Power T&D Solutions

Power System Technology Navigator (PSTN) Thursday, March 12, 21!
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Transormers
or navigation
generation plants to the consumers are in most cases
large. The map below shows the European situation.
There is one grid in estern 0uroe, one in 0astern
0uroe, one in the Nordic countries. /slands li#e reat
"ritain, /reland, /celand, Sardinia, +orsica, +rete,
otland, etc. also have their own grid with no +
connection to the continent. The other continents on
the globe have a similar situation.
0ven i the networ#s in 0uroe have the same nominal
re5uency, ! cycles er second or *ert8 (*8), there is
always some variation, normally less than 9 .1 *8,
and in certain cases it may rove diicult or imossible
to connect them with + because o stability concerns.
n + tie between two asynchronous systems needs
to be very strong to not get overloaded. / a stable +
tie would be too large or the economical ower
e:change needs or i the networ#s wish to retain their
indeendence, than a *%-+ lin# is the solution.
nd in other arts o the world (South merica and
;aan) ! and < *8 networ#s are bordering each
other and it would be imossible to e:change ower
between them with an + line or cable. *%-+ is then
the only solution.
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interconnected electrical system
congested transmission aths or interaces.
transmission ath or interace reers to a seciic set
o transmission elements between two neighboring
control areas or utility systems in an interconnected
electrical system. transmission ath or interace
becomes congested when the allowed ower transer
caability is reached under normal oerating
conditions or as a result o e5uiment ailures and
system disturbance conditions. The #ey imacts o
"ottlenec#s are reduction o system reliability,
ineicient utili8ation o transmission caacity and
generation resources, and restriction o healthy mar#et
cometition.The ability o the transmission systems to
deliver the energy is deendent on several main
actors that are constraining the system, including
thermal constraints, voltage constraints, and stability
constraints. These transmission limitations are usually
determined by erorming detailed ower low and
stability studies or a range o anticiated system
oerating conditions. Thermal limitations are the most
common constraints, as warming and conse5uently
sagging o the lines is caused by the current lowing in
the wires o the lines and other e5uiment. /n some
situations, the eective transer caability o
transmission ath or interace may have to be reduced
rom the calculated thermal limit to a level imosed by
voltage constraints or stability constraints. "ac# to $verview
noticeable changes in light outut.
%oltage 4lic#er can either be a eriodic or aeriodic
luctuation in voltage magnitude i.e. the luctuation
may occur continuously at regular intervals or only on
occasions. %oltage 4lic#er is normally a roblem with
human ercetion o lam =strobing> eect but can also
aect ower&rocessing e5uiment such as ?PS
systems and ower electronic devices. Slowly
luctuating eriodic lic#ers, in the .! @ A.*8 range,
are considered to be noticeable by humans. voltage
magnitude variation o as little as 1.B may also be
noticeable.
arc urnaces in the steel industry, welding machines,
large induction motors, and wind ower generators.
*igh imedance in a ower delivery system will
contribute urther to the voltage dro created by the
line current variation.
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distortion of currents and voltages
*armonics are comonents that ma#e u a waveorm
where each comonent has a re5uency that is an
integral multile o the undamental re5uency. The term
Harmonic is normally alied to waveorm comonents
that have re5uencies other than the undamental
re5uency. 4or a ! *8 or <*8 system the undamental
re5uency is !*C or <*8. waveorm that contains
any comonents other than the undamental re5uency
is non&sinusoidal and considered to be distorted .
Nonlinear loads draw currents that are non&sinusoidal
and thus create voltage dros in distribution conductors
that are non&sinusoidal. Tyical nonlinear loads include
rectiiers, variable seed drives, and any other loads
based on solid&state conversion. Transormers and
reactors may also become nonlinear elements in a
ower system during overvoltage conditions. *armonics
create many concerns or utilities and customers ali#e.
Tyical henomena include neutral circuit overloading in
three hase circuits, motor and transormer overheating,
metering inaccuracies and control system malunctions.
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nominal value
n /nterrution occurs whenever a suly>s voltage dros
below 1B o the rated voltage or a eriod o time no
longer than one minute. /t is dierentiated rom a voltage
sag in that the late is not a severe ower 5uality roblem.
The term sag covers voltage dros down to 1B o
nominal voltage whereas an interrution occurs at lower
than 1B. Sustained /nterrution occurs when this
voltage decrease remains or more than one minute.
n interrution is usually caused by downstream aults that
are cleared by brea#ers or uses. sustained interrution
is caused by ustream brea#er or use oeration.
?stream brea#ers may oerate due to short&circuits,
overloads, and loss o stability on the bul# ower system.
3oss o stability is usually characteri8ed by out&o&tolerance
voltage magnitude conditions and re5uency variations
which e:ceed electrical machine and transormer
tolerances. This henomenon is oten associated with
aults and deiciencies in a transmission system but can
also be the result o lac# o generation resources. The
concerns created by interrutions are evident and include
inconvenience, loss o roduction time, loss o roduct,
and loss o service to critical acilities such as hositals.
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Long lines
Long lines need special consideration in the planning of a power system.
