Levitating magnets
The transformer Stakeless earth
testing
threat
See page 6
See page 3
See page 5
ELECTRICAL
TESTER
Published by Megger
April 2011
The industry’s recognised information tool
Little known facts about tan delta/power factor testing
Dinesh Chhajer
Technical Support Group
With an increasing failure rate of substation
electrical equipment, utilities and heavy
industry must focus on preventive and predictive
maintenance to ensure power system integrity
and reliability. Electrical insulation is a common
reason for electrical equipment failures and
tan delta/dissipation/power factor (PF) testing
is a popular way of diagnosing and estimating
the condition of insulation as it ages. There
are, however, a number of issues relating to PF
testing that are not nearly as widely understood as they should be.
PF testing is widely used on electrical
equipment such as power transformers, circuit
breakers, generators and cables. PF values,
trended over time, can help in detecting
problems like contamination, high moisture
content and the presence of voids in insulation.
Excitation current tests, along with PF tests,
performed on power transformers, can also
help in detecting turn-to-turn insulation failure.
Dissipation factor tests are usually performed
at 10 kV or the readings are converted to
10 kV equivalent. The best voltage for PF tests
is a frequently debated topic as instruments
are now available that allow the tests to be
performed at voltages from 27 V to 12 kV.
What test voltage is “good enough” for
accurate and reliable measurements? The answer
depends on the type of test specimen and the
test conditions.
Most power transformers have oil-paper type
insulating systems that exhibit a flat response
when PF is measured as a function of test
voltage. However, motors and generators
typically have dry or solid insulation whose
PF values may vary with test voltage. Values
increase with increasing test voltage due to
the voids that are almost invariably present in
solid insulation. The increase in PF value as a
function of voltage corresponds to increasing
ionization in the voids.
One reason that industry has standardized on
a 10 kV test voltage is for immunity against
electrostatic interference; power transformers
operating in HV substations are subject to a
lot of electrical noise and interference. An
HV test signal provides better signal to noise
ratio, giving more accurate measurements. Test
instruments with very high noise suppression
capability are required for measurements in
HV substations as the test current is very low
in insulation tests and noise levels can be as
high as 20 times the test current.
Battery testing means
cruise passengers are
never in the dark!
www.megger.com
DELTA4000 performs automated power factor tests at up to 12 kV
along with that single capacitance, the results
For perfect insulation, the PF should be zero.
look strange. For example, when performing
In practice, any value close to zero is considered
tests on bushings, three-winding transformers
to indicate a good insulation system. PF test
or inter-phase insulation of rotating machinery,
sets always try to measure a single capacitor, but
the PF values will sometimes be negative.
if the test object has some phantom circuits
Tony Wills
Applications Engineer
Battery impedance testing is making life a
lot easier and more comfortable for Rey B
Crisostomo, an engineer who works on ships
operated by Royal Caribbean International, the
largest global cruise brand. Among many other
duties, Rey is responsible for ensuring that
the enjoyment of Royal Caribbean customers
is never interrupted by a power failure while
they are on board the company’s vessels.
‘Before I became aware of battery impedance
PF is a measure of watts loss in the insulation.
testing’, reports Rey Crisostomo, ‘I had some
bad experiences with batteries, usually finding
out when it was too late that my back-up
power source wasn’t able to supply power
when it was really needed. The result was
always the same – lots of time was wasted
and a lot of money was lost, impacting our
profits. And, since my salary comes out of
those profits, I had a very personal interest! In
addition, it was never a pleasant experience
explaining to my supervisor why the incident
had occurred.
Negative PF therefore corresponds to watts
generation. Obviously, insulation cannot
generate power, which shows that negative
PF values are not real but instead tell us that
the insulation does not behave as an expected
capacitance.
continued on page 2
Figure 1: Specimen in UST mode with surface
However, with a little help and support from
Megger, I discovered the BITE2P battery
impedance test set and learned how to use it
to check the condition of my batteries, and
to predict reliably when they need replacing.
Now I can be confident about relying on the
battery back up systems if there should be a
problem with our primary shipboard power
sources.
What I like most about battery impedance
testing is that I can use it to test the battery
continued on page 2
Megger ELECTRICAL TESTER April 2011 1
ELECTRICAL
TESTER
The industry’s recognised information tool
Contents
negative values after taking these precautions
could point toward contamination or a bad
insulation system.
A
Little known facts about tan deltal/
power factor testing........................... 1
Dinesh Chhajer, Technical Support Group
Battery testing means cruise
passengers are never in the dark!...... 1
Tony Wills, Applications Engineer
Putting electric vehicles to the test.... 3
Dave Moore, Product Manager
Mumbai technical conference goes
with a swing....................................... 3
Testing to address the transformer
threat.................................................. 3
Online testing of first trip analysis.... 4
Simanand Gandhi, Applications Engineer
Magnetic shielding............................. 5
Dr Stan Zurek, Magnetics Technical Specialist
Swiss army knife of testers!............... 5
loss components
Negative values also appear with some
specimens that have high surface leakage. As
shown in Fig 1, phantom circuits introduce a
current (Is) which changes the phase angle of
the measured test current (IT). The surface loss
current (Is) is predominantly resistive (Rs) and
has a very small phase angle with respect to
the applied voltage. Capacitive coupling (Cc)
may be present as a result of this parallel path
of Rs to main insulation under test.
Excitation current testing is commonly
performed along with PF testing. It is a voltage
dependent test and is always performed in
UST mode. Like PF tests, the excitation
current readings are normalized to 10 kV
equivalent values, using a linear approximation.
When dealing with specimens that are highly
inductive, such as power transformers, the
relationship between voltage and current is,
however, not linear. Assuming a linear relation to
determine 10 kV equivalent excitation gives
only approximate values. It is, therefore,
important to perform tests at the same voltage if
excitation current historical data needs to be
trended. Tests performed at different voltages
and then corrected to 10 kV may not be
comparable. This is important as trending data
is critical when evaluating problems with turnto-turn insulation.
Dave Moore, Product Manager
Earth testing without the stake
Part 2.................................................. 6
Paul Swinerd, Product Manager
Hannover 2011................................... 7
Georg Halfar, Marketing Communications
Manager, Germany
Figure 3: Excitation current measurement on
a Delta winding with third leg grounded
Q&A.................................................... 8
When performing excitation current measurements
on delta windings, it is important to ground
the third leg of the delta configuration as
shown in Fig 3. Since excitation current is a
UST test, grounding the third leg eliminates
the current flowing in the other two windings
from the measurement circuit. Depending on
the inductance and resistance of each winding,
if third leg is not grounded the results would
be approximately 30% to 50% higher than true
readings.
