Transformer acceptance test from Saudi Aramco

1. Previous Issue: New Next Planned Update: 28 October 2011
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Primary contact: Basel A. Ishwait on phone 966-3-8745133
Copyright©Saudi Aramco 2006. All rights reserved.
Best Practice
SABP-P-005 28 October 2006
Transformer Factory Acceptance Tests
Document Responsibility: Consulting Services Dept.
Saudi Aramco DeskTop Standards
Table of Contents
1 Introduction.................................................... 2
2 References.................................................... 2
3 Definitions...................................................... 3
4 Factory Acceptance Tests for Power
Transformers......................................... 4
Table I – Transformer Name Plate Rating
Information.................................................... 4
Table II – Design Tests........................................ 5
Table III – Transformer Routine Tests................. 5
Table IV – Transformer Applied Test Voltages
Levels............................................................ 7
Appendix A........................................................... 8

2. Document Responsibility: Consulting Services Dept. SABP-P-005
Issue Date: 28 October 2006
Next Planned Update: 28 October 2011 Transformer Factory Acceptance Tests
Page 2 of 8
1 Introduction
1.1 Purpose
The purpose of this Practice is to establish guidelines in reviewing power
transformers Factory Acceptance Test (FAT).
1.2 Scope
This Best Practice gives general guidelines for reviewing the requirements of
power transformers’ Factory Acceptance Tests i.e. routine tests and design tests.
1.3 Disclaimer
This Best Practice is being provided for the general guidance and benefit of
Saudi Aramco engineers reviewing Factory Acceptance Test (FAT). The use of
this Best Practice during factory acceptance test, however, does not relieve the
manufacturer from his responsibility or duty to confirm or to verify the accuracy
of any information presented or from his contractual liability to perform an
accurate FAT that conforms to Mandatory Saudi Aramco Engineering
Requirements. The use of the information or material contained herein will not
guarantee that the resulting product satisfies the applicable requirements of
Saudi Aramco Standards. Saudi Aramco assumes no responsibility or liability
whatsoever for any reliance on the information presented herein or for FAT
performed by manufacturer in accordance with this Best Practice document.
Moreover, this Best Practice is intended only to provide guidelines for Saudi
Aramco engineers and shall not be considered as a replacement for the
Mandatory Saudi Aramco Engineering Requirements. Saudi Aramco® is a
registered trademark of the Saudi Arabian Oil Company. Copyright, Saudi
Aramco, 2004.
1.4 Conflicts with Mandatory Standards
In the event of a conflict between this Best Practice and other Mandatory Saudi
Aramco Engineering Requirement, the Mandatory Saudi Aramco Engineering
Requirement shall govern.
2 References
This Best Practice is based on the below referenced standard:
2.1 Saudi Aramco References
Saudi Aramco Engineering Standard
SAES-P-121 Transformers and Reactors (31 July, 2004)

3. Document Responsibility: Consulting Services Dept. SABP-P-005
Issue Date: 28 October 2006
Next Planned Update: 28 October 2011 Transformer Factory Acceptance Tests
Page 3 of 8
Saudi Aramco Materials System Specifications
14-SAMSS-531 Power Transformers (29 June 2005)
2.2 Industry Codes and Standards
American National Standards Institute
ANSI C57.12.00 Standard General Requirements for Liquid-
Immersed Distribution, Power, and Regulating
Transformers
ANSI C57.12.10 American National Standard for Transformers
230 kV and below 833/958 through
8333/10,417 kVA, Single-Phase, and 750/862
through 60,000/80,000/100,000 kVA, Three-
Phase without load Tap Changing; and
3750/4687 through 60,000/80,000/100,000 kVA
with Load Tap Changing - Safety Requirements
3 Definitions
Factory Acceptance Test (FAT): A performance running test conducted at the factory
to check the integrity of the equipment.
Routine Test: A test to verify the quality control of the manufacturer and are
performed on all equipment. They ensure the quality and uniformity of the
workmanship and materials used. Routine tests are sometimes referred to as production
tests.
Design Test: A test made to determine the adequacy of the design of a particular type,
style, or model of equipment and its component parts to meet its assigned ratings and to
operate satisfactorily under normal service conditions or under special conditions if
specified; and to demonstrate compliance with appropriate industry standards.
Other Tests: Tests are specified by the user for specific applications.
Class I Transformers: Transformers which have winding voltage less 115kV.
Class II Transformers: Transformers which have winding voltage 115kV and greater.
Basic Impulse Insulation Level (BIL): This is the reference insulation level expressed
as an impulse crest (or peak) voltage with a standard wave not longer than a 1.2 x 50
microsecond wave. A 1.2 x 50 microsecond wave means that the impulse takes 1.2
microseconds to reach the peak and then decays to 50% of the peak in 50 microseconds.

4. Document Responsibility: Consulting Services Dept. SABP-P-005
Issue Date: 28 October 2006
Next Planned Update: 28 October 2011 Transformer Factory Acceptance Tests
Page 4 of 8
4 Factory Acceptance Tests for Power Transformers
Factory Acceptance Tests (FAT) are performed to ensure that the equipment has been
assembled properly and will perform reliably in accordance with its nameplate rating.
FAT consists of routine and/or design, and other tests as applicable in compliance with
specified international standards as well as operational tests of all ancillary equipment
and devices.
Commentary Note 6
The majority of transformers used in Saudi Aramco facilities are what designated in the
industry as fans-only auxiliary cooling with natural oil flow and defined in the standards
as:
• ONAN/ONAF (oil natural, air natural/oil natural, air forced) and the old designation
was OA/FA.
• ONAN/ONAF/ONAF (oil natural, air natural/oil forced, air forced/oil forced, air forced)
and the old designation was OA/FA/FA.
Table I - Transformer Name Plate Rating Information
Manufacturer (Name/Plant location)
Transformer Serial No.
KVA rating at ONAN (minimum) and ONAF
(maximum) ratings
High voltage winding (kV)
BIL of high voltage winding (kV)
Low voltage winding (kV)
BIL of low voltage winding (kV)
Impedance at ONAN (minimum) rating (%)
4.1 Design Tests
Data for the below tests should be witnessed and certified signed copies of the
test data should be obtained documenting the test results.