This transmission carries more than 12,000 MW over 800 km. There is an HVDC system with two 600 kV bio!es o" #1$0 MW each is %irect ro&te to '(o )a&!o whi!e the three 800 kV sh&nt an% series comensate% *C !ines has two interme%iate s&bstations that a!!ow connection to the !oca! +ri%s.
or !on+ *C !ines one m&st consi%er i.e. the reactive ower comensation, the transient stabi!ity an% switchin+ overvo!ta+es an% how many interme%iate s&bstations one nee%s. -" the !ine !en+th is !on+er than aro. 600 km one sho&!% a!so consi%er i" an HVDC a!ternative brin+s !ower investment costs an%/or !ower !osses or i" the inherent contro!!abi!ity o" an HVDC system brin+s with some other benets.
*nother "actor to consi%er is the !an% &se
The +&re at the ri+ht comares two #,000 MW HVDC !ines "or the 1,000 km Three or+es 'han+hai transmission, China, to ve $00 kV *C !ines that wo&!% have been &se% i" *C transmission ha% been se!ecte%.
o to !ong "a#les
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Cables have large capacitances and therefore$ if fed with AC$
large reactive currents. Cables for %C are also less e&pensive
than for AC. ne must distinguish between submarine cables
and land 'underground( cables.
Su#marine ca#les
Since no shunt reactor can be installed at intermediate oints
(in the sea) and -+ cables are less e:ensive, the ma'ority o
cables D ! #m are or -+.
$n%ergroun% ca#les
3ong underground cables (D ! #m) have been generally
avoided since the cost or an overhead line was deemed to be
only 1 @ 2 B o the cost or the cable. /n many arts o the
world it is now almost imossible to get ermission to build a
new overhead line. *%-+ 3ight E has changed the cost
relation and the cable solution is less e:ensive than beore.
3ayin+ o" the 200 km enno'kan HVDC cab!e 4$00 MW5.
3ayin+ o" the 180 km M&rray!ink HVDC 3i+ht cab!e 4220 MW5.
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)nscheduled power flow on a given transmission path in an
interconnected electrical system
The terms *oop +low and ,arallel ,ath +low are sometimes
used interchangeable to reer to the unscheduled ower lows,
that is, the dierence between the scheduled and actual ower
lows, on a given transmission ath in an interconnected
electrical system. ?nscheduled ower lows on transmission
lines or acilities may result in a violation o reliability criteria
and decrease available transer caability between neighboring
control areas or utility systems.

The reliability o an interconnected electrical system can be
characteri8ed by its caability to move electric ower rom one
area to another through all transmission circuits or aths
between those areas under seciied system conditions. The
transer caability may be aected by the Fcontract athG
designated to wholesale ower transactions, which assumes
that the transacted ower would be conined to low along an
artiicially seciied ath through the involved transmission
systems. /n reality, the actual ath ta#en by a transaction may
be 5uite dierent rom the designated routes, determined by
hysical laws not by commercial agreements, thus involving the
use o transmission acilities outside the contracted systems.
These une:ected low atterns may cause so&called 3oo
4low and Parallel Path 4low roblems, which may limit the
amount o ower these other systems can transer or their own
uroses.
Transmission 3oo 4lows or 1 H scheduled Transer rom
rea to rea + in an /nterconnected System
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,eriodic variations in generator angle or line angle due to
transmission system disturbances
associated with transmission system disturbances and can
occur due to ste changes in load, sudden change o generator
outut, transmission line switching, and short circuits.
-eending on the characteristics o the ower system, the
oscillations may last or A &2 seconds ater a severe ault.
-rawn out oscillations that last or a ew seconds or more are
usually the result o very light daming in the system and are
ronounced at ower transers that aroach the line>s stability
limit. -uring such angular oscillation eriod signiicant cycle
variations in voltages, currents, transmission line lows will ta#e
lace. /t is imortant to dam these oscillations as 5uic#ly as
ossible because they cause mechanical wear in ower lants
and many ower 5uality roblems. The system is also more
vulnerable i urther disturbances occur.
The active ower oscillations on a transmission line tend to limit
the amount o ower that may be transerred, thus may result in
stability concerns or utili8ation restrictions on the corridors
between control areas or utility systems. This is due to the act
that higher ower transers can lead to less daming and thus
more severe and ossibly unstable oscillations.
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Effects of reactive power on the efficiency of transmission and
distribution
eactive ower is deined as the roduct o the rms voltage,
current, and the sine o the dierence in hase angle between
the two. /t is used to describe the eects o a generator, a load,
or other networ# e5uiment, which on the average neither
sulies nor consumes ower. Synchronous generators,
overhead lines, underground cables, transormers, loads and
comensating devices are the main sources and sin#s o
reactive ower, which either roduce or absorb reactive ower
in the systems. To maintain eicient transmission and
distribution, it is necessary to imrove the reactive ower
balance in a system by controlling the roduction, absortion,
and low o reactive ower at all levels in the system. "y
contrast, ineicient reactive ower management can result in
high networ# losses, e5uiment overloading, unaccetable
voltage levels, even voltage instability and outages resulting
rom voltage collase. 3ocal reactive ower devices or voltage
regulation and ower actor correction are also imortant
esecially or balancing the reactive ower demand o large
and luctuating industrial loads.
hort duration decreaseincrease 'sagswell( in supply voltage
%oltage Sag or %oltage -ig is a decrease in suly voltage o
1B to IB that lasts in duration rom hal a cycle to one
minute. %oltage Swell is an increase in suly voltage o 1B
to JB or the same duration.
