Improving MV Network Efficiency With Feeder Automation
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Transcript of Improving MV Network Efficiency With Feeder Automation
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Improving MV Network Efficiencywith Feeder Automation
Yves Chollot - Schneider Electric - France
Jean-Marc Biasse - Schneider Electric - France
Alain Malot - Schneider Electric - France
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C I R E D - 21st International Conference on Electricity Distribution
Frankfurt, 6-9 June 2011
Summary
Abstract ......................................................................................................p 1Introduction ................................................................................................. p 2
Fault passage indicators .............................................................................. p 4
Remote control ............................................................................................ p 6
MV overhead eeder automation ..................................................................p 7
Conclusions ................................................................................................. p 8
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C I R E D - 21st International Conference on Electricity Distribution
Frankfurt, 6-9 June 2011 Paper 0245 | 1
Improving MV Network Efficiency with Feeder Automation
Abstract
This paper shows how improving the network management by increasing the
level o network automation and control improves the operating eciency o
medium voltage distribution networks. The presentation shows the steps to
equip the network according to progressive investment capability, rom ault
passage indicators (FPIs) and remote control, to automatic circuit reclosers
(ACRs) and sectionalizers used in a eeder automation scheme to minimize
the number o disturbances and the outage times experienced during them.
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C I R E D - 21st International Conference on Electricity Distribution
Frankfurt, 6-9 June 2011 Paper 0245 | 2
Improving MV Network Efficiency with Feeder Automation
Introduction
Depending on the technical solutions chosen,
it is possible to help chase the revenue losses
(nondistributed energy or nontechnical losses).
The present paper describes the benets o ault
tracking and network reconguration to help
achieve these goals.
An increasing demand for energyA direct consequence o population growth and
related economic development at the industrial,
commercial, and tertiary levels is an increasing
demand or energy. To meet that, utilities need
to produce more power but also to improve
their transmission and distribution networks or
customers who demand more energy reliability.
In countries with ast growing economies, MV
distribution networks spread at such a speed that
utilities and their employees need very ecientglobal solutions to decrease outage occurrences
and duration, hence improving the quality o
service.
Measuring the quality of supply
To reach the required level o quality o service, it
is rst necessary to accurately quantiy it. To do
so, utilities commonly use measurement indexes
(source: CEER EU25 3rd benchmarking report on
quality o electricity supply):
the "SAIDI" (System Average InterruptionDuration Index) measures the average cumulated
power outage time during one year and per
customer
the "SAIFI" (System Average InterruptionFrequency Index) measures the average number o
outages.
When comparing the SAIDI measured in the 1990s
on the LV standpoint, we can see that this index
varied rom 16 min to 11 h 30. In France, the
quality o service in the 10 largest cities continually
improved rom 1990 to 1997 thanks to EDF's
investment eorts: in seven years the SAIDI went
rom 2 h 00 to 19 min.
Fig. 1 - Source: CEER 2005 report
Fig. 2 - Source: CEER 2005 report
Fig. 2 - Source: CEER 2005 report
But the picture is not as nice when "exceptional
situations" are taken into account:
Last but not least, i we look at the cause o aults,
25 per cent come rom the HV network, 25 per
cent rom the LV network, and 50 per cent rom
the MV network. The MV network is thereore the
part o the overall network to which the greatest
care should be taken to improve the quality o
service.
Another variable to be taken into account in
the quality o service is the cost estimation or
nondistributed energy per year. It increases with
the number o aults per year, the peak power
demand, the length o distribution lines or cables
that are connected to each eeder, the length o
the outage, the billed price per kWh, and above all
the cost o consequences. That is why this cost
can vary rom 5 to 30 dollars per kWh.
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C I R E D - 21st International Conference on Electricity Distribution
Frankfurt, 6-9 June 2011 Paper 0245 | 3
Improving MV Network Efficiency with Feeder Automation
Each o the signicant problems listed here (saety,
voltage losses and drops, long outages, and
numerous short outages) can be solved by taking
appropriate actions on the MV network, such as
protection, reactive compensation, an adapted
neutral system with ASC, multiple sectionalizing,
and the use o appropriate ault detection tools.
Among these dierent problems, two kinds, long
outages and numerous short outages, can be
solved using dierent types o solutions:
standalone FPIs remote monitored FPIs remote controlled switchgears recloser and sectionalizer automation.
These solutions o eeder automation can be used
separately or together. Historically, the remote
control with SCADA comes rom European
networks, while the recloser and sectionalizer
automation without remote control is inspired
by American networks.