Safety in testing - Part 3..................... 8
Jeff Jowett, Applications Engineer
The past of PowerDB......................... 8
Mark Meyer, Director of Marketing
Pylons in dresses!............................... 8
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Editor Nick Hilditch.
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2
Fig 2 Vector diagrams with different Is phase
angles and different magnitude of I
NET
Smaller phase angles for surface loss current
(Is) can lead to negative PF values. Measured
test current (IT) is the vector difference of
total current (INET) and surface loss current
(Is). In UST or GST configurations, this
surface loss makes the measured test current
(IT) phase angle greater than 90º, and this
results in negative PF values.
It is important to understand where negative
PF values come from. For some specimens
it is just a result of design – for example, the
presence of electrostatic grounded shield
between the inter-windings of a transformer.
In other cases, where negative values are
encountered users should consider eliminating
all external effects by following best testing
practices such as verifying proper grounding
circuits, cleaning external bushing surfaces,
avoiding unfavorable weather conditions and
using guard circuits effectively. Repeated
continued from page 1
system without disturbing the normal operation
of the equipment it serves – I don’t need to
take the system off line, yet I can still test
each of the batteries in the strings.
Impedance testing also provides me with the
data I need to make an informed decision
about whether or not a battery needs to be
replaced. This saves a lot of money, as we
used to replace the batteries automatically
after a certain period of service, and our
experience with impedance testing has
shown that we were often replacing batteries
that were still serviceable.
Megger ELECTRICAL TESTER April 2011
A transformer with magnetized core can
exhibit higher excitation current measurements
than normal. IEEE 62-1995 section 6.1.3.4
states, “If a significant change in the test
results is observed, the only reliable method
of excluding the effect of residual magnetism
is to demagnetize the transformer core.”
The factors discussed here that affect excitation
current measurements should be borne in
mind before performing the test.
The dissipation factor values are highly
dependent on temperature. IEEE C57.12.90
section 10.10.4 Note 3 (b) states that “Experience
has shown that the variation in power factor
with temperature is substantial and erratic
so that no single correction curve will fit all
cases.” Nevertheless, correction factor tables
have traditionally been used to bring all data
to a common base of 20 °C. It is imperative
only to compare a specimen’s PF values that
are taken at a similar temperature or corrected
to the same temperature accurately. For
different specimens, changes in temperature
affect PF values in different ways. And even
the same specimen will become more
temperature dependent as it ages. Temperature
On board an ocean-going vessel it’s important
to know that all of the machinery will remain
operational in all circumstances, and battery
power is almost always the best alternative
power source to ensure this.
At Royal Caribbean, we have always worked
hard to make sure our customers have the
best vacation on earth. Now, thanks to battery
impedance testing, we can do even more by
testing our batteries regularly so that there will
never be any worries about a ship suddenly
being blacked out in the middle of the ocean!’
Megger BITE2P battery impedance test sets of
the type used by Rey Crisostomo are rugged
correction factors are highly dependent on
insulating material, its structure, ageing, presence
of moisture or contamination and other
influences. However, temperature correction
data is based upon the average values. Since
each test object is unique, using these average
corrections introduces errors.
New transformers have relatively weak
temperature dependence and the use of
standard tables overcompensates. As the
object ages, same average correction factors
would under compensate and error predominates in the other direction. Trending of
PF values becomes more critical in the second
half of the life cycle. In this second half,
correction factors should be larger because
of the increased effect of temperature on the
insulation. Using average factors can lead to
incorrect trending and inaccurate estimation of
the remaining healthy life of the object.
IEEE Standard 62-1995 states, “Testing at
temperatures below freezing should be
avoided, since this could significantly affect
the measurement. Among the primary reasons
for performing this test is the capability of
detecting moisture in insulation. The electrical
characteristics of ice and water are quite
different and it is much more difficult to
detect the presence of ice than it is to detect
water; sometimes it is impossible. ”Measuring
PF at too high or too low a temperature can
introduce errors, and the IEEE recommends
performing PF tests at or near 20 °C. However,
it’s not always practical to cool down or heat
up the test specimen to 20 °C.
Fortunately, new technology makes it possible to
accurately correct PF values to 20 °C without
resorting to correction factor tables based on
averages. Using dielectric frequency response
(DFR), the unique temperature correction
factor of each test object can be determined.
This is possible because a PF measurement
at a certain temperature and frequency
corresponds to a PF measurement made at
different temperature and frequency. Therefore by measuring PF at different frequencies,
it is possible to determine the temperature
dependence of the specific test object. With
this technique, PF can be measured at any
insulation temperature [5 °C-50 °C] and then
corrected to 20 °C accurately and precisely.
Electric apparatus has failed and will continue
to fail because of insulation deterioration. A
proactive approach is the key to monitoring
the integrity of the insulation system and
preventing or at least anticipating such failures.
Tan delta/power factor diagnostic testing is
an important tool in determining the quality
of the insulation and estimating its remaining
healthy life.
Dissipation factor readings are dependent on
various factors and it is important to be aware
of these. Test voltage, electrostatic interference,
temperature, humidity, surface losses and
other parameters can greatly influence PF
measurements. A better understanding of
the impact of these parameters will help in
obtaining accurate measurements that can be
relied upon in the decision making process.
self-contained units designed to determine the
condition of lead-acid and nickel-cadmium
cells up to 7000 Ah. They work by applying
a test current across the battery string while
on-line, then measuring the total current (ac
ripple + test current) and the voltage drop of
each cell. They then calculate the impedance,
which has been shown to be an excellent
indicator of battery condition.
The test sets also measure dc voltage and
interconnection (strap) resistance to help
determine the overall condition of the entire
battery string’s electrical path from terminal
plate to terminal plate.
www.megger.com
ELECTRICAL
TESTER
The industry’s recognised information tool
Putting electric
vehicles to the
test
Photo: Bosch
Dave Moore
Product Manager
As concern continues to grow over the
environmental impact of vehicles with
conventional petrol engines, the popularity of
electric and hybrid vehicles is increasing
rapidly. In fact, it has been reported that
vehicles with hybrid drives already mak e up
2% of new registrations worldwide, and that
this figure is expected to reach at least 7% in
the next five years.
Much more appropriate are handheld insulation
testers that work at 1 kV. What is important,
however, is that the instrument should have
a high maximum reading. There’s a lot of
difference between a tester that shows infinity
for everything over, say, 1 GΩ, and one that
gives dependable readings up to 200 GΩ,
because the latter provides much more
information about faults that may be developing,
but have not yet reached a critical stage.