%oltage sags are one o the most commonly occurring ower
5uality roblems. They are usually generated inside a acility
but may also be a result o a momentary voltage dro in the
distribution suly. ags can be created by sudden but brie
changes in load such as transormer and motor inrush and
short circuit&tye aults. sag may also be created by a ste
change in load ollowed by a slow resonse o a voltage
regulator. voltage swell may occur by the reverse o the
above events.
0lectronic e5uiment is usually the main victim o sags$ as they
do not contain suicient internal energy to =ride through> the
disturbance. 0lectric motors tend to suer less rom voltage
sags, as motor and load inertias will =ride through> the sag i it is
short enough in duration.
$n#alance% !oa%
A load which does not draw balanced current from a balanced
three-phases supply
n unbalanced load is a load which does not draw balanced
current rom a balanced three&hase suly. Tyical
unbalanced loads are loads which are connected hase&to&
neutral and also loads which are connected hase&to&hase.
Such loads are not caable o drawing balanced three&hase
currents. They are usually termed single&hase loads.
single&hase load, since it does not draw a balanced three&
hase current, will create une5ual voltage dros across the
series imedances o the delivery system. This une5ual
voltage dro leads to unbalanced voltages at delivery oints in
the system. "lown uses on balanced loads such as three&
hase motors or caacitor ban#s will also create unbalanced
voltage in the same ashion as the single&hase and hase&
hase connected loads. ?nbalanced voltage may also arise
rom imedance imbalances in the circuits that deliver
electricity such as untransosed overhead transmission lines.
Such imbalances give the aearance o an unbalanced load
to generation units.
n unbalanced suly may have a disturbing or even
damaging eect on motors, generators, oly&hase converters,
and other e5uiment. The oremost concern with unbalanced
voltage is overheating in three&hase induction motors. The
ercent current imbalance drawn by a motor may be < to 1
times the voltage imbalance, creating an increase in losses and
in turn an increase in motor temerature. This condition may
lead to motor ailure. "ac# to $verview
,ost-disturbance e&cursions of voltages at some buses in the
power system out of the steady operation region
%oltage instability is basically caused by an unavailability o
reactive ower suort in an area o the networ#, where the
voltage dros uncontrollably. 3ac# o reactive ower may
essentially have two origins7 irstly, a gradual increase o ower
demand without the reactive art being met in some buses or
secondly, a sudden change in the networ# toology redirecting
the ower lows in such a way that the re5uired reactive ower
cannot be delivered to some buses.
The relation between the active ower consumed in the
considered area and the corresonding voltages is e:ressed
in a static way by the P&% curves (also called FnoseG curves).
The increased values o loading are accomanied by a
decrease in voltage (e:cet in case o a caacitive load). hen
the loading is urther increased, the ma:imum loadability oint
is reached, beyond which no additional ower can be
transmitted to the load under those conditions. /n case o
constant ower loads the voltage in the node becomes
uncontrollable and decreases raidly. This may lead to the
artial or comlete collase o a ower system.
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+,ample o- application* 'e%ucing harmonics in heavy in%ustry
*armonic 4ilters may be used to mitigate, and in some cases, eliminate
roblems created by ower system harmonics. Non&linear loads such as
rectiiers, converters, home electronic aliances, and electric arc
urnaces cause harmonics giving rise to e:tra losses in ower e5uiment
such as transormers, motors and caacitors. They can also cause other,
robably more serious roblems, when interering with control systems
and electronic devices. /nstalling ilters near the harmonic sources can
eectively reduce harmonics. 4or large, easily identiiable sources o
harmonics, conventional ilters designed to meet the demands o the
actual alication are the most cost eicient means o eliminating
harmonics. These ilters consist o caacitor ban#s with suitable tuning
reactors and daming resistors. 4or small and medium si8e loads, active
ilters, based on ower electronic converters with high switching
re5uency, may be a more attractive solution.
Bene-its*
Technology ) System* Harmonic Filters
0:amle o alication7 egulation o the ower actor to increase the
transmission caability and reduce transmission losses as well as
reducing harmonics.
*armonic 4ilters roduced reactive ower as well as mitigate, and in
some cases, eliminate roblems created by ower system harmonics.
here the main need is ower actor comensation the best solution can
still be a harmonic ilter due to the amount o harmonics. Non&linear loads
such as rectiiers, converters, home electronic aliances, and electric
arc urnaces cause harmonics giving rise to e:tra losses in ower
e5uiment such as transormers, motors and caacitors. They can also
cause other, robably more serious roblems, when interering with
control systems and electronic devices. /nstalling ilters near the harmonic
sources can eectively reduce harmonics. 4or large, easily identiiable
sources o harmonics, conventional ilters designed to meet the demands
o the actual alication are the most cost eicient means o eliminating
harmonics as well as roducing reactive ower. These ilters consist o
caacitor ban#s with suitable tuning reactors and daming resistors. 4or
small and medium si8e loads, active ilters, based on ower electronic
converters with high switching re5uency, may be a more attractive
solution.
Benefits:
/mroved ower actor, educed transmission losses, /ncreased transmission caability
/mroved voltage control, /mroved ower 5uality, 0liminates harmonics
Other applications:
Factors ) Phenomena* Asynchronous connection
+,ample o- application* Interconnection o- power systems
/t is sometimes diicult or imossible to connect two + networ#s due to
stability reasons. /n such cases *%-+ is the only way to ma#e an
e:change o ower between the two networ#s ossible.
