3-D Modelling of Electrical Fields of Underwater Electrical Equipment

in the Marine Environment

A0078 Nicholas D. Warren School of Electrical and Information Engineering, University of Witwatersrand

A0077 George J.Gibbon School of Electrical Engineering, University of Witwatersrand

The elasmobranch family (sharks, rays and skates) has sensory organs

thatare sensitive to ultra low frequencies (ULF) in the range of 0

20Hz, detecting intensities as low as 1μV m 1 . There is an

increase in electrical activity in the marine environment, both

commercially and recreationally. From the recreational side this

electrical activity comprises of camera ashes, dive computers and cam-

eras and data transmission cables and sonar arrays from the commercial

side. The elasmobranch family has a reaction to these electromagnetic

(EM) waves, in some instances damaging valuable commercial equipment,

resulting in additional costs to prevent such damages occurring. Due

to the effect of these EM waves on the marine environment,

particularly to the elasmobranchii, and the corresponding cost

implications, there exists a need to model these waves, to determine

the propagation patterns and the exact effects they have in, and on,

the environment.

A finite elements method (FEM) approach is used to solve an equation

based on the electric field strength (E), derived from Maxwells

equations. ULF waves have long wavelengths and can be considered as

time-varying dc sources at distances close to the source. For this

reason the electrostatic dependance of E on voltage (V)can be used.

Initial simulations are conducted on a test block of seawater before

being ex-panded into a laboratory simulation, a circular tank filled

with seawater where various aparatus is being tested. The research is

being conducted in conjunction with another project focussed on

measuring EM fields in the marine environment.