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1 www.megger.com ELECTRICAL TESTER - August 2016
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Tesla P8
Published by Megger August 2016
Continued on page 2
Distribution network operators (DNOs) are facing
a tough challenge. They need to offer speedy
and reliable connections for a diverse range of
renewable energy sources, but at the same time
they must protect the reliability of their networks.
In the UK, the RIIO-ED1 regulation and price control
package from Ofgem, the government regulator
for the gas and electricity markets, means that if
they get it wrong they will potentially suffer severe
financial penalties.
The very nature of power generation and
distribution is changing, and this is creating a
real headache for DNOs. They have a distribution
network that was designed to accommodate
a comparatively small number of large power
stations, and are now having to adapt this to the
world of embedded generation, where a large
number of small power sources is the norm. The
changes required are by no means trivial, especially
as they must be accomplished while the network
remains fully operational, reliably delivering energy
to the DNOs’ customers.
It is clear that substantial investment may be
required, but DNOs operating in the UK are
comparatively well placed when it comes to
securing this investment. The energy market in
the UK is stable, and energy supply is a privatised
industry with established regulatory processes.
These factors make investments in energy
infrastructure an attractive proposition.
Nevertheless, DNOs will still have to demonstrate
that they can produce an attractive return on this
investment which, to put it bluntly, means that they
have to operate profitably. And their profitability is
now almost completely dependent on RIIO-ED1,
Ofgem’s regulation and price control instrument.
RIIO is an acronym for Revenue = Incentives +
Innovation + Outputs, a formula that neatly
encapsulates its intentions. In Ofgem’s own words,
these are “to drive real benefits for consumers,
by providing companies with strong incentives
to step up and meet the challenges of delivering
a low carbon, sustainable energy sector at value
for money for existing and future consumers.”
RIIO-ED1, which applies to the energy distribution
sector, came into force in April 2015, and will
remain in force for eight years.
Energy pricing is regulated by Ofgem and rises are
capped, so DNO revenue depends almost entirely
on RIIO. Innovation and outputs are measured, and
RIIO-ED1 has attractive incentives for exceeding
the targets. These are set for many aspects of
performance including customer satisfaction, safety,
network reliability and availability, environmental
impact, social obligations and connection terms.
Incentives are provided for speed of connection
and for customer engagement, factors that have
a particular relevance in relation to new energy
sources. Generating over-capacity in the UK
network in 2014 was around 6%, but a programme
of closing old environmentally damaging coal-fired
Damon Mount - Power sales manager
Between a rock and a hard place
Embedded or distributed generation schemes,
where a local generator is connected directly to the
distribution network, are becoming widespread.
The operators of these schemes face an important
challenge: how to ensure that the system behaves
safely and predictably if the local generator
becomes isolated from the network – a condition
known as islanding.
There are numerous potential hazards associated
with islanding, not the least of which is that engineers
working to restore the network connection may not
realise the system is still powered. Another hazard
is that the generator may continue to supply local
loads but, without support from the network, this
may result in it being heavily overloaded.
The solution usually adopted to address these
hazards is to immediately shut down the
islanded generator, but this can only be done if
a fast and dependable way of detecting islanding
is available. Many approaches are possible,
but one that is widely used is rate of change
of frequency (ROCOF) protection, which
has established a reputation for responding
faster and more reliably than alternative
protection techniques.
ROCOF protection relies on the fact that once a
generator is islanded, its output frequency will
no longer be locked to that of the network, but
will change rapidly to a frequency determined by
its own characteristics and those of the loads it is
still supplying. It is this change in frequency that is
detected by ROCOF protection devices.
ROCOF protection conforms to engineering
requirements such as G59/3 in the UK and
standards such as ANSI 81R in the USA. There
are strict guidelines for ROCOF settings and
unless these are optimised, the protection may
unnecessarily trip a generator when problems
Get your ROCOF right!Lennart Schottenius - Support Specialist
Niclas Wetterstrand - Program Manager
occur with the power network, and the resulting
loss of capacity may make the problems worse.
To help guard against this situation, G59/3
was revised in 2014 to require new settings for
ROCOF protection when used in conjunction with
generators connected to the UK power network.
The grace period that was granted for adoption of
the new settings in conjunction with certain classes
of equipment expires in July 2016. After this date,
ROCOF protection for all generating sites with a
capacity in excess of 5 MW that are connected to
the UK power network must comply fully with the
new requirements.
The foregoing makes it clear that a reliable method
of checking the settings and accuracy of ROCOF
protection is essential. Suitable functionality is
provided by Megger’s innovative three-phase
Sverker 900 instrument, which has been conceived
as an engineer’s multifunction test box for
protection testing.
This novel instrument does not need to be
connected to a PC and features an intuitive user
interface with a colour touchscreen. This provides
access to a wide range of pre-configured virtual test
instruments, allowing the required test function
to be selected quickly and easily. Full manual
control and configuration are also supported and,
in addition to the touchscreen, the Sverker 900
is provided with a large rotary knob that can be
configured as required to control the voltage and
current generators.
When testing ROCOF protection, the Sverker 900’s
ramping instrument is used. Because this generates
a very smooth and accurately controlled ramp, this
has proved to be an excellent and dependable tool
for these tests. The instrument is easy to configure
for ROCOF testing and, once the start and stop
criteria have been defined, it can be used to check
the operation of low and high level trips and also
to verify the trip time delay set for low and high
level operation.
Detailed guidance on ROCOF testing with
the Sverker 900, including information about
connections and instrument settings, is available
in the form of an application note. This can be
obtained free-of-charge on request from Megger,
or it can be found on the Megger website
(www.megger.com).
Rescuing refineries P6
Unfazed by 3 Phase P2
2 ELECTRICAL TESTER - August 2016 www.megger.com
The industry’s recognised information tool
ELECTRICALTESTER
Contents
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by them in accordance with the Copyright, Designs and Patents
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Electrical Tester by such owners.
Editor Jill Duplessis
Megger Limited
Archcliffe Road Dover Kent CT17 9EN
T +44 (0)1304 502100
www.megger.com
Between a rock and a hard place ....................p1,2
Damon Mount - Power sales manager
Get yor ROCOF right ...........................................p1
Lennart Schottenius - Support Specialist Niclas Wetterstrand, Program Manager
Three-phase support for substation test ...........p2
Matz Ohlen- Director transformer test systems
Turns ratio testing: Hand crank
versus automatic .................................................p3
Jill Duplessis - Global technical marketing
manager and Editor
Power Quality: Some Fundimentals ................p4-5
Andy Sagl - Product manager
Exhibit A: Megger hand cranked
insulation test set ................................................p5
Andrew Dodds - Group Technical Director
PD measurement saves refinery millions ........P6-7
Alexander Lüpschen - Asset Consulting Engineer, Koopmann Energie und Elektrotechnik
Wind farm cable failure averted! ........................ P7
Javier Luiz Leiva - Mexico Area Sales Manager Washington Cabrera - Regional Sales Manager, Mexico
Questions and Answers - Earth resistivity .........p8
Tesla and the Pigeon of death ...........................p8
Keith Wilson - Electrical engineer
Reminder: Knowhow delivered online .............p8
power stations and end-of-life nuclear facilities
means that the figure for 2015 was just 2.1%. The
intention is that the new small-scale generators will
fill this gap.
