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Insulation Diagnostics System
IDA 200
• Power factor measurement at multiple frequencies
• Differentiates between oil and cellulose ageing
• More data = better decisions
• Portable, for field use
Insulation diagnostics
The problem
The solution
Electric utilities globally are faced with an increasingly difficult
challenge - to secure a steady supply of electricity to demanding
customers while at the same time having to cut costs in operations and maintenance to remain commercially competitive.
The single largest cause of costly downtime in high voltage
installations is ageing of and damage to insulation materials.
One problem has been the lack of appropriate field tools to diagnose insulation materials reliably and non-destructively. The
diagnosis methods available have mostly been suitable only for
laboratory conditions and difficult to apply in the field. Alternatively, they have not provided sufficient information to form a
basis for further action. Other available methods have caused
too much electric stress on the object under evaluation.
Often, a combination of the above obstacles has resulted in
a situation where no or few measurements have been done in
the field after the object has been installed.
However, breakdowns are much more costly than planned
maintenance. Also, premature replacements will result in financial waste. It is therefore our conviction that there is an
unfulfilled demand for a light-weight, portable, user friendly
Insulation Diagnostics Systems that is suitable for field use.
At the same the measurement results should be accurate and
detailed enough to form a basis for decisions about maintenance and replacement. These were the challenges Programma
accepted as we set out to develop a new concept for Insulation
Diagnostics.
Consequently Programma is now able to present the Insulation
Diagnostics System IDA 200. The measurement and analysis
methods employed in IDA 200 are based on research carried
out at the Royal Institute of Technology in Stockholm with resources and input from major users and manufacturers of HV
equipment. These methods together with the design and selection of components have resulted in a unique diagnostics system. In regards to size and weight as well as to accuracy and
depth of analysis IDA 200 is definitely in a class of its own.
With IDA 200 it is possible to diagnose insulation material
in most objects in a high voltage installation (e.g. power transformers, measuring transformers, bushings, paper insulated
cables etc.) The diagnosis is done by applying a relatively low
voltage - up to 200 V. How is this possible?
Dielectric spectroscopy
For many ageing processes in insulation materials, detection
is not facilitated by diagnosis using high measuring voltages.
Rather, it could even be a disadvantage.
In the past, using traditional measuring methods (often variations of the classical Schering bridge), high voltages up to several thousand volts have been required in order to get accurate
results. One of the reasons for this has been the corruption of
measurements caused by mains frequency interference from
adjacent HV lines in the substation. In order to bring down resulting errors, a relatively high voltage has been required for
the diagnosis.
With the Insulation Diagnostics System IDA 200, Programma
has chosen a different path. IDA 200 measures the capacitance
and dielectric losses at discrete frequencies both above and below mains frequency (output signals with frequencies from
0.1 mHz to 1 kHz are available). By avoiding the mains frequency
and its harmonics, an efficient filtering of their corruptive effects
is enabled.
By measuring the capacitance and dielectric losses over a
frequency spectrum (rather than at a fixed frequency), plentiful information about the status of the insulating material can
be obtained. It is for example possible to distinguish between
different components and also to identify ageing processes in
the insulating material.
IDA 200 measures the capacitance and dielectric losses at
discrete frequencies both above and below mains frequency.
By avoiding the mains frequency and its harmonics, an
efficient filtering of their corruptive effects is enabled.
Application
IDA 200 is designed for diagnostic measurements of electrical
insulation. Examples of application areas: Power and instrument
transformers, Bushings, Cables.
Electrical insulation come in all three states of matter: solid
(such as cellulosic paper and porcelain), liquid (such as mineral oil), and gas. Electrical insulation systems as found in the
2
objects listed above usually consist of a combination of different materials. In the following, we will illustrate how
IDA 200 can be used to determine the condition in some of
the most commonly used insulation systems.
Application examples
Dielectric properties of mineral oils
Transformer oil is a non-polar liquid with a capacitance that
changes very little with frequency. But oil also has a DC conductivity that varies with the quality of the oil. As a result,
measured dissipation factor as a function of frequency will
slope downward in a straight line.
D is s ip a tio n fa c to r
(T a n δ )
2
10
T r a n s fo r m e r o ils
O il c o n d u c tiv ity = 1 0
10
O il c o n d u c tiv ity = 1 0
1
-12
-10
primary and secondary to tertiary windings on an auto power
transformer. At higher frequencies the pressboard and the oil
volume determine the dielectric loss, at medium frequencies
the oil conductivity is the dominant factor, and the lower frequency range is dominated by the pressboard dielectric loss.