Mumbai technical conference
goes with a swing!
Also important is support for diagnostic
insulation tests, such as Polarisation Index
(PI) and Dielectric Absorption Ratio (DAR). At
present, these tests are not widely used in
connection with electric vehicles but, when
performed regularly and the results logged
over time, they can provide useful additional
information about the life expectancy of
wound components like motors. The information
these tests provide is particularly useful in
applications where there is a risk of moisture
ingress and carbon deposits, as there invariably
is with the drive trains of electric vehicles.
Internal storage of test results and facilities
for downloading these results for inclusion
in reports are other highly desirable features,
since not only do they save time, they also
eliminate the risk of errors that is always
present when results are recorded manually.
While result down-loading via a USB cable
or similar is satisfactory, there is a lot to be
said for instruments that offer the added
convenience of Bluetooth wireless data
transfer.
®
This is good news for the environment,
but it does create challenges for the garages
and service agents that will be called upon to
maintain these new vehicles. In particular, they
will have to deal with electrical systems that
work at much higher voltages
than those found on traditional
vehicles. One important
consequence is that, in order
to ensure safety and reliability,
insulation testing will be a
prime requirement, in much
the same way that it currently
is for electrical installations in
buildings.
In the fullness of time, standards
will undoubtedly be developed for
insulation testing on vehicles but,
for the present, there are none. That
doesn’t mean, however, that there
are no instruments available. On
the contrary, a huge range of
insulation testers is currently
available, so the problem is
more likely to be choosing
the best option for vehicle
applications.
With this in mind, it’s worth looking at
the characteristics that are desirable in
insulation testers for use on electric vehicles.
High voltage types – instruments that test at
5 kV or above – are not necessary. While they
have advantages in some applications, for
example with large railway traction motors,
they are not needed for the current generation
of road vehicles.
The physical characteristics of the instrument
are also important. For regular use it needs to
be small and light, and it should ideally
allow one-handed operation.
It should have a large clear
display, and the provision of
an analogue arc alongside
the usual digital readout is
a distinct advantage, as the
behaviour of the analogue
display can provide useful extra
information when performing
insulation tests.
Finally, the ideal insulation tester
for electric vehicle applications
needs to be robust, and to have a
good ingress protection rating –
say IP54 – as garages and vehicle
service centres can be tough
operating environments.
Instruments that meet all of
these criteria are available today
– products in Megger’s
MIT400 range being
good examples
– and it is worth
bearing in mind that they will not
only fulfil the requirements of those called
upon to test electric and hybrid vehicles, but
will also find many applications in testing
the charging stations associated with these
vehicles.
“Minakshi” and her dance troupe perform a traditional Rajasthani folk dance
Delegates from Asian and Middle East countries
recently attended a Megger technical conference
in Mumbai, India. The aim of the conference
was to provide expertise and training to
engineers working to ensure electrical supply
in the fast growing economies of the countries
in these regions.
India is a country of colourful and proud
regional traditions, and dancers from the
different regions of India showed some
amazing energy and versatility in their
performances – not accidental, since these
were two of the values that the conference
organisers wanted to demonstrate to delegates!
The conference saw the first public
demonstration in Asia of the new SMRT
test set. Experts from Megger’s relay test set
manufacturing sites in Dallas, Texas and
Taby, Sweden flew in specially for the event,
and provided some hands-on training. SMRT
is physically much smaller and lighter than
comparable three phase instruments and has
a higher output. It’s very convenient to have a
test instrument that weighs only 12 kg, with a
power box that is specifically designed to test
protective relays that are used in conjunction
with CTs having 1 A and 5 A secondaries – a
common need not only in India, but throughout Asia. SMRT has a redesigned TVI (Touch
View Interface) and works with the world
renowned AVTS relay test software, so users
get up and running in very fast time.
Delegates reported that there is substantial
programme to bring new assets on line, but
it takes time to establish the new assets, there
are inevitable teething problems and the new
test set was seen as a great help.
As with much of the rest of the world, India
has a vast resource of legacy plant which
needs to be maintained to meet the demands
of the country’s rapidly growing economy.
Bruce Buxkemper
Delegates received
demonstrates the new MPRT1 theoretical and hands-on
smart touch view interface.
training.
Questions and Answers sessions are
always popular, and some robust
discussions were the result.
Testing to address the transformer threat
If the reliability of the public electricity supply
is to be maintained in the future, routine
diagnostic testing of transformers by the power
utilities is no longer optional – it’s necessity, says
Megger, one of the world’s leading developers
and suppliers of transformer test equipment.
Megger’s opinion is reinforced by an article
recently published by Lloyds of London, the
world’s largest insurance market, which
identifies transformer failures as one of the
biggest risks to the security of electrical
supplies to homes and businesses. The article
was published at www.lloyds.com/News-andInsight
Many of the transformers in the electrical
supply network have now reached or even
passed the service lives for which they were
www.megger.com
designed, which means that the possibility
of failure is increased. Replacing defective
transformers is, however, becoming increasingly
problematic.
Limited worldwide manufacturing capacity,
coupled with strong demand from economically
buoyant countries like India and China, means
that prices are rising fast and delivery times for
the largest types are now measured in years.
Failure of a major transformer in the supply
network can, therefore, give rise to long-term
problems that are very difficult and expensive
to address.
While routine testing cannot completely
prevent transformer failures, it is a very
effective means of identifying those units that
are particularly at risk, thus allowing palliative
measures to be put in place. In some cases,
for example, it may be possible to take action
to improve the condition of the transformer,
while in other cases an at-risk unit may be
moved to a less arduous duty to extend its
useful life.
Despite the benefits, there has in the past been
some reluctance to put in place programs of
routine transformer testing on the basis of the
cost and disruption involved. These arguments
are no longer valid.
In present day conditions, if a testing program
prevents one single transformer failure, it
will have paid for itself many times over.
In addition, modern transformer testing
techniques yield accurate results rapidly and
with a minimum of disruption.
Those utilities that have not already done so
have every reason, therefore, to implement
routine transformer testing without delay and
reap the benefits of doing so. Such a program
is an affordable measure that can play a big
role in ensuring the reliability and continued
resilience of the supply network.
To assist with routine testing, Megger offers
an extensive range of transformer test
equipment. This includes dielectric frequency
response analyzers for determining the
moisture content in transformer insulation,
and sweep frequency response analyzers that
can detect electromechanical changes inside
transformers. Also offered by Megger are turns
ratio test sets, transformer oil analyzers, and
transformer ohmmeters.