The RIIO-ED1 mechanism does not, however,
depend on incentives alone; there are also penalties
for DNOs who miss their targets. Performance
is reviewed retrospectively using agreed key
performance indicators (KPIs). Assessment criteria
include speed of connection, results of customer
surveys and views from stakeholders. Based on the
reviews, the Ofgem panel has the power to impose
penalties of up to 0.9% of a poorly performing
DNO’s revenue, and also to order it to make GSOP
(guaranteed standards of performance) payments
to customers for late delivery of services.
A key factor in determining the profitability of a
DNO is clearly its ability to handle new connections
quickly and efficiently without compromising
network performance. To help with this, the UK
Engineering Networks Association has produced a
series of Engineering Recommendations (ERs).
ER G81 provides a framework and guidance for
the installation and connection of commercial
and industrial loads. The applicant (that is, the
consumer) is responsible for the design, installation
and testing, along with the supply of all records
and documentation, while the DNO is responsible
for approving the design, defining the tests that
are needed, and providing the connection to
the network. ER G59/3 provides similar guidance
for the connection of distributed generation to
the network.
These ERs include examples of tests that the DNO
may require the consumer to perform before
providing a network connection, but these are very
general. ER G81, for example, states that tests must
be carried out “to verify the complete installation
has been installed correctly and is safe to energise.”
Wise applicants will, therefore, look to CIGRE
and even IEEE standards for further guidance, as
well as considering new test methods, such as
partial discharge analysis for cables, that provide
dependable results while saving time and money.
Being able to provide the DNO with comprehensive
and reliable test data will be increasingly important
since connecting an installation that does not
operate as expected may impact network
performance, leading to the imposition of financial
penalties on the DNO. With this in mind, the
DNOs can understandably be expected to take the
line that, “If you can’t prove that you’ve carried
out all of the necessary testing correctly, we won’t
connect you.”
This article has focussed for the most part on new
connections to the distribution network, but it is
important to remember that these are not the only
criteria against which the DNOs are measured,
nor are they the only factors that impact network
reliability. To ensure profitable operation, the DNOs
also need to monitor and care for key assets that
include transformers, circuit breakers and cables.
For all of these, regular testing is the key to
maximising availability and service life while
reducing as far as possible the risk of unexpected
failure. This is particularly beneficial for power
cables as poor joints and ageing insulation are
among the most common causes of failure and
downtime in power networks. However, modern
test methods can readily identify incipient problems,
allowing them to be remedied before they lead to
cable failure.
To cope with the move toward sustainable energy
from renewable resources, which means that huge
numbers of small generators are requiring new
grid connections, energy networks are currently
evolving faster than they have ever done at any
point in their history.
This presents DNOs with many challenges, but RIIO-
ED1 means that those who successfully address
these challenges have excellent opportunities
for financial reward. While it may not at first be
apparent that testing is a key element to achieving
this success, consideration of the points raised in
this article will hopefully demonstrate that testing
really does have a crucial role to play.
Engineers whose work involves testing in
substations face two important challenges. The
first is having the right equipment at hand to carry
out the wide range of tests that are often required,
and the second is carrying out those tests safely and
as quickly as possible, so as to minimise downtime
and cost. The recent appearance in the market of
versatile integrated substation test systems in the
Megger TRAX range has done much to help hard-
pressed engineers address these challenges.
These high-performance test sets have been
specifically designed to offer a convenient and
comprehensive solution for transformer and
general substation testing. They are capable of
performing more than 20 different test functions,
including measurement of winding resistance,
turns ratio, excitation current, short-circuit
impedance, tan delta / power factor, capacitance,
frequency response of stray losses, CT and VT
testing, and circuit breaker timing and motion
analysis. Clearly, when one of these novel test sets
is available, ensuring that all of the necessary test
equipment is at hand is no longer a challenge!
TRAX test sets also significantly reduce the time
taken to perform tests. They have an intuitive user
interface that offers full manual control or guided
testing using the built-in TRAX apps. Each of
these apps implements a specific test function –
for example, turns ratio measurement or winding
resistance measurement – and automatically
configures the instrument for the selected test.
All unnecessary information is removed from the
display, with only information relevant to the
test in hand remaining. This app-based approach
makes TRAX test sets safe, fast and easy to work
with as well as eliminates the need for extensive
user training.
But even the best can be made better! Until now,
one limitation of the TRAX test sets was that when
they were being used to test three-phase assets such
as transformers, it was necessary to change the test
connections after testing each of the phases.
In principle this isn’t a major issue, but in practice
it quickly becomes an annoyance, and the time
taken to change the connections soon adds up,
especially if those connections are on top of
transformer and every change means climbing up
and down a ladder!
With this in mind, Megger has introduced
the TSX130 three-phase switchbox. Available
as an optional accessory for all TRAX test
sets, this new unit allows three-phase
transformers to be conveniently tested without
the need to reconfigure the test lead connections
for each phase. An added benefit is that
switching between phases is controlled by the
test set, which means that test sequences can
be automated.
At the same time, Megger has further extended
the versatility of the TRAX system by launching
another invaluable accessory, the TDX120, which
facilitates the use of the test sets to perform tan
delta and capacitance measurements.
Despite the wide range of functions offered by
TRAX test sets, they are exceptionally light and
compact. The TRAX220, which has a maximum
AC current capability of 200 A, is the lightest test
set of its type, weighing just 32 kg in its transport
case, which means that it can be transported by air
as check-in luggage.
These innovative test sets can generate and measure
a wide range of currents and voltages with high
precision. While the TRAX220 has a maximum AC
current output capability of 200 A, the TRAX280
extends this to 800 A. The output current capability
of both units can be further extended to 2000 A
with an optional current booster.
Other key features of Megger’s new and innovative
TRAX test sets include state-of-the-art transformer
winding resistance measurements with true DC test
currents up to 100 A and up to 50 V compliance
voltage; dynamic on-load tap changer (OLTC)
measurements; and exceptional interference
suppression to secure accurate readings even in
high noise switchyards.
A wide operating frequency range of 5 to 500 Hz
(1 to 500 Hz for tan delta measurements) is also
included, as is individual temperature correction of
tan delta measurements using Megger’s patented
technology; and automatic voltage dependence
detection, which is another unique feature covered
by Megger patents.
