Method and protection device for identifying symmetrical short circuits in multiphase power transmission networks

Abstract

The invention relates to a method for detecting a symmetrical short circuit in an electrical transmission network, with a first protective device (15d) for a first section (C) of the electrical transmission network and with a second protective device (15a) for the transmission A second section (A) of the network monitors a symmetrical short circuit, wherein said second protection device (15a) is configured as a backup protection device which passes a prescribed stepped time limit in case a symmetrical short circuit is identified in the first section (C) A switch-off command is then issued to the power switch (14a), wherein an oscillation detection device (24) is provided, which, when an oscillation is detected in the power grid, emits an oscillation signal that counteracts the switch-off command issued by the second protective device (15a). In order to provide the possibility of opening the circuit independently of the oscillations that occur by means of an external symmetrical short-circuit, it is hereby proposed that, for the case where the symmetrical In the event of a short circuit, before the oscillation recognition device (24) detects oscillations in the power transmission network, a disconnection command is issued after a predetermined stepwise time limit, regardless of the presence of the oscillation signal.

Description

technical field [0001] The invention relates to a method for detecting a symmetrical short circuit in a polyphase electric power transmission network, wherein the symmetrical short circuit is monitored with a first protective device for a first section of the power transmission network and with a second protective device for a second section of the power transmission network Symmetrical short circuit. In this case, the second protective device is designed, as a backup protective device, while performing a remote protective function, also to monitor a symmetrical short-circuit in the first section of the power grid and when a symmetrical short-circuit is detected in the first section, a defined stepwise time limit elapses. Thereafter, an off command is issued to the power switch. In addition, an oscillation detection device is provided which monitors the electrical network for the presence of electrical oscillations and, when an oscillation is detected in the electrical networ...

AI Technical Summary

Problems solved by technology

Unintentional false disconnections of certain parts of the electricity transmission network may thus occur, which generally result in higher costs for the operator of the electricity transmission network

In addition, the abruptly changing network structure due to faulty disconnections leads to overloading of sections of the power transmission network that are still connected, which can lead to cascading disconnections up to so-called widespread blackouts.

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