Medium Voltage Switchgears for Offshore

Mario Haim R&D Director Medium Voltage Switchgears

OurOffshoreReferences
Horns Rev 2 (14) Meerwind (32) Beatrice (6)

West of Duddon Sands (18)

h s f f o s s l n e o n i a t a p c i 0 l 0 p 5 p 1 a n y a r h ma t e i r r o P M in
Dan Tysk (24) Robin Rigg (24) Walney I+II (20) Ormonde (90) Baltic II (30) Barrow (12) Greater Gabbard (420) Cote D'Albatre (16) Gunfleet Sands (10) Thornton Banks (85) Global Tech (370) Schneider Electric - Infrastructure Mario Haim 2012

Nordsee Ost (145)

e r o

Veja Mate (34)

Rdsand (16)

Alpha Ventus (28)

Riffgat (12)

Borkum West II (38)

With WS market leader in 5 MW offshore Windturbines

With GHA market leader in offshore substations

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Offer for any MV offshore application

GMA

WS

WI

GHA

Schneider Electric - Infrastructure Mario Haim 2012

Agenda
Market trend Wind park layout & Short circuit level Requirements Overvoltages & Insulation coordination Preferred Solution
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MainareasforWindOffshoreinEurope
MorayFirth FirthofForfh

DoggerBank NorthSea Hornsea IrishSea BalticSea

32GW 18GW
BristolChannel Hastings IsleofWight

EastAnglia

5GW 5GW

25GW 10GW

LeTreport Fecamp Courseuilles Saint Brieuc

SaintNazaire

6GW 6GW

*Capacitytobeintalleduntil2030 *Capacitytobeintalleduntil2020
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Carbon Trust
Carbon Trust has brought together 8 offshore wind developers in a joint industry project to work towards reducing the cost of offshore wind by at least 10% by 2015. DONG Energy EON, Mainstream Renewable Power, RWE Innogy, Scottish Power Renewables, SSE Renewables (formerly Airtricity), Statkraft, Statoil, http://www.carbontrust.com/our-clients/o/offshore-wind-accelerator

Schneider Electric - Infrastructure Mario Haim 2012

Market trend

Clear recommendation:

Go to 66 kV system voltage in tower to reduce costs

Schneider Electric - Infrastructure Mario Haim 2012

66 kV in tower + substation

-tower switchgear at 66 kV -platform switchgear at 66 kV -transformer at 66 kV -cable at 66 kV

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Agenda
Market trend Wind park layout & Short circuit level Requirements Overvoltages & Insulation coordination Preferred Solution
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Source: http://www.carbontrust.com/our-clients/o/offshore-wind-accelerator
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4 types of wind turbines

Induction (asynchronous) generator
Vestas (Neg Micon), Siemens (Bonus) Strong points: robust and simple Weak points: low efficiency (fixed speed), flicker, no control of reactive power

Induction (asynchronous) generator with slip control

Vestas (for US market), Gamesa (for US market), Suzlon Strong points: variable speed (limited range), low harmonics Weak points: low efficiency, no control of reactive power
G
Control R

GENERATOR
INDUCTION COUPLING

CAPACITOR BANK

8% of manufactured No converter Ageing technology

INDUCTION COUPLING

CAPACITOR BANK

20% of manufactured No converter Ageing technology

Doubly-Fed induction generator

Vestas, General Electric, Gamesa, Nordex Strong points: variable speed (wide range), control of reactive power Weak points: produces harmonics (but only 25% of the power goes through the converter)
G DC BUS L1 L2

Variable speed induction or synchronous generator Enercon, Multibrid,

General Electric, Siemens, Clipper, Vestas Strong points: total variable speed, control of reactive power, fast answers to bad electrical conditions coming from the grid Weak points: expensive, huge size, produces harmonics (100% of the power goes through the converter)
L1
G CONVERTER

CONVERTER Schneider Electric - Infrastructure Mario Haim 2012

42% of manufactured 25% power through converter Main Onshore technology

L2 30% of manufactured

100% power through converter Main offshore technology

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Wind park layout & grid model for 66 kV simulation

Based on the defined network architecture the model was created For this model a static simulation (short circuit level) and dynamic simulation (transient recovery voltage) had been done
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Voltage / Power-Factor 33 kV vs. 66 kV

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Static network simulation: Short circuit level

The thermic short circuit inside the 66 kV network architecture can be between 11,33 kA and 18,04 kA & 29,07 kAp and 46,24 kAp peak value for short circuit Inside the tower the maximum thermal short circuit level is between 10,94 kA and 17,13 kA & the peak value between 27,86 kAp and 43,17 kAp

A 25 kA System at 66 kV is fully sufficient

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Agenda
Market trend Wind park layout & Short circuit level Requirements Overvoltages & Insulation coordination Preferred Solution
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Key Requirements

Reliability

Safety

Cost efficient

Environment

Offshore Wind Power

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Reliability
General Service-Conditions for MV switchgear according to IEC 62271
In principle indoor switchgear according IEC 62271-1 Offshore Conditions exceeding the normal-conditions Standard -5.+40C, 24h average < 35C Ambient air not polluted with corrosive materials like salt etc. Relative 24h average humidity not exceeding 95% condensation occasionally Relative monthly average humidity not exceeding 90%

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Reliability
Additional Challenges for the switchgear: Harsh environment
saline atmosphere humidity Corrosion resistive Vibration due to operation of Windmill Low temperature operation without external power supply Operation starting at deep ambient temperature without any preload (cold start)

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Reliability
Design responding to additional challenges
Gas Insulated Switchgear with
Sealed Pressure System for Electrical active parts Hermetical closed gas tanks High-voltage parts are contained in a tightly sealed stainless steel tank

