Katherine Wright is a member of SRP ' s Electromagnetic Field & Optical Radiation Committee( EMFOR). She works at National Grid as an EMF Engineer, specialising in extremely low frequency electromagnetic fields in the electricity transmission industry.
National Grid and EMFs Electricity plays a central role in the life we all enjoy today. Electric and magnetic fields( EMF) are present wherever electricity is used. Most electricity supply in the UK is alternating current( AC) with a frequency of 50 hertz( Hz); the fields are often referred to as ' extremely low frequency '( ELF) fields. Offshore high voltage direct current( HVDC) transmission links and some low carbon technology installations are different as they have a frequency of 0 Hz; these are known as
static / direct current( DC) fields. This article will focus on 50 Hz fields.
Electric fields are produced by voltage, usually measured in volts per metre( V / m) and magnetic fields are produced by current, usually measured in microteslas(µ T).
Electricity Systems and Sources There are several stages involved in delivering electricity to you and different infrastructure is needed throughout. Examples, which all have different EMFs, are shown in the photographs below.
Other Electricity Sources
• Underground cables( electric fields are contained within the cable ' s protective insultation and sheath, so there are no external electric fields)
• Household wiring and appliances
• Electricity generation
High-voltage overhead lines Low-voltage overhead lines
High-voltage substations Low-voltage substations
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