Megger ELECTRICAL TESTER April 2011 3
ELECTRICAL
TESTER
The industry’s recognised information tool
Online testing with
first trip analysis
Simanand Gandhi
Applications Engineer
This is testing done on high voltage circuit breakers to evaluate their condition without taking
them out of service. Two options are available for online testing:
n
Capture the first trip test values (explained later) before removing the breaker from service for maintenance works.
n Perform a Reliability Centred Maintenance (RCM) task by closing the breaker
immediately (allowing for ionisation time) after the trip and make a close and first trip recording using a circuit breaker analyser.
Figure 3 Online first trip analysis of HV circuit breaker – typical OC recording
Based on the results obtained, an informed decision can be made about whether the breaker
can remain in service or whether it should be taken out of service for maintenance.
I C: 1 A/div
A circuit breaker in service may be in the closed position for months or even years without
tripping. In such cases, a circuit breaker analyser is hooked up to the system in live conditions,
as shown in the figure. A trip is initiated and the very first trip of the circuit breaker is recorded.
This trip recording obtained provides vital information that the classic offline tests done later will
not provide.
I B: 1 A/div
The following online tests can be carried out on site with Megger circuit breaker analysers.
Customers can select which of these they need to perform and can then connect and test
accordingly.
n
n
n
n
n
n
n
n
Coil current graph recording (three current coils simultaneously)
Coil voltage graph recording (three voltage coils simultaneously)
Three-phase load current graph recording from CT secondary
Motion trace recording of the mechanism movement (for breakers pre-mounted with motion transducers)
Auxiliary contact timing
Vibration recording
Spring charge motor current
Ambient temperature measurement
The circuit breaker analyser is taken to a live circuit breaker in a switchyard or an indoor
location. With extreme care, a fully authorised person connects the test leads as shown in the
figure. The circuit breaker analyser can be triggered remotely and this function is used so that
the operator can safely trip the breaker from control room. The analyser will start recording
with the same trigger. The recorded results should be compared with the previous reference
recordings made in the healthy condition. Deviations from the reference values will provide the
information about the condition of the circuit breaker.
I A: 1 A/div
I CIR: 5 A/div
V TCMD1: 10 A/div
0.0
5.0 10.0
15.0 20.0
25.0 30.0
35.0
40.0 45.0
50.0 55.0 60.0
65.0 70.0
75.0
Figure 4 Online first-trip analysis of HV circuit breaker – typical first-trip recording
n
n
To save time and resources
To obtain critical information from the circuit breaker
The mechanism of a circuit breaker that is in continuous service for months is likely to be stiff
because of the dried out lubricants sticking to the operating coil plunger mechanisms and levers.
Many years of experience has proved that because of this the results of a first-trip test carried
out on a circuit breaker that has been closed for a long period are often different from the
results provided by subsequent tests on the same breaker. Even though this may not be the
case for all circuit breakers in service, the first-trip results still provide valuable and critical
information that may be missed by classic off-line preliminary test methods. The lubrication
practice and environmental conditions also need to be considered. The results from vibration
analysis and coil-current graphs will almost always pinpoint any problems in a circuit breaker.
Another big benefit of on-line first-trip testing is the minimisation of outage time. The disturbance
caused on the power system because of circuit breaker maintenance work is considerably
reduced and hence the cost of testing is also substantially reduced. Whether the breaker can
subsequently remain in service or whether further analysis is needed can be decided on the
basis of the test results.
Some of the problems that can be revealed by online first-trip analysis are:
n
n
n
n
Figure 1 Online first-trip analysis of HV circuit breaker – typical connection scheme
n
n
n
n
Sticky trip latch components in the mechanism (revealed by trip coil current graph comparison)
Loose connections in the control wiring (revealed by trip/close coil current graph comparison)
Delay in trip or close initiation (revealed by auxiliary contact timing measurement)
Battery charger/battery/long distance cabling from control room to CB issues (revealed by coil voltage graph)
Sources of delay in the tripping or closing processes (pinpointed by vibration testing DTW (Dynamic Time Warping) analysis)
Sluggishness in spring or hydraulic or pneumatic operating mechanism (revealed by speed measurement from motion graph)
Sticky charging mechanism (first closed revealed by first motor current)
Difference in readings over a period revealed by ambient temperature
This is the most critical part of first-trip analysis and the part where many power engineers will
be puzzled. What is the next step if the values deviate from the last test value and the operation
of the breaker seems suspect during the first-trip analysis? Further analysis, such as dynamic
resistance measurement, multipoint vibration testing, along with timing, motion, and coil current
graph tests, should be done off line in different sequences. These tests will pinpoint the trouble
before any maintenance activity is initiated. The circuit-breaker analyser should be capable of
performing all these tests as well as first-trip analysis.
Figure 2 Online first-trip analysis of HV circuit breaker – wiring scheme
4
Megger ELECTRICAL TESTER April 2011
More than 4,500 Megger circuit breaker analysers are successfully performing circuit breaker
maintenance jobs all over the world. They can perform a complete circuit breaker analysis,
whereas many products claiming to be circuit breaker analysers provide only some of the tests
needed, which often means that more than one instrument has to be used. In spite of their
versatility, however, Megger circuit breaker analysers can be configured to suit specific requirements, ensuring that users never pay for features they don’t need. Whether it’s a 6.6 kV breaker,
a 132 kV breaker or even a 765 kV breaker, the flexible modular design of the instruments
makes it simple to configure them according to the need.
www.megger.com
ELECTRICAL
TESTER
The industry’s recognised information tool
Magnetic shielding
Dr Stan Zurek
Magnetics Technical Specialist
Shielding plays an important role in many
aspects of engineering and technology. It
can contribute to measurement accuracy,
electromagnetic compatibility (EMC), security
of signal transfer or even human safety in high
power devices. Of course shielding can be
applied to many different forms of energy,
but in this article we will focus on a just one –
low frequency magnetic shielding as a special
case of electromagnetic radiation.
The electromagnetic field can be analysed by
splitting it roughly into so-called “far field”
and “near field”. In the far field region the
electromagnetic radiation behaves just like any
other wave so similar concepts can be applied
there. The wave can be reflected, absorbed,
or passed through a medium (Fig. 1).
If the “shield” is made out of non-magnetic
material (e.g. plastic) then the magnetic field
penetrates it fully and the sensitive element
“B” is strongly affected by the field (Fig. 2a).