Several *%-+ lin#s interconnect + system that are not running in
synchronism with each other. 4or e:amle the Nordel ower system in
Scandinavia is not synchronous with the ?+T0 grid in western continental
0uroe even though the nominal re5uencies are the same. nd the
ower system o eastern ?S is not synchronous with that o western
?S. There are also *%-+ lin#s between networ#s with dierent nominal
re5uencies (! and < *8) in ;aan and South merica.
-irect current transmissions in the orm o classical *%-+ or *%-+
3ightE are the only eicient means o controlling ower low in a networ#.
*%-+ can thereore never become overloaded. n + networ#
connected with neighboring grids through *%-+ lin#s may as the worst
case loose the ower transmitted over the lin#, i the neighboring grid
goes down & the *%-+ transmission will act as a irewall against
cascading disturbances.
K n *%-+ lin# can never be overloaded
K*%-+ transmission will act as a irewall against cascading disturbances.
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!inks*
K*%-+ transmission or asynchronous connection
K lications in Power Systems7 /nterconnection
K "" *%-+ Portal
+,ample o- application* Interconnection o- power systems
"ottlenec#s may be relieved by the use o an *%-+ or *%-+ 3ight lin# in
arallel with the limiting section o the grid. "y using the inherent
controllability o the *%-+ system the ower system oerator can decide
how much ower that is transmitted in the +&lin# and how much by the
*%-+ system.
3onger + lines tend to have stability constrained caacity limitations as
oosed to the higher thermal constraints o shorter lines. "y using the
inherent controllability o an *%-+ system in arallel with the long +
lines, the ower system can be stabili8ed and the transmission limitations
on the + line can be increased.
Bene-its*
K/mroved Power and rid %oltage +ontrol
.
!inks*
K lications in Power Systems7 /nterconnection
K "" *%-+ Portal
Phenomena ) Factor* !ong lines
*%-+ transmission line costs less than an + line or the same
transmission caacity. *owever, the terminal stations are more e:ensive
in the *%-+ case due to the act that they must erorm the conversion
rom + to -+ and vice versa. "ut above a certain distance, the so&called
brea#&even distance, the *%-+ alternative will always give the lowest
cost. Thereore many long overhead lines (D O #m) articularly rom
remote generating stations are built as -+ lines.
Bene-its*
K3ower right&o&way re5uirement or -+ lines than or + lines
K*%-+ does not contribute to the short circuit current
/0 o to !ong Su#marine "a#les

.
!inks*
K*%-+ transmission has lower losses
K lications in Power Systems7 +onnection o generat
ion
Technology ) System* H(D"
+,ample o- application* long %istance water crossing
/n a long + cable transmission, the reactive ower low due to the large
cable caacitance will limit the ma:imum ossible transmission distance.
ith *%-+ there is no such limitation, why, or long cable lin#s, *%-+ is
the only viable technical alternative. There are *%-+ and *%-+ 3ight
cables rom #m u to !J #m in oeration or under construction with
ower ratings rom to O M.
Bene-its*
!inks*
Factors ) Phenomena* !oop Flow
Technology ) System* H(D" an% H(D" !ight
+,ample o- application* Interconnecte% power systems
3oo 4lows, or Parallel Path 4lows, may be alleviated by the use o
*%-+ or *%-+ 3ight. /n interconnected ower systems, the actual ath
ta#en by a transaction rom one area to another may be 5uite dierent
rom the designated routes as the result o arallel ath admittance, thus
diverting or wheeling ower over arallel connections.
The igure shows how arallel ath low can be avoided by relacing an
+ line with a *%-+Q*%-+ 3ight lin# between area and area +
Bene-its*
K*%-+ can be controlled to transmit contracted amounts o ower and
alleviate unwanted loo lows.
K n *%-+ lin# can alternatively be controlled to minimi8e total networ#
losses
. "ac# to $verview
!inks*
Factors ) Phenomena* Power scillations
+,ample o- application* Stea%y State an% Transient Sta#ility
Improvement
3ong + lines tend to have stability constrained caacity limitations as
oosed to the higher thermal constraints o shorter lines. "y using the
inherent controllability o an *%-+ system in arallel with the long +
lines, the ower system can be stabili8ed and the transmission limitations
on the + line can be increased.
The *%-+ daming controller is a standard eature in many *%-+
ro'ects in oeration. /t normally ta#es its inut rom the hase angle
dierence in the two converter stations.
Bene-its*
K/mroved Power and rid %oltage +ontrol
"ac# to $verview
!inks*
Applications in Power Systems* Interconnection
H(D" !ight System Interaction Tutorial1
ABB H(D" Portal
Factors ) Phenomena* Flicker
Technology ) System* 2ini"ap
+,ample o- application* Installation o- a 2ini"ap to re%uce -licker
%uring large motor starting
%oltage lic#er can become a signiicant roblem or ower distributors
when large motor loads are introduced in remote locations. /nstallation o
a series caacitor in the eeder strengthens the networ# and allows such
load to be connected to e:isting lines, avoiding more signiicant
investment in new substations or new distribution lines.
The use o the Mini+a on long distribution eeders rovides sel&
regulated reactive ower comensation that eiciently reduces voltage
variations during large motor starting.
