Project Subjects
Evaluation of Damage to Electric Transmission Facilities
Caused by Wind, Snow and Salt
Background and Objective
Severe snowstorms (called H18 GOUSETSU in Japanese) occurred on the coast of the Japan Sea in December 2005. These storms caused the failure of electrical insulators, or ﬂash-over caused by sea salt contained in thesnow, short circuit accidents in transmission lines caused by galloping*1, and the partial collapse of transmission
towers caused by weight of heavily accreted snow. These have given us valuable knowledge and veriﬁcation of theimportance of effective countermeasures against the snow-related damage for a stable electricity supply.
In this project, in order to reduce these snow-related accidents, prediction methods of snow damage andtechnology of the countermeasures might be improved by observing both atmospheric conditions and physicalprocesses to elucidate snow accretion mechanism.

Main results
1. Installation of ﬁeld observation systems and consolidated data management
Cooperating with the electric power companies, the observation systems have been installed at ﬁve areasin Japan by Nov. 2009 (Fig. 1). The systems have made it possible both to remotely monitor the real-time sitesituations and to manage the acquired data in uniform and centralized manners in our institute (CRIEPI). Since2008ʼs winter season, the measurement equipments (such as line tension load meter or conductivity sensor foraccreted snow) have been continuously operating speciﬁc to the observation purpose at each site. Besides, wehave been acquiring not only meteorological data such as local wind velocity and temperature, but also visual dataobtained by network cameras. The large amplitude conductor vibration, identiﬁed as galloping, have been successfully observed once during the last two winter seasons, with obtaining synchronized data of weather conditions and line tension at the site. In this way, we have been accumulating valuable data that were hardly available
in the previous studies. In the near future, based on the analysis of these observation data, the effectiveness ofcountermeasures and the phenomenal elucidation of snow-related damage in Japan might be veriﬁed furthermore.
2. Development of an experimental technique for elucidation of galloping phenomenon
An experimental technique to physically simulate the motion of actual transmission conductors has been
newly developed [N09022]. In the technique, a sector model of four-conductor bundle is supported at both ends
with multiple elastic cords. Such unique support allows to optionally and easily adjust vertical, horizontal andtorsional vibration properties, and to simulate conductorsʼ vibration with large amplitude at lower frequency (Fig.
2). In the near future, by applying this technique to wind tunnel tests, the effectiveness of vibration-suppression
measures might be veriﬁed and also the vibration occurrence condition for transmission lines subject to windmight be elucidated.
3. Development of estimation method for wide area distribution of airborne sea salt
Estimation of wide area distribution of airborne sea salt is needed to cope with degradation of electric
power facilities by sea salt pollution. A new numerical simulation method has been developed for estimation of
cumulative airborne sea salt in a wide area over a radius of tens of kilometers (Fig. 3) [N09007]. This method
allows us to make distribution maps of airborne sea salt regardless of the extent of maps reﬂecting the geographic
effects of local terrain and land use such as ﬂatlands, mountains and rivers. In the near future, we will proceedwith accuracy estimations of this method by comparison with observation data and apply to estimations of salt
damage of electric power facilities.
Other reports[N09006]*1: One of the conductor vibration phenomena: Due to wind and accreted snow or ice, when torsion and lift force are generated, the phenomenon occurs as large-amplitude self-excited vibration of transmission lines. If the amplitude becomeslarge or the vibration continues, the phenomenon leads to short circuit or facility failure through fatigue.

30Stable Power Supply Technology
Anemometer
Network camera

Observation system(Tower top)

Monitoring image (Snowaccretion on sample
Data are monitored and managed
ins area.
lators)solely at Abiko

LegendOverhead transmission facilities owned
by electric power companies
Full-scale testing transmission lines
owned by electric power companies
Sea salt particles and snowfall observationarea

Sea salt particles and snowfall
・observation
systemFig. 1 Location and summary of the ﬁeld observation systems
Data monitoring and recording are possible with the remote manipulation at Abiko area of CRIEPI. The observed data aremanaged in uniform and centralized manners, and are utilized in veriﬁcation of countermeasure technology and in elucidation of phenomena of snow-related damage.

Support point

Support standWind

Sag
Multiple elasticcords
Sector model of 4-conductor bundle
Span length of real transmission line is physically simulated
Fig. 2 A sector model and its supports simulating the vibration properties of real transmission lines
The use of multiple elastic cords in place of conductors enables the short model (10 – 15m) to simulate real scale (300 –500m) vibration with large amplitude at low frequency.
Airborne sea salt

Fig. 3 Sample of yearly mean distribution maps of cumulated airborne sea salt
This method allowed us to make distribution maps of airborne sea salt in a wide area, reﬂecting geographic effects of local
terrain and land use such as ﬂatlands, mountains and rivers.

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