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Electric and magnetic fields and health

index/glossary | EMFs At A Glance | EMF The Facts (pdf)
  • What are EMFs
    • Terminology – an introduction
    • Electric fields
    • Magnetic fields
    • Units for measuring EMFs
    • Measuring and calculating EMFs
      • “EMF Commercial”
    • Adding fields together
    • Radiofrequencies
    • Screening EMFs
  • Sources
    • Overhead power lines
      • Fields from specific power lines
        • 400 kV
        • 400 kV – specific cases
        • 275 kV
        • 132 kV
        • 66 kV
        • 33 kV
        • 11 kV
        • 400 V/230 V
        • Replacing a 132 kV line with a 400 kV line
      • Summaries of fields from all power lines
      • Factors affecting the field from a power line
        • Voltage
        • Current
        • Clearance
        • Height above ground
        • Conductor bundle
        • Phasing
        • Balance between circuits
        • Balance within circuit
        • Ground resistivity
        • Two parallel lines
      • Calculating and measuring fields from power lines
        • Geometries of power lines
        • Raw data
        • On-line calculator
      • Fields from power lines – more detail on the physics
        • Field lines from a power line
        • The direction of the field from a power line
        • Power law variations in the field from a power line
      • Statistics of power line fields
    • Underground power cables
      • Different types of underground cable
      • Fields from cables in tunnels
      • Gas Insulated Lines (GIL)
      • Underground cables with multiple conductors
      • Effect of height on fields from underground cables
      • Screening fields from underground cables
    • Low-voltage distribution
      • UK distribution wiring
      • USA distribution wiring
    • House wiring
    • Substations
      • National Grid substations
        • Static Var Compensators
      • Sealing-end compounds
      • Distribution substations
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        • Indoor substations
    • Transport
      • EMFs from electric trains (UK)
      • EMFs from cars
    • Appliances
    • Electricity meters
      • Smart meters
      • Traditional meters
    • Occupational exposures
      • Live-line work
      • Static Var Compensators
      • Occupational exposures on pylons
    • Field levels and exposures
      • Personal exposure
      • Other factors that vary with magnetic fields
      • Fields greater than 0.2 or 0.4 µT
    • Screening EMFs
      • Screening fields from underground cables
      • EMF Reduction Devices
  • Known effects
    • Induced currents and fields
    • Microshocks
      • Control of microshocks in the UK
      • Microshocks from bicycles
      • Bees and microshocks
    • EMFs and medical devices
      • Standards relating to pacemakers and other AIMDs
    • Effects of EMFs on equipment
  • Research
    • Types of research
    • Epidemiology
    • Animal and laboratory experiments
    • Mechanisms
    • Specific studies
      • UKCCS
      • CCRG
      • French Geocap study
      • CEGB cohort
      • Imperial College study
  • Current evidence on health
    • Childhood leukaemia
      • Survival from childhood leukaemia
      • Childhood leukaemia and Downs
      • Childhood leukaemia and night-time exposure
      • The “contact current” hypothesis
    • Other health effects
    • Scientific review bodies
      • WHO
      • IARC
    • Electric fields and ions
    • Comparing EMFs to other issues
  • Exposure limits for people
    • Limits in the UK
    • Limits in the EU
    • Limits in the USA
    • Limits in the rest of the world
    • Limits from specific organisations
      • ICNIRP 1998
      • ICNIRP 2010
      • NRPB 1993
      • NRPB 2004
      • EU 2004
      • EU 2013
  • Policy
    • UK policy
      • Power lines and property – UK
    • Compliance with exposure limits
    • European EMF policy
    • Precaution
    • SAGE
      • SAGE First Interim Assessment
        • Government response to SAGE First Interim Assessment
      • SAGE Second Interim Assessment
        • Government response to SAGE Second Interim Assessment
        • SAGE Second Interim Assessment – the full list of recommendations
  • Finding out more
    • EMF measurement and commercial services
    • Links
    • Literature
    • Contact us
  • Static fields
    • Static fields – the expert view
You are here: Home / Sources / Overhead power lines / Fields from specific power lines / 400 V/230 V

400 V/230 V

thumbnail of 400 V separate phases wood pole   thumbnail of 400 V aerial bundled conductor

400 V and 230 V refer to the same lines - 400 V is the designation when it is three phase, 230 V when it is single phase (more on single phase and three phase).  These voltages used to be 415 V and 240 V but were reduced to harmonise with Europe.