Today’s substation engineers are under constant
pressure to work faster and more efficiently while
maintaining the highest standards of safety. The
new integrated substation test sets, of which
the Megger TRAX instruments are the leading
example, make it possible to respond positively to
this relentless pressure.
Three-phase support for substation testMatz Ohlen - Director transformer test systems
Continued from page 1.
When you have finished with this magazine please recycle it.
3 www.megger.com ELECTRICAL TESTER - August 2016
The industry’s recognised information tool
ELECTRICALTESTER
Figure 1. Equivalent circuit diagram for a transformer with no load
Turns Ratio Testing: Hand crank versus automaticJill Duplessis - Global technical marketing
manager and Editor
A transformer turns ratio test provides a quick
verification of the most fundamental operational
characteristic of a transformer – its ability to
transform voltage as anticipated. In doing so, the
test provides invaluable reassurance to the operator.
Open- and short-circuit conditions in transformer
main and tap windings may cause the transformer
turns ratio to change and therefore this test is at
once providing useful diagnostic information.
Engineers have noted, however, that traditional
“hand-crank” TTR instruments sometimes give
values for turns ratio that are different from those
given by modern automated TTR instruments.
Indeed, many insist that the traditional instruments
provide results that are more dependable. But is
this actually true? And why do the instruments
produce different results?
Background
To answer these questions, let’s start by considering
an ideal transformer. For such a transformer, the
ratio of the terminal voltages (that is, the field-
measured no-load voltage ratio, V1/V2) equals the
true ratio of the number of turns on each winding,
N1/N2 – the ratio of transformation. This is not true
with a real transformer. Here’s why.
The turns ratio is equal to the ratio of the voltages
induced by the resultant mutual flux (E1/E2) when
a transformer is energized. The voltage induced in
a single turn is the same irrespective of whether
it is part of the primary or part of the secondary
winding, so the total voltage induced in each of the
windings by the common flux must be proportional
to the number of turns. That is E1/E2 = N1/N2. But in
a real transformer, E1, the primary induced voltage,
does not exactly equal the applied voltage, V1. In
fact, V1 is equal to the phasor sum of E1 plus the
primary leakage reactance voltage drop due to
the exciting current plus the voltage drop due to
the resistance of the primary winding multiplied
by the exciting current (Figure 1). The ratio of
transformation is therefore only approximately
equal to the ratio of the primary and secondary
terminal voltages, e.g., the “voltage ratio” as
termed in IEEE C57.152-2013.
In all real transformers, the no-load voltage ratio
(measured in the field) is less than the transformation
ratio (i.e., the turns ratio). This is because real
transformers have losses and magnetic leakage,
and they require excitation. Consider, for example,
the ratio of primary to secondary currents. Both
currents exist together only when the transformer
is serving a load so put aside the ratio testing
concept (a no-load test) for a moment. Primary
current, i1, is the sum of an exciting component,
iex, and a load component, iL. The ratio between
the secondary current, i2, and the load component,
iL, of the primary current is given by:
N1iL = - N2i2 (1)
This can be rewritten as:
N1/N2 = - i2/iL (2)
where the turns ratio = N1/N2, iL = i1 - iex, and iL is always < i1
For an ideal transformer, N1/N2 = i2/i1 (present at
the terminals), but for a real transformer, the actual
turns ratio (given by equation 2 and which cannot
be directly measured) is greater than the ratio of
the terminal currents (voltages).
In general, where transformers have large leakage
reactance, high magnetising current, high primary
resistance or a combination of these, a higher
error will be introduced into the measurement of
the turns ratio because these factors increase the
difference between V1 and E1.
Measuring techniques
Now let’s look at turns ratio measurement
techniques. An automated TTR instrument
measures the voltage applied to the primary
winding terminals and the resulting voltage at the
secondary terminals. The instrument calculates the
ratio of these voltages and presents this as the
transformer turns ratio.
Hand-crank turns ratio instruments work in a
different way. The test set is arranged so that
the transformer to be tested and the adjustable
ratio reference transformer within the test set are
connected in parallel and excited from the same
voltage source (see diagram). This measurement
technique is called a “transformer bridge”
measurement.
Note that the instrument normally excites the
transformer under test from its secondary (low
voltage) windings. The “secondary” windings
(which, in the case of the transformer under test,
is actually the primary winding) are connected in
series opposing through a null detector.
When the ratio of the reference transformer is
adjusted so that no current flows in the secondary
circuit, as shown by the null detector, two
conditions are simultaneously fulfilled. The first
is that the voltage ratios of the two transformers
are equal and the second is that there is no load
on either transformer. The no-load voltage ratio of
the reference transformer is known, so the voltage
ratio of the transformer under test is known, and
its turns ratio is therefore also known.
The main source of error with this method is that
the primary induced voltage in the transformer
under test, EX, and the primary induced voltage
in the reference transformer, ET, are likely to be
slightly different. Although the same voltage, Vo,
(e.g., 8 V) is applied to both transformers, the
reference transformer and the transformer under
test will have different characteristics, which
means that, in general, EX and ET will not be the
same. When the reference transformer and the
transformer under test both have the same turns
ratio – that is, when the null detector senses no
current flow – the secondary voltages of the
two transformers will also differ by this same
percentage error.
Note that the difference between ET and EX,
however, will always be less than the difference
between ET or EX (whichever is the smaller) and
Vo (which represents the error with the automatic
method). Also note that in some cases the
difference may be small, in which case the error in
the measured turns ratio will also be small. In fact,
where the transformer under test has the same
characteristics as the reference transformer, the
error in the turns ratio will be zero. For this reason,
TTR reference transformers are designed to match
typical distribution and power transformers.
Why choose automated over hand crank?
Transformer manufacturers provide true turns
ratio (N1/N2 or E1/E2) on the nameplates of their
products and for some transformers, a hand
crank TTR will give a result closer to this ratio
of transformation than measuring the terminal
voltages of the windings. Note, however, that
some users claim the hand-crank model provides
limited resolution on typical transformer ratios
such as 20/1.
If a transformer core is not of an optimum quality,
as is sometimes the case, the error in the ratio
measured with an automated test set will be
greater than the error in a measurement carried
out with a hand-crank instrument. In such cases, it
is common practice to acknowledge the deficiency
of the core, or to revert to the older, hand-crank
method. Another approach, provided that the
transformer has been operating correctly, is to use
the turns ratio measured with an automated TTR
as a reference point to which future measurements
can be compared.
There are very good reasons why hand
crank instruments are now being used less
frequently. These include:
1. Their use is considered dangerous because:
a. High voltages up to 1,000 V AC can be produced
at instrument terminals. Since the transformer
is tested from the LV side, a high voltage is
produced on the HV side. If the transformer
ratio is greater than 130:1, this voltage will be
in excess of 1,000 V.
b. The test leads must be short, which often means
that the user of the instrument has to stand on
the transformer during testing.