The choice between these kinds o solutions is
indeed a technicaleconomical choice, FPIs being
a very economical solution to signicantly improve
the quality o service, while remote controlled
systems require a bigger investment but allow an
even bigger impact.Pole mounted reclosers used
in distribution lines are a very ecient solution to
clear transient aults and isolate aulty sections,
however no utility is rich enough to install on everybranch.
The global approach concept aims to increase
the eciency o network management, in terms
o investment optimization, reduction o minutes
lost, reduction o customers concerned by loss
o voltage, and reduction o time to localize and
recongure.
It involves the segmentation o the network into
three levels. Three types o substations will split
the distribution network into three types o section.
Three types of substations
The ault location and network reconguration
scheme is dened by the use o three main types
A graduate solution
The concept o the denition o three main types
o sections helps to simpliy the investmentanalysis regarding the reality o the network. A
network could be equipped gradually according to
progressive investment capability.
The rst step is to place FPIs in all ground
mounted S/S. The benet is immediately visible
in terms o time to locate aults, but also in terms
o saving assets because FPIs are easy to install
in an existing network and the localization o the
aulty section is done relatively quickly by a patrol.
The second step is either to install ully remote
controlled S/S, which oers the benet o quickly
isolating the aulty section rom the control centre,
or to install an FPI connected to the control centre
in order to decrease the duration o outages.
A global approacho substation:
Type 1: S/S or pole mounted switch withstandalone FPI
Type 2: S/S or pole mounted switch tted withremote controlled FPI
Type 3: S/S or pole mounted switch tted with aremote control cabinet including FPI unction.
A tradeo is to mix the three types according
to various criteria such as number o customers,
accessibility o the S/S, importance o customers
in each section (hospital, ministry, plant, etc.).
According to all these above considerations, a
typical network eeder could be organised as
ollows:
1 to 3 S/S with ull remote control 5 to 10 S/S with remote controlled FPI all other S/S with 1 FPI or all other S/S.
Immediately isolated section
Immediately localized section
Manually localized and isolated section
Substations with remote
controlled switchgear
Substations with remote
controlled FPI
Substations with
standalone FPI
Fig.3
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C I R E D - 21st International Conference on Electricity Distribution
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Improving MV Network Efficiency with Feeder Automation
true RTU with advanced eatures like remote FPI
conguration (ault thresholds, etc.), more than
three FPIs connected to a receiver, and metering
unctions.
Fault passage indicators
Standalone FPIs
Remote controlled FPIs
The ault detection unction must be seen as a part
o the network protection plan. So, depending on
local specicity o line and cable distribution, the
setting should be adapted or greater accuracy o
the unction.
Clip-on FPIs
The rst solution was simply to add a radio chipinside an existing clipon FPI, which was sending
a short range radio signal to a radio receiver
located in direct line o sight at 10 metres rom it.
The contact o the receiver was connected to the
digital input o a small RTU that was orwarding the
signal to the SCADA. Since then, users have
discovered that this technical solution lacked three
main eatures:
First, it was impossible to remotely test the shortrange radio link: i a tree branch grew in the path
o the direct line o sight between the FPI and its
receiver, then the whole system stopped working.
Second, when the battery was empty, thereceiver could not be inormed and so the SCADA
operator would not get an alarm.
Third, given the act that there is a remotecommunicating indicator installed, it should be
possible to get current measurements as well, in
order to optimize the data communication costs
(GPRS, etc.).
Some manuacturers have covered the gap,
by designing a system where the FPI and the
receiver use a bidirectional radio communication
system, and where the receiver is based on a
Fig.5 - OH: clip-on fault passage indicators
Fig. 4 - UG: FPI embedded in the RMU
Fig.6
Wireless
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Improving MV Network Efficiency with Feeder Automation
Pole-mounted FPIsObviously such FPIs do not suer the drawbacks
o a wireless link. It is very easy to connect the dry
contact output relay o a standalone FPI to a small
RTU and this allows it to report an alarm to the
SCADA.
Underground cables
With underground cables, the solution is even
easier because there is no wireless link requested.
The FPI is connected to three phase CTs. From
a unctional point o view, this is a downsized
version o a true remote control cabinet, with the
However, it is not able to manage more than one
MV line, except when located near a branch. In
addition, it cannot accurately measure the load on
the phase conductors.
dierence that it does not have the power supply
to run a switch motor (it oers current and power
measurement, timestamped event recording,
remote parameter settings, etc.).
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Improving MV Network Efficiency with Feeder Automation
Fig.7- IRTU : integrated remote terminal unit for four feeders
In a remote controlled S/S, electronic components
have to perorm a number o unctions. The rst
one is an RTU unction to control the switchgear
rom the SCADA when a ault occurs. The RTU
supports a range o protocols (IEC, DNP3, etc.)
and MODEMs (GPRS, GSM, PSTN, radio, etc.).
