**1. Introduction**

The goal of finding methods and ways of warning and protecting the operating personnel, who perform maintenance programs on high voltage overhead power lines with double circuit, operating with a disconnected circuit, requires accurate knowledge of the electric and magnetic coupling mechanism as well as the voltages induced by these types of coupling at low frequency (50-60 Hz).

The experiments performed over the last 60 years in specialized laboratories around the world showed that low-frequency electromagnetic fields (50 Hz) generated by the overhead power lines affect both the functioning of electrical devices and equipments in the neighborhood and the health of living organisms in the area.

The experimental researches have showed that electromagnetic interferences of disturbing electromagnetic fields created by high voltage overhead power lines manifests itself mainly by two types of influences on the objects in the area, including the neighboring power lines, namely:


© 2014 Surianu; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The two types of influences are expressed, physically, through the values of the voltages induced in the elements of the electric conductor placed near the high voltage active power lines [1].

mined experimentally allow of validating the mathematical models which become, therefore,

Experimental Determinations and Numerical Simulations of the Effects of...

http://dx.doi.org/10.5772/57044

347

**2. A practical method for measuring on the ground the voltages induced by**

In the case of high voltage overhead power lines with double circuit having one of the electrical circuits disconnected for maintenance or repair, the active electrical circuit will induce electromotive voltages and will force the electric currents induced in the disconnected electric

Considering this phenomenon, between years 2006 - 2009, the author measured on the ground the voltages induced in the 220 kV power lines with double circuit from the Banat area - Romania. These measurements were aimed at determining the level of electromagnetic stress which appears in a disconnected circuit, when in parallel with it there is the second circuit which is operating in normal regime. Experimentally, there has been established that imme‐ diately after disconnecting the circuit, although it is disconnected and insulated from the earth, the voltages induced through electric (capacitive) coupling appear on each phase and at the moment when the short-circuit devices are closed, the voltages induced through electric coupling become null and voltages induced through magnetic (inductive) coupling appear and they force the appearance of currents induced in the loops formed by each of the three

Given the appearance of two types of disturbances affecting the disconnected power line, the measurements must firstly take into account the determination of the voltages induced through electric (capacitive) coupling on each of the three phases, and then, that of the voltages induced by magnetic (inductive) coupling in the three loops of the disconnected circuit and

There are several methods of determining the induced voltages, but we have opted for using classical measurement apparatuses accessible to everybody, namely an electrostatic voltmeter, with a scale of up to 30 kV, a common voltmeter with a scale up to 2.5 kV and Ditz pliers

For measuring the voltages induced electrically and magnetically by the active circuit into the power lines of the disconnected circuits, the following two methods have been adopted [6]: **a.** If the three-phase circuit conductors of the disconnected lines are not grounded through short-circuit devices, thus they being insulated from the ground, the disconnected circuit conductors will have a much lower potential than the active circuit conductor placed in close proximity. In this case, between the active circuit conductors and the disconnected circuit conductors there will take place electric (capacitive) couplings, the conductors playing the role of armature of the huge condenser having the air as a dielectric medium. Depending on the intensity of the electric coupling (depending on the distance between the conductor and the length of parallel lines), the potentials of the disconnected circuit

circuit, threatening the technical staff working on the respective line [3-5,7].

connected to the ground through short-circuit devices, at one of its ends.

useful tools for the professionals in electric power systems.

phases of the disconnected circuit and the earth.

ammeter, which is sensitive enough.

**the overhead power lines**

The accurate knowledge of these induced voltages, both electrically and magnetically, is necessary for searching the ways of reducing the adverse effects that these voltages produce and especially for ensuring the protection of the operating staff [2].

In practice, there are several ways of determining the electromagnetic values of the interfer‐ ences of the high voltage overhead power lines, namely:


It means that a realistic research requires, along with the advantages of mathematical modeling and numerical simulation of electromagnetic phenomena from the objective reality the necessity to validate them through experiments so that the mathematical models should be able to confer reliability on the instruments used for the accurate representation of the natural phenomena of electromagnetic interferences. Taking into account these observations, we are presenting, comparatively, the results obtained by the author through measurements on the ground of the voltages induced electrically and magnetically in the disconnected circuits of 220 kV power lines with double circuit, from the Banat area – Romania, with the results obtained through mathematical modeling and numerical simulation of the voltages induced through capacitive and inductive couplings in the measuring points of the respective power line conductors. The concordance of the mathematical simulation results with those deter‐ mined experimentally allow of validating the mathematical models which become, therefore, useful tools for the professionals in electric power systems.

The two types of influences are expressed, physically, through the values of the voltages induced in the elements of the electric conductor placed near the high voltage active power

The accurate knowledge of these induced voltages, both electrically and magnetically, is necessary for searching the ways of reducing the adverse effects that these voltages produce

In practice, there are several ways of determining the electromagnetic values of the interfer‐

**•** Measurements on the ground with specialized measuring instruments. This method has a special importance for establishing some relative values and therefore it can be considered as a reference for the other methods. But this method has disadvantages related to the very limited possibilities to achieve, physically, different operating regimes in the real conditions. This method can also lead to the occurrence of relatively large errors produced by the measuring instruments. We have to consider the impossible of taking measurements in all

**•** Experimental determinations in high voltage specialized laboratories, using physical models that simulate, on an appropriate scale, the real situations on the ground. The method allows, theoretically, of realizing any operating regime of the power lines, being intuitive in terms of physical phenomena, but it is affected by errors due to the specific laboratory conditions of the realization of the physical model because some conditions imposed by the physical parameters of the objective reality (temperature, pressure, humidity, dielectric rigidity of the atmosphere, electrical permittivity and magnetic permeability of the envi‐

**•** Mathematical modeling of the electromagnetic interferences using some modern ultra fast computing software which allows of obtaining through calculation the values of the electromagnetic values for any power line, at any point in the space around it in any operating regime. Mathematical modeling, although quick and easy in apply, has an inconvenience, namely: it doesn't offer reliability unless the results it produces are compa‐ rable to those obtained by at least one of the other two experimental methods mentioned

It means that a realistic research requires, along with the advantages of mathematical modeling and numerical simulation of electromagnetic phenomena from the objective reality the necessity to validate them through experiments so that the mathematical models should be able to confer reliability on the instruments used for the accurate representation of the natural phenomena of electromagnetic interferences. Taking into account these observations, we are presenting, comparatively, the results obtained by the author through measurements on the ground of the voltages induced electrically and magnetically in the disconnected circuits of 220 kV power lines with double circuit, from the Banat area – Romania, with the results obtained through mathematical modeling and numerical simulation of the voltages induced through capacitive and inductive couplings in the measuring points of the respective power line conductors. The concordance of the mathematical simulation results with those deter‐

and especially for ensuring the protection of the operating staff [2].

ences of the high voltage overhead power lines, namely:

the points of the proximate area of the power lines.

ronment) are neglected or circumvented.

lines [1].

346 Computational and Numerical Simulations

above.
