The impact of loss of mains detection on emergency reserve requirement

Embedded generation (EG) operating in parallel with a power system constantly faces the possibility of network disconnection due to nuisance tripping of `loss of mains´ protection, which mal-operates during grid frequency transients. The electricity supply regulations, however, require the installation of this equipment to protect against out-of-phase reclosures with the system. This paper presents a new technique for detecting loss of mains, utilizing a mains-borne radio frequency signal to sense the change in impedance that occurs when an EG becomes separated from the power network. The method of operation is independent of frequency variations, thus overcoming the deficiencies of more popular relays. The paper also demonstrates how this protection method can facilitate new operating regimes that will enable EG to become a more integral part of the generation mix. It shows how private generators can be used as a rapidly accessible form of spinning reserve, when allowed to remain connected to the grid during frequency transients, to support the reserve maintained by the utility