lightning strikes on the insulated wires. Then, since the necessity of attaching the overhead ground wire to the top of the support is lost, the inventor thinks that the effect of dispersing the lightning current can be maintained even if it is installed below the insulated wire, and the effect is confirmed. As a result, evaluation results were good.

  That is, according to the first aspect of the present invention, an insulated wire as a power line is installed between the upper parts of the support, and an aerial ground wire is installed at intervals along the insulated wire, and at least a plurality of supports are provided. In a lightning damage protection facility for an overhead cableway equipped with a lightning protection device everywhere, an overhead ground wire is placed below the insulated wire and the ground wire is grounded by a single ground wire or directly grounded. It is characterized by being grounded through a wire.

  The reason that “at least a plurality of supports are provided with lightning arresters” is that lightning arresters are provided for each support in places where lightning damage is high. In addition, “the ground wire is grounded with a single ground wire or grounded via a lightning arrester ground wire that is directly grounded” is a restriction condition (interpretation of technical standards for electrical equipment Article 42 However, this is for the purpose of excluding one that connects a plurality of lightning arrester ground wires to a low-voltage ground phase wire. In the case of connecting lightning arrester ground wires at multiple locations to the low-voltage grounding phase wire, in the targeted direct lightning protection, part of the direct lightning current flows to the low-voltage grounding phase wire. This is not an appropriate method because it may cause a large lightning overvoltage. It should be noted that the “overhead ground wire” does not include a messenger wire (a metal suspension line) installed to install a communication line or the like. This is not an appropriate method because if a messenger wire is used as an “aerial ground wire” and a current of direct lightning strikes, a large lightning overvoltage may be generated in a suspended communication line.

  According to the invention of claim 2, an insulated wire, which is a power line, is installed between the upper parts of the supports, and power is supplied to the insulated wires with respect to an overhead electric wire line provided with at least a plurality of lightning arresters. On the other hand, install the ground wire at a distance along the lower part of the insulated wire, and ground the ground wire with a single ground wire, or ground it directly through the ground wire for lightning protection devices. This is a method of constructing a lightning damage protection facility for an overhead electric line characterized by

  The installation time for the support of the overhead ground wire and the ground contact time of the overhead ground wire are not limited.

  The lightning damage protection equipment of the overhead wireway of the present invention has a lightning arrester to the extent that it is not inferior to the case where it is placed above the insulated wire that is a power line, even though the location of the overhead ground wire is below the insulated wire. The burnout prevention effect was obtained. And since an aerial ground wire is constructed below the insulated wire, it is possible to attach the aerial ground wire without a power failure. Further, the overhead ground wire fastener does not have to be a dedicated fastener attached to the top of the support as in the prior art, and cost reduction can be expected. When the overhead ground wire is grounded via a grounding wire for a lightning arrester that is directly grounded, the capital investment cost can be reduced as compared with the case where the ground wire is grounded by a single ground wire.

  Since the construction method of the present invention can construct an overhead ground wire while supplying electric power, negotiation with a customer in the event of a power failure is unnecessary, and has high practical value.

  As shown in FIG. 1, the lightning damage protection equipment for the overhead power line has an insulated wire (power line) 2 installed between the upper parts of the support 1 that stands up at intervals, and is insulated between the support 1 and three-phase. One overhead ground wire 3 is installed along the lower side of the electric wire 2. The vertical distance between the insulated wire 2 and the overhead ground wire 3 is a distance at which insulation can be maintained during normal power transmission. As shown in FIG. 1 (a), in the middle part of the track, lightning arresters as lightning arresters 4 are fixed to the support 1 every four or five of the support 1, and connected to the insulated wire 2, The ground wire 5 drawn from the lightning arrester 4 is connected to the grounding electrode in the ground through connection to the overhead ground wire 3. At the end of the line, as shown in FIG. 1 (b), the lightning arrester 4 is similarly secured to the support 1 at the end. The lightning arrester 4 normally insulates the insulated wire 2 and the overhead ground wire 3 from each other, but when a lightning overvoltage is generated, the insulated wire 2 and the overhead ground wire 3 are conducted to flow the lightning current to the ground. Protect the road. Although not shown, in places where lightning damage is high, lightning protection equipment as a lightning arrester is secured to the support that does not have a lightning arrester in the vicinity of the insulator for the insulated wire (power line) of the support. Uses the lightning resistance of the power line to prevent power line breakage and insulator damage. In addition, the support 1 is mainly comprised by the utility pole 6, the arm 7, the insulator 8, and various fasteners (for lightning arresters, overhead ground wires, etc.). When installing the overhead ground wire 3, attach it directly to the utility pole with a fastener. The fastener may be a general-purpose one, for example, a structure using a band 9 and a suspended bracket 10 as shown in FIG. The band 9 is a C-shaped band plate with protruding stoppers on both ends. The band 9 is wound around the utility pole 6 and the overlapped stopper pieces are screwed together to fasten the band 9 to the utility pole 6. The upper piece of the J-shaped suspended bracket 10 is overlapped with a part of the band 9 and screwed, the overhead ground wire 3 is passed through the U-shaped portion on the lower side of the suspended bracket 10, and the overhead of the screw is suspended. The ground wire 3 is pressed against the inner surface of the U-shaped portion and fixed. Therefore, the structure is simple compared to a conventional fastener (see FIG. 9, like a triangle) attached to the top of the utility pole.

