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This paper presents the experimental determination of the ZIP coefficients model to represent (static) modern loads under varying voltage conditions. ZIP are the coefficients of a load model comprised of constant impedance Z, constant current I, and constant power P loads. A ZIP coefficient load model is used to represent power consumed by a load as a function of voltage. A series of surveys was performed on typical residential, commercial, and industrial customers in New York City. Household appliances and industrial equipment found in the different locations were tested in the laboratory by varying the voltage from 1.1-p.u. voltage to 0 and back to 1.1 pu in steps of 3 V to obtain the individual P–V, Q–V, and I –V characteristics. Customer load tables were built using seasonal factors and duty cycles to form weighted contributions for each device in every customer class. The loads found in several residential classes were assembled and tested in the lab. It was found that modern appliances behave quite differently than older appliances even from only 10 years back. Models of the different customer classes were validated against actual recordings of load variations under voltage reduction. [ABSTRACT FROM AUTHOR]

Distributed generators are acquiring more attention in power systems because they can avoid distribution and transmission upgrade requirements and improve power quality issues. Islanding is one of the problems that arise with integrating these resources into the distribution system. In this article, a novel hybrid islanding detection technique is proposed which uses average rate of voltage change and capacitor bank tap switching. The proposed method is tested on a real system and different load characteristics with different dependence coefficients to voltage and frequency are studied. The power system is perturbed only when the method suspects that islanding has occurred. The proposed method could detect islanding conditions with very small power mismatches in them. [ABSTRACT FROM AUTHOR]