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P L C E
LA SALLEE
SCHOOLL OF
ENGINEERING
POW
WER LIN
NE COM
MMUNIC
CATION
NS FOR THE
ELECCTRICAL UTILITYY: PHYSSICAL LAYER DESIGN
N
AND CHANNEL MODELIN
O
NG
PhD Thesis
T
| Ricard
R
Aq
quilué de Pedro
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
Power Linne Communica
ations for the Electrical
E
Utilityy: Physical Lay
yer Design annd Channel Moodeling
Ricard Aq
quilué de Pedro
Research Group in Elecctromagnetism
m and Communnications (GRECO)
Enginyeriia i Arquitectuura La Salle
Universita
at Ramon Llull
Quatre Camins,
C
2
08022 Barcelona, Spa
ain
[email protected]
E-mail: ra
Advisor: Dr. Joan Lluís Pijoan i Vidal
Enginyeriia i Arquitectuura La Salle, Universitat
U
Ram
mon Llull, Barce
elona, Spain
2
Abstract
A Elisabeet y a mis pad
dres, Mari Feli y Miguel
3
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
4
Abstract
ABSSTRACT
The world of Pow
wer line commuunications (PLC
C) can be divvided into threee main typess: low voltage
e PLC (LVPLC), medium voltage PLC (MV-PLC) and high voltage PLC
C (HV-PLC). Thhese last years, LV-PLC has attracted
a great expectation since its wiideband capa
abilities has made
m
this technnology a suita
able choice for last-mile
acceess and in-hom
me communicattions. Moreoveer, LV-PLC also
o includes a uttility oriented low frequency
y and low
speeed applicationns, such as autoomatic meter reading (AMR
R), load distrib
bution, dynamic billing and so on. On
the other
o
hand, MV-PLC
M
and HV
V-PLC, historiccally oriented to teleprotecction and teleccontrol tasks, are being
consiidered as a reliable coommunication channel. The
e development of digital equipment and the
stand
dardization efforts are making thosse channels an attractivve medium for electrica
al utilities
teleccommunicationns services, sincce the networkk, as well as inn LV-PLC, is already deployyed.
In this PhD disserttation, the threee different PLC
P topologie
es are revieweed and the different comm
munications
posed. Then, a deep technological revieew of existing
g AMR solutions for the
technniques in such channels exp
European CENELEC
C band, as weell as HV-PLC systems is givven, showing thhat existing A
AMR systems deliver low
C systems are anchored in old
o fashioned standards.
s
frequency diversity and HV-PLC
This work
w
walks arround the three topologies, specifically, CENELEC
C
band
d utility orienteed applicationns, channel
measurement and modeling and
d channel mea
asurement and physical layeer design, rega
arding LV-PLC
C, MV-PLC
pectively. Exissting CENELEC
C compliant systems
s
deliveer low or none frequency
y diversity
and HV-PLC resp
mechhanisms, yield
ding in a low
w robustness against
a
colore
ed noise and interference.. This work propose
p
a
multiicarrier based physical layer approa
ach that, whiile keeping the complexiity low, delivers high
performance allow
wing a greatt level of freq
quency diverssity. Focusing on MV-PLC, a hybrid detterministicstatisstical channel model for urb
ban undergrouund rings is de
eveloped and,, finally, in HV
V-PLC systems,, this work
prop
poses, based on
o measuremeents and field tests, a wideb
band physical layer in ordeer to increase data rate
whilee keeping low
w both the pow
wer spectral deensity and posssible interfereence to other systems.
5
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
6
< Contentss
CON
NTENTS
Absttract ........................................................................................................................................................... 3
Conttents ........................................................................................................................................................... 7
List of
o figures and
d tables ................................................................................................................................ 9
Acro
onyms ...................................................................................................................................................... 11
Ackn
nowledgemen
nts ...................................................................................................................................... 15
Auth
hor’s presenta
ation ................................................................................................................................... 17
1.
Introduction .......................................................................................................................................... 19
1..1.
1.1.1.
Power Line Carrrier................................................................................................................................. 19
1.1.2.
Ripple Carrier Signaling ....................................................................................................................... 22
1.1.3.
Toowards the sta
andardizationn of the accesss and in–homee PLC technology ............................... 23
1..2.
2.
3.
Contents of the thesiss ....................................................................................................................................... 25
n
............................................................................................................................ 27
Power line networks
2..1.
High vooltage level ........................................................................................................................................... 28
2..2.
Medium
m voltage netw
works .............................................................................................................................. 32
2..3.
Low vooltage networkks ..................................................................................................................................... 36
Automatic meter
m
reading and low com
mplexity robust modem dessign ............................................... 41
3..1.
Introduction........................................................................................................................................................ 41
3..2.
Suitable modulationss for CENELEC A band................................................................................................. 42
3.2.1.
N
Narrowband
m
modulations
..................................................................................................................... 42
3.2.2.
W
Wideband
mod
dulations ........................................................................................................................ 42
3..3.
Manufa
acturer solutions .................................................................................................................................... 44
3..4.
Multica
arrier proposa
al for AMR systtems ........................................................................................................ 45
3.4.1.
Zero crossings as
a a time refeerence ..................................................................................................... 45
3.4.2.
SC-BPSK perfoormance in front of windowinng errors: Lea
ading to the M
MC approach .............. 46
3.4.3.
M
MCM
and mainns zero-crossinng jitter ................................................................................................... 46
3.4.4.
Residual inter-ssymbol interfeerence: cyclic prefix
p
and posstfix ...................................................... 47
3.4.5.
Frrequency offseet and system
m perfomance......................................................................................... 49
3.4.6.
Phase recoveryy ....................................................................................................................................... 51
3..5.
4.
Historyy of power linee communicatioons for the ele
ectrical utility ................................................................ 19
Conclussions ........................................................................................................................................................ 51
Medium voltage channel measuremen
nts and its detterministic-sta
atistical modeel .............................. 53
4..1.
Introduction........................................................................................................................................................ 53
4..2.
Characcterization and
d modeling ap
pproaches .............................................................................................. 53
4..3.
Measurrements ................................................................................................................................................... 54
4.3.1.
Fiield measurem
ments ............................................................................................................................... 55
4.3.2.
La
aboratory measurements .................................................................................................................... 60
7
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
4.3.3.
5.
4.4.
MV channell topology moodeling and va
alidation ......................................................................................... 64
4.5.
