IEC TS 61463:2016

Bushings - Seismic qualification

IEC TS 61463:2016(E), which is a Technical Specification, is applicable to alternating current and direct current bushings for highest voltages above 52 kV (or with resonance frequencies placed inside the seismic response spectrum), mounted on transformers, other apparatus or buildings. For bushings with highest voltages less than or equal to 52 kV (or with resonance frequencies placed outside from the seismic response spectrum), due to their characteristics, seismic qualification is not used as far as construction practice and seismic construction practice comply with the state of the art. This document presents acceptable seismic qualification methods and requirements to demonstrate that a bushing can maintain its mechanical properties, insulate and carry current during and after an earthquake. The seismic qualification of a bushing is only performed upon request.

General Information

• Status: Published
• Publication Date: 05-Jul-2016
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.080.20 - Bushings
• Technical Committee: SC 36A - Insulated bushings
• Drafting Committee: WG 6 - TC 15/WG 6
• Current Stage: PPUB - Publication issued
• Start Date: 30-Sep-2016
• Completion Date: 06-Jul-2016

Relations

• Revises: IEC TS 61463:1996 - Bushings - Seismic qualification
• Effective Date: 05-Sep-2023
• Revises: IEC TS 61463:1996/AMD1:2000 - Amendment 1 - Bushings - Seismic qualification
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC TS 61463 ®
Edition 2.0 2016-07
TECHNICAL
SPECIFICATION
Bushings – Seismic qualification
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IEC TS 61463 ®
Edition 2.0 2016-07
TECHNICAL
SPECIFICATION
Bushings – Seismic qualification

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.080.20 ISBN 978-2-8322-3518-8

– 2 – IEC TS 61463:2016 © IEC 2016
CONTENTS
FOREWORD .4
INTRODUCTION .6
1 Scope .7
2 Normative references .7
3 Terms and definitions .7
4 Symbols and abbreviated terms .8
5 Methods of seismic qualification .9
6 Severities . 10
6.1 At the ground . 10
6.2 At the bushing flange . 10
7 Qualification by static calculation . 11
8 Qualification by dynamic analysis . 13
8.1 General . 13
8.2 Modal analysis using the time-history method . 14
8.3 Modal analysis using the RRS . 14
9 Qualification by vibration test . 14
9.1 General . 14
9.1.1 General . 14
9.1.2 Mounting . 15
9.1.3 External load . 15
9.1.4 Measurements . 15
9.1.5 Standard frequency range . 15
9.1.6 Test methods . 15
9.1.7 Testing . 17
9.2 Test on complete apparatus . 18
9.3 Test on the bushing mounted on a simulating support . 18
9.4 Test on the bushing alone . 18
10 Evaluation of the seismic qualification . 18
10.1 Combination of stresses . 18
10.2 Cantilever test . 19
10.3 Acceptance criteria . 19
11 Necessary exchange of information . 20
11.1 Information supplied by the apparatus manufacturer . 20
11.2 Information supplied by the bushing manufacturer . 20
Annex A (informative) Flow chart for seismic qualification . 23
Annex B (informative) Natural frequency and damping determination: Free oscillation
test . 24
B.1 Free oscillation test . 24
B.2 Sine sweep frequency search . 25
Annex C (informative) Static calculation method – Additional considerations . 26
C.1 General . 26
C.2 Effect of the first bending mode . 26
C.3 Determination of S . 26
c
C.4 Value of a . 26
bg
C.5 Typical seismic response of cantilever type structures . 27

C.6 Superelevation factor K . 29
Annex D (informative) Qualification by static calculation – Example on transformer
bushing . 33
D.1 Seismic ground motion . 33
D.2 Critical part of the bushing . 33
D.3 Static calculation . 33
D.3.1 General . 33
D.3.2 Seismic load . 34
D.3.3 Wind load . 35
D.3.4 Terminal load . 35
D.4 Guaranteed bending strength . 36
Annex E (informative) Center clamped bushings . 37
Bibliography . 40

Figure 1 – Example of model of the transformer system . 14
Figure 2 – RRS for ground mounted equipment – ZPA = 0,5 g [1] [2] . 17
Figure 3 – Response factor R . 21
Figure 4 – Test with simulating support according to 9.3 . 22
Figure 5 – Determination of the severity . 22
Figure A.1 – Flow chart for seismic qualification . 23
Figure B.1 – Typical case of free oscillations. 24
Figure B.2 – Case of free oscillations with beats . 25
Figure C.1 – Single degree of freedom system . 27
Figure C.2 – Structure at the flange of a bushing with cemented porcelain [5] [7] . 28
Figure C.3 – Spring stiffness C in function of cemented part geometry [5] [7] . 29
Figure C.4 – Superelevation factor due to the existence of transformer body and
foundation [5] . 30
Figure D.1 – Critical part of the bushing . 33
Figure D.2 – Forces affecting the bushing . 34
Figure D.3 – Porcelain diameters . 35
Figure E.1 – Failure process [6] . 37
Figure E.2 – Failure process, flow chart [5] [6] . 38
Figure E.3 – Stress profile during the opening process [6] . 38
Figure E.4 – Relation between compression and tensile stress in the bottom edge of
the porcelain due to the opening process [6] . 39

Table 1 – Ground acceleration levels . 10
Table 2 – Dynamic parameters obtained from experience on bushings with porcelain
insulators (f = natural frequency, d = damping) . 12
Table 3 – Dynamic parameters obtained from experience on bushings with composite
insulators (f = natural frequency, d = damping) . 12
Table 4 – Example of qualification level: AG5: ZPA = 0,5 g. 17
Table 5 – Response factor R . 21
Table C.1 – Examples of typical seismic responses . 31

– 4 – IEC TS 61463:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
BUSHINGS – SEISMIC QUALIFICATION

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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