IEC61850 standard-based transformer tap changer control for power system stability

Abstract

Electrical transformers are one of the power system equipment widely used throughout the system. Generally, they alter voltage from one level to another as a function of turn ratio. In some cases, one of the windings is equipped with multiple taps for flexible output voltage. The tap changing mechanism is either an on-load or an off-load type. The onload type is manually operated or automatically utilizing a designated device. Automated control of a group of transformers operating in parallel is more involved and requires more considerations to ensure power system integrity. The research of this thesis presents the design and implementation of entirely decentralized and hierarchal transformer on-load tap changer controllers for a system of parallel transformers. The controllers are designed based on IEC61850 standards for communication. The design and implementation will be in the laboratory environment. IEC61850 standards present an endless number of features. However, the Generic object-oriented substation event (GOOSE) messaging service is mainly the feature of interest in this research. Schweitzer Engineering Laboratories (SEL) products are the preferred choice of intelligent electronic devices. The controllers are designed and implanted in these IEDs using the manufacturers programming tool. To achieve the aim of the research, a review of approaches for the design and execution of transformer tap changer controllers is conducted at first. Highlights of the applications of IEC 61850 standard for the implementation of the transformer tap changer controllers follows. An adjusted IEEE 12 Bus power system, allowing parallel operation of transformers, is then modelled in RTDS/RSCAD. The controllers are developed, implemented and hardware-in-the-loop (HIL) simulated under various conditions and disturbances. The simulation is carried out at the Centre for Substation Automation and Energy Management Systems (CSAEMS) at the Cape Peninsula University of Technology, Bellville campus.