Conclusions ........................................................................................................................................................ 66
Hig
gh voltage cha
annel measurrements and MC-SS
M
tests....................................................................... 67
5.1.
Introduction ........................................................................................................................................................ 67
5.2.
Manufacturer solutions .................................................................................................................................... 68
5.3.
Measuremeent and test sceenario ..................................................................................................................... 68
5.4.
Measuremeents and resultss............................................................................................................................... 69
5.4.1.
Attenuuation characteritics...................................................................................................................... 70
5.4.2.
Backg
ground noise ................................................................................................................................... 70
5.4.3.
Time spread
s
and frequency sprea
ad ................................................................................................... 71
5.4.4.
MCM design and teest: short link .......................................................................................................... 73
5.4.5.
MCM design and teest: long link ........................................................................................................... 77
5.5.
6.
Joint measurement:
m
input impedannce .................................................................................................. 63
Outcomes and
a conclusionss............................................................................................................................... 79
Con
nclusions and
d future work .....................
.
......................................................................................... 81
6.1.
Conclusions ........................................................................................................................................................ 81
6.2.
................................................................................................................................ 82
Next steps .........................
.
7.
Refferences ............................................................................................................................................. 83
8.
App
pendix A. Included paperss ............................................................................................................. 89
9.
8.1.
Appendix A.1
A ................................................................................................................................................... 91
8.2.
Appendix A.2
A ................................................................................................................................................ 101
8.3.
Appendix A.3
A ................................................................................................................................................ 109
8.4.
Appendix A.4
A ................................................................................................................................................ 117
8.5.
Appendix A.5
A ................................................................................................................................................ 125
8.6.
Appendix A.6
A ................................................................................................................................................ 137
App
pendix B. Autthor’s publica
ation list ............................................................................................... 149
9.1.
Conference contributions.............................................................................................................................. 149
9.2.
Journal conttributions ..................................................................................................................................... 149
8
List of figures and
d tables
LISTT OF FIGUR
RES AND T ABLES
pplications ............................................................................................. 21
Figurre 1 PLC transsceptor.data transmission ap
Figurre 2 OPERA powerline
p
acceess topology .................................................................................................................. 23
Figurre 3 The four main entities involved in PHY and MAC PLC
P specificatioons ........................................................ 25
Figurre 4 Power linne grid .................................................................................................................................................... 27
Figurre 5 “Egara” Distribution ESS, where the reeceiver is loca
ated ................................................................................ 28
Figurre 6 RF condittioning devicess at Endesa “EEgara” substattion ................................................................................ 30
Figurre 7 Line trap, coupling cap
pacitor and cooupling device in the HV netw
work .................................................... 30
Figurre 8 HV channnel model................................................................................................................................................ 31
Figurre 9 Star topoology. A singlee MV line feed
ds MV custome
ers and TS .................................................................... 32
Figurre 10 Star top
pology. Severa
al MV lines wiith branching ......................................................................................... 32
Figurre 11 Ring top
pology in norm
mal configurattion and in fauult configuratioon.......................................................... 33
Figurre 12 TS basicc scheme ................................................................................................................................................. 34
Figurre 13 MV Dim
mat CAMT cap
pacitive couplinng unit used inn the measurem
ments .................................................... 35
Figurre 14 Unipola
ar underground
d cable structuure........................................................................................................... 35
Figurre 15 MV channel model ............................................................................................................................................ 36
Figurre 16 LV grid devices .................................................................................................................................................. 38
Figurre 17 LV channnel model .............................................................................................................................................. 40
Figurre 18 CENELEC band maxim
mum levels ..................................................................................................................... 41
Figurre 19 DS-SS modulation
m
schheme................................................................................................................................ 43
Figurre 20 OFDM modulation
m
schheme ............................................................................................................................... 44
Figurre 21 SC-BPSK performance in front of windowing
w
erro
ors ................................................................................. 46
Figurre 22 MC-BPSSK performancce in front mains zero-crossiing jitter ........................................................................ 47
Figurre 23 MC systtem performannce for variouus CP lengths .......................................................................................... 48
Figurre 24 MCM sp
pectrum ................................................................................................................................................... 50
Figurre 25 System performance for a frequency offset of 253 Hz, 8 subccarriers at 8 kbps ............................. 51
Figurre 26 Endesa BA07155 and
d BA07460 TSSs ............................................................................................................ 54
Figurre 27 MV ring
g segment atteenuation .......................................................................................................................... 55
Figurre 28 MV ring
g segment dela
ay power proofile ......................................................................................................... 57
Figurre 29 MV ring
g segment bacckground noisee statistics............................................................................................... 58
Figurre 30 Impulsivve waveform parameters
p
.................................................................................................................... 58
Figurre 31 MV ring
g segment inteer-arrival and width times sttatistics........................................................................... 59
Figurre 32 MV ring
g segment pea
ak and averag
ge power statistics .............................................................................. 59
Figurre 33 MV cab
ble to N connector ................................................................................................................................. 60
Figurre 34 MV cab
ble S parameters................................................................................................................................... 61
