Electric and magnetic field surveys are often required to be carried out around high voltage substations.  This is because there has been many scare stories published in the Press and on TV about families living near to substations becoming ill.  This is a surprising outcome because substations are not the large sources of electric or magnetic fields (EMFs) that some people imagine.  Indeed there are many larger sources of EMFs within every home.

For example when you approach your TV to turn it on or off you will encounter magnetic fields as great as those found near your local substation door.  Which will you do regularly?  Which are you happy to let your children or grand children do?  So why do people fear substations?

The fear value is from the unknown.  Magnetic fields from substations have no smell, you can not see or feel them.  They are undetectable by all our senses so we are at a loss to know if they are present.  If someone now tells you they are dangerous and should be avoided you become anxious.  You cannot see it so how do you avoid it?

This process is the way that other people will try to influence you.  They will talk of unseen powers that are at work, something that only they can see, hear or feel.  This gives these people power over you.  You will need to employ them to look after your well being.  An example is your daily search through the newspaper to read your horoscope.  A belief that many have that distant stars can somehow mystically influence their life even though all the laws of physics say it is impossible and there is no logical reason for there to be any such influence.

What's this to do with substations you may ask?  Everything.  It was a similar mystic person who cast doubts about substations.  There was a family with a child that contracted Leukaemia and died.  This family was understandably heartbroken and searched for a reason as to why this should have happened.  Unfortunately they met a 'scientist' who pointed at a nearby substation more than 30 metres away and declared the illness could have been due to the magnetic fields coming from the substation.  The 'scientist' soon received sponsorship to study these magnetic fields and the health of people living near to them.  The newspapers now had a story to print.

Was the 'scientist' correct?  Well, study the following facts and come to your own conclusion.  The unit of measurement for environmental levels of magnetic field is usually microtesla.

A modern type of substation is shown opposite. 

It is a small building of say 2 by 2.5 metres with double doors at the front.  The magnetic field measured at the doors will probably be between 0.5 and 3 microtesla. 

An older style of substation is shown below.

These are slightly larger and create different magnetic field patterns. 

The highest external values of between 10 and 90 microtesla are usually found in a very small area on one of the side-walls.  Elsewhere around this type of substation the magnetic field values will be typically much less than 10 microtesla.  Even the highest value will reduce to less than 3 microtesla within 2 metres or so.

Almost everything that has an electric motor in it creates a magnetic field that is greater than that found near to a substation.  An electric razor is capable of producing a magnetic field of between 50 and 500 microtesla.  The National Radiological Protection Board (NRPB) have measured hair dryers at 2000 microtesla.  This is because the magnetic field is deliberately concentrated to make the motor spin.  In the very small gap between the spinning and stationary part, the magnetic field is approximately 1.25 million microtesla.  Although this magnetic field reduces rapidly within short distances, it can still be detected around the outside of the case or appliance.

A television will create magnetic fields of between 2 and 20 microtesla.  Battery Chargers and transformers for toys create magnetic fields in the range of 30 to 150 microtesla.  An office Bulk Tape Eraser may well be the creator of the highest magnetic fields we have measured to date, 5000 microtesla at the opening of the eraser when it was being operated.

The difference between appliances and substations is that magnetic fields from appliances reduce very rapidly with distance and may be below 2.5 microtesla within the first metre.

These are just a few examples of the magnetic sources inside and outside our homes.  There are many more magnetic field sources that are not associated with electrical equipment.  The underlying principle is that wherever an electrical current flows then there has to be a magnetic field.  It does not matter where it is.  Lightning creates magnetic fields.  This planet has a magnetic field.  Cars, boats, trains and planes create magnetic fields.

In one popular make of car, simply turning the engine on created a magnetic field of 0.27 microtesla at the front passenger seat.  This increased to 6 microtesla when the heater fan was switched to its maximum position.

If magnetic fields were blue, then we would all see that we are living in a blue world.


© 2005 Electromagnetic Surveys Limited