METHOD AND APPARATUS FOR DETECTING OF AN ISLANDING OF A DISTRIBUTED ELECTRICAL POWER SYSTEM

The invention relates to a method for detecting island formation of a distributed electrical power system (102), the distributed electrical power system (102) comprising at least one distributed electrical power generator (104) for generating and providing electrical power to a connection (108), in particular a power line for electrical power, wherein the distributed electrical power system (102) is inter-ruptibly coupled to an electrical power grid (110), the method comprising: - generating a reactive-power signal (700) having at least one probe-signal component (700.2, 700.4, 700.6) of a specified kind by an islanding-detection arrangement (106) coupled to the connection (108), - injecting the reactive-power signal (700) into the connection (108), - determining one or more monitored quantities, which are indicative of a response of the distributed electrical power system (102) to the injected reactive-power signal (700), and - applying an islanding-identification algorithm (211, 300a.7, 300b.7, 300c.7) to each of the one or more determined monitored quantities, wherein a result of the islanding-identification algorithm (211, 300a.7, 300b.7, 300c.7) is indicative of whether the distributed electrical power system (102) is decoupled from the electrical power grid (110). According to the invention it is provided that - the at least one of the monitored quantities involve a quantity from the group consisting of: - a second derivative (df/dt) with respect to time of the frequency (f) of a voltage (V, 108.1) associated with the generated electrical power (300b.6), - a first derivative (dVang/dt) with respect to time of a voltage angle (Vang) of the voltage (V, 108.1) associated to the generated electrical power (300a.6), and - a rotor angle (θrotor) of the at least one distributed electrical power generator (300c.6).