Figurre 35 Extracteed MV cable parameters
p
.................................................................................................................... 62
Figurre 36 MV coupler performa
ance variations .............................................................................................................. 63
Figurre 37 MV coupler S parameeters ............................................................................................................................... 63
9
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
Figure 38
8 Measured and real reflecction coefficiennt ..................................................................................................... 63
Figure 39
9 MV channel input impedance .......................................................................................................................... 64
Figure 40
0 MV model ............................................................................................................................................................ 65
Figure 41
1 Simulated toopology .......................................................................................................................................... 65
Figure 42
2 Measured and simulated attenuation
a
chharacteristics .................................................................................. 66
Figure 43
3 110 kV 4 cirrcuits line ........................................................................................................................................ 69
Figure 44
4 Link attenuation ................................................................................................................................................. 70
Figure 45
5 Background noise .............................................................................................................................................. 71
Figure 46
6 Background noise statisticss............................................................................................................................... 71
Figure 47
7 Channel delay profile ...................................................................................................................................... 72
Figure 48
8 Frequency autocorrelation
a
n function ................................................................................................................ 73
Figure 49
9 OFDM framee and symbol parameters .......................................................................................................... 75
Figure 50
0 OFDM perfoormance.......................................................................................................................................... 76
Figure 51
1 MC-SS perfoormance ......................................................................................................................................... 77
Figure 52
2 Long link atttenuation characteristic ................................................................................................................ 78
Figure 53
3 Long link delay spread .................................................................................................................................... 78
T
transp
port levels ....................................................................................................................................... 29
Table 1 Typical
Table 2 Skin
S and soil effect
e
attenuattions ........................................................................................................................ 31
Table 3 Main
M AMR PLC
C chip manufa
acturers.................................................................................................................... 45
Table 4 Zero-crossing
Z
jiter parameteers ........................................................................................................................... 46
Table 5 Proposed
P
systeem characterisstics ......................................................................................................................... 51
Table 6 MV
M PN sounding parameterrs ............................................................................................................................. 56
Table 7 Main
M HV poweer line carrier manufacturerrs...................................................................................................... 68
Table 8 MC-CDMA
M
pa
arameters ........................................................................................................................................ 75
Table 9 MC-DS-CDMA
M
A parameters ................................................................................................................................. 76
Table 10
0 Short link sysstem performa
ance ......................................................................................................................... 77
Table 11 Long link systtem performance .......................................................................................................................... 79
10
Acronyms
ACR
RONYMS
AM:
A
Amplitude
Moodulation
AMRR:
A
Automatic
Meter Reading
ASK::
A
Amplitude
Shift Keying
AWG
GN:
A
Additive
Whitte Gaussian Noise
N
BER:
Bit Error Rate
BPL:
Broadband Poower Line
BPSK
K:
Binary Phase Shift Keying
CEPC
CA:
C
Consumer
Elecctronics Powerrline Communiccation Alliancee
CP:
C
Cyclic
Prefix
CPE:
C
Customer
Prem
mises Equipmeent
DCSK:
Differential Code Shift Keying
DCTPP:
Digital Carrier Transmissionn over Power line
DCTSS:
D
Departament
d Comunicacions I Teoria deel Senyal, Dep
de
partment of Coommunicationss and
SSignal Theory
DHC
CP:
Dynamic Host Configurationn Protocol
DPLC
C:
Digital Power Line Carrier
DSB--AM:
Double Side Band
B
– Amplitude Modulatio
on
DS-SSS:
Direct Sequennce – Spread Spectrum
S
EHV::
Extremely Hig
gh Voltage
EMC
C:
Electromagnettic Compatibillity
EPR:
Ethylene Prop
pylene Rubber
ES:
Electrical Subsstation
ETSI::
European Teleecommunicatioons Standards Institute
EU:
Electrical Utilitty
FFT:
Fast Fourier Trransform
FH-SSS:
Frequency Hoopping – Sprea
ad Spectrum
FSK:
Frequency Shiift Keying
FTP:
File Transfer Protocol
P
GPS:
G
Global
Positiooning System
11
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
GRECO:
Grupp de Recerca enn Electromagneetisme I Comunicacions, Reseearch Group iin
Electromagnetism and
a Communiccations
HE:
Head
d End
HF:
High Frequency
HV:
High Voltage
HVAC:
High Voltage Alternating Currennt
HV-PLC:
High Voltage – Poower Line Com
mmunications
ICI:
Inter--Carrier Interfference
IEC:
Internnational Electrrotechnical Coommission
IEEE:
Instituute of Electrica
al and Electronics Engineerss
IFFT:
Inverrse Fast Fourieer Transform
IIIT:
Institut für Industrieelle Informationstechnik
IP:
Internnet Protocol
ISI:
Inter--Symbol Interfference
ISP:
Internnet Services Provider
LV:
Low Voltage
LV-PLC:
Low Voltage – Pow
wer Line Comm
munications
MAC:
Medium Access Coontrol
MBOK:
Maryy Biorthogonal Keying
MC:
Multiicarrier
MC-CDM
MA:
Multiicarrier – Code Division Mulltiple Access
MC-DS-C
CDMA:
Multiicarrier – Direect Sequence – Code Divisio
on Multiple Acccess
MCM:
Multiicarrier Modullation
MC-SS:
Multiicarrier – Spreead Spectrum
MV:
Medium Voltage
MV-PLC:
Medium Voltage – Power Line Communication
C
ns
MWNA:
Microowave Network Analyzer
OFDM:
Orthogonal Frequeency Division Multiplexing
M
OPERA:
ns European Research
Open Power Line Communicatio
C
R
Alliannce
PEP:
Peakk Envelope Pow
wer
PHY:
Physiical
12
Acronyms
PLC:
Power Line Coommunicationss
PN:
Pseudo-Noise
POP:
Point of Preseence
PPS:
Pulse per Secoond
PSD::
Power Spectra
al Density
PSK:
Phase Shift Keeying
N:
PTSN
Public Telephoone Switched Network
QAM
M:
Q
Quadrature
A
Amplitude
Keyying
RADIUS:
Remote Autheentication Dial--In User Server
RCS::
Ripple Carrier Signaling
RE:
Repeater
RF:
Radio Frequenncy
RMU
U:
Ring Main Uniit
RTTEE:
Radio Equipm
ment and Telecommunicationss Terminal Equuipment
SCM
M:
S
Single
Carrierr Modulation
S-FSK:
S
Spread
– Freq
quency Shift Keying
K
SS:
S
Spread
Specttrum
SSB--AM:
S
Single
Side Ba
and – Amplitude Modulation
TS:
T
Transformer
S
Station
V:
UHV
Ultra High Voltage
UPA:
Universal Pow
werline Alliancee
URL:
Universitat Ram
mon Llull, Ram
mon Llull Univerrsity
VoIPP:
V
Voice
over Intternet Protocol
VSF--OFCDM:
V
Variable
Spreeading Factor – Orthogonal Frequency and Code Divission Multiplexiing
XLPEE:
C
Cross-Linked
P
Polyethylene
13
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
14
A
Acknowledgem
ments
ACK
KNOWLEDG
GEMENTS 1
First of all, many thanks to Dr. Joan Lluís Pijjoan, who enccouraged me to pursue the PhD at the end
e of my
Mastter studies and for doing his
h best while pushing me thhrough this exxciting, lonely and fulfilling journey. I
don’tt want to forg
get the rest off the Researchh Group in Ele
ectromagnetism
m and Commuunications (GRECO) and
Communications and Signal Theeory Departmeent staff: Carlles Vilella, Miq
quel Ribó, David Badia, Joan Ramón
G
Javieer Pajares, Pa
ablo Rodrigueez and Alberrt Miquel Sánnchez, for
Reguué, David Miralles, Simó Graells,
makiing my PhD a great and unforgettablle adventure. I would likee to have a special mention to my
officcemates and friends,
f
Ismaeel Gutierrez, Pau Bergada
a and Marc Deumal,
D
greatt engineers and
a better
persons, for sharinng those funny moments, those great illusio
ons… Good luuck and may tthe force be with
w you…
Furthhermore, I would
w
like to express myy gratitude to
t the “Powerliners” at Institut für Inndustrielle
Inforrmationstechnikk (IIIT), Universsität Karlsruhee, in Germany
y, Timo Kistner and Michael Bauer, and to
o the other
IIIT sttaff, especiallly to Prof. Dr. Klaus Dostert for his hospita
ality and the others
o
PhD stuudents for makke me feel
as if I were at hom
me.