2. Using hand crank TTRs is inefficient because:
a. Only one phase at a time can be tested
b. The instrument requires manual balancing
c. The instrument must be cranked and balanced
at the same time
d. Leads must be changed for each phase tested
e. Results have to be recorded manually then
transferred manually to the test reports
f. Manual calculation is needed to determine the
percentage error
g. Total test time is approximately three to four
times longer than with an automatic TTR if the
time taken to complete the report is included
3. Hand-crank instruments have limited
capability when testing instrument
transformers. (They are designed to measure
accurately turns ratios of no more than 130/1).
4. Hand-crank instruments excite the
transformer under test from the LV winding.
Some transformers draw excessive magnetising
current and the instrument’s output may be
insufficient to excite them from the low voltage
winding – for example, network transformers of
the 15000/115 V class and some voltage regulators.
Conclusion
There are a few instances where hand crank TTR test
sets will give a result that’s closer to the nameplate
turns ratio than a modern automated TTR test
set. This apparent benefit is, however, more than
offset by the many disadvantages of hand crank
TTRs, which include time-consuming operation
and safety concerns. For these reasons, automated
TTRs are replacing their hand-crank counterparts,
and this is a trend that will undoubtedly continue.
4 ELECTRICAL TESTER - August 2016 www.megger.com
The industry’s recognised information tool
ELECTRICALTESTER
In our last issue, we reported that power quality
issues are a growing concern all over the world,
and we noted in particular that the adoption
of the smart grid would do little to address this
concern. The primary function of the smart grid is
to increase the reliability of power delivery – any
positive impact it may have on power quality is
no more than incidental. With these thoughts in
mind, in this issue we are going to look at some
of the fundamentals of power quality, and in
particular at the most common types of power
quality problems and why they occur.
Under-voltage
Under-voltage is a decrease in rms voltage to less
than 0.9 pu for a duration longer than one minute.
Typical values encountered in practice are between
0.8 and 0.9 pu. Under-voltages are most often
caused by the switching of loads and capacitor
banks and may persist until the voltage regulation
equipment on the system has time to react
and bring the voltage back within acceptable
tolerance. Overloaded circuits can also cause
under-voltages.
It is worth noting that the term “brownout” is
sometimes used to describe periods when the
supply voltage has been deliberately reduced as
a strategy for reducing power delivery. The type
of supply disturbance caused by a brownout is
essentially the same as an under-voltage, but
the term brownout has no formal definition
and, to avoid possible confusion, its use should
be avoided.
Over-voltage
Over-voltage is an increase in rms voltage to
more than 1.1 pu for a duration longer than
one minute. Typical values are between 1.1 and
1.2 pu. Over-voltages typically result from load
switching, particularly when large loads like
motors are switched off; variations in reactive
compensation, usually the switching of capacitor
banks; poor system voltage regulation capabilities;
and incorrect tap settings on transformers.
Voltage sags and swells
Voltage sags (also called dips) and swells are two
of the most common power quality problems.
They are impossible to eliminate completely; as
impedances change over the course of a day,
the system voltage will also momentarily change.
This is unfortunate, as even short duration sags
can lead to process shutdowns that take many
hours to re-start. Voltage swells are one of the
most frequent causes of circuit breaker nuisance
tripping. In short, sags and swells can cause
major financial losses, particularly in the
manufacturing sector.
Voltage sags are often caused by sudden increases
in load, such as short circuits or faults, motors
starting or electric heaters turning on. They can
also be the result of sudden increases in the source
impedance of the supply, typically caused by a
loose connection. Voltage swells are almost always
caused by sudden decrease in the load on a circuit
that has a poor or damaged voltage regulator,
although they can also be caused by loose or
damaged neutral connections.
For Class A sag detection on single-phase systems,
a voltage sag event begins when the Urms(1/2)
voltage (the rms voltage of the supply calculated
over a half cycle) falls below the sag threshold. The
event ends when the Urms(1/2) is equal to or greater
than the sag threshold plus the hysteresis voltage.
On poly-phase systems, the sag begins when the
Urms(1/2) voltage of one or more channels is below
the sag threshold and ends when the Urms(1/2)
voltage on all channels is equal to or greater than
the sag threshold plus the hysteresis voltage.
For Class A swell detection on single-phase
systems, a swell is defined as beginning when the
Urms(1/2) voltage rises above the swell threshold,
and finishing when the Urms(1/2) voltage is equal
to or less than the swell threshold minus the
hysteresis voltage. On poly-phase systems, the
swell begins when Urms(1/2) on one or more
channels rises above the swell threshold and
finishes when Urms(1/2) on all of the measured
channels is equal to or less than the swell threshold
minus the hysteresis voltage.
Transients
There are two main types of transients over
voltages. Low-frequency oscillatory transients
have frequency components in the hundreds-of-
hertz range. Low frequency oscillatory transients
are typically caused by capacitor switching.High-
frequency or impulsive transients have frequency
components in the hundreds-of-kilohertz range.
High frequency impulse transients are typically
caused by lightning or the switching of inductive
loads.
Transient over voltages can lead to dielectric
degradation or failure in all classes of equipment.
Large magnitude transients with a fast rise time
contribute to insulation breakdown in equipment
such as switchgear, transformers and motors, while
repeated exposure to lower amplitude transients
can cause slow degradation of insulation, leading
to eventual failure and reducing mean time
between failures (MTBF).
The mechanism by which transients damage
insulation can be understood by considering
cables and other forms of insulated electronics
as capacitors, with the insulation acting as the
dielectric of the capacitor. The capacitance of the
system provides a path for the transient pulse.
If the transient pulse has sufficient energy, it will
damage the insulation.
Lightning is a major source of transients. Lightning
strikes, which can be more than 8 km long and
reach temperatures in excess of 20,000 ºC, and
the electromagnetic fields produced by such
strikes, can induce voltage and current transients
in power lines and communication lines. These
transients are typically unidirectional.
The switching of capacitor banks is another
common source of transients. When a capacitor
bank is switched, there is an initial inrush of
current, which produces a low-frequency transient
that has an oscillatory ringing characteristic. Such
oscillatory transients can cause equipment to trip
out as well as malfunctions in uninterruptible
power supply (UPS) installations.
Less frequently encountered are extremely fast
transients (EFTs) that have rise and fall times in the
nanosecond region. These are caused by arcing
faults, such as bad brushes in motors, and are
rapidly damped by even a few metres of distribution
wiring. Standard line filters, which are included in
almost all electronic equipment, are very effective
at removing EFTs, but EFTs may still cause problems
in installations with very short cable runs, such as
those found on off-shore platforms.
Unbalance
Unbalance is a condition in a poly-phase system
where the values of the fundamental component
of the line voltages, or the phase angles between
consecutive line voltages are not equal, as
defined by IEEE 1159 and IEC 61000-4-7. Voltage
unbalance is most commonly seen in relation to
individual customer loads with an imbalance of
the loads on the phases, especially where large
single-phase loads, such as arc furnaces, are in
use. It is important to note that a small unbalance
in the phase voltages can produce a much larger
unbalance in the phase currents.
