Periodic testing of standby generators under real or simulated load, without which redundancy is claimed rather than demonstrated.
Load bank testing means running a site's standby generators against a real or resistive simulated load, long enough to prove not merely that they start but that they take load, hold frequency, cool properly and that the transfer switches operate. A generator run off-load every week proves almost nothing, because most failures seen in operation appear under load or during transfer. The whole chain has to be tested, from starter battery to fuel tank to the refuelling contract itself, since a claimed forty-eight hours of autonomy is worth something only if the supplier can deliver during a regional event that mobilizes every other site at the same time. Property insurers' survey grids commonly make this a condition of cover for critical sites, on a par with fire protection, and missing test records are a frequent basis for a reservation. The most common cause of major power outages is in any case not generator failure but the restoration maneuver itself, carried out by an operator who had never rehearsed it under real conditions.
On 27 May 2017, a power loss followed by an uncontrolled restoration at a British Airways data center near Heathrow halted the airline's operations for several days. British Airways put the cost of the incident at around 80 million pounds.
load bank testing, essai en charge, banc de charge, essai des groupes de secours