Finallly, I also wouuld like to meention Germánn Sánchez and
d José Comab
bella, from Enndesa Networrk Factory
S.L., a great modeel of support to the pure reesearch and development
d
f
from
the priva
ate sector, for the great
workk we have donne together.
1 Thee author wantts to acknowleedge the pre--doctoral granntship of the “Departament
“
d’Universitats,, Recerca i
Socieetat de la Infoormació de laa Generalitat de
d Catalunya” especially thhe program “Beques doctorrals per la
form
mació de persoonal investigaador (FI)” froom which the author has been beneficciary; and the
e Spanish
Government projeects REN2003
3-08376-C02-01 and CGL2005-24213
3-E, that havee partially fuunded the
initia
al work of this thesis.
15
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
16
Auuthor’s presenttation
AUTTHOR’S PR
RESENTATIO
ON
Ricarrd Aquilué recceived the BScc and MSc deg
grees in Telecommunicationss Engineering from La Salle School of
Enginneering, Ramoon Llull Universsity, in Barceloona, Spain, in 2003 and 20
004, respectivvely. Since 200
06 he is a
FI PhhD Fellow from
m the Catalann Governmentt (Departament d’Universitatts, Recerca i Soocietat de la Informació
I
de laa Generalitat de Catalunyaa). He joined the Research Group in Eleectromagnetism and Comm
munications
(GREECO) that belongs to the Department
D
off Communications and Signa
al Theory (DC
CTS) in 2003, where he
has participated in
i several pub
blic and priva
ate research projects,
p
mainly in high freq
quency (HF) io
onospheric
munications annd power line communicatioons. Nowaday
ys he continuess in the DCTS at the same university,
comm
comb
bining researcch and manag
gement activitiies, mainly focused on the fields of pow
wer line commuunications,
adap
ptive multicarrrier systems annd software defined
d
radio.
From
m September 2003,
2
he partticipated activvely into the Antarctic projecct “Characterization and mo
odeling of
the Antarctic
A
ionospheric channel: Advanced HF communiccations” fundeed by the Minnistry of Education and
Sciennce from the Spanish
S
Goveernment, wheree he worked in the design and implemenntation on the
e software
radioo based channnel sounding system and data
d
transceivver. Also, rela
ated to this prroject, from January to
Marcch, 2006, he realized
r
a twoo months stay in the Spanishh Antarctic Ba
ase “Juan Carlos I”. (For more details,
the reader
r
is referrred to refereence [1] and Appendix
A
A.1, where previoous work relateed to HF can be
b found).
At thhe beginning of
o 2006, conssequence of a private fund
ded project froom Endesa Diistribución Elécctrica S.L.,
the author
a
moved
d to power linne communica
ations, specificcally on low voltage
v
poweer line automa
atic meter
read
ding technolog
gy. Related too this researcch field, he did
d a three months
m
researcch stage at Institut
I
für
Indusstrielle Informaationstechnik (IIIT), Universitäät Karlsruhe, Germany.
G
Theen, due to a second projectt, this time
from
m Endesa Netw
work Factory S.L.,
S he focused his researchh activities to medium
m
and hhigh voltage power
p
line
comm
munications, reegarding modulation designn and channel modeling.
17
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
18
Introductionn
CHAPTTER 1
1. INTRODUC
CTION
1.1.. HISTORY OF
O POWERR LINE COM
MMUNICATI ONS FOR THE ELECTRRICAL UTILI TY
The power grid has been used as a communnications mediium since the beginnings of 20th century, when the
power grid main exploitation
e
p
purpose
was thhe transmission of voice in the
t high voltage (HV) netwo
ork [2][3].
Rapiidly, other ap
pplications suchh as operatioons manageme
ent, monitoring
g and troubleeshooting, thatt required
bidirrectional flow of messages,, took an imp
portant role inn the HV comm
munication sceenario. Since telephone
netw
work could not be found in every
e
point annd its reliability
y was not enoough to cope w
with the requirrements of
the services
s
mentiioned before,, these services were deployed on the power lines. Moreover, the use of
telep
phony or any other
o
kind of leased
l
line woouldn’t be eco
onomical for la
arge distances.
The electrical
e
utilitties (EUs) operrations on the high voltage lines can be grouped into thhree classes:
1.
2.
3.
Operatioon managemennt
Monitorinng
Limitationn and removall of failures
Opeeration management tasks ta
ake care for the optimum ennergy distribuution, trying to generate wha
at is to be
consuumed, keeping
g enough energy to cope with
w demand peaks
p
and avooiding the exccess of reserves around
the network.
n
In ca
ase of failure in the HV nettwork, the fasst and reliablee exchange of data betwe
een power
plants, transformer stations and substations, switching equip
pment and couupling points tto neighboring
g networks
k factor when trying to minimize
m
the im
mpact of that failure
f
to the rest
r of the network. The monnitoring of
is a key
that data, regardiing the network state, is carrried out by means
m
of tracking energy reequirement, voltage and
action capability in front of networks failures.
frequency, yielding to a fast rea
In the past, the data was transsmitted by ann operator thrrough the teleephone network but, in the course of
time,, the automatic, reliable annd fast transm
mission of all the
t data mentioned beforee became an important
issuee of the EUs. Since
S
most of them
t
have alw
ways seen the
e HV network as its natural medium to tra
ansmit the
mana
agement and monitoring innformation, EU
Us, pushed by the necessity of having theeir own data networks,
led to
t the quick deevelopment off power line ca
arrier (PLC) sy
ystems [4].
