mon soppe seismic considerations ppt

2013 Life of a Transformer™ Seminar

February 18-21, 2013

San Diego, California USA

Seismic Qualification

Requirements for Transformers

Travis Soppe, PE – W.E. Gundy & Associates Inc.

Mathew Brien – SPX Transformer Solutions, Inc. © Doble Engineering Company

©2013 Doble Engineering Company. All Rights Reserved

2013 Life of a Transformer™ 2

• Seismic Hazard Awareness

• Specifications Defining Seismic Design Requirements

– IEEE-693-2005

– IBC-2009, CBC-2010, ASCE/SEI 7-10, and UBC 1997

– IEEE C57.114-1990

• Seismic Strengthening Techniques

– Anchorage

– Core and Coil Restraint (Load Path)

– Appendage Bracing (Radiators, Conservator, Controls, Arresters)

– Bushings and Surge Arresters

OVERVIEW

© Doble Engineering Company



• Recent Earthquakes Serve as Reminders

– January 12, 2010: Magnitude 7.0 – Haiti

– February 27, 2010: Magnitude 8.8 – Chile

– April 4, 2010: Magnitude 7.2 – Baja California, Mexico

– March 13, 2011: Magnitude 9.0 – Honshu, Japan

– April 13, 2011: Magnitude 5.8 – Virginia

– June 13, 2011: Magnitude 6.0 – Christchurch, New Zealand

– November 06, 2011: Magnitude 5.6 – Oklahoma

Seismic Hazard Awareness





Magnitude Location and Date Magnitude Location and Date Magnitude Location and Date