Bene-its*
K/mroved voltage roile along the line
K0asier starting o large motors
KSel&regulation
+,ample o- application* Improve% voltage pro-ile o- long %istri#ution
lines #y a%%ing a 2ini"ap
The voltage roile on a radial circuit deends on the circuit arameters
and the load characteristics. The voltage roile can be signiicantly
imroved by installing a Mini+a along the line. tyical voltage roile
or a radial circuit with and without a series caacitor is shown below.
Note that the voltage roile curve has a 'um at the location o the series
caacitor which reresents a large voltage rise downstream o the series
caacitor.
The use o the Mini+a on long distribution eeders rovides imroved
voltage roile or all loads downstream o the installation.
Bene-its*
reactance
Keduced line losses
+,ample o- application* Improve% power -actor at the utility source
with a 2ini"ap
The reactive ower roduced by the series caacitor is roortional to the
caacitor imedance and the line current. ith the series caacitor
sulying a signiicant ortion o the reactive ower re5uirements o the
distribution line and o inductive motor loads, much less reactive ower is
drawn rom the utility source, resulting in a greatly imroved ower actor
at the sending end o the line.
The use o the Mini+a on a distribution eeder rovides sel&regulated
reactive ower or imroved ower actor at the utility source.
Bene-its*
K0asier starting o large motors
K/mroved voltage regulation and reactive ower balance
KSel&regulation
+,ample o- application* Phase angle monitoring
The hase angle monitoring alication acilitates the monitoring o
networ# stresses caused by heavily loaded lines. /t rovides oerators
with real&time inormation about voltage hase angle deviations @ a
crucial issue e.g. or the successul reclosing o transmission lines.
/ts main unction is to suly suicient inormation to the ower system
oerator to evaluate the resent angle dierence between two locations.
?on detection o an e:traordinary status, PSuard alerts the oerator by
giving an early warning or, in critical cases, an emergency alarm.
The resent version rovides monitoring unctionality, and its oututs are
intended as mature decision suort or oerators in ta#ing stabili8ing
measures. ctions that the oerator may ta#e to imrove grid stability
range rom generation rescheduling or actions on the reactive ower
comensation, bloc#ing o ta changers in the load area and load
shedding in e:treme cases.
K/mroved system stability, security and reliability
KSae oeration o ower carrying comonents closer to their limits
K$timi8ed utili8ation o transmission caacities
K0nhanced oerational and lanning saety
ther applications*
KPower $scillation Monitoring (P$M) "ac# to $verview
more a#out* PSuar% 3i%e Area 2onitoring System
an% Bottlenecks
early warning and emergency alarm
Technology ) System* PSuar% 3i%e Area 2onitoring System
+,ample o- application* !ine thermal monitoring
3oading o ower lines or *% cables is in many cases constrained by thermal limits
rather than by voltage instability concerns. thermal limit o a line is usually set
according to conservative and stabile criteria, i.e. high ambient temerature and calm
air. This yields assumtions o very limited cooling ossibilities and thus low loadability.
*owever, the ambient conditions are oten much better in terms o ossible cooling and
would allow higher loading o a line with a minimal ris#. This can be achieved i an on&
line tool or line temerature assessment is available. $ne o the algorithms o PSuard
serves this urose. *owever, its unctionality and alicability on the real ower
systems should be tested in the ractice.
The algorithm wor#s as ollows
KThe voltage and current hasors measured at both ends o a line are collected (the
hasors have to be measured at the same instant, which is ossible through the PS&
synchroni8ation o the hasor measurement units, PM?s)
K ctual imedance and shunt admittance o a line are comuted.
Kesistance o the lineQcable is e:tracted
K"ased on the #nown roerties o the conductor material (reerence temerature and
deendency coeicient are usually sulied by the manuacturer), the actual average
temerature o the line is determined.
The obtained temerature is an average, not the sot one. The relation between them
shall be veriied, i.e. through consideration o the imact o the various weather
conditions along the line at a given time.
Bene-its*
K/mroved ower low control
ther applications*
an% !ong !ines & "a#les
PSuard dislay7 3ine thermal monitoring with early
warning and emergency alarm
PSuard dislay7 3ine temerature attern comuted by PSuard
+,ample o- application* Power oscillation monitoring
Power oscillation monitoring is the algorithm used or the detection o
ower swings in a high voltage ower system. The algorithm rocesses the
selected voltage and current hasor inuts and detects the various ower
swing (ower oscillation) modes. /t 5uic#ly identiies the re5uency and the
daming o swing modes. The algorithm deloys adative Halman iltering
techni5ues.
