Detecting loss of earth for embedded generation

This paper describes research into new techniques for automatically detecting loss of earth for an embedded generator. The techniques investigated take advantage of the parasitic impedances associated with a practical generator. These are used to determine whether or not the system to which the embedded generator is connected is earthed. The protection algorithms are designed to use well established techniques and to provide high speed tripping. The principles of operation are such that they can be developed for a multi-function microprocessor based relay or used in a stand alone relay. The paper includes details of practical tests conducted on a LV embedded generator system to demonstrate the principles involved