6.8 VANUATU December 21, 2012 6.6 MOLUCCA SEA August 26, 2012 6.9 GULF OF CALIFORNIA April 12, 2012

7.1 BANDA SEA December 10, 2012 6.3 SULAWESI, INDONESIA August 18, 2012 6.5 MICHOACAN, MEXICO April 11, 2012

6.3 NEW ZEALAND December 07, 2012 7.7 SEA OF OKHOTSK August 14, 2012 5.9 OREGON April 11, 2012

7.3 HONSHU, JAPAN December 07, 2012 6.4 NORTHWESTERN IRAN August 11, 2012 8.2 NORTHERN SUMATRA April 11, 2012

6.4 KURIL ISLANDS November 16, 2012 6.5 PAPUA NEW GUINEA July 28, 2012 8.6 NORTHERN SUMATRA April 11, 2012

6.5 GUATEMALA November 11, 2012 6.7 MAURITIUS - REUNION REGION July 26, 2012 7.1 MAULE, CHILE March 25, 2012

6.8 MYANMAR November 11, 2012 6.5 SOLOMON ISLANDS July 25, 2012 6.6 PAPUA NEW GUINEA March 21, 2012

4.3 EASTERN KENTUCKY November 10, 2012 6.4 SIMEULUE, INDONESIA July 25, 2012 7.4 OAXACA, MEXICO March 20, 2012

7.4 GUATEMALA November 07, 2012 5.2 NORTHERN CALIFORNIA July 21, 2012 6.9 HONSHU, JAPAN March 14, 2012

7.7 QUEEN CHARLOTTE October 28, 2012 5.1 NORTHERN CALIFORNIA July 21, 2012 6.7 VANUATU March 09, 2012

6.5 COSTA RICA October 24, 2012 5.7 AFGHANISTAN June 11, 2012 4 BAY AREA, CALIFORNIA March 05, 2012

5.3 CENTRAL CALIFORNIA October 21, 2012 6.4 PANAMA June 04, 2012 6.6 LOYALTY ISLANDS March 03, 2012

6.2 VANUATU October 20, 2012 6.2 PANAMA June 04, 2012 6.7 SIBERIA, RUSSIA February 26, 2012

6.7 PAPUA, INDONESIA October 12, 2012 6.7 ARGENTINA May 28, 2012 6 OREGON February 15, 2012

6.4 ALEUTIAN IS., ALASKA September 26, 2012 5.6 BULGARIA May 22, 2012 6.4 SOLOMON ISLANDS February 14, 2012

5.6 CHINA September 07, 2012 6.7 TONGA April 28, 2012 5.6 NORTHERN CALIFORNIA February 13, 2012

7.6 COSTA RICA September 05, 2012 6.6 PAPUA, INDONESIA April 21, 2012 6.7 PHILIPPINES February 06, 2012

7.6 PHILIPPINE ISLANDS REGION August 31, 2012 6.8 PAPUA NEW GUINEA April 17, 2012 7.1 VANUATU February 02, 2012

6.8 JAN MAYEN ISLAND REGION August 30, 2012 6.7 CHILE April 17, 2012 6.3 CENTRAL PERU January 30, 2012

7.3 OFFSHORE EL SALVADOR August 27, 2012 6.5 VANUATU April 14, 2012 - Data obtained from USGS -

Major Earthquakes in 2012 - USGS




USGS National Seismic Hazard Map






Transformers will be Subjected to Seismic Loads




• Commonly Specified Standards for Seismic Qualification

– IEEE-693-2005: Recommended Practice for Seismic Design of Substations

– ICC IBC-2009: International Building Code

– CBC-2010: California Building Code

– ASCE/SEI 7-10: Minimum Design Loads for Buildings and Other Structures

– UBC 1997: Uniform Building Code

– IEEE C57.114-1990: Seismic Guide for Power Transformers and Reactors

Transformer Seismic Design Specifications




• IEEE 693-2005

– Specifically Developed for Seismic Design of HV Substation Equipment

– Standardize an Approach to Qualification of Equipment

– Working Group Consisting of

• Public Utility Engineers

• HV Equipment Manufacturing and Design Engineers

• Civil, Structural and Electrical Engineering Consultants

• Academics





• ICC IBC-2009, CBC-2010, UBC 1997, ASCE/SEI 7-10

– Specifically Developed for Building Design (all types of loading)

– Standard Approach to Seismic Design of Buildings and Associated

Mechanical and Electrical Equipment


• Public Building Officials

• Academic and Research Engineers

• Civil, Structural, Mechanical, and Electrical Engineering Consultants





• IEEE C57.114-1990

– Specifically Developed for Transformers and Reactors

– Standardize Approach to Seismic Design of Transformers and Reactors


• Public Utility Engineers

• HV Equipment Manufacturing and Design Engineers

• Civil, Structural and Electrical Engineering Consultants

• Academics





• Use IEEE 693-2005

– Designed Specifically for HV Substations

– Provides Standardized Methodology for

Seismic Qualification of Equipment

– Reduces Overlap and Expense of Seismic

Qualification for Manufacturers and

Utilities





• Provide a set of standard methods that can be used by

manufacturers to seismically qualify substation equipment

and support structures

• Provide a number of standard qualification levels to be used

for qualification

• Manufacturers only have to seismically qualify equipment

once such that it can be sold to multiple Private/Public Utilities

without overlap (less typical for large power transformers)

IEEE 693-2005 Purpose




• Qualification Levels are Based on the Site PGA – Seismic Hazard: Proximately to active faults – Ss (ASCE/SEI 7-10)

– Site Soil Conditions: Soil properties can amplify loading - Fa (ASCE/SEI 7-10)

– ASCE/SEI 7-10 Values to Calculate PGA = 0.4*SMS = 0.4*Fa*Ss

• Three Qualification Levels for Different Site Characteristics

IEEE 693-2005 Qualification Levels

Peak Ground Acceleration IEEE Qualification Level Static Design Acceleration

for Transformers

PGA ≤ 0.1g Low NA

0.1g > PGA ≤ 0.5g Moderate 0.25g

0.5g < PGA High 0.50g




• Selection of Qualification Levels – Seismic Hazards of Service Area in Consideration

– Type, Rating, and Size of Transformer

• Can the transformer be easily moved and utilized at many locations or will the

transformer be at a fixed location.

– Risk Management Strategies of Operating Utility

• Seismic Hazards are predictions and the earthquake can be higher / lower than

the design earthquake

• Identify risk associated with loss of transformer during seismic event

IEEE 693-2005 Qualification Level Selection

Peak Ground Acceleration IEEE Qualification Level

PGA ≤ 0.1g Low

0.1g > PGA ≤ 0.5g Moderate

0.5g < PGA High




• “LOW” Level Qualification – Full analysis and report is not required

– Ensure CNC has a well defined load path

– Analyze anchorage for combined 0.20g horizontal and 0.16g vertical load.