Displaye% results
K-aming o the dominant oscillatory mode (time window, i.e. trend dislay)
K4re5uency o the dominant oscillatory mode (time window, i.e. trend dislay)
K mlitude o the oscillation (time window, i.e. trend dislay)
ptional
K-aming o other oscillatory modes (all in one time window, distinguished by dierent
colors)
K4re5uencies o other oscillatory modes (all in one time window, distinguished by dierent
colours
Alarms
hen the daming o any oscillation mode decreases to below a redeined value (in two
stes, irst is alert, the second emergency alarm)
'ea% more
Measurements by PSuard MS7 The loss o a ower
lant in Sain (1 M) initiated ide rea $scillations
Measurement by PSuard
+,ample o- application* Power oscillation monitoring
Bene-its*
Short4term operation #ene-its*
K/mmediate awareness o the ower system state in terms o the resence o oscillations,
thus an oerator sees the urgency o the situation
K/ndication o the re5uency o an oscillation which may then be associated with the #nown
e:isting mode o the ower system, i.e. the oerator may distinguish i a local or inter&area
mode is e:cited
!ong4term #ene-its*
Kith the hel o the stored data, long&term statistics can be collected and, based on their
evaluation, the system reinorcements can be erormed (such as retuning o Power
System Stabili8ers (PSS) to dam the re5uencies aearing most oten as dangerous
ones).
an% Power scillations
Technology ) System* PSuar% 3i%e Area 2onitoring System
+,ample o- application* (oltage sta#ility monitoring
The voltage stability monitoring alication acilitates the monitoring o the
grid>s dynamic behavior and rovides stability calculations or steady state
situations as well as stability redictions in contingency cases. /t builds on
and e:tends the basic unctionality o PSJA with unctions related to the
monitoring o voltage stability or a transmission line Q corridor.
/t>s main unction is to rovide the oerator o the ower system with
suicient inormation to evaluate the resent ower margin with resect to
voltage stability, that is, the amount o additional active ower that can be
transorted on a transmission corridor without 'eoardi8ing the voltage
stability. The resent version rovides monitoring unctionality, and its
oututs are intended as mature decision suort or oerators in ta#ing
otimi8ing res. stabili8ing measures. ctions that the oerator may ta#e to
imrove voltage stability range rom generation rescheduling or actions on
the reactive comensation, bloc#ing o ta changers in the load area and
to load shedding in e:treme cases.
lied directly, the alication is assigned to a single line or cable.
*owever, on a case&by&case basis, the method can be alied also to
transmission corridors with more comle: toologies.
Bene-its*
K/mroved system stability, security and reliability
Keduced cost and greater unctionality o Protection 6 +ontrol systems
K$timi8ed utili8ation o transmission caacities "ac# to $verview
an% (oltage Insta#ility
+,ample o- application* Transient Sta#ility Improvement
"ottlenec#s may be relieved by the use o Series +omensation. 3onger
lines tend to have stability&constrained caacity limitations as oosed to
the higher thermal constraints o shorter lines. Series +omensation has
the net eect o reducing transmission line series reactance, thus
eectively reducing the line length. Series +omensation also oers
additional ower transer caability or some thermal&constrained
bottlenec#s by balancing the loads among the arallel lines. 4igure shows
a two&area interconnected system where the ower transer rom area to
area " is limited to 1!M due to stability constraints. dditional
electricity can be delivered rom area to area " i Series +omensation is
alied to increase the ma:imum stability limits.
Bene-its*
K/mroved rid %oltage +ontrol
ther applications*
Factors ) Phenomena* !oop Flows
Technology ) System* Series "ompensation
+,ample o- application* Power Flow "ontrol
3oo 4lows, or Parallel Path 4lows, may be alleviated by the use o Series
+omensation. /n interconnected ower systems, the actual ath ta#en by
a transaction rom one area to another may be 5uite dierent rom the
designated routes as the result o arallel ath admittance, thus diverting
or wheeling ower over arallel connections.
4igure shows arallel ath low alleviation by the use o Series
+omensation. ith a reduction in the direct interconnection imedance
between area and area +, the Parallel Path 4low which is routed through
area " is decreased.
K3ower Transmission 3osses
ther applications*
Technology ) System* Shunt "apacitor
+,ample o- application*
egulation o the ower actor to increase the transmission caability and
reduce transmission losses
Shunt caacitors are rimarily used to imrove the ower actor in
transmission and distribution networ#s, resulting in imroved voltage
regulation, reduced networ# losses, and eicient caacity utili8ation. 4igure
shows a lot o terminal voltage versus line loading or a system that has a
shunt caacitor installed at the load bus. /mroved transmission voltage
regulation can be obtained during heave ower transer conditions when
the system consumes a large amount o reactive ower that must be
relaced by comensation. t the line surge imedance loading level, the
shunt caacitor would decrease the line losses by more than A!B. /n
distribution and industrial systems, it is common to use shunt caacitors to
comensate or the highly inductive loads, thus achieving reduced delivery
system losses and networ# voltage dro.
Bene-its*
'eactive Power Factor
Technology ) System* Shunt 'eactor
transmission line an% ca#le line voltage sta#ility
The rimary urose o the shunt reactor is to comensate or caacitive
charging voltage, a henomenon getting more rominent or increasing
line voltage. 3ong high&voltage transmission lines and relatively short cable
lines (since a ower cable has high caacitance to earth) generate a large
amount o reactive ower during light ower transer conditions which must
be absorbed by comensation. $therwise, the receiving terminals o the
transmission lines will e:hibit a Fvoltage riseG characteristic and many tyes
o ower e5uiment cannot withstand such overvoltages. 4igure shows at
to level voltage at the receiving end when transmission line is loaded with
rated ower. Then shunt reactor is not needed. Ne:t igure shows a
voltage increase when line is lightly loaded and bottom igure shows what
haens when a shunt reactor is connected. The voltage stability is #et
due to the inductive comensation rom the reactor.
better ine tuning o the reactive ower can be made by the use o a ta
changer in the shunt reactor. /t can be ossible to vary the reactive ower
between ! to 1 B o the needed ower.
