This is primarily because power outages are very common, and operation on generator power can keep the plant operational. It is important to note that in areas where there is an acute shortage of power, power outages are typically scheduled on a rotating basis. This allows industrial plants to coordinate their plant holidays, or to schedule operation with internal generators. This suggests that a more important problem is impaired industrial productivity due to the occurrence of random events such as transients, voltage sags and brownouts, and not due to power outages. The primary focus of this paper is to examine problems and solutions which can reduce the susceptibility of an industrial plant to power quality related problems.
Voltage sags are inevitable on the power system, even in the most advanced utility networks.
These are mostly caused by faults on the system, with line to ground faults being most frequent. In industrialized countries, it is very rare to have outages that extend significantly beyond the time required to clear the fault, and to re-close a breaker to connect the customer to a different part of the utility network. In fact, one of the more promising solutions which is being actively pursued for industrialized countries is the use of static transfer switches, where two independent power feeds are brought into the plant, and the plant supply can be rapidly switched from the faulted line to the unfaulted line so as to maintain power to the plant. The static transfer switch is an expensive solution, unless the second feed is already present. The biggest problem associated with voltage sags is the tripping of sensitive equipment such as motor drives.