1.1 .1. POWERR LINE CAR RIER
The power grid was
w not origina
ally designed to transmit da
ata through itts circuits; how
wever, the relia
able data
transsmission is posssible with low
w power, over a relatively broad
b
availab
ble spectrum. IIn HV networkks, the PLC
frequency range is
i upper limiteed by standarrd at 500 kHzz [5][6] and loower limited b
by the same at
a 40 kHz,
d by the coupliing capacitor), though.
loweer frequencies can be achievved in practicee (15 kHz – 25 kHz, limited
At thhe beginning, the
t task handlling was donee by means of voice. The voice frequency band (300 - 2400 Hz)
had to be transmiitted successfuully under marrginal conditio
ons. Only amp
plitude modula
ation (AM) wa
as suitable
to transmit data through
t
the HV links. The equipment
e
req
quirements forr transmitting and receiving
g a simple
doub
ble-sideband AM (DSB-AM)) without supp
pressed carrier are considerrably less than the ones req
quired for
the same approa
ach with suppressed carriier. Although suppressing the carrier means a red
duction of
interrmodulation rissk when dealiing with multip
ple channel PLLC, this approoach was not cconsidered for PLC due
to the high receiveer cost, and DSSB-AM withoutt suppressed carrier
c
was used until aboutt 1940.
The increasing lacck of free frrequency rang
ge, forced the
e EU to repla
ace their DSBB-AM links wiith singlesideb
band AM (SSBB-AM). An SSBB-AM system occupies
o
half the
t bandwidthh that a DSB-A
AM does. This migration
to SSSB-AM systems caused the current
c
typical 4 kHz channe
elization of thee HV frequenccy range.
19
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
In the couurse of time, the
t quality of service that thhe EUs desired
d from their data
d
network became difficcult to
achieve, even impossib
ble, by means of voice channnels. Moreove
er, human based systems tra
ansmitting the data
v
channels couldn’t supp
port a real fulll-time monitoring of critical data as they were suppose
ed to.
through voice
The measurement and transmission of the netwoork state and management operations ccould be trigg
gered
much fastter, reliable and
a easier usinng digital systtems. These digital systems didn’t get thee redundancy level
that can be found inheerently in huma
an voice (the corruption
c
of one
o single datta bit can lead
d to critical errrors),
as quite good
d knowledge of
o coding techhniques, the hardware
h
plattforms didn’t allow
and althoough there wa
their implementation. Actually,
A
the data
d
protectioon technique used on these channels was based on ma
ajority
vote at thhe receiver sitee from the muultiple replicas of the information sent by the transmitter.
At the beeginning of thheir deploymeent, the digita
al systems’ da
ata rates weree low, i.e. 50
0 bps in a 12
20 Hz
bandwidth using amplitude shift keyying (ASK) or frequency shift keying (FSK). This alloweed the transm
mission
gital channels in one 4 kHzz voice channeel. Soon, the data
d
rates rosse from 50 bp
ps to 100 bpss and
of 33 dig
200 bps.. With the incrrease of the power
p
grid auutomation leve
el, the needed
d data rates reequirements grown
g
to support the transmiission of such a complex syystem. Higherr rate digital transmission cchannels with 600,
d 2400 bps had to be used
d. At 2400 bp
ps, the whole 4 kHz channel was used [4].
1200 and
Nowadayys, PLC system
ms are based
d on the comb
bination of annalog and dig
gital techniques. This prese
ents a
higher deegree of flexxibility for thee customer. At
A the same time,
t
it solvess the problem
m of relatively
y low
reliabilityy of the digita
al PLC for taskks such as teleeprotection annd overcomes the rate limita
ation of the annalog
PLC.
b
analog and digital sysstems.
If focusing in data transmission, the state of the art of PLC still comprises both
s
(designed by analoog or digital technology)
t
usse SSB-AM with
w suppressed
d carrier on 4 kHz
Analog systems
channels in order to keeep compatible with legacyy equipment. These
T
analog systems
s
allow the transmissiion of
d data by meeans of a digital modulatioon stage befo
ore the SSB-AM
M modulator, with speeds up to
voice and
2400 bp
ps. On the otheer hand, digita
al systems alloow access to data
d
servers, data
d
networkss and manage
ement
applications (Figure 1).
20
Introductionn
Line trap
Coupling
C
device
Matching
M
device
M
Management
u
unit
PLC transceptor
Voicce lines
Data servers
IP network
n
Figure 1 PLC tran
nsceptor.data transmission appliccations
o quadraturee amplitude modulation
m
(QA
AM) single ca
arrier modulattion (SCM)
Current digital sysstems based on
u to 80 kbp
ps in a 16 kH
Hz bandwidth [7]. Orthogoonal frequenccy division
can reach a net bit rate of up
multiiplexing (OFD
DM), the most efficient multiicarrier modullation (MCM), begins to pla
ay an importa
ant role in
HV communication
c
ns due to its inherent robuustness against multipath effects
e
and nnarrowband innterferers.
OFD
DM is becoming
g the choice for
f manufacturrer’s next genneration HV power line com
mmunications equipment,
e
delivvering a data rate of 256 kbps
k
availablee to the user in a bandwidtth beyond the typical 4, 8 or
o 16 kHz,
extending the usable carrier freequency rangee up to 1 MHzz [8].
Besid
de traditional core servicess mentioned before,
b
(opera
ation manageement, monitorring and limitation and
remooval of failurees), EUs would
d like to satisfy increasing need
n
of new internal
i
servicces, taking benefit from
the use
u of their ow
wn power grids, like [9]:
•
•
•
•
•
•
Demand prediction
mer overload analysis
Transform
Outage Localization
L
Support for
f advanced grid control & automation
Network Optimization
Security related
r
commuunication (videeo / audio)
Now
wadays, the sttandards rega
arding HV coommunications are obsoletee. IEC-TC57 W
Workgroup 20
0 recently
startted to work on
o the new sta
andard includ
ding HV digita
al carrier trannsmission overr power line (DCTP) or
digittal power line carrier (DPLC
C).
21
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
1.1.2. RIPPLE CARRRIER SIGN
NALING
Regardinng the medium
m and low volttage levels (M
MV and LV), thhe main data application p
performed on these
networks is load distrib
bution. MV annd LV networkks were used as a communication medium
m for the firstt time
around 1930.
