ABB Components USA Seismic Considerations & Power Bushings Using IEEE Standards ABB Components USA.

ABB Components USA

Seismic Considerations &Power Bushings

Using IEEE Standards

ABB Components USA

ABB Components USA

IEEE 693 - 1997

IEEE Recommended Practice for Seismic Design of Substations

djr 2/00 ABB Components USA

IEEE Std 693 - 1997

Electrical Equipment for Sub Stations Based on IEEE 693-1984

Very major revision Basically a new standard

Three Qualification Levels Low, Moderate & High

User determines Qualification Levels

ABB Components USA

European Standards

IEC Technical Report 1463


IEC Technical Report 1463

Covers seismic qualification of power bushings

Based on static coefficient calculations Based on cantilever withstand of bushing Not widely accepted in North America


IEEE 693-1997

Performance Levels Selection of performance Level Requirements for bushings Test Methods Qualification of bushings < 161 kV Qualification of bushings 161 kV


Performance Levels (ground acceleration)

Low = 0.1 g, horizontal acceleration peak

Moderate = 0.5 g, horizontal acceleration peak

High = 1.0 g, horizontal acceleration peak

Vertical acceleration = 0.8 x horizontal


Selection of Performance Level

By User of equipment Expected ground acceleration by

earthquake hazard method or … … by seismic exposure maps and site

conditions Select Performance Level to match the

expected ground acceleration


General Requirements for Bushings

Bushings as components of larger equipment

Annex D of IEEE 693 - Transformers

Requirements depend on system voltage


Testing for Seismic Performance Levels

Low: 0.1g, horizontal Equipment testing not required

Moderate: 0.5 g, horizontal Testing required (when practical with equipment size)

High: 1.0 g, horizontal Testing required (when practical with equipment size)


Qualification of Bushings

Less than 161 kV Static Pull Test Force = 2 x weight Applied horizontally at top of bushing Duration = 2 seconds

161 kV and Higher Shake Table test Time history method Test by design family Test most seismically

vulnerable family member

Pass = no damage & no leakingPass = no damage & no leaking


Bushing Seismic Considerations

Bushing is not at ground level Bushing acceleration is amplified by

transformer structure Bushing acceleration = 2x ground acceleration Transformer tank:

Amplification factor = 2, or Super Elevation factor (IEC) = 1.5


Transformer Tank Amplification Factor = 2

1.0 g

2.0 g


Shake Table Testing of Bushings

Method 1 Test at 1/2 level and Calculate to demonstrate a 2x safety factor

Method 2 Test at full level


Shake Table Testing of Bushings

1/2 Test + Calculation Method Only practical method for some large equipment Good when structure behaves in linear fashion and

is predictable Not good for bushings because of the non-linearity

of the bushing’s mechanical system, ie, gasket + porcelain + spring clamps


Shake Table Testing of BushingsUsing 1/2 Level Test Method

For large equipment where not practical to test at full level.

Must demonstrate by calculation that equipment can withstand forces 2 times as great as test values


Example of 1/2 Test Method(Power Transformer)

Purpose of test: demonstrate that transformer is qualified for the High Performance Level where ground acceleration = 1.0 g

Shake Table set-up at 1/2 value = 0.5 g

Use calculations to show that the test results at 0.5 g can be extended to 1.0 g


Example of 1/2 Test Method(Transformer Bushings)

Purpose of test: demonstrate qualification at High Performance Level ground acceleration = 1.0 g

Bushing acceleration is 2 times ground acceleration because of tank effect

Bushing must withstand 2 x 1.0 g = 2.0 g Shake Table set-up at 1/2 value = 1.0 g Use calculations to show that the test results at 1.0

g can be extended to 2.0 g


Shake Table Testing of BushingsUsing Full Test Method (Full Performance Level Test)

Purpose of test: demonstrate qualification at High Performance Level ground acceleration = 1.0 g

Bushing acceleration is 2 times ground acceleration because of tank effect

Bushing must withstand 2 x 1.0 g = 2.0 g Shake Table set-up at full value = 2.0 g Bushing directly qualified by Test Calculations not required


Shake Table Testing of BushingsUsing Full Test Method (Full Performance Level Test)

Moderate Level (0.5 g) Bushing tested at 1.0 g

High Level (1.0 g) Bushing tested at 2.0 g


2 g

Bushing Qualification @High Level by Direct Testing


1 g

Bushing Qualification @ Moderate Level by Direct Testing


Shake TableTest Set-up


ABB Components USA

Qualify bushings based on IEEE 693-1997 Actual shake table test used for higher

voltage bushings ABB full line of ANSI/IEEE bushings has

been tested and qualified according to IEEE 693-1997


ABB Bushing Qualification Summary

Qualified @ High - Static Pull Test Bushings 25 kV through 138 kV

Qualified @ High - Shake Table Bushings 161 kV through 196 kV

full test of seismically worse bushing in family

Qualified @ Moderate - Shake Table Bushings 362 kV

full test of seismically worse bushing in family


ABB Bushing Qualification Summary

500 kV bushing not qualified at moderate passed 0.45 g at flange equivalent to 0.22 g, ground acceleration

(with tank amplification factor = 2) failure mode (@ 0.50 g at flange)

slight leak at flange during shake test re-sealed after test no worse after second test


ABBComponents USA

ABB Components USA Seismic Considerations & Power Bushings Using IEEE Standards ABB Components USA.

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