However, if the shield is made out of
appropriate magnetic material, it creates a low
reluctance path shunting the field away from
the sensitive area (Fig. 2b). However, we
can see that the number of field lines did
not change. The field was not destroyed or
absorbed – it could only be diverted from one
location to another.
a)
million times lower than the Earth’s magnetic
field, which makes the measurements very
difficult. Special high performance shielding
is therefore required to reduce the ambient
magnetic noise. This usually involves multiple
layers of thick high permeability material.
An example of shield capable of lowering
the Earth’s field by around 1000 times is
shown in Fig. 3. The magnetically “quietest”
place in the world is a unique shielding room
in Physikalisch-Technische Bundesanstalt in
Berlin, Germany. However, even inside that
room, which is used for research in biomagnetism, the residual field is still higher
than the magnetic field produced by the
human brain.
b)
Fig. 3. A high performance magnetic shield
made from five layers of 10 mm thick
mumetal sheets, the drum is around 1 m in
diameter
Fig. 1. Definition of shielding for far fields
However, this sort of analysis fails when
applied to magnetic field emanating from
50/60 Hz frequency equipment, and of course
from DC currents and sources like the Earth’s
magnetic field. Due to low frequency the
wavelength is hundreds of kilometres, and for
instance the reflection could happen only if
the structures were similar in size. Hence, the
“near field” effects will be dominating and
different approach is required.
In the near field the purely inductive effects
will dominate. The reflection and absorption
can be neglected and the effect of “shielding”
has to be achieved in a completely different
way. Fortunately, the “near field” effect decays
very quickly with the distance, so this type of
shielding is required in fewer situations than
the far field.
The low frequency magnetic shielding is in
some way similar to the lightning protection.
In the latter the voltages are so high that it is
impossible to electrically insulate them. So the
only solution is to introduce a low resistance
path and re-direct the dangerous bolt of
current away from sensitive areas.
Magnetic shielding uses an analogous
approach. The magnetic field cannot be
eliminated or pushed away – it can only be
directed away with passive shielding. This
is achieved by inserting a suitable low
reluctance path (an analogy of low resistance
in our example of lightning above), through
which the magnetic field is shunted away
from the sensitive area or element. The
concept is visually demonstrated in Fig. 2.
There are two elements: “A” is a wire with
current which generates some magnetic field
around it, and “B” is the sensitive element we
want to protect by putting a shield around it.
www.megger.com
Fig. 2. Illustration of magnetic shielding: a)
element “B” being affected by the magnetic
field emanated from “A”, b) high permeability
shield directs the field away from the element
“B”
By doing this, we achieved the desired result
– the sensitive element is no longer exposed
to the high field. (Actually the field still
penetrates the shield, but it is weakened
inside, proportionally to magnetic performance
of the shield.)
However, it is evident that the re-directed
energy has some impact on the shield. Some
heat will be dissipated in the shield, because
it can be magnetised to quite high levels (see
the intense colours). If the configuration is
such that eddy currents can be induced then
this might cause for the shield to reach very
high temperatures, which will have an adverse
effect on the efficiency of the whole device.
For instance, the oil tank of a power transformer is usually made of steel sheet. This
offers the required mechanical strength and
also some additional magnetic shielding.
However, the losses dissipated in the oil tank
due to the shielding effect must be taken
during the design process in order to avoid
overheating.
In very sensitive equipment, current transformers (CTs) are sometimes heavily shielded
to improve their electromagnetic compatibility
or reduce measurement noise. Ideally, the
whole CT would need to be shielded, but this
cannot be done as it would make a single
shorted turn and would render the device
useless, and probably also lead to a small
explosion of molten metal! The shield must be
simply designed to have a controlled gap so
as to avoid it acting as a shorted turn.
The most sensitive magnetic sensors can
detect activity of the human heart or even
the brain. These magnetic fields are around
In some cases superconductors are used as
magnetic shields. Under their “normal” operating
conditions (at the temperatures of liquid
helium or nitrogen) they behave like perfect
diamagnets – the magnetic field cannot
penetrate a superconductor. However, this is
actually occurring due to the surface currents
induced in the superconductors. These currents
can flow without losses for infinite length of
time and their orientation is such as to oppose
any external field. This leads to such interesting
effects as magnetic levitation, in which the
surface currents are strong enough to suspend
a substantial metal body (Fig. 4). So if something is placed “inside” a superconductor then
it will be quite well protected from the external
fields – this is therefore magnetic shielding in
its true meaning.
Swiss army knife
of testers!
Dave Moore
Product Manager
Electrical engineers and technicians working
in the industrial and utility sectors often see
multifunction installation testers as instruments
that are only of interest to contractors. That’s
unfortunate, as the best multifunction testers
are not only sufficiently versatile to meet a
whole range of day-to-day testing requirements, they are also easy to use, convenient
as they combine several testers into one small
instrument, and they offer excellent value for
money in both initial outlay and reduced
cost of ownership in calibration.
All modern multifunction testers offer facilities
for insulation testing up to 1 kV, continuity
testing at 200 mA, earth loop impedance
testing and fault current measurement across
phases, and also 3-phase RCD testing. Most
types also incorporate a convenient voltmeter function. The best instruments, however, offer even more, such as frequency
measurement, phase rotation, and the ability
to measure the resistance of earth electrodes
- functions that are definitely going to be of
interest and value to those working in industry
and the utilities.
The latest multifunction testers are also
designed to be small and light, so easy to
carry around, while fast and easy to use.
They incorporate dual displays – a digital
readout that is convenient for results that
have to be recorded in test reports, and
an analogue arc that allows many types
of test to be carried out more quickly and
conveniently. The top instruments also have
a secondary display that shows additional
useful information, such as the actual test
voltage when an insulation test is being
performed.
RCD testing, a common requirement in the
industrial sector, is easy to carry out with a
multifunction tester, and the latest instruments
can be expected to offer facilities for testing
type A, AC and S devices. Some now also
offer a pass/fail ramp test, which is a big
time saver in applications where it is only
necessary to show that the RCD trips
between pre-set minimum and maximum
limits.
Safety is, of course, always a vital concern
and it is important to remember that transient levels in industrial systems may well
be higher than in ordinary domestic and
commercial installations. When choosing a
multifunction tester for use in industry it is,
therefore, essential to ensure that it has a
CAT IV 300 V rating in line with IEC 61010.
Fig. 4. A magnet levitates above a superconductor (cooled to -200 ºC)
However, for our everyday measurement,
testing and production equipment the costs of
superconductors are prohibitive, so we need
to keep using the boring old high-permeability
materials like iron and nickel...
Finally, it is worth noting that multifunction
testers are now available with internal
memory for storing results, so that these
can be subsequently recalled to the display
or downloaded to certification software. This
eliminates the need for results to be recorded
manually, which not only saves time but also
eliminates the all-too-common problem of
transcription errors.