• “MODERATE” Level Qualification

– Full analysis (load path or static based on kV) and report is required

– 0.25g Horizontal Load and 0.20g Vertical Load (load path members)

• “HIGH” Level Qualification

– Full analysis (load path or static based on kV) and report is required

– 0.50g Horizontal Load and 0.40g Vertical Load (load path members)

IEEE 693-2005 Qualification Levels




• Requirements Transformers with kV Ratings < 35kV

– Inherently Acceptable – Less Vulnerable to Seismic Loads

– Full analysis and report is NOT required

– Inherently Acceptable Requirements

• Document/Define Load Path of CNC – No Calculations

• Anchorage Analysis

– Same Acceleration Values for Moderate and High Level

– 1.0g in most vulnerable horizontal direction

– 0.80g in vertical direction

IEEE 693-2005 Qualification – kV < 35 kV




• Transformers with kV Ratings ≥ 35kV and < 115kV

– Qualified by Load Path Analysis • Develop Seismic Loads from the Core and Coil through the tank to the

anchorage and evaluate these members

• Include loads from appendages (radiators, conservators, ect.) but evaluation of

appendages is not required

– Acceleration Levels for Analysis

• 0.5g High Level Horizontal Load or 0.25g Moderate Level Horizontal Load

• 0.4g High Level Horizontal Load or 0.20g Moderate Level Horizontal Load

• Combine resulting stresses from the two horizontal directions with vertical

direction using square root of the sum of the squares SRSS method

IEEE 693-2005 Qualification – 35 ≤ kV < 115




• Load path free body diagram (IEEE 693-2005) and

model showing load path of core and coil






Evaluate Stress in CNC Restraint, Tank Walls, and Anchorage




• Transformers with kV Ratings ≥ 115kV

– Qualified by Static Analysis • Develop Seismic Loads from the Core and Coil through the tank to the

anchorage and evaluate these members

• Include loads from appendages (radiators, conservators, ect.)

• Evaluate appendages using 3 times static seismic loads

• Radiators required to be braced horizontally and vertically to the tank side wall

– Acceleration Levels for Analysis (High/Moderate)

• Load Path Members - 0.5g/0.25g Horizontal and 0.4g/0.20g Vertical Load

• Appendages – 1.5g/0.75g Horizontal and 1.2g/0.60g Vertical Load

• Combine resulting stresses from the two horizontal directions with vertical

direction using square root of the sum of the squares SRSS method

IEEE 693-2005 Qualification kV ≥ 115kV




Load Path Members

Appendages - 3 times loading.

IEEE 693-2005 Qualification – kV ≥ 115kV




Evaluate Stress in CNC Restraint, Tank Walls, Appendages, and Anchorage

IEEE 693-2005 Qualification




• Building Codes developed for design of buildings, building

type structures, and equipment located in buildings.

• ICC IBC-2009 replaces outdated UBC1997 code

• CBC-2010 has similar requirements to ICC IBC-2009

• ASCE/SEI 7-10 is used by both ICC IBC-2009 and CBC-2010

for developing seismic loads - Focus on ASCE/SIE 7-10

• Discussion on Building Codes Shall Cover

– Seismic Hazards (Current ASCE/SEI 7-10 and past UBC 1997)

– Transformer Qualification Methods (testing or analysis)

ICC IBC-2009, CBC-2010, ASCE/SEI 7-10, UBC 1997




• Hazard Maps developed by USGS identify accelerations for

Maximum Considered Earthquake (SS – used for transformers)

ASCE/SEI 7-10 Seismic Hazards

http://geohazards.usgs.gov/designmaps/us/application.php




• Calculation of Site Specific Design Earthquake Spectral

Response Acceleration Parameter SDS

– Short Period Spectral Acceleration from Hazard Maps Ss (3.75g max)

– Adjust SS for soil conditions using Fa

– Assume site class D if soil properties are unknown, then Fa ranges

from 1.0 to 1.6 depending on SS.

• SDS is used to develop loading to the transformer according to

either Chapter 13 or Chapter 15 of ASCE/SEI 7-10

ASCE/SEI 7-10 Seismic Hazards

𝑆𝐷𝑆 =2

3𝑆𝑆𝐹𝐴 © Doble Engineering Company



• Seismic Design Requirements for Nonstructural Components

– Determine Importance Factor IP for the Transformer (IP = 1.5 or 1.0)

