Examples of harmonics-related malfunctions in electrical installations : case of “Overloads in neutral conductors”
I come back here with an other case of malfunctions due to Harmonics
This article will present briefly the case of overloads in neutral conductors by third-order harmonics created by single-phase loads, leading to tripping, overheating and even cable damage
The third-order harmonic currents created by non-linear single-phase loads (IT, lighting) connected between phases and neutral accumulate in the neutral conductor.
In extreme cases, the current in the neutral conductor may be greater than the current in the phases.
This results in overloads and even damage of the neutral conductor, in particular if the neutral cross-section is half of that of the phase conductors.
A well-known example concerns the headquarters of Groupama in Paris.
In January 1992, a new computer system was installed.
Soon after commissioning, the main circuit breaker tripped, interrupting the operation of the entire system.
Following lengthy and costly investigations, it was established that the interruption was due to an overload in the neutral of the three-phase system, despite the fact that the system was perfectly balanced.
Strangely enough, the current in the neutral conductor was equal to 65% of the current in the phase conductors, whereas the protection relays had been set to 50%.
As the story goes, following the incident, all Groupama staff knew what harmonics were…
see you in 10 days with an other case