Corrosion resistive components:

Drive for devices Housing Connections LV-equipment

Vibration withstand
Vibration tests with dedicated frequencies

Low temperature withstand

Mechanical operations tests at low temperature Dielectric performance at low temperature

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Safety
Design responding to safety requirements

Optimum safety of operation due to a complete interlocking system Degree of protection: IP65 for the primary part Personal safety due to Internal Arc withstand: IAC AFLR up to 40 kA Switchgear tested and certified according to IEC 62271

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Safety for operating personal

Internal arc classification according IEC 62271-203 Internal arc events could cause effects like pressure increase and burn through of enclosure (no effect on personnel is considered) Durations of 0.1 s up to 0.3 s are considered (switch off by protection equipment) No test procedure to qualify personnel safety in high voltage standard

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Safety is no Option!
Internal arc classification according IEC 62271-200
Internal arc test as Type Test according t0 IEC 62271-200 Chapter 6.106 safety for personnel as important feature Improved safety for the operator (defined areas of access for the user) Durations of arcing from 0.1 s up to 1 s are considered and tested (min selectivity) All criteria to pass the test have to be fulfilled:
Doors / covers do not open No fragmentation of enclosure No holes on accessible areas Indicators do not ignite Earthing remains in service

Design for safety according IEC 62271-200

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Cost efficient
Size is Key!
Less material Less weight Less space Less volume inside the tower Less transportation costs

Predefined interface between MV switchgear and:

wind turbine MV-cable control and protection Metering mechanic
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Cost efficient
Switchgear section preinstalled on base frame
Completely pretested in factory Less transport efforts

Predefined interface
No erection on site Commissioning of protection and control done in factory
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Environment
Environmentally friendly construction

No gas handling at site Space saving due to compact design Switching in Vacuum with Vacuum Interrupter All materials are fully recyclable At end of life time, the SF6 gas will be fed into recycling process hence
- no factory-special tool required for gas removal - all gas tanks are equipped with a valve in standard use
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Agenda
Market trend Wind park layout & Short circuit level Requirements Overvoltages & Insulation coordination Preferred Solution
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Insulation level based on Ur=72.5 kV

Except of IEC 62271-1 [1]

Usys = 66kV; = 10%

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Ur = 72.5 kV
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[1] IEC 62271-1: High voltage switchgear and controlgear Part 1: Common specifications, Edition 1.1, IEC 2011

Overvoltages Insulation Level (BIL)

Overvoltages mainly due to lightning strike or switching operations (TRV) (IEC 60071-2) Lightning strike mainly in overhead-lines Switching operations, especially in case of switching inductive or capacitive loads, e.g. cables

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Transient recovery voltage

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Lower Insulation level required

With surge arrester installed directly at the switchgear (L=0), the effect of travelling wave can be disregarded. Thus, the second part of the equation will equal to 0: BIL Ks Ures As recommended in [2], Ks = 1.15 should be applied as safety factor for internal insulation coordination: required BIL for the switchgear

BIL = 1.15 x 3.33 x 72,5 kV = 277 kV << 325 kV

[2] IEC 60071-2: Insulation co-ordination Part 2: Application Guide, Third edition, IEC 1996
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Transient recovery voltage

Excerpt of IEC 62271-100

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Transient recovery voltage

-20MVA@0.8 Utility data: Ur (kV) 155 kV Rated short-circuit power 9000 MVA
PQ Loadflow

MODEL

TRV

EMTP-ATP simulation in 66kV windpark with one wind turbine in operation, in parallel with utility network
Y BCT

Aux. TR

400mm2

3.3/66kV

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WT@5MVA

UI

155/66kV
BCT

400mm2 BBAR FAULT

UI

VCB
FAULT

FEEDER FAULT

BCT Y BCT

Aux. TR

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Transient recovery voltage

TRV envelopes for feeder fault Uc = 129kV and busbar fault Uc = 114kV (red) (green)
150 Uc.kV 120 120 Uc.kV 100 80 90 60 60 40 30 20 0 69,55

0 63,470

63,616

63,762

63,908

64,054

t.ms64,200

69,68

69,81

69,94

70,07

t.ms 70,20

Conclusion: TRV parameters are within IEC 62271-100, recalculated for rated voltage Usys = 66kV
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Lower Insulation level required

Maximum voltage level for insulation coordination including safety factor is

277 kV BIL
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Agenda
Market trend Wind park layout & Short circuit level Requirements Overvoltages & Insulation coordination Preferred Solution
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Preferred Solution What is really needed?

IEC 62271 differentiate between applications (Transmission or Distribution) and voltages (IEC 62271-200 vs. 62271-203) Offshore application inside & between tower is 100% distribution All benefits & requirements of distribution (IEC 62271-200) are mandatory
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66 kV switchgear acc. to IEC 62271-200

Reliability:
Fully tested for required ratings (Ur = 72.6 kV, BIL <= 277 kV)

Environment:
Vacuum circuit breaker, less material, no gas handling

Safety:
IAC acc. IEC 62271-200 Chapter 6.106, complete interlocking

Cost efficient:
less CAPEX, less transport costs, less OPEX Less size: 600 mm width for 3 Phase metal enclosed switchgear
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Preferred Solution What is really needed?

Ratings
Us BIL Ir Isc = 66 kV; Ur = 72.5 kV <= 277 kV = 1,250 A / 2,500 A = 25 kA

Requirements
Cost efficient Reliability Safety is no Option! Environmental friendly

66 kV Switchgear acc. IEC 62271-200

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Schneider Electric Infrastructure Equipment Mario Haim R&D Director Rathenaustr. 2, 93055 Regensburg, Germany +49 151 14758993 mario.haim@schneider-electric.com
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