Protection device against earth shorts in high-voltage three-phase networks

摘要

The invention relates to a protection device against earth shorts in high-voltage three-phase networks (1) each having three conductors L1, L2, L3 which lead from a transformer (2), which has a star point which is insulated or is earthed in a high impedance manner, into electrical loads. Measurement devices are provided in order to monitor the currents and/or voltages in the conductors L1, L2, L3. The conductors L1, L2, L3 are each connected to a single-pole earthing switch (28, 29, 30) which has the same switching capacity as the switches in the high-voltage three-phase network (1) and is monitored by means of short-circuit and overcurrent protection relays having a fast switch release. The earthing switches (28, 29, 30) are provided with metallic connections (31, 32, 33), which have virtually no resistance, to an earth (34), and the measurement devices control the single-pole earthing switches (28, 29, 30) via a sequence controller (24) and operating elements (25, 26, 27), such that the single-pole earthing switch (28, 29, 30) which is assigned to the conductor L1, L2, L3 having excessive values of the maximum or minimum voltage is closed if the maximum or minimum voltage in one of the conductors L1, L2, L3 exceeds freely selectable values which are stored in the sequence controller (24). <IMAGE>