Sweep Frequency Response Analyzer
FRAX 150
Sweep Frequency Response Analyzer
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Highest dynamic range and accuracy
in the industry
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Built-in PC with powerful backlit screen
for use in direct sunlight
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Highest possible repeatability by
using reliable cable practice and
high-performance instrumentation
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Fulfills all international standards
for SFRA measurements
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Advanced analysis and decision support
built into the software
FRAX 150
DESCRIPTION
Power transformers are some of the most vital components
in today’s transmission and distribution infrastructure.
Transformer failures cost enormous amounts of money
in unexpected outages and unscheduled maintenance. It
is important to avoid these failures and make testing and
diagnostics reliable and efficient.
The FRAX 150 Sweep Frequency Response Analyzer
(SFRA) detects potential mechanical and electrical
problems that other methods are unable to detect. Major
utilities and service companies have used the FRA method
for more than a decade. The measurement is easy to
perform and will capture a unique “fingerprint” of the
transformer. The measurement is compared to a reference
“fingerprint” and gives a direct answer if the mechanical
parts of the transformer are unchanged or not. Deviations
indicate geometrical and/or electrical changes within the
transformer.
FRAX 150 detects problems such as:
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Winding deformations and displacements
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Shorted turns and open windings
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Loosened clamping structures
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Broken clamping structures
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Core connection problems
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Partial winding collapse
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Faulty core grounds
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Core movements
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Imports data from other FRA test sets
Collecting fingerprint data using Frequency Response Analysis (FRA) is an
easy way to detect electro-mechanical problems in power transformers
and an investment that will save time and money.
APPLICATION
Power transformers are specified to withstand mechanical
forces from both transportation and in-service events, such
as faults and lightning. However, mechanical forces may
exceed specified limits during severe incidents or when
the insulation’s mechanical strength has weakened due to
aging. A relatively quick test where the fingerprint response
is compared to a post event response allows for a reliable
decision on whether the transformer safely can be put back
into service or if further diagnostics is required.
FRAX 150
Sweep Frequency Response Analyzer
Method Basics
A transformer consists of multiple capacitances, inductances
and resistors, a very complex circuit that generates a unique
fingerprint or signature when test signals are injected at
discrete frequencies and responses are plotted as a curve.
Capacitance is affected by the distance between conductors.
Movements in the winding will consequently affect
capacitances and change the shape of the curve.
The SFRA method is based
on comparisons between
measured curves where
variations are detected. One
SFRA test consists of multiple
sweeps and reveals if the
transformer’s mechanical or
electrical integrity has been
jeopardized.
Practical Application
In its standard application, a
“finger print” reference curve
for each winding is captured
when the transformer is new
or when it is in a known good condition. These curves
can later be used as reference during maintenance tests or
when there is reason to suspect a problem.
The most reliable method is the time based comparison
where curves are compared over time on measurements
from the same transformer. Another method utilizes type
based comparisons between “sister transformers” with
the same design. Lastly, a construction based comparison
can, under certain conditions, be used when comparing
measurements between windings in the same transformer.
These comparative tests can be performed 1) before and
after transportation, 2) after severe through faults 3) before
and after overhaul and 4) as diagnostic test if you suspect
potential problems. One SFRA test can detect winding
problems that requires multiple tests with different kinds of
test equipment or problems that cannot be detected with
other techniques at all. The SFRA test presents a quick and
cost effective way to assess if damages have occurred or if
the transformer can safely be energized again. If there is a
problem, the test result provides valuable information that
can be used as decision support when determining further
action.
Having a reference measurement on a mission critical
transformer when an incident has occurred is, therefore, a
valuable investment as it will allow for an easier and more
reliable analysis.
Analysis and Software
As a general guideline, shorted turns, magnetization and
other problems related to the core alter the shape of the
curve in the lowest frequencies. Medium frequencies
represent axial or radial movements in the windings and
high frequencies indicate problems involving the cables
from the windings, to bushings and tap changers.
An example of low, medium and high frequencies
The FRAX Software provides numerous features to allow
for efficient data analysis. Unlimited tests can be open
at the same time and the user has full control on which
sweeps to compare. The response can be viewed in
traditional Magnitude vs. Frequency and/or Phase vs.
Frequency view. The user can also choose to present the
data in an Impedance or Admittance vs. Frequency view
for powerful analysis on certain transformer types.
The figure above shows a single phase transformer after a service
The figure above shows a single phase transformer after a service
overhaul where, by mistake, the core ground never got connected (red),
overhaul where, by mistake, the core ground never got connected (red),
and after the core ground was properly connected (green). This potential
and after the core ground was properly connected (green). This potential
problem clearly showed up at frequencies between 1 kHz and 10 kHz and
problem clearly showed up at frequencies between 1 kHz and 10 kHz and
a noticeable change is also visible in the 10 kHz - 200 kHz range.
a noticeable change is also visible in the 10 kHz - 200 kHz range.
FRAX 150
Sweep Frequency Response Analyzer
Test Object Browser — Unlimited number
of tests and sweeps. Full user control.
