Methods of Calculation of Electric Field
- There are different graphical, experimental and numerical field calculation methods. Special methods like method of images, conformal mapping, co-ordinate transformation are applied to simple geometrical configuration.
- The experimental measurement of field strength in small air gaps stressed by high voltages is a very difficult process and not quite accurate.
- The insertion of a measuring arrangement like probe rear the stressed electrode is not very easy and it affects the distribution of the field and influences results.
- The analysis of proper models of air gap electric fields using Laplace’s and Poisson’s equations for general two to three dimensional fields in mathematical way is more accurate but in some cases it has many difficulties and takes to much time.
- The most convenient way is to use numerical procedures. Several numerical methods for solving partial differential equation have become available in recent years like.
- Finite difference method, Finite element method, charge simulation method and surface change simulation method, Boundary element method, out of these widely and successfully used method is charge simulation method and is preferred over others due to following reasons :
- Its accuracy and speed is greater.
- This can be applied to open arrangement.
- Positioning of the contour points and charge points can be automated.
- Fundamentals of this method is followed by most of the electrical engineers as it is based upon frequently used analytical field computation methods.
- As the solution satisfies the Laplace or Poisson’s equation it will be very smooth and always gives a small dense matrix and therefore can be easily handled using personal computers.
- Other methods can be used only with fields which are bounded while charge simulation method can also deal with unbounded fields.
- Other methods require entire field region to be meshed but this method require only the outer surface of electrode and the outer layer of the dielectric to be meshed.