Prague, 8-11 June 2009
Insulation Coordination Best Practices Leading to Improving
Continuity of SupplyA. Herculano P. Nunes M.T. Correia de Barros
EDP Distribuição - Portugal LABELEC - Portugal LABELEC – [email protected] [email protected] [email protected]
C. S. Engelbrecht P. HesenKEMA - Netherlands KEMA – Netherlands
[email protected] [email protected]
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Introduction• EDP Distribuição is the Portuguese electricity distribution
company, supplying more than 5 million clients;• Operates at 60 kV, 30 kV, 15 kV, 10 kV and LV network; • EDP Distribuição carried out actions for improving the
quality of service.
Pedro Nunes-PORTUGAL Session 5 Paper 0777
TIEPI MV (min)638
456 420341
215 175 176
0100200300400500600700
2000 2001 2002 2003 2004 2005 2006
TIEPI MV Goals
155 145150175 162,5
0
50
100
150
200
2005 2006 2007 2008 2009
min
GOOD RESULTS WERE ACHIEVED
Prague, 8-11 June 2009
Introduction• In 2003 EDP Distribuição invited KEMA to conduct an
independent review and assessment• KEMA perform a QRA (Quantitative Risk Assessment)• An Improvement Program was established, encompassing
several Projects, which cover a diversity of areas, among which INSULATION COORDINATION
• Insulation Coordination project partners, was set up
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Prague, 8-11 June 2009
Methodologies• Insulation Coordination (IC) project developed in 2 phases;• 1st Phase (2004-2005)
– Independent review and assessment conducted by KEMA ;– Root causes were established for reviewing IC practices;
• 2nd Phase(2006-2007) – identify IC best practices leading to improve continuity of
supply;– Studies were carried out by LABELEC for evaluating systems
behaviour under transient conditions;– Study by EDP Distribuição to classify and rationalize the
distribution line structures;– Conclusions and validation by EDP Distribuição, LABELEC
and KEMA
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Insulation Coordination Studies
• Line Insulation Coordination
• MV/LV Transformers Insulation Coordination– Pole Top Transformers– Cable Fed Indoor Transformers– Overhead Line Fed Indoor Transformers
• HV/MV Substations Insulation Coordination
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Insulation Coordination Studies
• Line Insulation Coordination
• MV/LV Transformers Insulation Coordination– Pole Top Transformers– Cable Fed Indoor Transformers– Overhead Line Fed Indoor Transformers
• HV/MV Substations Insulation Coordination
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Line Insulation Coordination• MV OH Lines are mostly
involved in the technical causes of outages;
• EDP opted to insulate all MV OH Lines LIWL = 250 kV
Pedro Nunes-PORTUGAL Session 5 Paper 0777
0
10
20
30
40
50
60
70
80
90
100
0 50 100 150 200 250 300 350 400 450 500
Lightning Impulse withstand level [kV]
Line
out
age
rate
(fau
lts/1
00 k
m/y
ear)
Direct strikes
Indirect strikes
Combined Direct and indirect strikes
Prague, 8-11 June 2009
Line Insulation Coordination• Overvoltage Protection of Equipment on the Line
– Install surge arresters to protect vulnerable equipment
– Priority given to equipment containing non-self-restoring insulation and locations that experiences frequent flashovers
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Only install arresters if location experiences frequent outages
LowIsolating switches
Only install arresters if location experiences frequent outages
LowLoad break switches
Install at both cable terminationsVery HighCable sections
Install on the MV side of MV/LV transformersVery HighPower transformers
Install on both sides of the deviceVery High Automatic reclosers (OCR)
RemarkSurge arrester priorityEquipment Type
Prague, 8-11 June 2009
Line Insulation Coordination• A range of
standardized structures have been designed to meet the insulation level;– Defined 73
standardized structures;
– Defined clearances between phases and phase to earth
Pedro Nunes-PORTUGAL Session 5 Paper 0777
a) Distance between phases -> 540 mm
b) Distance phase to earth -> 480 mm
a) Distance between phases -> 540 mm
b) Distance phase to earth -> 480 mm
Prague, 8-11 June 2009
Line Insulation Coordination• Pilot Experience
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Insulation Coordination Studies
• Line Insulation Coordination
• MV/LV Transformers Insulation Coordination– Pole Top Transformers– Cable Fed Indoor Transformers– Overhead Line Fed Indoor Transformers
• HV/MV Substations Insulation Coordination
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
MV/LV Transformers IC
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Insulation Coordination Studies
• Line Insulation Coordination
• MV/LV Transformers Insulation Coordination– Pole Top Transformers– Cable Fed Indoor Transformers– Overhead Line Fed Indoor Transformers
• HV/MV Substations Insulation Coordination
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Pole Top Transformers• Proposed configuration on LV
side– Separated earths– High insulation levels in LV
cabinet
– Spark gap on LV cabinet
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QGBT
TransformerMV LV
Protection earth≤20 Ω
Service earth≤20 Ω
Global Neutral earth <10 Ω
QGBT
TransformerMV LV
Protection earth≤20 Ω
Service earth≤20 Ω
QGBT
TransformerMV LV
Protection earth≤20 Ω
Service earth≤20 Ω
Global Neutral earth <10 Ω
18 kV8 kV----Gap in QGBT
----20 kV10 kVQGBT Cabinet