From analysis of the measurement results, taking the design into account, moisture content of 1 - 1.5% was deduced.
Normally, moisture content above 3.5 - 4% should result in a
replacement of the transformer to avoid insulation breakdown.
S /m
S /m
D is s ip a tio n fa c to r
(T a n δ )
10
10
10
10
1 0 k V w in d in g s
-1
-1
-2
-3
10
10
400 kV / 121 kV -
0
10
10
P o w e r T r a n s fo rm e r
0
-2
-4
0 ,0 0 1
0 ,0 1
0 ,1
1
10
F re q u e n c y [H z ]
1 00
1000
The figure shows a typical response of oil with low conductivity
and another oil with higher conductivity.
Dielectric properties of cellulosic paper
Oil impregnated cellulosic paper, e.g. transformer pressboard and
paper cable kraft paper, has a more complex structure and it is
characterized by frequency dependence in capacitance and loss.
Since ageing produces moisture, the moisture content of cellulose is used as an aging status indicator.
D is s ip a tio n fa c to r
(T a n δ )
1
10
K r a ft p a p e r
W a te r c o n te n t = 1 .5 %
10
-3
0 ,0 0 1
0 ,0 1
0 ,1
1
10
F re q u e n c y [H z ]
100
1000
Measurement results of the insulation between primar y and
secondar y to tertiar y windings on a power transformer.
Diagnosis of cellulosic power cable
insulation
Since moisture gives a characteristic change of cellulosic paper response, IDA 200 is very suitable for assessing the average moisture content in cellulosic insulated power cables (PILC
cables).
W a te r c o n te n t = 3 .5 %
10
D is s ip a tio n fa c to r
(T a n δ )
1
10
0
1 1 k V P IL C c a b le s
"Goo d"
"N o t g o o d "
10
-1
10
10
-2
10
10
0
-1
-3
0 ,0 0 1
0 ,0 1
0 ,1
1
10
F re q u e n c y [H z ]
1 00
1000
Here an example of how moisture affects the dissipation
factor of kraft paper at 20° C is plotted.
Diagnosis of insulation in power
transformers
The insulation system of most power transformers consists of
oil and cellulose. Both these materials change their dielectric
properties over the transformer’s life span. When measured at
a fixed frequency only, the property changes in the different
materials cannot be discerned.
An analysis of the measured dissipation factor frequency
characteristic allows for a more complete diagnostics of the
examined insulation. The graph below shows the result of
measurements done with IDA 200 on the insulation between
10
10
-2
-3
0 ,0 0 1
0 ,0 1
0 ,1
1
10
F re q u e n c y [H z ]
1 00
1000
The graph shows the results from measurements of a new
cable and a ser vice aged cable.
Diagnosis of insulation in instrument
transformers
Instrument transformers are vital components in electrical
transmission and distribution networks. Since both the insulation material properties and the actual design will influence
the measurement results, diagnosis with IDA 200 in the frequency domain offers a unique possibility to form a correct
picture of the insulation material’s status.
3
IDA 200 – Insulation diagnostics system
Mains switch / indicator
Computer screen for integrated PC
Ethernet Inter face
USB-port
Keyboard with integrated trackball mouse
4
Terminal for connecting optional
external voltage amplifier
Measuring status indicator
Output On/Off buttons
Terminal for connecting sample to be diagnosed
(Voltage output / measuring input )
Floppy Disk Drive (1.44 MB)
5
Technical description Specifications
The system measures the complex impedance of a specimen at
a variable voltage and frequency. A Digital Signal Processing
(DSP) unit generates a test signal with the desired frequency.
This signal is amplified with an internal amplifier and then applied to the specimen. The voltage over and the current through
the specimen are measured with high accuracy using a voltage
divider and an electrometer.
General
Description
Portable, computerized insulation diagnostics
system
Design
The instrument is intended for use in high-voltage
substations and industrial environments
Measurement
Capacitance and dielectric losses in insulating
materials at variable frequency
Application
Preventive maintenance - diagnostic measurements of electrical insulation in, eg:
• Power transformers
• Bushings
• Instrument transformers
• Cables
Measurement signal
Voltage / current
0 - 10 Vpeak / 0 - 50 mApeak (low range)
Voltage / current
0 - 200 Vpeak / 0 - 50 mApeak (high range)
Frequency
1000 Hz* - 0.0001 Hz
* Upper frequency current limited
Measurement ranges
Capacitance
Range
10 pF - 100 µF
Dissipation factor
Range
0 - 10 (with retained accuracy of capacitance otherwise higher)
Schematic block diagram of the IDA 200-system.
