Volumetric Energy Density - The ratio of the energy output of a cell or battery to its volume (Wh/L).
MTTR (Mean Time To Repair) - Mathematical calculation (or statistical average if available) of the time required to repair a device.
Earthing system TT - Earthing system in which the neutral and the exposed conductive parts are directly earthed. The installation must be de-energized immediately in the event of an insulation fault.
Transformer short-circuit voltage (Uscx %) - Relative measurement (%) of the internal impedance of a transformer. This short-circuit impedance is commonly called the short-circuit voltage because it is measured during a short-circuit test (shorted secondary winding subjected to a current set to In). For most common three-phase transformers, this value ranges between 3 and 6%.
Coulomb - The amount of electricity transported by a current of one ampere flowing for one second.
Redundancy (standby) - UPS configuration in which one or several UPS units operate on stand-by, with no load or only a partial load, and can immediately back up a faulty UPS unit by no-break transfer of the load, carried out by a static switch.
Top-Up Charge - A low rate charge following the main charge, designed to ensure maximum capacity.