Abstract
The paper analyzes the components of the magnetic field of a three-phase overhead line at an arbitrary point on pole, where a device for detecting and diagnosing a earth-fault is usually placed. The work shows that by measuring the horizontal and vertical components of the magnetic field at some point on the pole under the conductor of the overhead line, it is possible to detect and diagnose not only the occurrence of a fault in the overhead network, but also the type of fault. Phase currents of an overhead line with an earth fault are calculated without using symmetrical components, but by writing Kirchhoff's rules for voltages and currents in a three-phase network. It is shown that the criterion for recognizing the type of failure, in addition to the increase and decrease of the magnetic field components, can also be the quotient of the vertical and horizontal components of the field, ⁄ The quotient modulus | ⁄ | and the phase angle ( ⁄ ) can be used to diagnose and determine the type of failure. A general mathematical model and a numerical example on a specific line on which the author installed devices, are given.
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