Seismic code and design standard for transmission line and substation in Japan September 3, 2003 Hajime Imura The Kansai Electric Power Co.,Inc.

Contents 1. Basic concepts on seismic design of electric facilities 2. Seismic design of electric facilities - Overhead transmission line - Underground transmission line - Substation 3. Evaluation of the present seismic design 4. Summary

Basic concepts on seismic design of electric facilities Category 1Category 2 Dams LNG tanks Oil tanks Power generation facilities Transmission lines Substations Distribution lines Load dispatching center Telecommunications a) No serious trouble occurs for a Level A earthquake. There are two categories(Category 1 & 2) according to the kinds of facilities. Electric facilities performance that can be expected is decided by intensity of earthquake(Level A & Level B). Level A : An earthquake which occurs once or twice in the lifetime of facilities. Level B : An earthquake with a vertical shock or a trench-type earthquake which seldom occurs (ex. Hanshin-Awaji earthquake). a) No serious trouble occurs for a Level A earthquake. b) No serious damage on human lives occurs for Level B earthquake.

Seismic design of electric facilities 1. Overhead Transmission Line No criteria in the aspect of seismic design 40m/s wind earthquake [Overhead transmission tower is designed so as not to be fallen down by 40m/s-wind (typhoons are assumed). The wind force is severer than earthquake motions.]

Seismic design of electric facilities 2. Underground transmission line No criteria in the aspect of seismic design [Reason] Cables have flexibility and strength against earthquake motions, and it is laid with off-set considering thermal elasticity and good working conditions. (1) Cables It is designed based on seismic design of substation equipment. (2) Cable heads and oil supplying systems(for OF cables) [Reason] Polycon FRP Pipes (PFP) have been usually adopted. They have flexibility on their joints and can withstand earthquake motions. (3) Conduit and human maintenance hole No criteria in the aspect of seismic design

Seismic design of electric facilities 3. Substation (Outdoor) Porcelain type equipment (CB, DS, PCT, Cable head) Transformer BodyBushing Design force (horizontal) 3 m/s 2 5 m/s 2 － The force is assumed to be applied to the lower end of the equipment Design Technique * 1F and underground of indoor substation : Same as outdoor Others :designed one by one considering the motion of the building foundation Position of the force being applied foundation Transformer body Pocket Bushing Dynamic Static Resonant sine wave, 3 cycles －－ 5 m/s 2

Evaluation of the present seismic design The present seismic design was established in 1980 based on the experience of “Off-Miyagi earthquake”, which occurred in We reviewed the present design after Hanshin-Awaji earthquake. Hanshin-Awaji earthquake occurred in 1995 [The viewpoints of evaluation] - Theoretical evaluation - Demonstrative evaluation earthquake Seismic Design of Substation ▼Off-Miyagi ▼Hanshin-Awaji ■ 1980 Dynamic Seismic Design □ (1998) review

Theoretical evaluation on Hanshin-Awaji earthquake 1) Frequency Expectation in return period is around 1000 years. Maximum acceleration Response coefficient Response acceleration Dominant frequency Shin-Kobe S/S5.84m/s m/s Hz KEPCO R&D Center 6.48m/s m/s Hz KOBE meteorological observatory Present seismic criteria 8.18m/s m/s Hz 3.0 m/s m/s 2 (1)(2)(1) * (2) Hz 2) Actual earthquake motions and response acceleration

Theoretical evaluation on Hanshin-Awaji earthquake 3) Response acceleration spectrum at Shin-Kobe S/S 4) Seismic strength of substation equipment - Porcelain insulators and bushings have some margin(about 2 times) of its strength considering the strength variation on the process. - Even if considered the variation of it strength, only 1% of the insulator would be damaged. Safety Factor Maximum Acceleration 26m/s 2 at 3.05Hz Acceleration(m/s 2 ) Natural frequency (Hz) (Cont’d) Design:14m/s 2 In specific frequency range( Hz), response acceleration exceeds the present seismic criteria(14m/s 2 ).

Demonstrative evaluation on Hanshin-Awaji earthquake 1) Strong earthquake motions, but little serious damage 2) Damaged equipment was designed based on older design. - Many of damaged equipment were designed based on older seismic design before 1978 and almost all of the equipment designed on the present design do not suffer significant damage. - Strong earthquake a) Shin-Kobe S/S : 5.84 m/s 2 b) KEPCO R&D center : 6.48 m/s 2 c) Kobe meteorological observatory : 8.8 m/s 2 - Some equipment were damaged in Itami & Shin-Kobe S/S, but not so much serious damage which leads to loss of function. 3) Experiences of other big earthquakes - There were strong earthquakes other than the Hanshin-Awaji, but we did not suffer severe damage.

Evaluation of the present seismic design (Cont’d) [Overhead transmission] According to the analysis of seismic response by using the waveform observed at Kobe meteorological observatory (8.1m/s 2 ; maximum acceleration in the Hanshin-Awaji), typical transmission towers of 500, 275, 77 kV have enough strength against maximum possible acceleration. [Underground transmission] Only some of the transmission line based on former design (laid without off-set) suffered damage. The present seismic design has good performances.

Summary (1) The present seismic criteria is: a) Substation Resonant 3 cycles sine wave - Porcelain type equipment : 3m/s 2 (Horizontal acceleration) - Transformer : 5m/s 2 (Horizontal acceleration) b) Overhead transmission line No criteria in the aspect of seismic design (If the structure withstand 40m/s-wind, enough strength for earthquake) c) Underground transmission line No criteria in the aspect of seismic design (The components have various flexibility and have enough strength.) (2) Experiences of strong earthquake such as the Hanshin-Awaji, proved good performance of the present seismic design.

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