Improving MV Network Efficiency With Feeder Automation

7/28/2019 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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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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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



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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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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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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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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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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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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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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Improving MV Network Efficiency With Feeder Automation