  The construction method of the above-mentioned lightning damage protection equipment for the overhead wireway is to use power for the existing support 1 (with the insulated wire 2 and the lightning arrester 4 grounded by the ground wire 5 and no overhead wire). The method of connecting the aerial ground wire 3 to the ground wire 5 of the lightning arrester 4 by fastening the aerial ground wire 3 with a fastener while the state is supplied can be exemplified.

  Evaluate lightning protection effects for the above-mentioned lightning damage protection equipment for overhead power lines. Insulated wires used for power lines in overhead power lines (hereinafter referred to as tracks) have the feature of being harder to strike than bare wires, and the top of the track support is lightning shielded without having to install overhead ground wires above the power lines. It can be expected to prevent or reduce lightning strikes on insulated wires. Therefore, first, the probability of lightning strike to the track (the top of the support and the insulated wire) when there is no overhead ground wire is estimated. The probability of a lightning strike to an imaginary ground line when there is an imaginary ground line can be similarly estimated by the following method.

Various prediction formulas have been proposed for calculating the lightning strike distance, but the IEEE Std is highly versatile.
1410-1997 “IEEE Guide for Improving the Lightning Performance of Electric Power
The following formula (1) shown in “Overhead Distribution Lines” was used.

As shown in FIG. 2, it is assumed that there is one track within 1 km ^{2 of} flat ground, and the probability of lightning strike to the top of the support or an insulated wire (hereinafter, wire) is obtained. The calculation method is as follows. For each peak value Ip of the lightning strike current, the lightning strike range of each place such as the top of the support or the electric wire is obtained from the above equation (1) as shown in FIG. The lightning strike range is set to a probability s (Ip) per unit area of 1 km ² and is multiplied by the occurrence probability of the lightning strike current peak value Ip. By integrating the probability of the lightning strike range and the probability of occurrence of the lightning strike current peak value Ip over the distribution of lightning strike current peak values, the lightning strike probability at that location can be obtained. Equation (2) for obtaining the lightning strike probability Pr is shown below. Table 1 below shows the cumulative frequency distribution constant of the lightning current peak value used in the calculation.

  In order to quantitatively confirm the effects of lightning damage protection, the lightning arrester lightning burnout rate was obtained using EMTP analysis. The lightning arrester lightning burnout rate is the “probability that a lightning arrester burns out due to a single line lightning strike”.

As shown in Table 2, the analysis conditions for calculating the lightning arrester lightning burnout rate are as follows. The analysis track is basically composed of three phases of support and horizontally arranged wires, and an overhead ground wire is added according to the presence of the overhead ground wire and the location of the overhead ground wire. The ground height of the support and power line was 11.6 m, and the span length was 40 m. Line resistance and inductance constants were calculated using the EMTP JMARI setup program. Both ends of the line were terminated with matching resistors corresponding to the surge impedance of the multiconductor line.
At present Japanese electric power companies, there is a track record of installing a set of three-phase lightning arresters every four spans (one out of five supports). A lightning arrester was attached, and a circuit for grounding (30Ω grounding resistance Ra) was set (see FIG. 3). For other supports, lightning-proof equipment was attached to the two outer phases with the middle phase omitted. There is also a method of attaching lightning-proof equipment in three phases, but this difference in this study is assumed to have no significant effect. The grounding of the lightning-resistant equipment was connected to the grounding resistance Rb (150Ω) of the support in consideration of the fact that the buried part of the support becomes a grounding electrode against lightning. The processing energy resistance that causes lightning arresters and lightning protection equipment to burn out by lightning was set to 15 kJ. The facility position of the overhead ground wire was changed to 0.8 m above the track in the conventional method and 1 to 5 m below the track in the present invention. Grounding of the overhead ground wire was connected to the grounding resistance Ra of the lightning arrester for the support with the lightning arrester, and to the grounding resistance Rb of the buried part of the support for the support with the lightning protection device.

  Lightning strike locations were as follows according to circuit conditions. When the overhead ground wire is below the track, the lightning strike is considered to be the top of the support or the center of the span of the wire. The eight lightning strike points shown in FIG. 4 can be roughly divided from the arrangement of lightning arresters (lightning arresters and lightning protection equipment) on the examination line. From the track conditions, there are five types (a) to (e) in Fig. 4. Analyzes are made on the top lightning strikes of the support (a), (c), and (e) and the external phase lightning strikes of (b) and (d). went. On the other hand, the lightning strike location when the overhead ground wire was above the track was analyzed as five overhead ground wires (a), (b), (c), (d), and (e).

  In order to investigate the lightning burnout of the lightning arrester, the lightning current was assumed to be a winter lightning with large energy. The current waveform was a triangular wave having a wavefront length of 1 μsec shown in FIG. 5, and the wave tail length and the peak value were changed as parameters. Table 1 shows the waveform parameters of the lightning strike current used for the analysis.