Quick Select Tabs
presentation view for different
perspectives and analysis tools.
— Quickly change
Quick Graph Buttons — Programmable
graph setting lets you change views quickly
and easily.
Sweep/Curve Settings — Every sweep
can be individually turned on or off,
change color, thickness and position.
Built-in-decision support is provided by using a built-in
analysis tool based on the international standard DL/T 911-2004.
Automated analysis compares two curves using
an algorithm that compare amplitude as well as
frequency shift and lets you know if the difference
is severe, obvious, or light.
Dynamic Zoom — Zoom in and
move your focus to any part of
the curve.
Operation Buttons — All essential functions
at your fingertips; select appropriate
function keys on screen with mouse.
FRAX 150
Sweep Frequency Response Analyzer
Considerations When Performing
SFRA Measurements
SFRA measurements are compared over time or between
different test objects. This accentuates the need to perform
the test with the highest repeatability and eliminates
the influence from external parameters such as cables,
connections and instrument performance. FRAX offers
all the necessary tools to ensure that the measured curve
represents the internal condition of the transformer.
Good Connections
Bad connections can compromise the test results which
is why FRAX offers a rugged test clamp that ensures good
connection to the bushings and solid connections to the
instrument.
Contacts made with the C-clamp guarantee good connections
Shortest Braid Concept
The connection from the cable shield to ground has to be
the same for every measurement on a given transformer.
Traditional ground connections techniques have issues
when it comes to providing repeatable conditions. This
causes unwanted variations in the measured response for the
highest frequencies that makes analysis difficult.
The FRAX braid drops down from the connection clamp next
to the insulating discs to the ground connection at
the base of the bushing. This creates near identical
conditions every time you connect to a bushing whether it is
tall or short.
Import and Export
The FRAX software can import data files from other FRA
instruments making it possible to compare data obtained
using another FRA unit. FRAX can import and export data
according to the international XFRA standard format as well
as standard CSV and TXT formats.
Optimized Sweep Setting
The software offers the user an unmatched feature that
allows for fast and efficient testing. Traditional SFRA
systems use a logarithmic spacing of measurement points.
This results in as many test points between 20Hz and
200Hz as between 200KHz and 2MHz and a relatively long
measurement time.
The frequency response from the transformer contains a
few resonances in the low frequency range but a lot of
resonances at higher frequencies. FRAX allows the user to
specify less measurement points at lower frequencies and
high measurement point density at higher frequencies. The
result is a much faster sweep with greater detail where it is
needed.
Variable Voltage
The applied test voltage may affect the response at lower
frequencies. Some FRA instruments do not use the 10 V
peak-to-peak used by major manufacturers and this may
complicate comparisons between tests. FRAX standard
voltage is 10 V peak-to-peak but FRAX also allows the user
to adjust the applied voltage to match the voltage used in a
different test.
FTB 101
Several international FRA guides recommends to verify the
integrity of cables and instrument before and after a test
using a test circuit with a known FRA response supplied by
the equipment manufacturer. FRAX comes with a field test
box FTB101 as a standard accessory and allows the user to
perform this important validation in the field at any time
and secure measurement quality.
FRAX 150 with Built-in PC
FRAX 150 has a built-in PC with a high contrast, powerful
backlit screen suitable for work in direct sunlight. The cursor
is controlled via the built-in joystick or using an external USB
mouse and the built-in keyboard makes data entry easy.
All data is stored on the built-in hard drive. The data can be
moved to any other computer using a USB memory stick.
FTB 101 Field Test Box
FRAX 150 has a built-in computer with high contrast
and powerful backlit screen suitable for use in direct
sunlight.
Solid connections using the C-clamps and the
shortest braid method to connect the shield to
ground makes it possible to eliminate connection
problems and cable loops that otherwise affect the
measurement.
FRAX 150
Sweep Frequency Response Analyzer
DYNAMIC RANGE
Making accurate measurements in a wide frequency range
with high dynamics puts great demands on test equipment,
test leads, and test set up. FRAX 150 is designed with
these requirements in mind. It is rugged, able to filter
induced interference and has the highest dynamic range
and accuracy in the industry. FRAX 150 internal noise
level is shown in red below with a normal transformer
measurement in black. A wide dynamic range, i.e. low
internal noise level, allows for accurate measurements in
every transformer. A margin of about 20 dB from the lowest
response to the internal noise level of the instrument must
be maintained to obtain ±1 dB accuracy.
An example of FRAX 150’s dynamic limit (red) and transformer
measurement (black)
OPTIONAL ACCESSORIES
The FRAX Demo box FDB 101 is a transformer kit that
can be used for in-house training and demonstrations. The
small transformer is a single-phase unit with capability to
simulate normal as well as fault conditions. Open as well
as shorted measurements can be performed. The unit also
contains two test impedances, one of them the same as
used in the FTB101 field test box.
