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region, contributing then for value aggregation to services provided by the distribution
company, since the available tools proportionate more optimized analyses in relation to the
procedures involved with the protection specification.
Therefore, in this chapter, the particularities for estimation of induced voltages in real
distribution networks, such as the network discontinuity, the phase conductor arrangement,
the intrinsic characteristics of the incident atmospheric discharges in each region of the
considered distribution system, are taken into account by the expert system. Performance
evaluations indicate that the expert system provides coherent results and its practical
application contributes to optimize the processes involved with parameters specification
related to the protection of equipments and transformers.
For such purpose, this paper is organized as follows. In Section 2, a brief summary about
induced voltage estimation techniques are presented. In Section 3, the achieved
modifications in relation to the conventional techniques are introduced in order to produce
a greater accuracy when compared to the results obtained from real situations. The expert
system for protection specification against atmospheric discharges, named by Protection
Plus, is briefly described in Section 4. The expert system for optimized design of grounding
systems is presented in Section 5. Finally, in Section 6, the key issues raised in the paper are
summarized and conclusions are drawn.
2. Rusck's conventional model for induced voltage estimation in overhead
distribution lines
In this section the main aspects concerning to Rusck's methodology for induced voltage
estimation in distribution lines caused by atmospheric discharges are presented.
Therefore, it is achieved a general study regarding induced voltage estimation in
distribution lines through use of conventional methods discussed in the technical
literature.
Although the methodology originally developed in Rusck (1957) has some limitations to
areas with soil resistivity less than 100 m, it is still widely used for induced voltage
estimation in overhead distribution and transmission lines generated from indirect
atmospheric discharges occurred near to the respective line.
The induced voltage estimation methodology presented in Rusck (1957) has as start point
the modeling of the return current imposed by the atmospheric discharge in the distribution
line. Rusck's method calculates the electric field generated by this return current in the
ground surface and, from this electric field and from the line multi-wire arrangement, the
theory provides the resultant values of induced voltages along the distribution line.
In Rubinstein & Uman (1989) is mathematically demonstrated that the studies presented in
Rusck (1957) for resultant electric field computation of return current is correct. This fact has
contributed to increase the reliability in relation to method developed by Rusck. Other
additional procedures involved with models for induced voltage are also found in Cooray
(2003).
An existent question related to this theory is that it estimates induced voltage values for
conductors of a multi-wire line taking just into account the conductor geometric