Unbalanced voltages can adversely affect many
types of equipment including induction motors
and variable speed drives. In addition, unbalanced
voltages can cause heating in transformers and
neutral conductors.
Flicker
Flicker is a very specific problem related to human
perception of the light output of incandescent
light bulbs. It is not a general term for voltage
fluctuations. The human eye is very sensitive to the
light flicker that is produced by voltage variations.
Because of this, flicker is almost always the limiting
criterion for controlling small voltage fluctuations.
If the sensitivity of the human eye to flicker
is assessed by considering the eye’s response
to flicker from a 60-watt incandescent bulb
for rectangular voltage variations at various rates,
it is found that that the sensitivity is a function
of the rate of fluctuations and is also to
some extent dependent on the voltage of the
lighting supply.
In general, flicker is measured using the method
defined in IEC 61000-4-15. This method takes
the instantaneous voltage and compares it with
a rolling average voltage. The deviation between
these two is multiplied by a value taken from a
weighted curve based on the sensitivity to flicker of
the human eye to incandescent bulbs operating at
either 120 V 60 Hz or 230 V 50 Hz. The result – the
percentile unit – is subjected to further statistical
analysis in order to calculate two values, Pst and Plt.
Pst, or short-term flicker is calculated from the
percentile unit and is based on behaviour over
a 10-minute interval. Plt, or long-term flicker is
calculated from Pst and is based on a two-hour
interval. The criteria for evaluating the results are
straightforward. If Pst is less than 1.0, the flicker
levels are good but if Pst is greater than 1.0, the
flicker levels may be high enough to be annoying.
All of this applies only to incandescent lighting
Power Quality: some fundamentalsAndy Sagl - Product manager
5 www.megger.com ELECTRICAL TESTER - August 2016
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Power Quality: some fundamentals
Megger’s test instruments are well known for their
reliability and versatility – and the many decades
of reliable service they’ve provided in the electrical
industry can certainly testify to that. However, it is
this versatility that has landed a 1950s version of
the popular insulation test set … in court!
The test set in question, which is at present
exhibited in New Scotland Yard’s Black Museum, is
a nicely dovetailed, wooden cased, 1950s Series 1
Megger - a 500V hand cranked insulation test set.
Unfortunately, the series of events that landed this
instrument in court, and subsequently in a crime
museum are quite gruesome – so read on at your
own risk!
It all started in the 60s in London, when gangsters
like the Krays and the Richardsons ruled the back
streets. Murder, extortion, torture and everything
in between were everyday activities for these
perpetrators.
Charlie and Eddie Richardson, crime gang leaders
from Camberwell in South East London, were
running a series of unsavoury businesses behind the
camouflage of a respectable (and thriving) scrap
metal merchant and a fruit machine dealership. In
reality, the brothers were involved in racketeering,
illegal drugs, extortion, money laundering, robbery,
prostitution and when necessary, contract killing.
The Richardson gang were also known as the
Torture Gang given their reputation for intimidating
their victims with sadistic methods of persuasion.
These included but were not limited to severe
beatings, nailing feet to the floor, cutting off toes
and fingers, extracting teeth and electrocution!
A public turf war and shoot-outs with rival firm
the Krays in the 1960’s, along with increasing
pressure on the police from the gangsters’ victims
led to the Richardsons’ capture. Key evidence was
provided by Lawrence “Johnny” Bradbury, who
was convicted for the murder of Tom Waldeck, a
mineral prospector and business partner of Charlie
Richardson in the Perlite Mining Company which
– other types of lighting cannot be evaluated in
this way. In addition, the weighting curves apply
only to lighting that operates at 120 V 60 Hz or
230 V 50 Hz.
Harmonics
Harmonics are sinusoidal periodic waves with
frequencies that are integer multiples of the
fundamental frequency. Harmonics can cause
many problems, including excessive heating in
neutral conductors, overheating of motors and
transformers, and failure of electronic equipment.
IEEE 519 defines a harmonic as a component of
order greater than one of the Fourier series of
a periodic quantity. IEC 61000-4-30 defines a
harmonic frequency as a frequency which is an
integer multiple of the fundamental frequency,
and defines a harmonic component as any of the
components having a harmonic frequency.
Linear loads such as incandescent lights and
heating elements draw current equally at every
point of the supply waveform. These loads do not
generate harmonics. However, non-linear loads
such as switching power supplies and variable
speed drives usually draw current only at the peaks
of the supply waveform. It is these non-linear
loads that cause harmonics. Typically, current
harmonics do not propagate through a system,
but voltage harmonics will propagate as they can
pass through transformers. Voltage Harmonics
occur when current harmonics are great enough
to start clipping the voltage in various locations
throughout the waveform.
Harmonics can be characterised by their order –
which is equal to their multiple of the fundamental
frequency. Thus a 180 Hz harmonic in a 60 Hz
supply system is a third order harmonic. Odd
harmonics are harmonics with odd order numbers
and even harmonics are those with even order
numbers.
Even harmonics are often produced by faulty
rectifiers and produce waveform distortion that
is non-symmetrical. Triplens are harmonics with
orders that are multiples of three. These do not
cancel out in three-phase systems and, as a result,
they give rise to high neutral currents.
Harmonics can also be characterised by sequence,
based on the direction of rotation of the magnetic
field they produce. Positive sequence harmonics
create a magnetic field in the direction of rotation
of the fundamental. Indeed, the fundamental can
be considered to be a positive sequence harmonic.
Negative sequence harmonics produce magnetic
fields that rotate in the opposite direction, which
reduces torque in motors and increases the current
required to drive a given load. Zero sequence
harmonics do not produce a rotating magnetic
field. Zero sequence harmonics can be in phase.
This can lead to high neutral currents, high neutral
to ground voltages, transformer losses as well as
equipment overheating.
Positive, negative and zero sequence harmonics
run in sequential order – positive, negative and
then zero. Since the fundamental frequency is
a positive sequence harmonic, the second order
harmonic is a negative sequence harmonic and the
third order harmonic is a zero sequence harmonic.
In balanced three-phase systems, the fundamental
currents cancel each other out, so that there is no
current in the neutral. Zero sequence harmonics
however, such as the third harmonic, add together,
resulting in high neutral currents.
Total harmonic distortion
Total harmonic distortion (THD) is a measure
of the sum of the harmonic components in a
distorted waveform, and it can be calculated for
either current or voltage. THD is the rms sum of
the harmonics, divided either by the rms value
of the fundamental or the rms value of the
total waveform. Most often, THD is quoted as a
percentage of the fundamental.