400 V lines are mostly carried on wood poles with four (or sometimes five) wires in a vertical array, but sometimes the conductors are twisted together in a single "aerial bundled conductor" (abc).

All 400/230 V lines are inherently compliant with the public exposure limits - see more details

Magnetic field

At 400 V, the magnetic field depends as much on the net current as on the load current.

The maximum field shown here is produced when the ground clearance is the minimum allowed – 5.5 m. The maximum loads assumed are 200 A load current and 10 A net current but higher values might exceptionally be found.

 graph of maximum field 400 V

Typical fields are lower than the maximum field because the clearance is usually higher and the loads are usually lower. This graph is for 8 m clearance, load current 50 A and net current 5 A.

graph of typical field 400 V 

Sometimes, the separate conductors are insulated and twisted together, called “aerial bundled conductors” (abc). Then the fields are even lower.  The load currents make no contribution to the magnetic field, which now comes solely from the net current:

graph of typical field 400 V abc 

Please note the fields depend on the current that is assumed.  That is, of course, true for all power lines, but is particularly important for 400 V lines, where the currents can vary greatly.

This table gives some actual field values for the same conditions.

 magnetic field in µT at distance from centreline
maximum under line10 m25 m50 m100 m
400 Vwood polevertical array 50 mm2maximumclearance 5.5 m
single circuit
load 0.2 kA
net 0.01 [email protected]°
1.2270.2770.0880.0410.020
typicalclearance 8 m
single circuit
load 0.05 kA
net 0.005 [email protected]°
0.2150.0990.0410.0200.010
abctypicalclearance 8 m
single circuit
net 0.005 kA
0.1430.0820.0390.0200.010

Note:

1. All fields calculated at 1 m above ground level.
2. All fields are given to the same resolution for simplicity of presentation (1 nT = 0.001 µT) but are not accurate to better than a few percent.
3. Supplies to single houses could be carried on different arrangements of conductors which could produce different fields.

Electric field

400 V lines are mostly carried on wood poles with four (or sometimes five) wires in a vertical array.  The bottom wire is an earth wire which screens the fields produced by the wires above it, making electric fields from 400 V lines very low.

The maximum field shown here is produced when the ground clearance is the minimum allowed – 5.5 m.

graph of maximum field 400 V 

Typical fields are lower than the maximum field because the clearance is usually higher.  This graph is for 8 m clearance.

graph of typical field 400 V 

Sometimes, the separate conductors are insulated and twisted together, called “aerial bundled conductors” (abc).  Then the fields are even lower.

This table gives some actual field values for the same conditions.

     

electric field in V m-1 at distance from centreline

maximum under line

10 m

25 m

50 m

100 m

400 V

wood pole

vertical array

50 mm2

maximum

clearance 5.5 m
single circuit

1

1

0

0

0

typical

clearance 8 m
single circuit

0

0

0

0

0

Note:

1. All fields calculated at 1 m above ground level.

2. All electric fields are calculated for the nominal voltage.  In practice, voltages (and hence fields) may rise by a few percent.

3. All electric fields calculated here are unperturbed values.

4. All fields are given to the same resolution for simplicity of presentation (1 V/m) but are not accurate to better than a few percent.

5. Calculations ignore zero-sequence voltages.  This means values at larger distances are probably underestimates, but this is unlikely to amount to more than a few percent and less closer to the line.

6. Supplies to single houses could be carried on different arrangements of conductors which could produce different fields.

Underground cables

400 V underground cables are usually a single cable: the three cores are twisted round each other in a single outer sheath. Because the cores are so close together and twisted, the fields they produce directly are very small.  Instead, the field comes from any net current in the sheath.  This is very variable and cannot be predicted accurately.  The average is about 4 A.  more on net currents.

The following graph shows typical fields from the net current in a 400 V cable.

graph of typical field 400 V underground cable 

Underground cables do not produce any external electric fields.

This table gives some actual field values for the same conditions.

    

magnetic field in µT at distance from centreline

0 m

5 m

10 m

20 m

400 V

single cable

0.5 m depth

typical

0.50

0.14

0.07

0.04

Notes

1. All fields calculated at 1 m above ground level

2. All fields are given to the same resolution for simplicity of presentation (0.01 µT = 10 nT) but are not accurate to better than a few percent.