Bene-its*
KSimle and robust customer solution with low installation costs and
minimum maintenance
KNo losses rom an intermediate transormer when eeding reactive
comensation rom a lower voltage level.
KNo harmonics created which may re5uire ilter ban#s.
"ac# to $verview
Static %ar +omensators are used in transmission and distribution
networ#s mainly roviding dynamic voltage suort in resonse to system
disturbances and balancing the reactive ower demand o large and
luctuating industrial loads. Static %ar +omensator is caable o both
generating and absorbing variable reactive ower continuously as oosed
to discrete values o i:ed and switched shunt caacitors or reactors.
4urther imroved system steady state erormance can be obtained rom
S%+ alications. ith continuously variable reactive ower suly, the
voltage at the S%+ bus may be maintained smoothly over a wide range o
active ower transers or system loading conditions. This entails the
reduction o networ# losses and rovision o ade5uate ower 5uality to the
electric energy end&users.
K/mroved rid %oltage Stability
K/mroved Power 4actor
"ac# to $verview
Factors ) Phenomena* Power scillations
Technology ) System* Static (ar "ompensator 5S("6
+,ample o- application* Power scillation Damping
Static %ar +omensators are mainly used to erorm voltage and reactive
ower regulation. *owever, when roerly laced and controlled, S%+s
can also eectively counteract system oscillations. S%+, in eect, has
the ability to increase the daming actor (tyically by 1&2 M er Mvar
installed) on a bul# ower system which is e:eriencing ower oscillations.
/t does so by eectively modulating its reactive ower outut such that the
regulated S%+ bus voltage would increase the system daming caability.
4igure shows ower oscillation romted by a disturbance on a
transmission system. The uncomensated system undergoes substantial
oscillations ollowing the disturbance while the same system with S%+
e:eriences much imroved resonse.
Bene-its*
K/mroved -ynamic Stability
Krid %oltage Suort
"ac# to $verview
Power scillations
Technology ) System* Static (ar "ompensator 5S("6
+,ample o- application* ri% (oltage Support
Static %ar +omensators are used in transmission and distribution
networ#s mainly roviding dynamic voltage suort in resonse to system
disturbances and balancing the reactive ower demand o large and
luctuating industrial loads. Static %ar +omensator is caable o both
generating and absorbing variable reactive ower continuously as oosed
to discrete values o i:ed and switched shunt caacitors or reactors.
4urther imroved system steady state erormance can be obtained rom
S%+ alications. ith continuously variable reactive ower suly, the
voltage at the S%+ bus may be maintained smoothly over a wide range o
active ower transers or system loading conditions. This entails the
reduction o networ# losses and rovision o ade5uate ower 5uality to the
electric energy end&users.
"ac# to $verview
(oltage Insta#ility
+,ample o- application* Power 7uality Improvement8 Flicker
2itigation
S%+ is used most re5uently or comensation o disturbances generated
by the 0lectrical rc 4urnaces (04). ith a well&designed S%+,
disturbances such as lic#er rom the 04 are mitigated. 4igure shows the
lic#er mitigation eect o a S%+ installed at a steel ma#ing lant.
4lic#er, the random variation in light intensity rom incandescent lams
caused by the oerating o nearby luctuating loads on the common
electric suly grid, is highly irritating or those aected. The random
voltage variations can also be disturbing to other rocess e5uiment ed
rom the same grid. The roer mitigation o lic#er is thereore a matter o
ower 5uality imrovement as well as an imrovement to human
environment.
Bene-its*
ther applications*
Krid %oltage Suort "ac# to $verview
more a#out S(" 5In%ustry6 an% Flicker
+,ample o- application* 'eactive Power "ompensation at Steelworks
Static %ar +omensators rovide dynamic voltage suort to balance the
reactive ower demand o large and luctuating industrial loads. Static
%ar +omensator is caable o both generating and absorbing variable
reactive ower continuously as oosed to discrete values o i:ed and
switched shunt caacitors or reactors. ith continuously variable reactive
ower suly, the voltage at the S%+ bus may be maintained smoothly
over a wide range o oerating conditions. This entails the imroved ower
actor and suicient ower 5uality, leading to better rocess and roduction
economy.
Bene-its*
K*armonic 4iltering
KPower Luality /mrovement, %oltage "alancing
"ac# to $verview
'eactive Power Factor
Factors ) Phenomena* $n#alance% !oa%
Technology ) System* S(" 5In%ustry6
+,ample o- application* 'ailway Fee%er connecte% to the Pu#lic ri%
The traction system is a ma'or source o unbalanced loads. 0lectriication
o railways, as an economically attractive and environmentally riendly
investment in inrastructure, has introduced an unbalanced and heavy
distorted load on the three&hase transmission grid. ithout
comensation, this would result in signiicant unbalanced voltage aecting
most neighboring utility customers. The S%+ can elegantly be used to
counteract the unbalances and mitigate the harmonics such that the ower
5uality within the transmission grid is not imaired. 4igure shows a tyical
traction substation arrangement with a load balancer (an asymmetrically
controlled S%+). The load balancer transers active ower between the
hases such that the balanced voltage can be created (seen rom the
grid).
