DEVICE OF RELAY PROTECTION FOR LOCAL BACKUP OF AUTO-TYPE TRANSFORMER PROTECTIONS Russian patent published in 2017 - IPC H02H7/04 

FIELD: electricity.

SUBSTANCE: device of relay protection for local backup of auto-type transformer protections contains a measuring device - a current relay, the input of which is connected to the current transformer. The current transformer is included in common parts of windings of high and medium voltage phases of the auto-type transformer, and through its outputs its measuring body - the current relay is series-connected to a time-delay device and an executive device, the outputs of which are connected with the control circuits of switches for the auto-type transformer on the sides of high, medium and low voltage. If the increased selectivity is required, the second measuring device is added to the relay protection device for local backup of auto-type transformer protections. It is designed as a minimum voltage relay. The logical "and" element is also introduced with two inputs, while the second input of the second measuring device is connected to the voltage transformer on the lowest voltage side of the auto-type transformer and the output is connected to one of the inputs of the logical "and" protection element, the other input of which is connected to the output the first measuring device - current relays, while the output of the logical "and" unit and is connected to the input of the time-delay device.

EFFECT: prevention of damage from the nonrecoverable damage of the auto-type transformer due to the prolonged flow of short-circuit current through the auto-type transformer, which occurred on the lowest voltage side and under fault conditions in the activation of the main or backup relay protection of the auto-type transformer.

2 cl, 2 dwg