THD values can be misleading, especially when
used in relation to current. The THD value is
typically calculated with reference to the amplitude
of the fundamental. With voltage calculations, this
voltage fundamental will always be present, but
the amplitude of the current fundamental changes
according to the load – as the load decreases,
so does the fundamental current amplitude. If
the current drawn by the load is low – close to
zero – the THD value will, therefore, appear to be
very high.
For example, if the total harmonic current in a
circuit is 0.2 A and the fundamental current is
200 A, the THD is 3.16%, but if the fundamental
current being drawn by the load drops to 0.2
A, and the harmonic current remains the same,
the THD is now 100%! This is deceptive as THD
appears to be very high, but the only reason for
this is that the load is drawing so little current at
the fundamental frequency.
To avoid this problem, total demand distortion
(TDD) measurements should be used for current
harmonic measurements. TDD references the total
root-sum-square harmonic current distortion to
the maximum average demand current recorded
during the test interval. The reference value is,
therefore, the same throughout the test interval,
ensuring that the TDD result obtained is valid.
TDD is calculated in accordance with the IEEE
519 document, “Recommended Practices and
Requirements for Harmonic Control in Electrical
Power Systems.”
In summary, the power quality industry has
developed certain index values that can be
used to assess the waveform distortion caused
by the presence of harmonics. The two values
most frequently encountered are THD and TDD.
Individual harmonic values are also indexed in
various specifications, such as the North American
IEEE 519 document and the European EN 50160
standard issued by CENELEC.
Conclusion
This article has introduced some of the most
important concepts relating to power quality, and
future articles in this series will build on these.
The next article will look at Class A recording and
this will be followed by an article examining the
impact of transients and harmonics on motors
and transformers.
Exhibit A: Megger hand cranked insulation test set
controlled a mineral claim in the Ghost Mountains
of the Transvaal.
The murder, it later transpired, was the result of
misunderstandings and voting rights amongst
the mine shareholders. When sentenced to hang,
Bradbury offered to turn Queens evidence and
informed on the Richardson gang of which he was
part, in exchange for a pardon and immunity.
The Richardson brothers were found guilty of
fraud, extortion, assault and grievous bodily harm.
Charlie Richardson was sentenced to twenty-five
years in prison, and Eddie had ten years added
to his existing five year sentence for affray. Roy
Hall got ten years for his acts of torture with an
electrical generator.
The “Torture Trial” convened at the Old Bailey in
April 1967 and amongst the evidence and exhibits
was a Megger insulation tester – the “electrical
generator” –which was operated by gang member
Roy Hall to inflict pain on torture victims.
Stories in the press describe the so-called ‘black
box of torture’, with claims that the generator
came from an army field telephone or from a
WWII bomber. A keen electrician however will be
able to spot the fact that the item on display at
New Scotland Yards Black Museum is not a death
box, but rather a 500 V hand cranked insulation
test set which was built with the absolute opposite
intentions – to make equipment and buildings safe
for users!
The history of the Megger insulation testers is
interesting and without a doubt exciting to follow.
Yet the use of this particular instrument will go
down in history for all the wrong reasons!
Andrew Dodds - Group Technical Director
6 ELECTRICAL TESTER - August 2016 www.megger.com
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ELECTRICALTESTER
With a Megger Centrix cable test van, Koopmann Energie und Elektrotechnik, a service company that specialises in handling emergencies in the energy supply sector, was able to prevent losses amounting to millions of Euros at an oil refinery in Germany. The emergency arose when a medium-voltage cable failed, causing a circuit breaker to trip and stopping the oil transport pumps. Not only did this halt production, but if the situation had not been remedied rapidly, very costly damage to the plant would have resulted.
Background Network operators responsible for supply reliability usually want cable test vans that are perfectly tailored to suit their own infrastructure. Before a test van is purchased however, the question often arises whether it should be used exclusively to deal with urgent incidents, or whether it would be more beneficial to use its diagnostic systems for status-oriented servicing to help ensure that cable faults do not occur in the first place.
Today, many sophisticated cable diagnostic techniques are available, including tan delta measurements as well as PD measurements using VLF test voltages with 50 Hz slope technology or damped AC (DAC) voltages, which can be used to test underground cables in a gentle, non-destructive manner. These methods have become widely known and accepted.
What is less well known is that these tried-and-tested techniques also significantly improve the ability to respond effectively to emergencies, as well as making it much easier to determine the location of a cable fault. This means that from the perspective of a service company like Koopmann, the question of whether or not a cable test van should incorporate diagnostic tools is completely redundant. The answer, unequivocally, has to be yes.
In fact, status-oriented servicing is now well established as the best and most efficient servicing strategy for network operators. This is the only servicing strategy that Koopmann recommends to its customers, as it demonstrably offers the best balance between economic efficiency and supply reliability.
This is because the network operator only needs to take action if the cable diagnostic tests indicate that problems exist, rather than acting purely on suspicion by replacing cables for no better reason than their age or, even worse, waiting until cable faults occur and cause damage, meaning that costly rectification work is carried out far too late. Of all available servicing strategies, this last one – waiting until a fault occurs – is the most expensive and the least efficient, but unfortunately it is still the strategy most frequently adopted.
This can have serious consequences, as is clearly shown by the following report, which describes a situation where, by using Megger DAC diagnostic systems, Koopmann saved an oil refinery from the threat of millions of Euros worth of damage.
It is worth mentioning, however, that had the diagnostic tests been carried out earlier, even the limited damage that did occur could have been avoided.
The incident The Koopmann 24-hour service team was called to an incident in an oil refinery. A 20 kV medium voltage cable had appeared to fail suddenly, with the result that the circuit breaker supplying power to a high-pressure tank had tripped. For the refinery, the consequence was devastating – all of the pumps failed. Operations came to a complete standstill because the oil being supplied via the pipelines could no longer be processed. The refinery was facing enormously costly damage that would be almost impossible to rectify, and the immediate challenge was to contain this damage within tolerable limits.
Insulation measurement The first action taken by the emergency team was to switch the power supply to another cable to put at least some of the pumps back into operation. But where was the original fault? As a first step to answering this question, the team used its Centrix cable test van to carry out a standard DC insulation measurement at 1000 V, along with capacitance measurements on the 20 kV cable. This preliminary insulation measurement usually determines whether the fault is solely the result of a short circuit, whether it is a high impedance fault or indeed whether there is any fault at all. Comparing the insulation resistances and capacitance values of all phases often gives an indication of the type of cable fault. This was not the case here, however. There was no short circuit and no significant differences in the insulation resistances of the phases.
Reflection measurement The service team then carried out a traditional reflection measurement using a Megger Teleflex VX test set. It proved very easy to recognise the end of the cable, thanks to the length-dependent amplitude compensation. There were no significant variations between the phases, which reliably indicated that there were no particular issues anywhere between the measuring point and the end of the cable. Neither was any problem found at the end of the cable.
