Powerlines

Studies of electric and magnetic fields associated with overhead electric power lines are often commissioned by land development companies prior to purchase or development. Numerous projects have been carried out to assist developers in meeting environmental assessment requirements imposed by planning departments.

These investigations have often included both on-site field measurements as well as computer modeling of expected fields. A representative study in Redwood City, California, using historical line loading data, permitted an insight to the time variation of magnetic fields over long periods of time, assisting in interpretation of actual measurement data taken at specific times.




Although electric field strengths do not vary because of electrical loading like magnetic fields do, accurate measurement of electric fields is more problematic due to the strong propensity of electric fields to be perturbed by the local environment. E-field measurements are typically performed with displacement current sensors that operate on the basis of measuring the displacement current that flows between two closely spaced electrodes immersed in an electric field. Here the sensor is placed on a non-metallic tripod to prevent the influence of the operator's body on the measured field value.




Alternatively, the electric field meter is supported with a long, non-conductive handle (typically between 3 and 10 feet long) to minimize field distortion by the presence of the observer.