1DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

TRANSFORMERS FOR WIND TURBINES NEED FOR NEW DESIGNS OR

BUSINESS AS USUAL

 Dr. Jan Declercq

2DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Grid developments … todayEHV transmission Generation

100 MW >220 kV

Transmission

Sub-transmission 110 – 70 kV

Distribution 0.5-4 MW 30 kV

3DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Grid developments … todayEHV transmission Embedded

Generation 100 MW >220 kV

Transmission

Sub-transmission 110 – 70 kV

Distribution 0.5-4 MW 30 kV

Overloading, power quality, economics, environment, maintenance, reliability

4DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Types of distribution transformers

• Mineral oil filled transformers

• Cast resin transformers

• SLIM® technologysilicon oil and aramid insulation

5DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Distribution TransformersMineral oil Cast Resin SLIM®

– Power in MVA 0.5..10..500 0.5..10 1..10– High voltage kV 10..36..500 10..33 10..36..– Low voltage V 400..6300.. 400..3000 400..3000– Impedance 4..10..25 4..8 5..10

Same operating range of voltages and powerWhat about other specifications?

6DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Distribution Transformers

– No load losses and load losses– Dimensions– High load, ambient temperature and harmonics– Environmental issues– Fire behavior– Enclosures and cable boxes– Vibrations

7DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Fit the door

8DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

No load losses, load losses, Dimensions

• No load losses– Ex. 2 kW * 8760 h/y * 0.05 EUR/kWh

• Load losses– Ex. 18 kW*Load factor2* 0.05 EUR/kWh*duration

so important how long and load level– Heat dissipation in turbine or substation

• Dimensions– Mass for nacelle installation– Flexibility to install, “fits the door”– Option to replace

9DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

High load, ambient temperature and harmonics

• Maximum allowable temperatures depend on insulation material– Mineral oil, cellulose 100°C– Cast Resin 155°C– Silicon oil 150°C, aramid insulation 200°C

• Maximum operating temperature depend on– Ambient temperature for transformer !!– Load and duration– Harmonic content

• Transformer specification– Ex. 60 K rise at full load and 30°C leads to 90°C

10DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

High load, ambient temperature and harmonics

Load P

Current I

Losses RI2

Temperature

11DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

High load, ambient temperature and harmonics

Load P

Current I

Losses RI2

Temperature

Lifetime

Tins 100 C

12DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

On-site measurements of thermal performance of a 2 MVA SLIM

transformer in a windturbine

13DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Results and discussionPower in period 1vermogen

-500

0

500

1,000

1,500

2,000

0 200 400 600 800 1000 1200 1400 1600

Series1

14DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Results and discussionTemperatures in period 1

0

10

20

30

40

50

60

70

80

90

100

10

/23

/20

01

10

/23

/20

01

10

/24

/20

01

10

/24

/20

01

10

/24

/20

01

10

/25

/20

01

10

/25

/20

01

10

/26

/20

01

10

/26

/20

01

10

/26

/20

01

10

/27

/20

01

10

/27

/20

01

10

/27

/20

01

10

/28

/20

01

10

/28

/20

01

10

/28

/20

01

10

/29

/20

01

10

/29

/20

01

10

/30

/20

01

10

/30

/20

01

10

/30

/20

01

10

/31

/20

01

10

/31

/20

01

10

/31

/20

01

11-0

1-0

1

11-0

1-0

1

11-0

2-0

1

11-0

2-0

1

11-0

2-0

1

11-0

3-0

1

11-0

3-0

1

11-0

3-0

1

11-0

4-0

1

11-0

4-0

1

11-0

4-0

1

Time

Te

mp

C

TR - Top oil

AIR - in

TR - Bot oil

HV - cab

HV - con

LV- bus

LV - cab

LV - bar

LV - bcap

LV - tcap

AIR - out

AIR - bot

AIR - top

AIR - amb

15DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Fire behavior

• Depend on standards, laws, policies, habitsno strict guidelines for windturbines

• Transformers not treated active to fire– Source : do not start fire themselves

good reputation – Victim : depends on material

Technical specifications• Mineral oil class O (fire point 150 C)• Silicon oil class K3 (fire point 360 C )• Cast resin classes F0, F1 (similar numbers)

16DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Vibrations• Transformers designed for transport

accelerations up to 3 g

• Wind turbine specificationsaccelerations <1 g, continuous and <100 Hz

Point 12 tank long side

0

0.2

0.4

0.6

0.8

1

0 25 50 75 100 125 150 175 200

Hz

XF

Rfu

nc

Ma

g

17DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Increased failures• Much more voltage fluctuations due to step up • Sharp load fluctuations (1 to 100 % in 1 minute)• Fast Transient overvoltages between CB and

transformer (increased number of failures in Scotland and Denmark. Cigre 12-15 WG)

• More than 50 switching events per year• Increased average loading and harmonics• Vibrations• Moisture• Remote locations, reduced maintenance

18DECLERCQ Jan BE Alpha 4 – Block 2

Barcelona 12-15 May 2003

Increased failures

• Multiple transformers went on fire, even dry type

• On average 30 % more failure rate

• No possibility for replacement

• Long time for restart