5. Document Responsibility: Consulting Services Dept. SABP-P-005
Issue Date: 28 October 2006
Next Planned Update: 28 October 2011 Transformer Factory Acceptance Tests
Page 5 of 8
Table II - Design Tests
Test Description
Test completed
(Yes/No) or
Not Applicable
Comments
Temperature rise at ONAN and ONAF (minimum
and maximum) ratings
Lightning impulse test of high and low voltage
windings (Class I transformers)
Audible sound level at minimum and maximum
ratings
Load test of tank moving and lifting devices
Pressure test of transformer tank
4.2 Routine Tests
Generally, routine tests are performed on a basic transformer that is not
completely assembled. The radiators, cooling fans, conservator tank, and
protective devices such as the temperature, oil level, pressure vacuum gauges
and pressure relief may not be installed. However, the basic transformer and
components should be completely assembled, i.e. tap changer, current
transformers, control cabinets etc.
Data for the below tests should be witnessed and certified signed copies of the
test data should be obtained documenting the test results.
Table III - Transformer Routine Tests
Test Description
Test Completed
(Yes/No) Comments
Resistance measurement of all windings
Winding insulation resistance
Core insulation resistance

6. Document Responsibility: Consulting Services Dept. SABP-P-005
Issue Date: 28 October 2006
Next Planned Update: 28 October 2011 Transformer Factory Acceptance Tests
Page 6 of 8
Ratio test of all windings on all voltage taps
Verify polarity of windings
Verify phase relation of windings
Measure winding Insulation power factor
Measure the no-load losses and excitation current at
rated voltage and rated frequency on the rated
voltage connection
Measure no-load losses and excitation current at
110% of rated voltage and rated frequency on the
rated voltage connection
Impedance voltage and load loss at rated current
and rated frequency on the rated voltage
connection, and at the tap extremes (minimum and
maximum voltage taps)
Zero-phase sequence impedance voltage
(applicable to transformers 5,000KVA and larger
only)
Lightning Impulse test (routine test for Class II
transformers)
Low frequency induced voltage
Low frequency applied voltage
Low frequency applied voltage on auxiliary devices
and control circuits. (1500 VAC for one minute)
Low frequency applied voltage on current
transformer circuits. (2500 VAC for one minute)
Insulating oil test/analysis
Dissolved gas in oil analysis
Leak check
Operational test of all devices
Check operation of No Load Tap Changer through
the complete tap range
Check operation of Load Tap Changer through the
complete tap range. Operate the tap changer
mechanism manually as well as electrically
Check Current transformer ratio and polarity
Check operation of cooling fans. Verify correct
rotation of fan blades, measure and record the
running current and operating voltage
Verify correct operation of circuits and devices in the
control cabinets

7. Document Responsibility: Consulting Services Dept. SABP-P-005
Issue Date: 28 October 2006
Next Planned Update: 28 October 2011 Transformer Factory Acceptance Tests
Page 7 of 8
Verify operation of pressure relief device
Verify operation of sudden pressure relay
Verify correct operation of top oil and winding
temperature gauges
Verify operation of oil level gauge
Check application of breather
Check painting and positioning of parts
Verify that transformer dimensions comply with
project drawings and requirements
Note: Impulse and partial discharge tests are considered to be routine tests for transformers with windings 115kV and
higher.
Commentary Note 6:
A special routine impulse test for distribution transformers is required for overhead-type,
pad-mounted type, and underground-type liquid-immersed distribution transformers. This
test is specified in 10.4 IEEE C57.12.90.
Test voltages listed in the following table are the most common utilized within
Saudi Aramco.
Table IV - Transformer Applied Test Voltages Levels
Winding
Nominal
Voltage
(kV rms)
Basic Impulse Level (BIL)
(kV crest)
Induced Potential
(kV rms)
(7200 cycle duration)
Applied Potential
(kV rms)
0.48 45 0.96 10
2.4 60 4.8 15
4.16 75 8.3 19
13.8 110 27.6 34
34.5 200 69 70
69.0 350 138 140
115.0 450 120 (phase to gnd) 185
230.0 900 240 (phase to gnd) 395
Revision Summary
28 October 2006 New Saudi Aramco Best Practice.

8. Document Responsibility: Consulting Services Dept. SABP-P-005
Issue Date: 28 October 2006
Next Planned Update: 28 October 2011 Transformer Factory Acceptance Tests
Page 8 of 8
Appendix A
Impulse Tests
Impulse Test Sequence:
Lightning impulse voltage tests, when required, shall precede the low-frequency tests.
Switching impulse voltage tests, when required, shall also precede the low-frequency
tests.
For Class II transformers, the final dielectric test to be performed shall be the induced
voltage test.
If not otherwise specified by the buyer, the test sequence for an impulse test should be
in the following order:
1) Switching impulse test, if applicable
2) Lightning impulse test.
Chopped wave should be at 110% of the BIL value and the front-of-wave should have
amplitude according to Table 5 of ANSI C57.12.00.
For chopped-wave tests, the minimum time to flashover shall be 3.0 µs except for 110
kV BIL, in which case the minimum time to flashover shall be 2.0 µs.
1.2 µs
50 µs
Time
1
0.5
Applied Voltage Test Level
Figure A.1: Lightning impulse full wave; IEC and IEEE