Cold load pickup model parameters based on measurements in distribution systems

The electric power demand after an outage can be significantly different from normal values. A major cause of this is the loss of statistic diversity in load devices that interact with some kind of storage. Examples are heating and cooling appliances as well as some applications of pumps and devices with integrated batteries. This phenomenon is known as cold load pickup (CLPU). Changes in load after an outage are of high relevance for investigations of power system restoration, especially active power control and balancing of generation and load. Besides the very fast inrush effects relevant for fast acting protection and short-term stability, long-term dynamics, thermal overload of equipment and active power balancing in the presence of uncontrolled distributed generation consider a time frame of minutes to hours. To predict CLPU from physical models, a lot of knowledge is required. Since this information is rarely available in the real-world applications, the authors investigate typical ranges of CLPU behaviour. The authors analyse measurement data from reconnections after real outages of medium voltage feeders in Germany and provide parameters for the exponential decay model of CLPU. The relevance of the application of the presented model for long-term stability studies is demonstrated by an example.