VLF test Next, the team enhanced protection and connected its VLF system. A voltage of 3 x Vo 36 kV was used, with the intention of causing a breakdown. As a service provider, Koopmann
needs to be prepared for all possible incidents that can occur on site. That’s why the company relies on the most powerful VLF testing systems with cosine-square technology from Megger, which are integrated into all of its test vans.
These systems are the only way of testing extremely long cable routes in a way that complies with the applicable standards, a feature that the Koopmann engineers find particularly valuable. Contrary to expectations, however, no breakdown occurred; the cable at the refinery withstood this high stress without any problems. Apart from slightly increased leakage current, yet again no abnormalities were discovered. The cable fault, which certainly seemed to exist, was proving elusive!
An air of tension admittedly started to spread slowly among the members of the experienced Koopmann team. All of the standard methods that had always been so successful did not seem to be yielding results this time.
The circuit breaker For safety reasons, it was then decided to check contact resistances at the circuit breaker, as the pumps would stop only if this breaker tripped. The Koopmann team routinely carries a Megger MOM2 micro-ohmmeter in its emergency kit for situations of this type. Its compact dimensions and convenient weight of just 1 kg means that it is easily stored in any test van and, despite its small size, the MOM2 provides a test current of 200 A.
But even the contact resistance measurements at the circuit breaker did not yield any explanation. In fact, all of the tests performed indicated that the supply network was essentially in tip-top condition. The decision was therefore taken that it was safe to re-energise the cable. When this was done, everything worked perfectly; the problem appeared to have been resolved. The refinery was once again running at full output, much to the satisfaction of the client. But still no one knew why the problem had occurred.
The second event Three days later, Koopmann received another call from the refinery. The section had tripped again. Once again, the standard tests described above were carried out without success, raising suspicions that this was a periodically occurring fault that would continue to elude all traditional fault location methods, unless someone happened to be testing the cable section at exactly the right time.
PD measurement saves refinery millions
Alexander Lüpschen - Asset Consulting Engineer,
Koopmann Energie und Elektrotechnik
The Koopmann 24-hour deployment team was quickly on site
7 www.megger.com ELECTRICAL TESTER - August 2016
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PD measurement saves refinery millions
Mexico already has over 3 GW of installed wind power capacity and plans are in place to increase this to more than 9.5 GW by the end of 2018. This ambitious target can only be achieved if the installation and commissioning of a new plant proceeds smoothly and the plant proves reliable in operation.
To help achieve the necessary high levels of reliability, partial discharge (PD) analysis is routinely carried out on newly installed cables and has proved invaluable in detecting poor workmanship and splice defects. This was amply confirmed by a recent experience with a 6.3 km XLPE cable.
The cable was tested with a Megger TDS NT 60 kV test set using standards-compliant VLF cosine-rectangular test technology operating at a frequency of 0.1 Hz. This test technology is ideally suited to testing the long cables often encountered in wind farm applications, as these
are difficult or impossible to charge with VLF sine-
wave equipment unless the frequency is reduced
below 0.1 Hz, which then makes the testing non-
compliant with IEEE 400.3.
For the cable at the Mexican wind farm however,
the test set was configured to operate at 20
kV. Partial discharge activity was immediately
detected on all three phases at the near ends
of the cables, and at 1.8 km on phases L1 and
L2. The near-end activity was of little concern,
because the connection between the test set
and the cables is rarely PD free. The PD activity at
1.8 km was much more puzzling as the cable
operator had no knowledge of any cable feature
at this distance.
Despite this, the indication provided by the TDS NT
test set was clear and unequivocal, as is shown by
the screen capture in Figure 1. With this in mind,
the cable operator checked the documentation for
the installation and discovered that this had been
updated. The new version revealed that there was
a joint in the cable at 1.8 km, in exactly the location
where unexpected PD activity had been detected.
The splices were removed and opened, and a
visual inspection revealed that no sealing mastic
had been used in the mechanical connector screw
housings on the L1 and L2 phases. (See Figure
2). This shortcoming was quickly remedied and,
on retesting, the cable was found to be free of
PD activity.
This exercise in preventive and predictive
maintenance revealed a problem that was possible
to address relatively easily and inexpensively. Had
the lack of mastic remained undetected and
the cable been put in service, however, it would
almost certainly have failed in a relative short time,
causing costly disruption and damage.
With modern test equipment that uses cosine-
rectangular waveform technology, experience
on Mexican wind farms has clearly shown that
PD analysis, even on long cables, is a convenient
and cost-effective form of insurance against
premature failure.
Luckily for the refinery, the Koopmann team on
site that day had a Megger Centrix 1 80 PD partial
discharge analysis system, which incorporates
sophisticated diagnostic functions for DAC testing.
The team recommended to the refinery that a
partial discharge (PD) measurement be carried out.
Koopmann has been using DAC test equipment
from Megger for PD measurements for years, as
it is still to this day the only non-destructive PD
measurement device on the market. When this
equipment is used, even critical cables can be put
back into service following PD diagnostics.
The fault is found!
It was precisely this test that ended up paying
off in this situation, as it revealed increased PD
levels at a coupling, which were indicative of a
serious abnormality.
The accompanying image clearly shows partial
discharges at a coupling 120 metres away (the
x-axis is the cable length, the y-axis the PD level).
In Koopmann’s experience, it is the PD frequency
rather than its level that is the decisive factor in
intermittent faults. As there was only this one PD
weak point in this particular case, it was easy to
work out what had caused this intermittent fault.
Using the refinery’s exemplary documentation,
the Koopmann team was immediately able to
work out exactly where the faulty coupling was
located, and what type of coupling it was – an oil-
filled coupling sleeve. Without further delay, the
team found and replaced the coupling. A repeated
VLF test, as prescribed by VDE Standard 0726 (HD
XY) and additional PD measurements showed no
further abnormalities. The partial discharges at the
coupling were no longer there. Full operation was
immediately resumed, and the cable section has
not failed since.
Summary
A cable fault location system with a non-destructive
PD measurement function, as is currently offered
only by Megger’s DAC technology, is undoubtedly
the best cable fault location system. Without this
technology or with another cable fault location
system from other manufacturers, the Koopmann
team would not have been able to finally locate
this elusive cable fault. The refinery’s exemplary
documentation also played an important role, as it
allowed the correct coupling to be located quickly
and accurately.The central Centrix control unit means that tests can be carried out in quick succession
Mapping for V <= Vmax (L1, L2, and L3)
Javier Luiz Leiva - Mexico Area Sales Manager
Washington Cabrera - Regional Sales Manager, Mexico
Figure 1. PD activity showed by the TDS NT software in circuit 7 of the wind farmFigure 2. Circuit 7, L1 joint without seal mastic in the mechanical connector screw house
Wind farm cable failure averted!
8 ELECTRICAL TESTER - August 2016 www.megger.com
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Q&AQ: When I’m measuring the resistance
of an earth electrode or system, how far away
from it should I place my test spikes?
