Each of these electrical characterisitcs for the signal to be transmitted can contain the actual information to be transferred. Therefore, the signal must not be influenced intol- erably by the use of lightning current and surge arresters in measuring and control installations. Several points must be taken into account when choosing protective devices for measuring and control systems. They are described below for a universal protective devices (BLITZDUCTOR CT) and illustrated by means of application examples (Figures 7.76 and 7.77).
7.4.1.1 Technical data
Voltage protection level Up
The voltage protection level is a parameter that characterizes the performance of an SPD in limiting the voltage at its terminals. The voltage protection level must be higher than the maximum limiting voltage measured. The measured limiting voltage is the maximum voltage measured at the terminals of the SPD when exposed to a surge current and/or surge voltage of a certain waveform and amplitude.
Measured limiting voltage with a steepness of the applied test voltage
waveform of 1 kV ms21
This test is to determine the response characteristics of gas discharge tubes (GDT). These protective elements have a ‘switching characteristic’. The mode of functioning