The ONLLY Relay Protection Tester ONLLY-AT1266-40AH is an advanced and highly reliable testing device specifically designed for testing relay protection systems in electrical networks, substations, and power plants., founded in 1994, is a professional manufacturer specializing in the research, development, production and sales of testing equipment for power system. This is done to ensure a power system's reliability and safety during installation and commission. More than 20,000 relay test kits has been supplied to users in China and other countries, including 6-phase, 3-phase, single.