Profile: Reyrolle Ltd designs, manufactures, installation & commissioning of protection and control equipment for electricity industries. Rho 3 is a multi-function numerical motor protection relay suitable for all types of AC induction motors up to the highest ratings available. Whilst medium voltage 3-phase motors are very reliable and robust, modern designs operate much closer to the limits of thermal margins and to give adequate protection, sophisticated protection relays are required. The ohmega relays are a range of numeric impedance measuring distance protection relays.