Clearly, the appeal of multifunction testers
is not limited to electrical contractors; they
also have much to offer for engineers and
technicians working in other sectors. It is,
therefore, well worth taking a little time to
check out the latest models, such as those in
the new MFT1700 range from Megger.
Megger ELECTRICAL TESTER April 2011 5
ELECTRICAL
TESTER
The industry’s recognised information tool
The previous part of this article provided an
introduction to the stakeless measurement
of earth resistance and looked at some
applications where this method is particularly
suitable. This second and concluding part
looks at further applications, potential sources
of error, and the benefits of stakeless testing.
If you would like to see the first part, please
email us at [email protected]
Telephone pedestal electrodes can also be
tested using the stakeless method. Cable
sheaths are all connected to an earth bar,
which in turn is connected to earth electrode.
The instrument clamp can be placed around
the cable connecting the ground bar to the
electrode to perform a test. If access is difficult
a temporary extension cable can be fitted to
accommodate the clamp.
Earth testing without the
stake – Part 2
Paul Swinerd
Product Manager
The stakeless measuring technique is well
suited to testing earth electrodes installed
within primary cross-connection points, which
are sometime called street cabinets or flexibility
points (Figure12). These electrodes typically
need to have a resistance below 25 Ω. In this
application there may only be two parallel
earth paths in series with the electrode. However, provided that the stakeless method gives
a result below 25 Ω, then the resistance of the
electrode itself must certainly be below 25 Ω.
Figure 15 - Telephone pedestal
Figure 12 – Street cabinet
Potential sources of error
When applied correctly and a good quality
instrument is used, the stakeless method gives
very reliable measurements. Nevertheless, it is
well to be aware of factors that may introduce
errors. Among these are:
A very similar application is cable TV street
cabinets
Figure 13 shows the stakeless technique
being used at a remote switching site. In
this application, the object of the test is not
to measure the earth resistance but to verify
earth connections. By recording the test results
and trending these over time, it is possible
to identify the onset of problems such as
corrosion.
Figure 13 – remote switching site
Cellular sites/microwave and radio towers are
another good application for stakeless earth
resistance testing. Figure 14 shows a typical
four-leg tower. Each leg has been individually
earthed and connected to a buried copper
ring. As with the remote switching site, this
test is used to verify an electrical connection,
and is not a true measurement of earth
resistance.
Switchyard and substation earths are yet
another good application for stakeless testing.
The method is ideal for checking connections
to earth mats, but caution needs to be exercised
over possible interference from induced
ground currents.
Substation and switchyard metal fencing
connections to earth mats can be easily
checked for continuity using the stakeless
method.
Stakeless testing is very useful to transformer
test engineers. Pad-mounted transformer earths
can be readily verified. However sometimes
there are a number of connections to the same
electrode. In such cases, it may be necessary
to clamp around the electrode itself, below the
connections.
Poor understanding of the circuit under
test
Remember the two rules of stakeless testing:
n There must be a loop resistance to measure.
n The earth path must be included in the circuit unless the test is being carried out solely to verify a connection.
Dirt trapped in the clamp head
n Dirt trapped between the closing faces of the clamp will modify the magnetic
circuit. The result will be false low readings and, in some cases, this could
result in a poor electrode being measured as good.
n Many instruments use interlocking laminations (teeth). These trap dirt and are difficult to clean. They are also easily damaged. Damaged teeth will produce inaccurate measurements and may even render the instrument unusable.
Noise currents affecting measurement
n In noisy environments, high noise currents may be flowing in the electrode under test. This can cause readings to fluctuate making them difficult to interpret or, if the noise current is too high, it can make measurement impossible. To avoid these problems, clamp-type earth resistance testers with good noise immunity should be used.
The benefits of stake-less earth resistance
testing
n Tests can be carried out without dis connecting the earth electrode from the system. This method is, therefore, safer and less time consuming.
n Loop testing includes bonding and grounding connections. Because of this, it identifies poor continuity anywhere in circuit
earth current. If an electrode is to be disconnected, the instrument can be used prior to disconnection to measure the current flowing in it, thereby confirming whether or not it is safe to proceed.
It is worth noting, however, that the results
from stakeless measurements will rarely be
the same as those obtained with a three-pole
instrument, as the stakeless test is technically a
loop resistance measurement. In applications
with only one or a small number of return
earth paths the measurement may be higher
than the expected electrode resistance limit. In
this case the stakeless method is still a useful
tool to identify changes over time.
The benefits of Megger instruments
The latest Megger digital clamp-type earth
resistance testers, models DET14C and
DET24C, offer a number of additional benefits.
These include:
n
n
n
n
n
n
Elliptical clamp with a slim profile, which
facilitates access to earth straps and electrodes in pits.
Large clamp capacity, allowing tapes up to
50 mm wide as well as electrodes and cables up to 39 mm in diameter to be easily accommodated.
Low maintenance flat jaw faces, with no interlocking teeth that easily become bent and damaged.
CATIV 600 V safety rating in line with IEC 61010. This is the highest safety rating currently available for an instrument of this type.
Auto-current measurement safety feature
that provides an instant warning if current exceeds a user-set limit.
Automatic noise filter function that reduces the effect of noise current in electrically noisy environments such as substations.
n
Figure 14 - Cellular sites/microwave and
radio tower
6
Figure 16 – Pad mounted transformers
Megger ELECTRICAL TESTER April 2011
There is no need to drive auxiliary test
spikes into the ground, so testing can be carried out easily in locations with hard
ground or concrete surfaces. There are
also timesavings as there is no need to run out test leads.
n Clamp-type earth electrode resistance
testers can also be used to measure
The most common reason given by users for
not being able to use the stakeless method is
poor access. Often cable or tape sizes are too
large for the clamp. Until now 50 mm wide
earth tapes could not easily be tested. To
circumvent this problem, some users resorted
to cutting the tape and welding in a round
cable to make their earth clamp testers usable.
This time-consuming procedure is not required
with the Megger DET14C and DET24C clamps
as their elliptical heads can accommodate
50 mm tapes with ease.
www.megger.com
ELECTRICAL
TESTER
The industry’s recognised information tool
Accuracy
built-in
manufacturers of the testers quote accuracy
levels for their products. For example, a
particular tester may be specified as providing
Accuracy Level III or even Accuracy Level IV.
These levels define the accepted maximum
deviation from baseline measurements and
therefore guarantee that the required level
of accuracy is achieved for the test being
performed.
