Both basic requirements cannot be fulfilled independently. A reduction of the protective
level automatically means a higher specific electrical stress during continuous operation, and conversely, the continuous operating voltage of an arrester cannot be
increased arbitrarily without raising its protective level as well. Both operating points
are – at least for a given type of MO resistor – strictly associated with each other
through the voltage-current (U-I-) characteristic curve.
Additional requirements involve the electrical characteristics of an arrester: they
should not change during its life span, and insensitivity to environmental influences,
such as pollution, solar radiation or mechanical strain, must be maintained.
In Figure 19 a flow chart illustrates an approach to configuring an arrester. In this
case a high-voltage arrester is depicted, since, in comparison to a distribution arrester,
more and higher demands are made here. The steps shown in the picture will be discussed
below in more detail in the sequence in which they are carried out.