An electrical generator network and a local electrical system: avoiding the non-detection zone of passive loss-of-mains (Islanding) relays for synchronous generation by using low bandwidth control loops and controlled reactive power mismatches

A local electrical system having an electrical generator is connected to an electrical generator network. The local electrical system has a controller to avoid the non-detection zone of loss-of-mains relays. The controller is arranged to monitor the real power flow from the electrical generator network to the local electrical system and to determine if the absolute value of the real power flow is below a first predetermined value to determine if there is a close match between the power requirements of the local electrical system and the electrical generator. If there is a close match, then the controller is arranged to monitor the reactive power flow the same way. If there is a close match also with the reactive power, then the controller is arranged to adjust the target reactive power output from the electrical generator of the local electrical system.