SPECIFICATIONS
General
FRA Method: Sweep frequency (SFRA)
Frequency Range: 0.1 Hz - 25 MHz, user selectable
Number of Points: Default 1046,
User selectable up to 32,000
Measurement time: Default 64 s, fast setting,
37 s (20 Hz - 2 MHz)
Points Spacing: Log., linear or both
Dynamic Range/Noise Floor: >130dB
Accuracy: ±0.5 dB down to -100 dB
(10 Hz - 10 MHz)
IF Bandwidth/Integration Time: User selectable (10% default)
Software: FRAX for Windows
Calibration Interval: Max 3 years
Standards/guides: Fulfill requirements in Cigré
Brochure 342, 2008
Mechanical condition assessment of
transformer windings using
FRA and Chinese standard DL/T
911-2004, FRA on winding
deformation of power transformers,
as well as other international
standards and recommendations
Input Power
90 - 264 V ac, 47 - 63 Hz
Analog Output
Channels: 1
Compliance Voltage: Output voltage 0.2 - 24 V p-p
(open circuit)
Measurement Voltage at 50 Ω: 10 V (adjustable 0.1-12 V)
Output Impedance: 50 Ω
Protection: Short-circuit protected
Analog Input
Channels: 2
Sampling: Simultaneously
Input Impedance: 50 Ω
Sampling Rate: 100 MS/s
Operating System
Windows® based
Memory
1000 records in internal memory. External storage on USB stick
Physical
Dimensions: 305 mm x 194 mm x 360 mm
(12 in. x 7.6 in. x 14.2 in.)
Weight: 6 kg (13 lb)
Environmental
Operating Ambient Temp: 0° C to +50° C / +32° F to +122° F
Operating Relative Humidity: < 90% non-condensing
Storage Ambient Temp: -20° C to 70° C / -4° F to +158° F
Storage Relative Humidity: < 90% non-condensing
CE Standards: IEC61010 (LVD) EN61326 (EMC)
FRAX 150
Sweep Frequency Response Analyzer
CLOSE-UP OF FRAX 150 CONTROL PANEL
Test button
Built-in mouse with
Left and Right click
buttons (sealed to
protect from dust and
other contaminants)
Navigation arrows
Enter key
INCLUDED ACCESSORIES
Included accessories shown above: Mains cable, ground cable, (2) ground
braid sets, (2) earth/ground braid leads (insulated), (2) C-clamps, generator
cable, measure cable, field test box, nylon accessory pouch, (2) earth/
ground braids with clamp, and canvas carrying bag for test leads
ORDERING INFORMATION
Item (Qty) Cat. No.
FRAX 150 with 18 m (60 ft) Leads AC-39090
FRAX 150 with 9 m (30 ft) Leads AC-39092
Included Accessories
AC Power Cord (IEC60320-C13 to US standard) 17032
AC Power Cord (IEC60320-C13 to Schuko CEE 7/7) 17032-13
Canvas Carrying Bag (for leadset) 30915-211
Ground Cable 5 m (16 ft) 1001-428
FRAX software for PC 1001-427
2 x 3 m (9 ft) Earth/Ground Braid Lead GC-30033
2 x 3 m (9 ft) Earth/Ground Braid Lead (insulated) GC-30036
2 x C-clamp (Bushing Clamps) GC-80010
2 x G-clamp (Ground Braid Clamps) GC-80020
FRAX Generator Cable, 2xBNC, 9 m (30 ft) GC-30040
for use with AC-39092 only
UK
Archcliffe Road, Dover
CT17 9EN England
T +44 (0) 1 304 502101
F +44 (0) 1 304 207342
UKsales@megger.com
UNITED STATES
4271 Bronze Way
Dallas, TX 75237-1019 USA
T 1 800 723 2861 (USA only)
T +1 214 333 3201
F +1 214 331 7399
USsales@megger.com
Item (Qty) Cat. No.
FRAX Measure Cable, 1xBNC, 9 m (30 ft) GC-30050
for use with AC-39092 only
FRAX Generator Cable, 2xBNC, 18 m (60 ft) GC-30042
for use with AC-39090 only
FRAX Measure Cable, 1xBNC, 18 m (60 ft) GC-30052
for use with AC-39090 only
Field Test Box, FTB-101 AC-90060
2 x 305 mm (1 ft) Earth/Ground Braid with Clamp GC-30035
Nylon Accessory Bag GD-31040
User’s Manual AVTMFRAX150
Optional Accessories
Calibration Set AC-90020
FRAX Demo Box FDB 101 AC-90050
OTHER TECHNICAL SALES OFFICES
Valley Forge USA, College Station
USA, Sydney AUSTRALIA, Täby
SWEDEN, Ontario CANADA, Trappes
FRANCE, Oberursel GERMANY, Aargau
SWITZERLAND, Kingdom of BAHRAIN,
Mumbai INDIA, Johannesburg SOUTH
AFRICA, and Chonburi THAILAND
Registered to ISO 9001:2000 Cert. no. 10006.01
FRAX150_DS_en_V04
www.megger.com
Megger is a registered trademark.
Specifications are subject to change
without notice.
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