The purpose of my thesis is studying the programmable low-voltage circuit breakers, including test some specific parameters of one particular device and subsequent analysis of the implementation of the protection.
There are two parts of my thesis. In the first part I review the theory of circuit breakers and the related standards. In the second part I examine some specific parameters of the circuit breaker, and make some necessary measurement with the test transformer to adjust the protection.
I determined by measurements of the no-load and short-circuit current with a few measuring points. Based on the results the Masterpact NT circuit breaker may not be able to protect the network against short circuit. Cannot be found a setting that adapts to all conditions, because of the extreme operating conditions of the test transformer.
The Micrologic 2.0 A protection also has delayed thermal overcurrent release. However the already installed wires has lower current capacity then the adjustable in the protection. Due to intermittent operation of the test transformer, probably it will not be a problem during use.
Based on the results I recommend the installation of Schneider Masterpact NT circuit breaker to increase the security of the test transformer. Furthermore I propose the installation of additional protection against the cable fault on the 10 kV network.