Hornsea Offshore Wind Farm

Project One

Environmental Statement

Volume 6 – Onshore

July 2013

ii

SMart Wind Limited

Hornsea Offshore Wind Farm

Project One – Environmental Statement

Volume 6

Annex 6.9.1 – Electromagnetic Fields Study

SMart Wind Limited

11th Floor

140 London Wall

London

EC2Y 5DN

Tel 0207 7765500

Email info@smartwind.co.uk

Copyright © 2013

All pre-existing rights reserved.

Liability

This report has been prepared by SKM and RPS, with all reasonable skill, care and diligence within the terms of their contracts with SMart Wind Ltd or their subcontractor to RPS placed under RPS’ contract with SMart Wind Ltd as the case may be.

Document release and authorisation record

PINS Document Reference 7.6.9.1

Report Number UK04-050700-REP-0071

Date July 2013

Client Name SMart Wind Limited

Client contact(s)

Chris Jenner

Penny Pickett

Rachael Mills

Rosemary Tingle

Liam Leah

Sheelagh Guilmartin

Ditte Bilde

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Table of Contents

1 Introduction ........................................................................................................... 1

1.1 Scope of Report .................................................................................................... 1

1.2 Sources of EMF .................................................................................................... 1

1.3 Cable Configuration .............................................................................................. 2

2 Calculations and Results ....................................................................................... 3

2.1 Approach ............................................................................................................... 3

2.2 Cases Studied ....................................................................................................... 3

Table of Figures

Figure 1.1 Magnetic field produced by current in conductor. ...................................................1

Figure 2.1 3 x 335 MW circuit arrangement. ...........................................................................3

Figure 2.2 4 x 300 MW circuit arrangement. ...........................................................................4

Figure 2.3 2 x 600 MW HVDC circuits arrangement. ..............................................................5

Figure 2.4 3 x 335 MW + 5 x 360 MW HVAC circuits arrangement. .......................................6

Figure 2.5 2 x 600 MW + 3 x 600 MW circuit arrangement. ....................................................7

Table of Graphs

Graph 2.1 Magnetic field density due to 3 x 335 MW circuits. ................................................4

Graph 2.2 Magnetic field density due to 4 x 300 MW circuits. ................................................5

Graph 2.3 Magnetic field density due to 2 x 600 MW circuits. ................................................6

Graph 2.4 Magnetic field density due to 3 x 335 MW circuits + 5 x 360 MW circuits. .............7

Graph 2.5 Magnetic field densities due to 2 x 600 MW + 3 x 600 MW circuits. .......................8

Table of Tables

Table 2.1 Magnetic field densities due to 3 x 335 MW HVAC circuits. ...................................4

Table 2.2 Magnetic field densities due to 4 x 300 MW HVAC circuits. ...................................4

Table 2.3 Magnetic field densities due to 2 x 600 MW HVDC circuits. ...................................5

Table 2.4 Magnetic field densities due to 3 x 335 MW + 5 x 360 MW HVAC circuits. ............6

Table 2.5 Magnetic field densities due to 2 x 600 MW + 3 x 600 MW circuits. .......................7

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Glossary

Term Definition

Project One

With a maximum capacity of 1.2 Gigawatts (GW) or 1,200 MW, Project One is the first offshore wind farm project within the Hornsea Round 3 Zone and includes all necessary offshore and onshore infrastructure required to connect to the existing National Grid substation located at North Killingholme, North Lincolnshire. Project One is the first of a number of wind farm projects planned for the Hornsea Zone to meet a target Zone capacity of 4 GW by the year 2020. Project One will be the subject of a single application to PINS for a DCO under the Planning Act 2008.

Project Two

With a maximum capacity of 1.8 Gigawatts (GW) or 1,800 MW, Project Two is the second offshore wind farm project within the Hornsea Round 3 Zone and includes all necessary offshore and onshore infrastructure required to connect to the existing National Grid substation located at North Killingholme, North Lincolnshire. Project Two is the second of a number of wind farm projects planned for the Hornsea Zone to meet a target Zone capacity of 4 GW by the year 2020. Project Two will be the subject of a single application to PINS for a DCO under the Planning Act 2008.

Round 3

Round 3 was announced by The Crown Estate in 2008 with nine development zones. The successful bidders were announced in January 2010 with a potential generating capacity of 32 GW. The Crown Estate announced the first round of UK offshore wind farm development in December 2000 and the second round of larger sites in July 2003.

Cable circuit and phase

A cable or cables that make up an entire electrical circuit. Usually used in reference to export cables. Where the cables are AC, a circuit could consist of a single three-core cable or three single-core cables. Each core carries one phase of electrical power. Where the cables are DC, the circuit could consist of a single two-core cable or two single-core cables. Typically, offshore AC cables are three-core and onshore cables are single-core. Typically, both offshore and onshore DC cables are single-core.

Acronyms

Acronym Full term

A Amperes

DCO Development Consent Order

EMF Electromagnetic Field

GW Gigawatt

H Henrys

HVAC High Voltage Alternating Current

HVDC High Voltage Direct Current

MW Megawatt

OFTO Offshore Transmission Operator

PINS The Planning Inspectorate

RMS Root Mean Squared

T or µT Tesla (more commonly µT – microtesla – due to magnitude)

1

1.1.1 SMart Wind has been awarded a licence by The Crown Estate to develop

approximately 4,000 MW of wind capacity off the coast of East Yorkshire known as

Zone 4 under the Round 3 Offshore Wind Licensing Arrangements.

1.1.2 As part of the initial design process, SMart Wind has requested that SKM studies the

electromagnetic field (EMF) densities produced by each of the cable connection

arrangements that are being considered for the first two stages of the development

zone (1.2 GW + 1.8 GW), Project One and Project Two respectively. The cable sheath

material will fully shield the electric field at ground level. Therefore only the magnetic

field has been assessed. This note covers the following arrangements:

 The HVDC onshore connection between the onshore transition pit at the landfall

and the OFTO converter station; and

 The HVAC onshore connection between the onshore transition pit at the landfall

and the OFTO substation.

1.1.3 Calculations of the maximum expected magnetic field strength in the vicinity of the

cable trench have been made which include the combined effect of the cables

operating in parallel. The connections will be made in two stages. Results have been

provided for both Project One (1.2 GW) and when Project One and Project Two (3

GW) are connected.

1.2.1 When a current passes through a conductor a magnetic field is produced around the

conductor. The direction of the field depends on the direction of current flow in the

conductor as shown below in Figure 2.1.

Current

Conductor

Direction of EMF

produced

Figure 1.1 Magnetic field produced by current in conductor.

1.2.2 With an AC current source the density and direction of the field will vary with the

current. With a DC source the field will have a constant magnitude (providing the

current stays constant) and will be in a constant direction.

1.2.3 The density of the magnetic field is proportional to the current flowing through the

conductor and the distance between the conductor and point of measurement. The

magnitude of the field density is calculated using the Biot-Savart law, from which the

following equation can be derived:

Equation 1 Magnetic flux density.

1.2.4 Where:

B = Magnetic flux density (T)

μ0 = Permeability of free space = 4 x  x 10 -7 (H m-1)

I = Current through conductor (A)

r = Distance from centre of conductor (m)

1.2.5 An additional source of EMF is the natural static magnetic field produced by Earth

which has a (relatively) constant strength and direction at any specific location. For DC

cables this will interact with the magnetic field produced by the