Bene-its*
Krid %oltage Suort
"ac# to $verview
$n#alance% !oa%
STT+$M, when connected to the grid, can rovide dynamic voltage
suort in resonse to system disturbances and balance the reactive
ower demand o large and luctuating industrial loads. STT+$M is
caable o both generating and absorbing variable reactive ower
continuously as oosed to discrete values o i:ed and switched shunt
caacitors or reactors. ith continuously variable reactive ower suly,
the voltage at the STT+$M bus may be maintained smoothly over a wide
range o system oeration conditions. This entails the reduction o networ#
losses and rovision o suicient ower 5uality to the electric energy end&
users.
Bene-its*
"ac# to $verview
mitigation
STT+$ME is an eective method used to attac# the roblem o lic#er.
The unbalanced, erratic nature o an electric arc urnace (04) causes
signiicant luctuating reactive ower demand, which ultimately results in
irritating electric lam lic#er to neighboring utility customers. /n order to
stabili8e voltage and reduce disturbing lic#er successully, it is necessary
to continuously measure and comensate raid changes by means o
e:tremely ast reactive ower comensation. STT+$ME uses voltage
source converters to imrove urnace roductivity similar to a traditional
S%+ while oering suerior voltage lic#er mitigation due to ast resonse
time. 4igure shows the lic#er mitigation eect o an STT+$ME installed
at a steel ma#ing lant.
Bene-its*
ther applications*
KPower Luality /mrovement
Technology ) System* STAT"2 .
+,ample o- application* 'ailway Fee%er connecte% to the Pu#lic ri%
Modern electric rail system is a ma'or source o unbalanced loads.
0lectriication o railways, as an economically attractive and
environmentally riendly investment in inrastructure, has introduced an
unbalanced and heavy distorted load on the three&hase transmission grid.
ithout comensation, this would result in signiicant unbalanced voltage
aecting most neighboring utility customers. Similar to S%+, the
STT+$M can elegantly be used to restore voltage and current balance in
the grid, and to mitigate voltage luctuations generated by the traction
loads. 4igure shows a concetual diagram o STT+$M alication or
dynamic load balancing or traction.
Bene-its*
Krid %oltage Suort
"ac# to $verview
Technology ) System* STAT"2 .
STT+$M, when connected to the grid, can rovide dynamic voltage
suort in resonse to system disturbances and balance the reactive
ower demand o large and luctuating industrial loads. STT+$M is
caable o both generating and absorbing variable reactive ower
continuously as oosed to discrete values o i:ed and switched shunt
caacitors or reactors. ith continuously variable reactive ower suly,
the voltage at the STT+$M bus may be maintained smoothly over a wide
range o system oeration conditions. This entails the reduction o networ#
losses and rovision o suicient ower 5uality to the electric energy end&
users.
Bene-its*
"ac# to $verview
+,ample o- application* Transient Sta#ility Improvement
"ottlenec#s may be eectively relieved by the use o entirely or artially
thyristor controlled series comensation. s with conventional S+
technology, T+S+ can imrove stability o ower transmission, reactive
ower balance, and load sharing between arallel lines, thus mitigating the
imact o transmission bottlenec#s. 4igure shows a two&area
interconnected system where the ower transer rom area to area " is
limited to 1!M due to stability constraints. dditional electricity can be
delivered rom area to area " i series comensation is alied to
increase the ma:imum stability limits. *igh degree o series comensation
level is ermitted with the controlled series comensation achieving urther
imroved transmission caacity utili8ation.
Bene-its*
K/mrove -ynamic Stability
K/mmunity against Subsynchronous esonance
Factors ) Phenomena* !oop Flows
+,ample o- application* Power Flow "ontrol
3oo 4lows, or Parallel Path 4lows, may be eectively alleviated by the
use o entirely or artially thyristor controlled series comensation.
/n interconnected ower systems, the actual ath ta#en by a transaction
rom one area to another may be 5uite dierent rom the designated routes
as the result o arallel ath admittance, thus diverting or wheeling ower
over arallel connections. +ontrolled series comensation is a useul
means or directing ower lows along contracted aths under various
loading and networ# conigurations. 4igure shows arallel ath low
alleviation by the use o controlled series comensation. ith a reduction
in the direct interconnection imedance between area and area +, the
Parallel Path 4low which is routed through area " is decreased.
Bene-its*
K3ower Transmission 3osses
ther applications*
+,ample o- application* Power scillation Damping
Thyristor +ontrolled Series +aacitors may be used to dam bul# ower
system oscillations. T+S+, in eect, has the ability to increase the
daming tor5ue (or daming ower) on a bul# ower system which is
e:eriencing angular oscillations between the two terminals o the
comensated transmission line. /t does so by eectively modulating the
amount o ower that lows through the line. hen an angular increase
occurs between the two terminals o a line during an oscillation, the T+S+
will increase ower low in order to oose the increase in angle li#ewise,
the T+S+ will decrease ower low through the line during the angular
decrease ortion o the oscillation cycle. 4igure shows angular oscillation
romted by a temorary short circuit on a transmission system. The
uncomensated system undergoes substantial oscillations ollowing the
short circuit while the same system with T+S+ e:eriences much
imroved resonse.
K/mroved Transient Stability
K/mmunity against Subsynchronous esonance
more a#out T"S" an% Power scillations

Power T&D Solutions

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