ELF Earth Return Coupling Into Power Systems

With the advent of the U.S. Navy´s proposed ELF Communications System (Sanguine System), which would use an earth-return circuit to excite the earth-ionosphere cavity, earth-return current coupling into power systems has become important. The theoretical basis for coupling into power distribution systems is developed. A comparison is made between measured and predicted values of the induced voltage. Techniques which are useful in eliminating the effects of the induced voltage are described. The effectiveness of these interference mitigation techniques is demonstrated by comparing measurements on actual systems. Finally, data on power system interference are developed for use in communication system design tradeoff studies.