High availability electrical power distribution

Continuous voltage supply

The objective of this «Cahier Technique» is to explain to electrical installation designers how to design electrical power distribution systems that fulfil the objective of continuous voltage supply across the feeder terminals.

In other words: how to master power availability so as to achieve: “the operating DEPENDABILITY objective”.

Introduction

Operating dependability is a fundamental characteristic of all systems, installations and products. It is determined by design and use. Dependability describes the aptitude of a system to «operate properly» throughout its service life. Proper operation implies:

• not breaking down (reliability),
• not experiencing dangerous failures (safety),
• being in good operating condition as often asz possible (availability),
• being quickly repairable (maintainability).

Whatever the system and the efforts implemented in its design and use, the level of dependability is a concrete reality. It must be:

• taken into account starting at the design phase,
• observed a posteriori: by counting the operating hazards that occur during installation operation.

Electricity, a modern source of energy, contributes to the level of dependability through the fact that it is needed for operation. Its availability, or rather its unavailability, has increasingly important consequences on companies’ competitiveness:

• in industry, lack of power causes production losses,
• in the service sector, lack of power causes computer blockages and utility shutdowns (lighting, heating, lifts…).

The more complex the systems, the higher the risk that even a brief power failure will have major consequences. Safety and availability have been particularly well developed and mastered in previous years in fields such as nuclear, military and space. Nowadays, energy availability is a definite concern with regard to intelligence, monitoring of the most widely varied systems and, to an increasing extent, with regard to the power supply of those same systems.

Electrical power installations, especially those containing sensitive feeders, must be designed so as to limit the occurrence and consequences of failures in the public distribution network.

AUTHOR: Schneider Electric expert | Guy GATINE