Artículo sobre puesta a tierra

Ground Fault Protection
Multisource Application

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Ground Fault Protection
Multisource Application

An operator had installed a main LV switchboard with 2 incomers in anticipation of the power extension of his LV electricaldistribution. When the 2nd source was commissioned, a large number of Ground Fault Protection operating anomalies occurred on the installation. Analysis of the diagram revealed the problems and their cause: multiple Grounding of LV distribution.

maintain continuity of supply on the other loads in the same switchboard.

The building’s electrical installation
The building’s electricalconnection consisted of two external MV/LV transformers, owned by the electrical utility, supplying a 480/277 V 2-incomer switchboard, with 2 main 2000 A circuit-breakers and one interconnection circuit-breaker. The circuitbreakers were equipped with the Ground Fault Protection required by the NEC, with an external CT on the Neutral bar of each main LV switchboard incomer.

Analysis of the diagram
Thistype of diagram is common. Its drawback is the large number of ground fault current run-off paths (see figure 1): n The current can return to the source directly via the Grounding of the Neutral of the associated source transformer. n The current can also return to the source through the Grounding of the Neutral of the second source transformer and of the Neutral of the main Busbar.
E54523

Agood grounding is a single grounding!
When the owner of a high-rise building – a block of offices – decided to extend his installation, thus naturally resulting in a power increase of his electrical distribution system, the task turned out to be more complicated than expected! For economic reasons, an operating requirement of the various companies, it was necessary to preserve the existing...