----30 kV10 kVTransformer
LIWVAC (50 Hz)LIWVAC (50 Hz)
LV-protection levelLV-insulation levels
Prague, 8-11 June 2009
Pole Top Transformers
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Insulation Coordination Studies
• Line Insulation Coordination
• MV/LV Transformers Insulation Coordination– Pole Top Transformers– Cable Fed Indoor Transformers– Overhead Line Fed Indoor Transformers
• HV/MV Substations Insulation Coordination
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Cable Fed Indoor Transformers
Pedro Nunes-PORTUGAL Session 5 Paper 0777
MV -LV
trafo
Surge arrester
MandatoryMandatoryLc ≥ 70 m
Not mandatoryMandatoryLc < 70 m30 KV
MandatoryMandatoryLc ≥ 50 m
Not mandatoryMandatoryLc < 50 m10 KV and 15 KV
Surge arresters at transformersSurge arresters at line to cable transition
Cable length Lc (m)Voltage level Un (kV)
Prague, 8-11 June 2009
Insulation Coordination Studies
• Line Insulation Coordination
• MV/LV Transformers Insulation Coordination– Pole Top Transformers– Cable Fed Indoor Transformers– Overhead Line Fed Indoor Transformers
• HV/MV Substations Insulation Coordination
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Overhead Line Fed Indoor Transformers
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Phase leads
Surge arrester
Earth leads
Insulator with protective gaps
Transformer
LV neutral
Bushing
Phase leads
Surge arrester
Earth leads
Insulator with protective gaps
Transformer
LV neutral
Bushing
Prague, 8-11 June 2009
Overhead Line Fed Indoor Transformers
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Surge arrester
Insulator without protective gaps
Transformer
LV neutral
Surge arrester
Surge arrester
Insulator without protective gaps
Transformer
LV neutral
Surge arresterB
A
C
D
E
Maximum separation distances:
A – B: 1.0 meterA – E: 4.0 meterB – C: 0.4 meterC – D: 6.5 meter
Prague, 8-11 June 2009
Insulation Coordination Studies
• Line Insulation Coordination
• MV/LV Transformers Insulation Coordination– Pole Top Transformers– Cable Fed Indoor Transformers– Overhead Line Fed Indoor Transformers
• HV/MV Substations Insulation Coordination
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
HV/MV Substations IC
Transformer panel
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Line entrance panel
Prague, 8-11 June 2009
HV/MV Substations IC• HV Overhead Line Entrance
Recommendations
– New substations• Tower footing resistance ≤ 30 Ω
(within 1km from the substation)• Installation of surge arrester• Surge arrester polymeric housing
– Existing substations• Same measures should be taken as
for new substations• Replace the spark gaps and install
surge arresters
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
HV/MV Substations IC• HV Transformer Panel
– New Substations according 2006 HV/MV substations type project
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d
d2
d1+d
v S
Ures
LIWVA
d2
d1+d
v S
Ures
LIWV
Initial distances in EDP’s type project 2006:d1+d = 2,12 mdA = 1,26 md2 = 3,36 m
Prague, 8-11 June 2009
HV/MV Substations IC• HV Transformer Protection
– Existing installations• Remove spark gaps• Apply whenever possible the protective distances of EDP
type-project• Lengths of connection leads should be short as possible • When is not possible to apply the type-project distances:
Pedro Nunes-PORTUGAL Session 5 Paper 0777
10Cable entrance
10Double circuit overhead line entrance to different panels
7Double circuit overhead line entrance to one panel
10One or more single circuit overhead lines
Maximum protective distance d+d1+dA+d2 [m]
Prague, 8-11 June 2009
HV/MV Substations IC• HV Cable Entrance
– Surge arresters installed at the overhead line to cable transition
– Surge arresters are not required on substation side
– The cable sheaths are earthed on both sides
– When problems arise the cable should be earthed on the substation side only. The cable sheath on the line side should be protected by a cable sheath arrester
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
HV/MV Substations IC• MV Cables in the Substation
– The sheaths of the cables between the switchgear and the transformers are earthed on the switchgear side
– The cable sheath on the transformer side is protected by a cable sheath arrester
– The sheaths of the cables between the switchgear and the auxiliary transformers, reactors and capacitor banks are earthed on both sides
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
HV/MV Substations IC• MV OH line entrance
– surge arresters at MV-line entrance• MV cable entrance
– cable length between the transition tower and the circuit breaker ≤ 110 m
– The cable sheaths are generally earthed on the substation side only
– The cable sheath on the line side should be protected by a cable sheath arrester
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Conclusions• 2nd phase of the Insulation Coordination project was successfully completed
• Insulation Coordination Guidelines to be applied throughout the HV and MV networks
• Uniform insulation coordination philosophy throughout the whole system was achieved
• A training program given to targeting key people
• Key success factors– adopted methodology– effective leadership– fruitful collaboration of the EDP Group project partners (EDP Distribuição
and Labelec) together with KEMA.
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Prague, 8-11 June 2009
Pedro Nunes-PORTUGAL Session 5 Paper 0777
Thank you for your attention