Evolution des systèmes de protections : Sélectivité
Logique
4
SUMMARY
In the context of my study which is intended to improve protection systems by studying the
settings of sets 60/22kV, I dealt with the following issues:
a- Setting of the short circuit of electric current phenomenon,
b- Setting the capacitive zero sequence current phenomenon,
c- Automatic switching of transformers phenomenon,
d- The Accumulated time phenomenon,
To carry out my work, I followed these steps:
1. Studying the operating transmission and distribution activities;
2. Studying the operating principles of protecting the substations;
3. Studying the substations’ settings;
4. Studying the selectivity process between starting 60KV, 22kv transformer and 60/22KV
Afterwards, I propose at the end of the project’s report a set of recommendations summarized as
follows:
The Electromechanic and static protection systems should be replaced by digital protection
ones.
Avoiding the accumulation of time causing false triggering of the arrival of 22 KV as a
consequence of the succession of one or more defects on 22kV sources. This can be done by
putting in place the logical selectivity of digital sets.
Avoiding the overload triggering of the back-up transformer that received an request of
activation from the second faulty transformer‘s ATLT. This is done by the introduction of a
selectivity automatism which insures a temporary load shedding; then, a reconnection after the
activation of the back-up transformer takes place.