Analysis and Design of Electrical Power Systems

13Equipment for Overcurrent Protection

This section will discuss all types of protection equipment, switching Devices, and interconnecting devices in low‐voltage systems, including fuses, which in contrast to switching devices function only once and then melt in the event of a fault.

13.1 Electric Arc

When the contacts of a current‐conducting switch (Figure 13.1) are opened, the pronounced heating at the base points of the current with a large contact resistance results in an electric arc, which the voltage at the contacts then maintains.

The electrons emitted from the hot cathode are accelerated by the electrical field and thus transported to the anode. At a high enough velocity, collisions occur between atoms and electrons, ionizing the ...