3. These calculations are for a single, isolated cable.  This is rare in practice.  Other nearby cables would modify the field.

Other voltages:

  • 400 kV
  • 400kV special cases
  • 275 kV
  • 132 kV
  • 66 kV
  • 33 kV
  • 11 kV
  • 400 V/230 V

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Navigation
  • What are EMFs
    • Terminology – an introduction
    • Electric fields
    • Magnetic fields
    • Units for measuring EMFs
    • Measuring and calculating EMFs
      • “EMF Commercial”
    • Adding fields together
    • Radiofrequencies
    • Screening EMFs
  • Sources
    • Overhead power lines
      • Fields from specific power lines
        • 400 kV
        • 400 kV – specific cases
        • 275 kV
        • 132 kV
        • 66 kV
        • 33 kV
        • 11 kV
        • 400 V/230 V
        • Replacing a 132 kV line with a 400 kV line
      • Summaries of fields from all power lines
      • Factors affecting the field from a power line
        • Voltage
        • Current
        • Clearance
        • Height above ground
        • Conductor bundle
        • Phasing
        • Balance between circuits
        • Balance within circuit
        • Ground resistivity
        • Two parallel lines
      • Calculating and measuring fields from power lines
        • Geometries of power lines
        • Raw data
        • On-line calculator
      • Fields from power lines – more detail on the physics
        • Field lines from a power line
        • The direction of the field from a power line
        • Power law variations in the field from a power line
      • Statistics of power line fields
    • Underground power cables
      • Different types of underground cable
      • Fields from cables in tunnels
      • Gas Insulated Lines (GIL)
      • Underground cables with multiple conductors
      • Effect of height on fields from underground cables
      • Screening fields from underground cables
    • Low-voltage distribution
      • UK distribution wiring
      • USA distribution wiring
    • House wiring
    • Substations
      • National Grid substations
        • Static Var Compensators
      • Sealing-end compounds
      • Distribution substations
      • Final distribution substations
        • Indoor substations
    • Transport
      • EMFs from electric trains (UK)
      • EMFs from cars
    • Appliances
    • Electricity meters
      • Smart meters
      • Traditional meters
    • Occupational exposures
      • Live-line work
      • Static Var Compensators
      • Occupational exposures on pylons
    • Field levels and exposures
      • Personal exposure
      • Other factors that vary with magnetic fields
      • Fields greater than 0.2 or 0.4 µT
    • Screening EMFs
      • Screening fields from underground cables
      • EMF Reduction Devices
  • Known effects
    • Induced currents and fields
    • Microshocks
      • Control of microshocks in the UK
      • Microshocks from bicycles
      • Bees and microshocks
    • EMFs and medical devices
      • Standards relating to pacemakers and other AIMDs
    • Effects of EMFs on equipment
  • Research
    • Types of research
    • Epidemiology
    • Animal and laboratory experiments
    • Mechanisms
    • Specific studies
      • UKCCS
      • CCRG
      • French Geocap study
      • CEGB cohort
      • Imperial College study
  • Current evidence on health
    • Childhood leukaemia
      • Survival from childhood leukaemia
      • Childhood leukaemia and Downs
      • Childhood leukaemia and night-time exposure
      • The “contact current” hypothesis
    • Other health effects
    • Scientific review bodies
      • WHO
      • IARC
    • Electric fields and ions
    • Comparing EMFs to other issues
  • Exposure limits for people
    • Limits in the UK
    • Limits in the EU
    • Limits in the USA
    • Limits in the rest of the world
    • Limits from specific organisations
      • ICNIRP 1998
      • ICNIRP 2010
      • NRPB 1993
      • NRPB 2004
      • EU 2004
      • EU 2013
  • Policy
    • UK policy
      • Power lines and property – UK
    • Compliance with exposure limits
    • European EMF policy
    • Precaution
    • SAGE
      • SAGE First Interim Assessment
        • Government response to SAGE First Interim Assessment
      • SAGE Second Interim Assessment
        • Government response to SAGE Second Interim Assessment
        • SAGE Second Interim Assessment – the full list of recommendations
  • Finding out more
    • EMF measurement and commercial services
    • Links
    • Literature
    • Contact us
  • Static fields
    • Static fields – the expert view