For the measuring input, IDA 200 uses an advanced DSP unit
that multiplies the input (measurement) signal with a reference
sine voltage, and then integrates the results over a number of
cycles. With this method, noise and interference is almost completely rejected - allowing IDA 200 to work with low voltage
levels up to 200 V and still achieve high accuracy.
Man Machine Communication
IDA 200 includes an integrated PC and proprietar y IDA 200 application software based on a Windows embedded NT platform.
Display screen
16 cm (6.4") TFT Color Monitor
Mouse / Keyboard Included as standard accessor y
Floppy Disk Drive
1.44 MB
USB por t
For external keyboard
Ethernet
Serial por t
RS232
Parallel por t
Principle of the sine correlation technique.
6
Analog video por t
SVGA
Environmental conditions
Operating temperature
-20°C to +55°C (-4°F to 131°F)
Storage temperature
-40°C to +70°C (-40°F to 158°F)
Ordering information
IDA 200 Insulation Diagnostic System
Art. No.
CK-19090
For mains voltage 115/230 V AC (switch selectable)
Humidity
<95% RH (Non condensing) 30 days / year, 85%
RH remaining time
LVD
73/23/EEC: EN 61 010-1 (Section 6),
EN 61 010-1/A2
IDA 200 instrument
EMC
89/336/EEC:
Emission EN 50 081-2: EN 55 011
Immunity EN 61 000-6-2: EN 61 000-4-2,
EN 61 000-4-3, EN 61 000-4-4,
EN 61 000-4-5, EN 61 000-4-6,
ENV 50 140, ENV 50 141, ENV 50 204
Quick guide
Mechanics
EN 60 068-2-31, EN 60 068-2-32
Transpor t case
User’s manual
Mains supply cable
Keyboard with integrated mouse
Calibration box
Termination box IDA 200
10 m multi-cable (blue) with terminals
for connecting instrument to termination box
Other
Mains voltage:
Complete with:
115 / 230 V AC (switch selectable)
± 10%, 50-60 Hz.
Power Consumption:
Max. 250 VA
1 pce 0.25 m (0.8 ft) jumper cable (black)
1 pce 5 m (16.4 ft) guard cable (black)
1 pce 5 m (16.4 ft) measurement cable (red)
Dimensions:
450 x 160 x 410 mm (17.7" x 6.3" x 16.1")
1 pce 0.5 m (1.6 ft) measurement cable (blue)
Weight:
15 kg (33 lbs) instrument only. 28 kg (62 lbs)
with accessories and transport case.
1 pce 5 m (16.4 ft) ground cable with alligator clip
3 pcs alligator clips (1 black, 1 red and one blue)
The above specifications are valid at nominal input voltage and an
ambient temerature of +25°C (+77°F). Specifications are subject to
change without notice.
IDA 200 can be operated while it is in the transport case.
Calibration box, termination box, multi-cable and measurement cables.
Related references
A. K. Jonscher, “Dielectric relaxation in solids” ISBN 0-9508711-0-9, Chelsea dielectric Press, London, U.K., 1983.
U. Gäfvert and B. Nettelblad, “Measurement techniques for dielectric response characterisation at low frequencies“ Nordic
Insulation Symposium, Lyngby, Denmark, Paper No. 7.1, 1990
U. Gäfvert, “Condition assessment of insulating systems, analysis of dielectric response methods” Nordic Insulation Symposium,
NORD-IS, Bergen, Norway, June, 1996.
R. M. Morra, J. M. Braun and H. G. Sedding, “Assessment of Cable Insulation Systems by Low-Frequency Dielectric Characterisation”, p. 408, Annual Report CEIDP, 1991
A. Helgesson and U. Gäfvert, “Dielectric Response Measurements in Time and Frequency Domain on High Voltage Insulation
with Different Response“ Proc. of 1998 Symposium on electrical Insulation Materials, Japan, 1998.
U. Gäfvert et al., “Dielectric Spectroscopy in Time and Frequency Domain Applied to Diagnostics of Power Transformers”, 6th
International Conference on Properties and Applications of Dielectric Materials, Xi’an Jiatong University, Xi’an, China, June 21-26,
2000.
R. Neimanis, T. K. Saha and Roland Eriksson, “Determination of Moisture Content in Mass Impregnated Cable Insulation Using
Low Frequency Dielectric Spectroscopy”, IEEE Power Engineering Society Summer Meeting, Seattle, Washington, USA, 2000.
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Subject to change without notice. Printed matter No. ZI-CK02E R01B. 2000