1
Initial ripple carrier signaling (RRCS) practical applicationss were perfoormed in Potssdam,
Germanyy, at 1930, unnder the frameework of a Sieemens’ projectt called Teleneerg. The first p
practical use of
o this
technolog
gy was also ca
arried out in Germany,
G
in Sttuttgart and Magdenburg,
M
i 1935 by AEEG.
in
While thee HV level prresents a rela
atively easy too match (200
0 – 400 Ω) frriendly overheead lines for data
transmissiion for frequeencies up to 500 kHz and
d even 1 MHz, MV and LV
V are hostile environmentss with
unpredicttable branchinng (LV) and coonnected load
ds that decrea
ase the channeel input imped
dance down to
o tens
even tentths of ohm. Thiis scenario calls for a high power
p
injection dimensioned
d for the network peak load
d (this
causes the impossibilityy of transmitting data in thee uplink), in order to cover the maximum
m MV and LV area.
ghly populateed network can represent a very
Since eveery active consumer adds itts load to the network, a hig
low load
d. Due to the large number of differentt network connfigurations, thhe exact trannsmit power values
v
cannot bee given, but trransmission poowers between 10 and 100
0 kW are com
mmon. To let thhe informationn flow
from the power supply to the custoomers, the aud
dio band freq
quency rangee was chosen for signaling.. That
frequencyy (often beloow 1 kHz) pa
assed throughh the MV to LV transform
mers experiencing only a minor
attenuation. The data
a rates were obviously very low, but enough
e
for ta
ask regarding
g load distrib
bution
d transmission.. However, thiis transmission has to be hig
ghly reliable, even with no feedback channel
command
availablee.
Initially, multiple freq
quency RCS systems
s
weree used: the receiver
r
has to correctly detect the exact
e
combinattion of frequeencies beforee triggering itts related funnction. Since generating and injecting single
s
frequencyy signals into the network was seen to be more cost effective, in 1940 RCS syystems began their
migrationn to this approach. Due to its low generration complex
xity, ASK wass the modulatiion scheme ussed in
single freequency networks. The duration of an RCS
R
ASK modulated telegram could takke from 28 to
o 180
seconds. 10 to 60 imp
pulses (with a guard time after each im
mpulse) were transmitted p
per telegram. Such
ansient interfe
erers and impulse events. Inn order to incrrease
lasting signals offer a high robustneess against tra
the safetyy of RCS systeems, the digita
al message is coded
c
onto a high dimensioon codeword b
before transmiission.
Since theere are forbid
dden binary combinations
c
o that codew
of
word, this technnique permits the detectionn and
even the correction of received messsages. Moreoover, if this is not enough, the
t transmitteed message will
w be
retransmiitted at interva
als of several minutes [4].
Recently, EUs realized that RCS is still
s a good soolution for loa
ad balancing management but their techhnical
limitations cannot copee with current utilities needs like telecontrrolling and telemetering, moost especially after
the dereg
gulation of thee energy markket, e.g., selecctive addressing (with RCS all customers in the same MV-LV
M
mesh aree addressed in parallel). Moreover,
M
withh the telecomm
munications market liberalizzation EUs can use
their ownn infrastructuree, the power line grid (speecially the MV
V and LV netw
works), to delivver communica
ations
services. Figure 2 show
ws the power line access top
pology propossed by OPERA
A (Open PLC EEuropean Rese
earch
V channel in a non
Alliance) [10]. In this new scenario, several techhnologies try to exploit thee MV and LV
standardized way. Thee multivendor interoperabillity issue represents a serioous problem foor the PLC ind
dustry
developm
ment.
22
Introductionn
PTSN
A
Autoconfiguration
Database
D
DH
HCP Server
Internet
RAD
DIUS Database
FTP Server
RADIUS Server
VoIP Gatew
way
ISP PO
OP
Core Network
POP
LV Cell
Optical Backbone
B
PLC to Op
ptical Bridge
PLC to Optical
O
Bridge
MV Ring
MV node / LV HE
MV
V Ring
M node / LV HE
MV
E
MV nod
de / LV HE
CPE
LV
V Cell
POP
P: Point of Presen
nce
HE:: Head End
CPE
E: Costumer Prem
mises Equipment
RE:: Repeater
ISP: Internet Service
e Provider
VoIP
P: Voice over IP
IP: Internet
I
Protocol
PTS
SN: Public Teleph
hone Switched Ne
etwork
FTP
P: File Transfer Protocol
DHC
CP: Dynamic Hos
st Configuration Protocol
P
RAD
DIUS: Remote Au
uthentication Dial--In User Server
LV RE
LV Cell
C
L RE
LV
CPE
C
LV RE
R
CPE
CPE
Figure 2 OPERA
O
powerlinee access topology
y
1.1 .3. TOWARRDS THE STTANDARDIZZATION OF THE ACCE SS AND IN –HOME PLC
C
TECHNO LOGY
Standardization makes
m
devices be compatib
ble with each others.
o
Devicees compliant w
with different standards
n be able too coexist in thee same grid. This
T is a seriouus impairment for power linne communicattions (PLC)
will not
indusstry developm
ment and an inconvenient forr end-users.
23
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
There aree four main alliances
a
or consortiums that are working (or have worrked) on PLC p
physical (PHY) and
medium access
a
control (MAC) level specifications (Figure
(
3):
1.
al Powerline Association).
A
W
While
supportting OPERA and
a its access specification,, UPA
UPA (Universa
works on its own
o in-home sp
pecification. Within
W
others, UPA
U has the foollowing memb
bers:
•
•
•
•
•
•
•
2.
