Cold Load Pick-up

Doktorsavhandling, 1999

The load behaviour of the industrial and residential sector following different types of outages is dealt with in this dissertation. Data on the power consumption after these outages have been used for deriving models of the cold load pick-up. In the industrial sector the investigation covers a variety of branches and special attention has been given to plants having a high degree of electric energy consumption. Data of the power consumption after planned and forced outages have been collected and descriptions over typical restarting procedures and common restoration problems have been summarized. Due to the fact that the production can not start immediately after voltage is restored, the power consumption from the industrial sector will be lower after an outage as compared with the pre disturbance condition. The time it takes to enter a normal production again varies considerably and may take minutes or up to days for sensitive processing industries. When studying the residential sector, individual load objects, individual houses and residential areas have been investigated by laboratory and field measurements. The reason for this is to get a better understanding of how different load objects and electric heating behave after an outage. This knowledge is then used when analysing measurements of the cold load pick-up in residential areas. The measurements clearly indicate that the cold load pick-up for residential load has the opposite behaviour as compared with industrial load which means that it is (much) higher after an outage and then decreases to its normal level after a time. As residential load often is used in schemes of rotating load curtailment, simulations of such a scheme have been performed. The results show that it is important to tune this scheme properly in order to achieve the desired operation.