– IP = 1.5 for Transformers essential to the functionality of a Risk

Category IV structure or required for life-safety purposes after and EQ

– IP = 1.0 for all other Transformers qualified according to Chapter 13

• Shake Table Testing Required for Transformers with IP = 1.5

– Testing shall follow guidelines of ICC-ES AC156

– Testing more typical on distribution transformers

– Typically test most seismically vulnerable transformers to qualify an

entire product line of transformers

• Analysis Required for Transformers with IP = 1.0

ASCE/SEI 7-10 Transformer Loading: Chapter 13




– Test to verify electrical

functionality before and

after a seismic event

– Functionality can’t be

verified by analysis

– Perform the same factory

tests on the transformer

that would be performed

prior to shipping the unit





• Seismic Design Load Calculation (FP) for Analysis of

Transformers with IP = 1.0





• Seismic Design Requirements for Nonbuilding Structures

– Importance factor Ie can be 1.0, 1.25, or 1.5 and is used to amplify

loading to the transformer (no testing requirements).

• Seismic Design Base Shear (V) for Analysis assuming the

transformer acts as a rigid nonbuilding structure

• Seismic loads (V) are distributed relative to the

height of the transformer not applied at the

CG as done in Chapter 13


𝑉 = 0.3𝑆𝐷𝑆𝐼𝑒 © Doble Engineering Company



• Many specifications call out seismic zones as defined in UBC

UBC-1997 Seismic Hazards

Map from UBC - 1997




• Need to Determine Seismic Coefficient Ca for Analysis

UBC-1997 Seismic Hazards

Tables from UBC - 1997




• 1632 – Nonstructural Components (testing not required)

UBC-1997 Transformer Loading: Section 1632 or 1634

𝑉 = 0.7𝐶𝑎𝐼

• 1634 – Nonbuilding Structures




• Developed specifically for Transformers and Rectors

• IEEE 639-2005 qualification will meet C57.114-1990

objectives and requirements

• Seismic Hazards identified for site specific according to UBC

• Techniques for qualification in the standard include

– Shake table testing (preferred qualification method)

– Analysis (when testing is deemed impractical)

– Rail Shipment Test

• Instrument the transformer during shipment and show that the loading and

stresses due to transport are equivalent to seismic loading

• Ensure transformer meets certain performance objectives

IEEE C57.114-1990 Seismic Requirements




• When writing your specification, be specific!

• Is a report required?

• What standard needs to be met?

– IEEE 693-2005 – What qualification level needs to be met

– ICC IBC-2009, CBC-2010

– UBC-1997 – Specify the current standard ICC IBC-2009

– IEEE C57.114-1990 – Specify the current standard IEEE 693-2005

• Stating the site conditions alone is not sufficient information

Preparing Specifications for Seismic Conditions




• Examples of IEEE 693-2005 Specification

Preparing Specifications for Seismic Conditions

• Remember when specifying timelines, that your transformer is unique, and so is the

seismic qualification report. The report cannot be completed before the design and

drawings are finalized.




Seismic Design Considerations




There are several aspects of

transformer and substation

design to consider for seismic

areas

• Anchorage

• Internal Locking

• Radiator Bracing

• Conservator Support Bracing

• Bushings and Arresters





• Ensuring a unit is properly

anchored is an extremely

effective way to reduce the

probability of damage during an

earthquake

• Anchorage should be designed

for the seismic forces and take

into account the transformer

weight and geometry

• Base shear and overturning

moments should be evaluated

for the worst case direction

Seismic Design Considerations: Anchorage

Sherman – NISEE / EERC




Seismic Design Considerations: Anchorage Forces

Steinbrugge Collection – NISEE / EERC





Seismic Design Considerations: Transformers on Rails

Whittaker – NISEE / EERC

Whittaker– NISEE / EERC

Fierro - PEER




• Welded Anchorage (Preferred) – The base of the

transformer is welded directly to members embedded in the

foundation

• Bolted Anchorage

– Cast in place anchorage: Anchor rods are embedded in the

concrete foundation. Typically have higher strength capacity

– Post Installed anchorage: Mechanical anchors or epoxied

anchors placed in drilled holes. Easier to install but typically have

lower strength capacity which is challenging for large power

transformers.

