Method for detecting a symmetrical short-circuit in a multiphase electrical power supply network, wherein - a first section of the power supply network is monitored for a symmetrical short-circuit by means of a first protective device; - a second section of the power supply network is monitored for a symmetrical short-circuit by means of a second protective device, wherein - the second protective device is configured for the purpose of additionally monitoring the first section of the power supply network for a symmetrical short-circuit as a standby protective device while executing a distance protection function and, if a symmetrical short-circuit is detected in the first section, of issuing a shutoff command to a circuit breaker after a predefined grading time has elapsed; and wherein - an oscillation detection device is provided which monitors the power supply network for the presence of an electrical oscillation and emits an oscillation signal blocking the issuing of the shutoff command by the second protective device if an oscillation has been detected in the power supply network; characterised in that - in the event that a symmetrical short-circuit in the first section has been detected by the second protective device before an oscillation in the power supply network has been detected by the oscillation detection device, the shutoff command will be issued irrespective of the presence of an oscillation signal if the grading time has elapsed; and - in the event that an oscillation has been detected by the oscillation detection device before a symmetrical short-circuit in the first section has been detected by the second protective device, the shutoff command will be blocked by the pending oscillation signal. - a first section of the power supply network is monitored for a symmetrical short-circuit by means of a first protective device; - a second section of the power supply network is monitored for a symmetrical short-circuit by means of a second protective device, wherein - the second protective device is configured for the purpose of additionally monitoring the first section of the power supply network for a symmetrical short-circuit as a standby protective device while executing a distance protection function and, if a symmetrical short-circuit is detected in the first section, of issuing a shutoff command to a circuit breaker after a predefined grading time has elapsed; and wherein - an oscillation detection device is provided which monitors the power supply network for the presence of an electrical oscillation and emits an oscillation signal blocking the issuing of the shutoff command by the second protective device if an oscillation has been detected in the power supply network; - the second protective device is configured for the purpose of additionally monitoring the first section of the power supply network for a symmetrical short-circuit as a standby protective device while executing a distance protection function and, if a symmetrical short-circuit is detected in the first section, of issuing a shutoff command to a circuit breaker after a predefined grading time has elapsed; and wherein - an oscillation detection device is provided which monitors the power supply network for the presence of an electrical oscillation and emits an oscillation signal blocking the issuing of the shutoff command by the second protective device if an oscillation has been detected in the power supply network; - in the event that a symmetrical short-circuit in the first section has been detected by the second protective device before an oscillation in the power supply network has been detected by the oscillation detection device, the shutoff command will be issued irrespective of the presence of an oscillation signal if the grading time has elapsed; and - in the event that an oscillation has been detected by the oscillation detection device before a symmetrical short-circuit in the first section has been detected by the second protective device, the shutoff command will be blocked by the pending oscillation signal.