The acceptable accuracy limits vary by
frequency. To give an example, Level III
accuracy is specified by the standards for
CAT 6 installations, whereas for CAT 7
installations, Level IV accuracy is required.
Note that Level IV accuracy is superior to
Level III, so instruments with Level IV
accuracy can be used in all applications
where Level III accuracy is specified. There
is absolutely no need to buy a tester with
Level III accuracy for use on CAT 6 systems
and another with Level IV accuracy for use
on CAT 7 systems, since the higher level
of accuracy is always indicative of a closer
match to baseline measurements.
Bryan Phillips
Market Development Manager
Anyone who buys test equipment can reasonably
expect it to give accurate results but, in this
context, what exactly does accuracy mean?
Purchasing decisions are often made without
examining in detail the specification of an
instrument, but it is always worth bearing in
mind that the accuracy specified for an
instrument has a big impact on its usefulness
and, ultimately, its capabilities.
When looking for LAN certification equipment,
this issue is even more crucial, as the testing
of networks is carried out to confirm that
those networks will deliver certain specified
performance levels. Fortunately, when the
network test standards were formulated,
much thought was given to accuracy and,
as a result, accuracy requirements were
incorporated into all published standards.
When purchasing a LAN tester, therefore,
it’s most definitely worth choosing an
instrument that meets or, like the Megger
SCT2000, exceeds the requirements for
Level IV accuracy, as this guarantees maximum versatility and the best possible future
proofing. If you choose such an instrument,
you can be certain that, when you carry
out network certification, your work has
accuracy built in!
In order to allow the users of LAN testers
to relate the performance of their instruments
to the requirements of the standards, the
Visit Megger in
Hall 12
Stand E37
Georg Halfar
Market Communications Manager, Germany
Training
a la carte!
Good training is essential if utility staff are to
work safely and efficiently, but releasing staff
for training costs money. And that money is
not particularly well spent if the training they
receive is only partly relevant to their work. If
this sounds as if it’s an unlikely scenario, think
again! Many training providers offer a regular
programme of courses with predetermined
The training can be provided either at the
content.
customer’s premises or at Megger’s comprehenThat sounds fine in principle, but the content sively equipped training centre in Dover. The
workshops currently available have been careoften isn’t a very good match for the requirefully
tailored to suit the utilities sector and are:
ments of those attending. Some may be
interested, for example, by the topic that’s
•
Diagnostic insulation testing
covered in the morning but have very
•
Transformer testing
little need to learn about the afternoon topic,
Protection testing
while for other attendees the situation may be •
•
Earth testing
exactly vice versa. Either way, such a course
Cable fault location
is not an efficient use of the trainees’ valuable •
•
Power quality testing
time, nor of hard-pressed training budgets.
•
Introduction to 17th testing
•
Portable appliance testing
So what’s to be done? After extensive
•
Battery testing
discussions with its customers, Megger has
developed a new “à la carte” training service
All of the workshops are delivered by
to solve this problem.
experienced engineers, and all have a high
level of hands-on practical content. Megger
Users of the service simply choose from a
will also be pleased to discuss requirements
menu of training workshops that can be
for custom workshops on subjects not covered
delivered in any combination; currently there
are nine different workshops to choose from. in the list above. Further details of the training
The time needed for each workshop is clearly workshops and how they help users to make
the best use of staff time and training budgets
shown on the menu, so it is easy to work
can be obtained by calling the Megger support
out whether the required training can all be
delivered in half a day or whether a full day – team on 01304 502101, or by sending an email
or even several days, consecutive or separate to [email protected]
– will be needed.
www.megger.com
Hannover Messe is the world’s biggest industrial tradeshow. This year, the organisers are
expecting 6,000 trade stands and over 200,000 visitors. Hannover Messe acts as an umbrella
for 13 international tradeshows, and while exhibitions in other parts of the world have declined, this one seems to grow during periods of recession and growth. Megger’s stand this
year will be in hall 12 stand. You will be able to see these new products on the stand and
talk with Megger’s technical experts about how they could be used in your business.
MOM2 microohmeter
DET14c and DET24c earth clamp
MIT1020/2 10 kV Diagnostic insulation resistance tester
DET3TD earth ground resistance testers
BITE3 Battery Impedance test equipment
OTS60/80PB Oil test set
TT300 series Transformer turn ratio test equipment
PFL40 Cable fault location system
MCT1605 Multi-Tap Automatic Current Transformer test set
FRAX 150 SFRA Frequency spectroscopy analysers
We will be delighted to see you – and if you complete and bring along this
coupon, you can collect a free Megger hard hat conforming to EN397 from
the stand!
Name ................................................................................................................................
Position................................................................. Company...............................................
Address..............................................................................................................................
Country................................................................ Post Code..............................................
Telephone...........................................................................................................................
Email .................................................................................................................................
Megger ELECTRICAL TESTER April 2011 7
ELECTRICAL
TESTER
The industry’s recognised information tool
Q&A
In this issue, Megger’s technical support
group experts tackle some rather general
but surprisingly common questions
relating to installation testing in
commercial and industrial buildings.
Q: In addition to performing tests on power
systems, my team and I are often asked to
carry out routine tests on ordinary building
electrical installations, so what’s the best type
of instrument to use?
A: Although some engineers who regular
carry out installation testing prefer to use
separate instruments for each of the main
tests involved, the most popular solution is a
multifunction tester. This provides, in a single
instrument, facilities for all of the tests needed
to certify an installation in line with current
regulations. Modern multifunction testers are
compact, dependable and easy to use.
Q: Do these testers have any facilities for
working on three-phase systems?
A: Most of them don’t, but there are a few
exceptions. Some of the latest, for example,
Safety in
Testing –
Part 3
Jeff Jowett
Applications Engineer
Parts 1 of this article, which dealt with general
considerations, CAT ratings and safety in
insulation testing, and Part 2, which dealt with
test leads and multifunction testers, appeared in
previous issues of Electrical Tester. If you missed
these parts, email us at [email protected]
com. This third and final part considers safety
in relation to ground testers, and the particular
safety hazards associated with high-voltage
testing.
Ground testers don’t get a lot of attention in
safety discussions because grounds tend to
be out of sight, out of mind. But grounding
electrodes can come on line and can also
carry surprising levels of constant current.
Older testers produced higher voltages and
currents to allow accurate measurements to be
made in widely varying soil types. Geophysical
models still use high voltages and currents,
but for normal tests on electrical grounding,
microprocessor sensitivity has permitted test
voltages and current to be brought down to
much safer levels.