A: As far away as possible – and ideally at
least 6 to 10 times the maximum dimensions of
the earth system. To provide some rough rules of
thumb, for a single earth electrode, the current
reference spike C can usually be placed 15 m
from the electrode under test, with the potential
reference spike P placed about 9.3 m (62% of the
distance to C) away. With a small grid of two earth
electrodes, C can usually be placed about 30 to 40
m from the electrode under test; P correspondingly
can be placed about 18.6 to 24.8 m away. If the
earth electrode system is large, consisting of
several rods or plates in parallel, for example, the
distance for C must be increased to possibly 60 m,
and for P to some 37 m. You’ll need even greater
distances for complex electrode systems that
consist of a large number of rods or plates and
other metallic structures bonded together.
Q: My earth system is very large, so
to make measurements in the usual way I
would need very long leads. This simply isn’t
practical. What’s the alternative?
A: You can work with the test spikes at
shorter distances from the earth system if you use
the slope test technique. With this technique, the
current spike is inserted at a distance of about 2
to 3 times the maximum dimension of the earth
system. Measurements are then made with the
voltage spike at 20%, 40% and 60% of the
distance to the current spike. By using various
criteria to evaluate the results obtained from these
three tests and, if necessary performing further
tests, a reliable value for the resistance of the
earthing system can be obtained. There’s no space
here for the full details, but they can be found in
Megger’s invaluable publication, “Getting Down
to Earth”, which can be downloaded free of
charge from the Megger website.
Q: I’ve used the ‘stakeless’ technique to
measure the resistance of an earth electrode
and the result is very obviously too low.
What’s going on?
A: The most likely answer is that you’re actually
reading a metallic loop in the earth system. This
is a very common problem as most equipment is
bonded to ground, and this bonding frequently
creates earth loops. Unfortunately, you may not
be able to use the stakeless technique in your
application.
Q: What are the applications that
require high-resolution measurements of
earth resistance?
A: While in most cases it is only necessary
to show that the earth electrode resistance is
below some specified maximum acceptable
value, there are certain applications where high-
resolution measurements are necessary. These
include the determination of earth resistance
using the slope technique mentioned in an earlier
question, and the evaluation of earth resistivity
over large areas. High-resolution instruments,
such as the Megger DET2/2 automatic earth
tester, typically use the four-terminal method of
measurement and include additional features
such as variable test frequency, that help users to
obtain good results even in difficult conditions. As
well as earth electrode resistance measurements,
these instruments are ideally suited for soil
resistivity measurements, which can be used
to establish the optimum electrode design and
location, as well as for performing archaeological
and geological investigations.
Not long ago, the need to measure earth resistivity or the resistance of an earth electrode was, for most engineers, a rare occurrence. With the advent of small generating schemes and, in particular, solar and wind energy schemes, this situation has changed. Most of these schemes have their own earthing systems and, to ensure safe operation, these need to be checked. This has led to a large increase in the number of questions our helpline receives about earth testing; here is a selection of the most common.
Nikola Tesla’s name is synonymous with pioneering
electrical developments, and he is accepted as
the originator of many devices – not the least of
which is the AC induction motor – which we now
take for granted. His inventions form the basis
of much of the technology we currently use and
although controversial, his life is now celebrated
by engineers and history pundits alike.
However, this was not always the case and during
his lifetime, Tesla rarely received the recognition he
deserved for his work. Ironically, when in 1917 the
American Institute of Electrical Engineers finally
decided to award him a medal for his contribution
to technology, it was the Edison Medal. This was
indeed bittersweet recognition, as the accolade
was set up by Thomas Edison’s supporters – the
same Thomas Edison who took Tesla’s patents and
made a fortune out of them without crediting him.
The award meeting took place at the Engineering
Society Building in New York on May 18. Modestly,
the 60-year-old Tesla graciously accepted the award
for his lifetime achievements, and then proceeded
to hold an extremely lengthy acceptance speech
that went on for hours, much to the desperation
of his captive audience.
Keith Wilson - Electrical engineer
In the February issue of ET, special note was
made of Megger’s series of live monthly
webinars that make it easier for busy power
engineers to keep up to date with the latest
testing techniques and technology. These have
been formulated by the company’s experts,
who have consulted widely with customers
to identify the topics that are of the most
immediate interest. Register today at http://
us.megger.com/company/media-centre/events/
for an upcoming webinar, including:
� Friday, August 19th 2016 – Improving the
efficiency of transformer commissioning
� Friday, September 23rd, 2016 – An
approach to CT testing in the field
� Friday, October 21st, 2016 – Testing
complex relays
All of the webinars start at 10:00 United States
Central Time. For the benefit of anyone who
finds these times and dates inconvenient,
the seminars are being recorded and will be
available to view online on the Megger website
(www.megger.com) within a few days of being
presented.
Reminder: Knowhow delivered online!
Tesla and the pigeon of deathThis event was proof, once again, that despite his
outstanding intellect, Tesla lacked social skills and
refused to observe societal norms, considering that
only science is ever of any use to human beings.
All other things were considered to be trivial and
non-important in the greatness of the universe he
was hoping to build.
Unfortunately, as he aged, Tesla started showing
signs of obsessive-compulsive disorder, and was
potentially a high-functioning autistic.
He gradually withdrew from public life and his
quirks slowly took over. He became obsessed with
hygiene and when he shook people’s hands he
felt compelled to wash his hands three times. The
fixation on number three and its multiples was
affecting every area of his life – for instance he
had to have 18 napkins at the dinner table and
he would count the steps he walked during a day.
Tesla also claimed to have an abnormal sensitivity
to sounds, as well as an acute sense of sight. By his
own admission, he had “a violent aversion against
the earrings of women,” and “the sight of a pearl
would almost give me a fit” – he even sent his
secretary home one day upon seeing her choice
of accessories!
As Tesla’s world became more and more contorted,
he found solace in observing and feeding pigeons.
Having remained a bachelor his entire life, his
twilight years were spent fixating on a specific
white female pigeon, which he claimed to love
almost as one would love a human being.
Allegedly, the white pigeon visited Tesla one night.
The bird flew in his hotel room though an open
window. He believed the bird had come to tell him
she was dying. Tesla apparently saw “two powerful
beams of light” in the bird’s eyes: “Yes, it was a
real light, a powerful, dazzling, blinding light, a
light more intense than I had ever produced by the
most powerful lamps in my laboratory.”
The white pigeon died in the inventor’s arms,
which made a profound impact on his already
anguished psyche. He believed that the
pigeon’s death symbolized his own mortality and
that he had now accomplished all that he was
supposed to.
Nikola Tesla died in 1943, in debt, at his apartment
in the New Yorker hotel. His passing was at the
time unremarkable and only decades later was his
reputation restored as one of the greatest thinkers
of the twentieth century.