A demanding task

Interlinked networks guarantee security of supply, reliable protection and control units allow smooth operation. That sounds quite simple so far, but: short cables, small impedances, high level of interlinking, multiple feeds – how can such structures be protected without affecting network stability?

A versatile solution

The SG-50 offers a solution to this: a compact, modular combination protection device with sophisticated protective functions and many different possibilities for use. Thanks to H2 logic, it can be used e.g. to realise a busbar protection system using stacked protective units. Or the subject of earth faults in the cable network: They sometimes result in double earth faults; in this case intermittent faults are hard to localise. The SG-50 uses a unique, patented method to detect these faults.

Overhead cable networks

Overhead cable networks can also be protected. As well as the fault locator with parallel cable compensation, 6-system distance protection for cable-to-cable and cable-to-earth faults is available. Added to this are 7 polygon zones, which can be programmed in the forward and reverse directions, and a controlled zone. Short circuit switch-on protection is likewise integrated, as well as automatic restart.

Transformers and machinery

Transformers and machinery can also be protected, from undercurrent and unbalanced load, among other things. The SG-50 even offers protection against locked rotors; sudden increases in load are detected and documented. In the process the unit ensures better network stability, as it uses primary technology properties to trigger only in serious cases. For instance, with the aid of a thermal two-body image, transformers can remain monitored in the network for longer before the assembly has to be shut down owing to thermal overloading.