The calculation method of the lightning arrester lightning burnout rate is as follows. First, for each analysis condition, the minimum lightning current peak value that causes the lightning arrester to burn out for each wave tail length of the lightning strike current is obtained by EMTP analysis, and the relationship between the lightning current wave tail length and lightning current peak value that causes the lightning arrester to burn out. Is obtained (see FIG. 6). Then, in the relational curve of FIG. 6, the probabilities of the wave tail length Tt and the peak value Ip of the lightning strike current are shown in Table 1 for the range (shaded area in FIG. 6) that exceeds the threshold at which the lightning arrester burns out. Then, the lightning arrester lightning burnout rate Pf can be obtained. Equation (3) for obtaining the lightning arrester lightning burnout rate Pf is shown below.

  Here, the probability density function of the logarithmic value of the lightning current wave tail length and the probability density function of the logarithmic value of the lightning current wave peak value are calculated according to a normal distribution and are independent.

  The average value of the lightning arrester lightning burnout rate due to the top lightning strike of the support when the overhead ground wire is below the track is the occurrence probability of lightning strikes (a), (c) and (e) in FIG. %, The average value of the lightning arrester lightning burnout rate due to the lightning strike is obtained by averaging the occurrence probability of lightning strikes (b) and (d) in FIG. 4 from 50% and 50%, respectively.

  Regarding the lightning arrester lightning damage rate due to lightning strikes to the overhead ground wire when the overhead ground wire is above the track, the lightning damage of the support part of the overhead ground wire and the overhead lightning of the lightning strikes (b) and (d) in FIG. It is determined by dividing it into two types of lightning strikes at the center of the span of the ground wire. The average value of the lightning arrester of the lightning arrester at the support spot of the overhead ground wire is obtained by averaging the occurrence probability of lightning strikes (a), (c), and (e) in FIG. 4 from 25%, 50%, and 25%. . The average value of the lightning arrester lightning burnout rate of the lightning strike device at the center of the span of the overhead ground wire is obtained by averaging the occurrence probability of lightning strikes (b) and (d) in FIG.

The lightning arrester lightning burnout rate is finally obtained by multiplying the lightning strike probability of each condition and the lightning arrester lightning burnout rate. An example of the lightning arrester lightning burnout rate F when the overhead ground wire is below the track is shown in equation (4).

FIG. 7 shows the results of analysis and examination based on the above conditions. It can be seen that if the overhead ground wire is attached below the track, the lightning arrester lightning burnout rate when there is no overhead ground wire can be reduced to about 63%. And it turns out that the same effect can be expected with a difference of about 5% from the case where the conventional overhead ground wire is attached above the track.
In addition, although the lightning damage protection equipment used for the above-mentioned lightning protection evaluation uses the ground wire of the lightning arrester for grounding the overhead ground wire, even if grounding the overhead ground wire with a single ground wire, the equivalent The effect can be expected.

(A) and (b) are explanatory diagrams showing the lightning damage protection equipment. It is explanatory drawing which shows the lightning strike range to an overhead electric wire path when an overhead ground wire does not exist above an overhead electric wire path. This is an analysis circuit when an overhead ground wire is installed below the overhead electric wire path. It is an assumption figure of the lightning strike location when an overhead ground wire is constructed under the overhead electric wire way. It is a graph which shows the lightning strike current waveform used for analysis. It is a graph which shows the relationship between the lightning current wave tail length and current peak value which a lightning arrester leads to burning in the case of no overhead ground wire and lightning of a support top. It is a graph which shows the relationship between a lightning arrester lightning burnout rate and an overhead ground wire installation height. It is explanatory drawing which shows how to stop an aerial ground wire with respect to a support. (A) and (B) are a front view and a side view showing a conventional fastener.

Explanation of symbols

1 Support, 2 Insulated wire (Power line), 3 Overhead ground wire, 4 Lightning arrester (Lightning arrester), 5 Ground wire, 6 Telephone pole, 7 Arm, 8 Insulator, 9 band, 10 Suspended bracket

Claims (2)

An insulated wire (2), which is a power line, is installed between the upper parts of the support (1), and an aerial ground wire (3) is installed at intervals along the insulated wire (2). At least a plurality of supports In the lightning damage protection equipment of the overhead power line with a lightning arrester (4) every
The ground wire (3) is disposed below the insulated wire (2), and the ground wire (3) is grounded by a single ground wire or directly grounded for a lightning arrester (4) (5) Equipment for lightning damage protection of overhead electric lines characterized by grounding via In addition to installing an insulated wire (2), which is a power line, between the upper parts of the support (1), and for an aerial cable path including at least a plurality of lightning arresters (4) every other support,
While supplying power to the insulated wire, install the overhead ground wire (3) at a distance along the lower side of the insulated wire (2) and ground the overhead ground wire (3) with a single ground wire or A method of constructing a lightning damage protection facility for an overhead power line characterized by grounding via a grounding wire (5) for a lightning arrester (4) grounded on the ground.

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