It concentrates existing intelligent electronic
devices (FPIs, protection relays, power
measurement devices, etc.).
The remote controlled S/S also serves as a backup
power supply or switchgear motorization, becausemost remote controls are operated during outages.
The FPI unctions include direct acquisition rom
current transormer, phase over current and earth
ault thresholds, load, and/or power measurement
acility.
The devices also have interace unctions: a
dedicated interace with the switchgear, ready to
connect, with a graduated capacity rom one to
numerous eeders and operating local interace
and maintenance acilities.
Such a control cabinet may be built rom standard
components: however, a specially designed control
cabinet (IRTU or integrated remote terminal unit),
is cost eective. Fully tested units rom complete
control cabinet manuacturers are more attractive,
or they guarantee a sae installation, a simplied
commissioning, ull EMC compatibility, and the
minimum wiring and cabling, which dramatically
increases the reliability and the availability o the
control system.
Remote control
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C I R E D - 21st International Conference on Electricity Distribution
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Improving MV Network Efficiency with Feeder Automation
change the protection settings in anticipation o
power fowing in the opposite direction.
The normally open tierecloser closesautomatically.
Due to the ault still being present, the recloser
immediately downstream o the ault trips, and
locks out without reclosing. This will automatically
restore power to the healthy parts o the network.
An operator can now despatch line crews to the
aulted segment.
presence o a ault and the sectionalizers count
the throughaults similarly to the sectionalizing
switchgear network described earlier. The
dierence is that i the ault occurs downstream
o a sectionalizer, the sectionalizer closest to the
ault will open beore the recloser reaches lockout.
Thereore, or this system to work correctly, it
is essential that the recloser is congured withour trips to lockout and the sectionalizers are
congured with supply interrupt counters o three
and two respectively.
assistance would be required to clear the ault.
Some aults are however more permanent.
Examples include distribution equipment, such as
transormer ailures and allen power lines due to
motor accidents or storms. Protection equipment
is designed to minimise damage by interrupting the
supply to a segment containing a ault. The supply
will remain o until the ault is removed and the
protection equipment is turned back on.
Todays reclosers are capable o sophisticatedprotection, communication, automation and
analytical unctionality. It is possible to operate in
either a 'manual' mode where the operator has
to perorm the reconguration o the network, or
in a 'loop automation' mode where the reclosers
perorm the task automatically.
Loop automation
Recloser and sectionalizer automation
Loop automation uses time, voltage, power
fow, and these simple rules to isolate the
ault and recongure the network, without any
communications or operator assistance. In a loop
automation network, the ollowing actions will take
place when a ault occurs:
The recloser immediately upstream o theault automatically trips, recloses to lockout, and
remains open.
Reclosers downstream o the ault automatically
A eeder automation network combines reclosers
and sectionalizers in a eeder to provide grading
on both current/time and number o operations.
This is accomplished by introducing up to two
sectionalizers in each zone protected by a recloser.
In a eeder automation network the reclosers
protect the downstream portion o the eeder up to
the next recloser.
Similarly to the recloser network described
earlier, the recloser will trip and reclose in the
In an eort to improve the reliability o supply,
providers are rethinking the levels o sophistication
deployed in their medium voltage (MV) overhead
eeders. An autoreclose cycle should clear a
transient ault without interrupting supply to the
customer. In most cases no urther operator
MV overhead feeder automation
Fig.8 - Solid dielectric recloser
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Improving MV Network Efficiency with Feeder Automation
It is now clear that in most countries, delivering
electricity with a high level o quality and availability
is becoming a priority challenge. For years and
years the utilities have experimented with various
solutions. It is now time to take advantage o all
this experience.
It appears clear that remote control and ault
detection are two o the key solutions. The
customers are mainly aected by aults on the
distribution MV network, to which, consequently,
we have to pay particular attention.
The introduction o ault detection, network
monitoring and control and automation needs to
be driven by pragmatic and optimized actions.
The icing on the cake when using remote
controlled FPIs and IRTU tted with load
measurement and eeder automation, is that
utilities can easily optimize their power generation
and chase nontechnical losses.
Conclusions
The global concept described here synthesizes the
experience cumulated rom various utilities world
wide (France, Spain, UK, Australia, Canada, etc.).
The components which must be associated to
such a concept, such as IRTU, remote controlled
FPIs, reclosers, and sectionalizers are available on
the market.
Cost eective solutions are also being proposed by
the main manuacturers with embedded concepts.
This allows the proposal o FPIs, IRTUs, and other
electronic devices built into the RMU or into theMV cubicle.
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