•
•
•
•
•
•
A
Arteche
C
Comtrend
C
Cypress
IIlevo
K
Korea ERI
PPirelli
Linksys
Motorola
Gigle
Ariane Conntrols
Korea ERI
Belkin
Philips CE
Texas Instruuments
Analog Devvices
•
•
•
•
•
•
•
•
•
Comcast
Samsung
Huawei
COMTek
STMicroelectroniics
D-Link
ZyXEL
2Wire
Fujitsu Siemens
•
•
•
•
•
•
•
•
Intel
SSharp
Intellon
C
Current
Y
Yitran
Electricite de Frannce
LG
France Telecom
ACN
Hitachi
Philips
SiConnect
Toshiba
•
•
•
•
•
Analog Devices
Mitsubishi
Pioneer
Sony
Xeline
•
•
•
•
•
D
Delta Electronics
PPanasonic
SSanyo
SST&T
Y
Yamaha
PERA project 1 has finished
d with a com
mplete
OPERA (Open PLC Europeean Research Alliance). OP
f access netw
works, involvinng both the LV
V and the MV grid. Within others, OPERA
A has
specification for
the following members:
•
•
University of Co
omillas
•
U
University of Dressden
•
University of Ka
arlsruhe
•
•
•
•
•
Swiss Federral Institute of
Technologyy
University of
o DuisburgEssen
University Ramon
R
Llull
Iberdrola
Celg
Amperion
•
•
•
•
Electricite de Fra
ance
LinzAG Strom
CTI
Dimat
•
•
•
•
•
Eichhoff
•
Telvent
•
U
University Politécnnica
M
Madrid
EEnergias de Portuugal
U
Union Fenosa
D
DS2
SSchneider Electricc
PPowerline
C
Communications
RRobotiker
•
24
Ambient
BPL
Current
DukePower
Itochu
Netgear
Watteco
CEPCA (Conssumer Electronnics Powerlinee Communication Alliance). CEPCA is working on in-home
specification for
f audiovisua
al applicationss. Within otherrs, CEPCA has the following members:
•
•
•
•
•
4.
•
•
•
•
•
•
•
Homeplug. Firstly
F
focused
d on in-homee networking (version1.0 and recentlyy version AV
V for
audiovisual applications) Homeplug
H
has also released
d specifications regarding a
access (versionn BPL)
W
others, Homeplug
H
has the following members:
and control (vversion CC). Within
•
•
•
•
•
•
•
•
•
3.
AcBel
Buffalo
Corinex
DS2
Intersil
Logitec
Toshiba
Introductionn
Figure 3 Th
he four main entities involved in PHY and MAC PLC
P specificationss
arding access and in-home services, PLC technology ne
eeds, in a short time frame,, the specifications from
Rega
the previous
p
organizations to yield
y
in one, or
o several well accepted sta
andards, in orrder to avoid a serious
damage to the PLC
P industry. Currently,
C
onee internationa
al standardiza
ation body, i.e. the IEEE (Innstitute of
Electtrical and Elecctronics Engineeers), and twoo European bodies,
b
i.e. thee ETSI (Europeean Telecomm
munications
Standards Institutte) and the CENELEC (European Comm
mittee for Electrotechnical Standardiza
ation) are
a
concerned with acccess, in-homee and their cooexistence. ETTSI and CENELEC work on same field addressing
d aspects [9][11][12].
diffeerent standard
The interested entities,
e
such as the four mentioned before, will submit their specificationns to the
dardization bodies in orderr to contributee to the accesss and in-homee standardizattion process. Inn order to
stand
adop
pt one, or sevveral standard
ds from one, or
o many prop
posals, a minim
mum consensuss has to be re
eached, so
discuussions and coompromises frrom the differrent players will
w be needeed. Standardizzation bodiess can only
recommend a stanndard proced
dure to exploitt the PLC channel, but the regulatory enntities in each region or
eachh country are the ones thatt will allow or not the PLC
C devices acceess to the market. The most relevant
direcctives involved
d with PLC reg
gulation are:
1.
2.
3.
4.
EMC2 dirrective 2004/108/EG
Low Volta
age Directive 73/23/EEC
RTTE3 dirrective 1999/5
5/EC
And seveeral directives concerned witth the liberalizzation of the telecommunica
t
ation sector.
Rega
arding the low
w frequency ra
ange of the Euuropean powe
er grid, the European standa
ard CENELEC EN50065
ruless the PLC frequency range from
f
9 to 148
8.5 kHz. This sttandard mana
age that frequuency range inn 4 bands,
nameed A, B, C annd D band. Thhe first one iss reserved forr the EU and its licensers, w
while the last three are
intennded for priva
ate use [13].
1.2.. CONTENTSS OF THE THESIS
T
After this introducttion to the PLC
C and its rolee regarding EU
Us, a brief exxplanation of tthe PLC channnel will be
oncerning the LV PLC will b
be presented. This work
given, for the LV, MV and HV networks. Then, the work co
will focus
f
on the sttate of the arrt of the AMR systems, and a new multica
arrier based low complexity
y physical
layer scheme. Currrent manufaccturer solutions, as well as existing prop
posals in the literature, offfer limited
c
to be
e implemented
d at a large sccale with reduuced costs.
diversity or, on thee other hand, they are too complex
m
bassed physical layer seems too be the curreent trend in ro
obust AMR
A zeero-crossing syynchronized multicarrier
modem design.
M channel measurements and
a the formuulation of a deterministic-st
d
tatistical channel model
Afterwards, the MV
d. Current MV channel topoology model proposals
p
dea
al with particular issues or are
a based
will be introduced
on behavioral
b
cha
aracterization (multipath moodels), providinng a non complete or an im
mprecise channnel model.
2
3
Eleectromagnetic Compatibility
Rad
dio Equipmentt and Telecom
mmunications Teerminal Equipm
ment
25
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
For this kind of scennario and foocusing on thhe channel trransfer function, by meanns of a strucctural
characterrization of thee MV network devices, this work will prop
pose a low coomplexity and
d high versatile
e MV
network channel
c
transfer function moodel.
Then the reader will be driven to the HV measureements and fie
eld tests, show
wing the chara
acteristics of thhe HV
p
of a multica
arrier spread
d spectrum m
modulation in such
communiccation channeel and the performance
environment. This workk will show whhy the evolution of HV-PLC
C should pointt to the use of large bandwidth
modulatioons in order too enhance thee link capacityy while keepinng the power spectral denssity low, two of
o the
main handicaps in the current
c
HV-PLC implementations. Moreover, the readerr will see how the combinatiion of
d spectrum tecchniques can beat
b
all the existing and deeployed syste
ems in
multicarriier modulationns with spread
terms of user
u data ratee while delivering high adaptive and qua
ality of servicee capabilities.
Finally, thhe concluding remarks will be summarizeed and afterw
wards, the rea
ader will find in the appendixes
the three main papers regarding thee LV, MV and HV work:
LV: PHYSICAL LAYER DESIIGN
beira, “A Low Complexity Multicarrier
M
Proposal for Me
edium
R. Aquilué, M.. Deumal, J.L. Pijoan, L. Corb
Rate Demand
ding Automattic Meter Rea
ading Systems”, in Proc. IEEE Symposiuum on Powerr Line
Communicatioons and its App
plications (ISPLC2007), Pisa
a, Italy, 2007.