Electrical systems can now also be tested
while on line without interference. But danger
to the operator can occur if the system being
tested comes on line, as it might during a fault
when the tester and its leads could become
part of the clearance path. The best protection
resides with safe working practices, such as
the use of insulated boots, gloves and mats, as
defined in standards such as those of the IEC.
It is also a good idea to check for current
before connecting to test. A clamp-on
ammeter is a simple and effective way to do
this, and modern ground testers sometimes
come with built-in current clamps.
The more an instrument eliminates opportunities
for error, the better the safety program will
perform. As an example, the greatest safety
challenge comes in high-voltage maintenance,
where hotline poles and voltage detectors
must first be employed to determine that the
test item is in fact de-energized. The detectors
indicate voltage by visual and audible signals.
They should be ready to operate at all times,
can check phase rotation and have facilities for
testing three-phase RCDs in installations where
a neutral is not available. When working on
three-phase systems or indeed on single-phase
systems close to the point where the supply
enters the building, the CAT rating of the
instrument needs to be given careful attention.
In general an instrument rated CAT IV 300 V
or better should be chosen, as this is safe to
use on all parts of low voltage installations.
Q: Apart from the features routinely needed
for installation testing, do multifunction
instruments typically offer an “extras” that
might be useful?
A: Almost all will offer facilities for measuring
voltages and some for checking supply
frequency. The latest models, however, like
Megger’s new MFT1730, can also be used to
with no on/off switches that could be forgotten.
Industry practice is to first test the tester, so
that an inoperative unit won’t be mistaken for
a lack of voltage on the circuit under test. A
built-in test circuit facilitates this life-saving
check. A green light should then remain on
to indicate that the unit has been checked.
This protects the operator from picking up the
wrong unit after, say, putting the tested one
down to put on gloves. The test is performed
on the supposedly de-energized circuit, and
then the tester is tested again. This prevents a
unit that was damaged by the performance of
the test from being returned to stores. This is
the kind of redundancy that is necessary for
assured safety.
Safe working distances must also be maintained when approaching energized lines to
prevent arcing to the worker, and the indicators
may have collapsible poles with markings for
safe distances from different voltages across
the range that the indicator covers. These
poles also must be regularly maintained
against cracks, dirt and corrosive materials that
could facilitate current flow along the pole.
In conclusion it is important to note that no
matter how good, the instrument’s safety
features are only ever a second line of
defence. A well-trained and alert operator is
the most important part of electrical safety,
with a well-designed instrument providing the
necessary redundancy.
Pylons in
dresses!
Before Elena’s ideas could be translated into
reality, however, eighteen months of study
were needed for, among other things,
technical validation of the proposed methods
for transforming the towers and the selection
of suitable materials that would ensure the
sustainability and resistance to degradation of
the installations.
8
The past of
PowerDB
Mark Meyer
Product Manager
In our regular series of articles looking at
the histories of the many companies that
form the core of today’s Megger family, the
focus this time falls on PowerDB. Although
PowerDB is one of the youngest family
members, its influence is having a big impact
on a wide range of Megger products,
particularly those aimed at users in the
power sector.
PowerDB has its roots in Optima Systems,
a company started in 1994 by Bruce
Buxkemper who had previously worked for
Megger in Dallas as a software developer.
Located in College Station, Texas and with
strong connections to the Texas A&M
University, Optima Systems initially focus
ed on developing automation systems and
software for industry.
In the late 1990s, the company won a
contract from Megger to develop the
company’s AVTS software, a powerful yet
easy to use package that complements
Megger protection relay test sets.
By the turn of the century, Optima Systems
was also hard at work on an important
project of its own – the development of
PowerDB, a new software system that would
provide a common user interface and uniform results handling facilities across a wide
range of power instruments. This groundbreaking concept generated widespread
interest and PowerDB was launched in the
USA to considerable acclaim in 2002.
For many engineers, the transmission towers
that span the countryside are works of art in
their own right, but for installation artist
Elena Paroucheva, who lives and works in
France, these towers were just the beginning.
In her work, Elena searches for connections
between art, energy and the environment, and
she saw that transmission towers provided her
with, in effect, a blank canvas that she could
use to develop and display these ideas.
Accordingly, she entered into discussions
with RTE, the organisation responsible for
the French electricity transmission network,
and after two years of negotiation, she was
granted permission to transform the
appearance of four high-voltage transmission
towers on the 225 kV line between the French
cities of Amnéville and Montois. RTE also
sponsored and supervised her work.
measure earth electrode resistance. This is
an increasingly common requirement in
photovoltaic and other types of “green”
energy systems and, indeed, in power
installations. Another useful feature provided
by some multifunction instruments is internal
results storage, with facilities for Bluetooth
wireless download to a laptop computer or
even a smartphone. The best units of this
type are complemented by software that
automatically fills in the test certificates as the
results are received by the laptop or smartphone. This saves a lot of time as well as
eliminating the errors that are almost
inevitable when the certificates are filled out
by hand.
Examples of Elena Paroucheva’s work
Ultimately Elena Paroucheva started work on
her metamorphosis of the transmission towers
in August 2001 and completed it by December
2003. The project was no minor undertaking –
in total it used 3,284 m of steel cable, 2,708 m of
stays, 525 m of plastic canvas, 576 m of steel
tube and 40 light projectors that are
controlled via a satellite communications link.
For this project, which has been much
admired by the public in general and by the
art world, Elena has received widespread
recognition, including most recently the
laureate award for Science and Technology in
European Art in a competition organised by
SUPELEC within the framework of the French
Presidency of the European Union.
The title of the project is “Source – A Monumental Artwork” and the
themes for the four transmission towers are
“Source – Light”, “Source – Water”, “Source –
Energy” and “Source – Flame”. As the pictures
accompanying this article show, the results
she has achieved are both inspirational and
impressive.
Much more information about Elena Paroucheva’s
unique “Source” project can be found on her
website at www.art-elena.com, and there can
certainly be no doubt that she has made her
own rather special contribution to the art of
power transmission!
Megger ELECTRICAL TESTER April 2011
In 2005, Optima Systems was purchased by
Megger, an arrangement that has made it
possible for the PowerDB system to be sold
and supported in markets worldwide, and
also provided access to the resources needed
for its continuing development. Following its
purchase by Megger, Optima Systems
became PowerDB Inc., a Megger subsidiary.
From its early days as a one-man operation,
PowerDB has now grown to employ many
more fulltime staff and continues its partnership with Texas A&M University by regularly
giving experience to interns. Its primary
focus is on the PowerDB system, which is
now available in a range of implementations
including an on-board version designed
for total integration with instruments. The
company continues, however, to develop
other innovative hardware and software
solutions for industry.
www.megger.com