報告書番号

T60

タイトル（和文）

交流架空送電線から発生するコロナハム音の諸特性，予測法，ならびに低減対策に関する研究

タイトル（英文）

A Study on Characteristics, Prediction Methods, and Reduction Countermeasures of Second Harmonics of Audible Noise from AC transmission Lines

概要 （図表や脚注は「報告書全文」に掲載しております）

コロナハム音はUHV交流送電線の電線設計における支配要因である。このため，電線からの発生量ならびに音場分布を解明し，予測法を開発するとともに低減対策を確立した。（１）発生量は導体方式，電圧，ならびに降雨強度等の気象条件に大きく影響される。電線表面のエージングの進行によって発生量は大幅に低減する。風騒音対策用のスパイラル線の取り付けは発生量を大幅に増大させる。（２）定在波上のコロナハム音レベルの統計的分布は，提案したランダムウォークモデルで近似できる。谷間地形は音を多重反射し，騒音レベルを上昇させる。（３）送電線下におけるコロナハム音レベルの時空間平均値を計算する予測法を新たに開発した。本予測法は比較的簡単な実験式からなり，送電線の電線設計において容易に使用でき，実用的である。（４）電線の素導体配列の非対称化と添線の付加によりコロナハム音を低減できることを実証した。

概要 （英文）

The audible noise produced by corona discharge from transmission line conductors is composed of two major components, namely "hum noise" and "random noise". Hum noise is a pure tone that has a frequency of twice the power line frequency and is generated primarily in rain, fog, and highly humid environments. It is one of the major factors affecting conductor design of overhead transmission lines for voltages above 500 kV. We have studied the characteristics of hum noise, methods for predicting hum noise level, and methods for reducing. Our main results are as follows:(1) The generated pressure level (GPL), which is the sound pressure level at a point one meter away from a conductor bundle of infinite length, of hum noise from conductor bundles is significantly affected by the number of subconductors, subconductor diameter, subconductor spacing, voltage, and climate conditions (for example, rainfall rate). GPL decreases drastically as the subconductor surface aging. The spiral wires that are used to reduce aeolian noise increase GPL significantly.(2) Hum noise from conductor bundles generates a complex standing wave near and perpendicular to transmission lines and the level of hum noise varies greatly. The statistical distribution of hum noise levels near transmission lines can be approximated by the distribution derived from a random-walk model that is proposed in this report. Bulk transmission lines tend to pass through hilly areas and cross ravines frequently. The slopes of ravines cause multiple reflection of sound waves and increase the hum noise levels in ravines.(3) We developed a prediction method for temporal and spatial average levels of hum noise near transmission lines because hum noise level varies with both measurement position and time. The prediction method is practical because it employs simple experimental equations and is easy to use it at the conductor design stage. (4) In full-scale tests at our Akagi test line, we found that it is possible to reduce hum noise using asymmetrical bundles and the added system that has an additional subconductor strung at the bottom of the existing conductor bundles. Both the added system and asymmetrical bundles are simple and effective means of reducing hum noise levels after the construction of transmission lines.

報告者

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