MV: CHANNEEL MODEL
R. Aquilué, M.
M Ribó, J.R. Regué,
R
J.L. Pijoan, G. Sánchez, “Urban Underground
d Medium Vo
oltage
Channel Measurements and
a
Charactterization”, inn Proc. IEEEE Symposium on Power Line
plications (ISPLC2008), Jejuu, South Korea, 2008.
Communicatioons and its App
AL LAYER DESSIGN
HV: PHYSICA
R. Aquilué, J.LL. Pijoan, G. Sánchez,
S
“High Voltage Chhannel Measurrements and FField Test of a Low
Power OFDM
M System”, in Proc.
P
IEEE Sym
mposium on Po
ower Line Com
mmunications a
and its Applica
ations
(ISPLC2008), Jeju, South Koorea, 2008.
Then, two extended versions of the two latter papers reccently accepteed for publiccation on the
e IEEE
f
Transactions on Power Delivery will follow:
MV: CHANNEEL MODEL
R. Aquilué, M. Ribó, J.R. Regué, J.L. Pijoa
an, G. Sánchezz, “Scattering Parameters Based Undergrround
Medium Volttage Power Line Commuunications Cha
annel Measurements, Cha
aracterization and
Modeling”, acccepted for puublication in IEEEE Transactions on Power Delivery,
D
June 2008.
AL LAYER DESSIGN
HV: PHYSICA
R. Aquilué, I. Gutiérrez, J.LL. Pijoan, G. Sánchez,
S
“Highh Voltage Mullticarrier Spreead Spectrum Field
Test”, accepteed for publication in IEEE Tra
ansactions on Power Deliverry, May 2008
8.
As well as
a the paper regarding
r
HF ionospheric communicationss, which can be
b considered as an introduuctory
work to frequency
f
seleective and inteerference limiteed environmennts:
HF: PHYSICA
AL LAYER DESIIGN
R. Aquilué, P.. Bergadà, M.
M Deumal, J.L. Pijoan, “Mullticarrier Symbol Design foor HF Transmissions
from Antarctica Based onn Real Channnel Measurem
ments”, in Prooc. IEEE Military Comunica
ations
MILCOM2006
6), Washingtonn, United State
es, 2006.
Conference (M
26
Poower line netw
works
CHAPTTER 2
2. POWER LIN
NE NETWO RKS
The EU
E power grid
d can be divid
ded into three stages:
1.
2.
3.
Generatiion stage
Transportt stage
Distributioon stage
The generated
g
energy flows froom the powerr plants throug
gh the power line grid (Figuure 4) until rea
aching the
final customer. Tyypically, poweer is generateed at tenths of
o kV. Before transporting this power to
owards its
ation (ES), usua
ally located cloose to the genneration point,, increases
consuumption point,, a step-up eleectrical substa
the voltage
v
to thee high voltagee (HV) levels, decreasing thhe current flow
w in order to reduce the tra
ansmission
lossees [21]. At this point, one can
c define the frontier bettween the geeneration and the transportt network.
Those HV levels ra
ange from 10
00 kV up to 400
4 kV appro
oximately. Althhough every lline transportiing power
with voltages oveer 100 kV cann be considerred HV, transm
mission levels over 500 kV
V are often pa
articularly
referrred as ultra HV
H levels. Steep-down transformation cann be done proogressively as the power ap
pproaches
its coonsumption point in step-d
down ESs. Thee ESs that tra
ansform MV levels
l
to LV levels are referred as
Transform Substations (TS) [22].
ES
TS
TS
TSS
TS
ES
Mete
er
Generation
Highh voltage (>100 kV)
k
Transport
Mediuum voltage (≈ 10
0
kV
k - 30 kV)
Distributionn
Low voltage
e (<400 V)
F
Figure
4 Power liine grid
arding its loca
alization among the power line grid, the ESs
E can be classified by the following way
y:
Rega
1.
Generatiion ES: Located close to the generation points,
p
they steep-up the pow
wer plant outgoing level
to the HV
V transport onee, incorporatinng the genera
ated power intto the grid.
27
Pow
wer Line Comm
munications for the Electrical Utility: Physiccal Layer Design and Channnel Modeling
2.
3.
Transport ES: Interconnectioon node of a variable
v
numb
ber of transport lines. They a
also can step-down
levels from tra
ansport to sub
btransport volttages, both of them in the HV range.
Distribution ESS and TS: Theey step-down the incoming HV transport level to med
dium voltage (MV)
and (LV) leveels (primary annd secondary distribution), suitable for loocal distributioon. The distrib
bution
ES, located neear the end user,
u
is the froontier betweenn the HV and the MV level.. The MV leve
el can
be distributed
d into commerccial or residenntial areas to a posterior steep-down into the LV range at TS
or can be delivered directlyy to a high coonsumption industrial customeer.
In Figure 5 one imagee of the “Egarra” distributioon ES (Endesa)) is shown. At the right, thee 110 kV to 25
2 kV
step-dow
wn transformerr can be found
d. At the left, there
t
is a 110
0 kV to LV trannsformer. This one is in charge of
feeding the
t ES. Behind
d, the switching
g, buses and protection
p
devvices can be seen,
s
as well a
as the incominng HV
line that feeds
f
the ES.
Figure 5 “Egara” Distributiion ES
Usually, an
a ES is opera
ated remotelyy, so a reliable communicatiion network iss mandatory. A
An ES can perform
one or moore than one of
o the followinng functions:
•
•
•
•
•
Voltage transsformations.
Switching funcctions:
o Switcching transporrt and distribuution circuits intto and out of the power griid.
o Connnecting and diisconnecting power plants to
o the power network.
o Provviding automattic disconnectioon of line segm
ments experieencing faults.
Measure of thhe electric pow
wer quality thrrough measure
ement transforrmers.
Provide proteection against power grid fa
aults and other unexpected events such ass lightings.
Coupling of thhe communicattions equipment.
The TSs are
a those prem
mises located at
a the distribution stage that separate thee MV from thee LV level. From the
TS, several feeders deepart to the customer premisses [22].
2.1. HIG
GH VOLTAG
GE LEVEL
The HV leevel comprises the power grid
g transport stage. The typical levels thhat can be fouund in such nettwork
are show
wn in Table 1 [22]4.
4
Only HV
V Alternating Current (HVAC) levels are took
t
into account
28
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