• Anchor Clips – The base is held in place by clips which can

either be bolted or welded to the foundation

Seismic Design Considerations: Anchorage Methods




• Welding is the preferred

method of anchorage due

to excellent field

performance

• Requires steel embedded

in the foundation

• Typically not an option on

older retrofit foundations

Seismic Design Considerations: Welded Anchorage





• If welding to the base is

not possible, a bolted

anchorage may be used

• Allows for mobility and

retrofit to existing bases

• Can use embedded

studs for greater strength

Seismic Design Considerations: Bolted Anchorage




• Anchor clips can be

bolted to the foundation,

or welded to imbed

plates

• Allows for flexibility in

anchorage location for

retrofits and ease of

installation

• Clips should be designed

to restrict vertical

movement

Seismic Design Considerations: Anchor Clips




• Internal Locking is

required to ensure the

active part of the

transformer does not

shift during a seismic

event

• Typically a standard

design which meets

shipping requirements

is sufficient to resist

seismic forces

Seismic Design Considerations: Internal Locking




• Brace radiators to restrict movement which

may cause damage to the panels and

leakage at joints

• Bracing limits moment demands on

radiator valve pipes

• Bracing should resist movement in the

horizontal and vertical directions and limit

loading to radiator valve connections

• Bracing is required per IEEE 693 for

transformers with kV ratings > 115

• Standard designs for high wind areas will

be insufficient to resist high seismic forces

Seismic Design Considerations: Radiator Bracing





Braced and Unbraced Radiator Bank Subjected to Seismic Loading





• Moment demand on radiator valve pipe and connection is significantly

reduced when bracing is added (previous video, IEEE time history)

• Detail bracing to withstand lateral loading from the radiator bank, brace

member and connection should have equivalent capacities




Seismic Design Considerations: Conservator Bracing

• Conservators are vulnerable to

earthquake loading due to their

significant mass and height above

the transformer

• Bracing adds stiffness and reduces

seismic response of conservator

• Detail piping to transformer to allow

for differential displacements

between the conservator and tank





Braced and Unbraced Conservator Subjected to Seismic Loading





• Moment demand on conservator support and connection is significantly

reduced when bracing is added (previous video, IEEE time history loading)

• Detail bracing to withstand lateral loading from the conservator, brace

member and connection should have equivalent capacities





• Stresses in conservator and support are significantly reduced when

bracing is added (previous video, IEEE time history loading)




• Typical construction with heavy brittle

porcelain material

• Use of polymers is becoming more

popular, better seismic performance

• Failures often due to line loading or

amplified support loading (flexible

support conditions)

• Bushings and arresters should be

qualified to meet the requirements of

IEEE 693 (testing required)

• Evaluate supporting elements of the

transformer to ensure sufficient

strength and rigidity

Seismic Design Considerations: Bushings and Arresters

Northridge – NISEE / EERC




500kV Bushing IEEE 693-2005 Qualification - PL




Don’t Forget to Adequately Anchor Your Spares

Whittaker– NISEE / EERC

Halil– NISEE / EERC




– National Information Service for Earthquake Engineering, EERC, University of California, Berkeley

– Fierro, E. January 19 2010 Photo Gallery – Haiti 2010. Pacific Earthquake Engineering Research Center

– Institute of Electrical and Electronic Engineers (IEEE). “IEEE 693-2005, IEEE Recommended Practice for

Seismic Design of Substations”, The Institute of Electrical and Electronic Engineers, Inc. 3 Park Avenue, New

York, NY10016

– International Code Council (ICC). “2012 International Building Code”, International Code Council, Inc. 4051

West Flossmoor Road, Country Club Hills, IL, 60478

– California Building Standards Commission (CBSC). “2010 California Buldign Code of Regulations Title 24,

Part 2, Volume 1 of 2”, California Building Standards Commission, 2525 Natomas Park Drive, Suite 130

Sacramento, CA 95833

– American Society of Civil Engineers (ASCE). “ASCE/SEI 7-10, Minimum Design Loads for Buildings and

Other Structures”, The American Society of Civil Engineers, 1801 Alexander Bell Drive, Reston, Virginia

20191

– International Conference of Building Officials (ICBO). “1997 Uniform Building Code Volume 2”, International

Conference of Building Officials, 5360 Workman Mill Road, Whittier California, 90601

– Institute of Electrical and Electronic Engineers (IEEE). “IEEEC57.114-1990, IEEE Seismic Guide for Power

Transformers and Reactors”, The Institute of Electrical and Electronic Engineers, Inc. 345 East 47th Street,

New York, NY10017

References


2013 Life of a Transformer™ Seminar

February 18-21, 2013

San Diego, California USA

Seismic Qualification

Requirements for Transformers

Travis Soppe, PE – W.E. Gundy & Associates Inc.

Mathew Brien – SPX Transformer Solutions, Inc. © Doble Engineering Company

mon soppe seismic considerations ppt

Documents

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