SU913515A1 - Device for protecting three-phase rectifier - Google Patents

Description

The invention relates to the protection of high-power converters against internal short circuits.

A device for protection of rectifiers is known, which contains current sensors, logic elements and the executive body [1].

The disadvantage of it is reduced sensitivity.

The closest to the proposed technical means and the achieved result is a device for protection of a three-phase rectifier containing intermediate current transformers, the primary windings of which are connected in each phase to the secondary windings of protective current transformers, and to the ends of the secondary windings of intermediate current transformers are connected in series positive pulse polarizers and time delay elements, between the outputs of which and the protection executive bodies are included Kie elements AND, OR, NOT. [2]

The disadvantage of this device is reduced reliability.

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The purpose of the invention is to increase reliability.

This goal is achieved by the fact that the outputs of the time-delay elements connected to the same ends of the secondary windings of intermediate current transformers of different phases are pairwise connected to the inputs of elements AND of the first group, the outputs of each pair relating to a particular pair of phases are connected to the inputs of the elements OR, the outputs which are connected to the first inputs of elements And the second group, the outputs of which are connected to the executive bodies of the same pair of phases, and the outputs of each element And the second group are connected to the second th and third inputs of the other two elements AND the second group through the elements NOT.

The drawing shows a diagram of the device.

The device contains current transformers 1, rectifier 2, phase switches A, B, C 3, intermediate current transformers 4, resistors 5, diodes 6, shapers of rectangular pulses 7, time delay elements 8, logic elements (input 2 913515

AND 9 schemes, OR 10 schemes, three-input schemes AND 11, NOT schemes 12).

When internal rectifier short circuits caused by a breakdown of the shoulder or bypassing the shoulder with an external resistance when there are short circuits to ₅ earth in the supply network and the rectifier grounded pole, in the rectifier phase wires from the power source in the intact phases the current has the same direction these are in intact phases and directed oppositely.

When the phase currents exceed the value of the actuation current at the outputs of the formers 7 pulses of positive polarity <5, rectangular pulses appear, at the outputs of the elements 8 permanent signals appear, the duration of which is chosen longer than the switch off time. You·

_ Phenomenon intact phases pair, koto- ₂₀ ryh current has the same direction, by means of control elements 9. For each pair of phases used by the two elements 9, since the polarity of the current in the healthy phases could be any. The outputs of the 25 moves of the pairs of elements 9 that control each pair of phases (AV, AC, BC) are connected to the inputs of logic elements 10.

Elements 11 and 12 are used to prevent the generation of a signal for disconnecting the damaged phase after the appearance of a signal for disconnecting intact phases, which is possible due to distortion of the secondary current of transformer 1 after saturation of their magnetic cores with aperiodic components of primary currents and the appearance of negative half-waves exceeding the pick-up setting. In normal mode, the signals at the outputs of elements 10 and 11 correspond to the logical “0”, and at the outputs of elements 12 of logical “1”, therefore the signals at two inputs from three for each element 11 correspond to ”1”. If an internal damage to the rectifier occurs, a signal ”1” appears at the output of one of the elements 10. At the output of the element 11 connected to it, the signal ”1” will also appear, and at the output of the element 12 - the signal ”0”. The same signal will appear on

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one of the inputs of the other two elements 11. Therefore, the appearance of the signal “1” on either of the two other elements 10 as a result of distortion of the secondary current form will not cause the signal ’!” on the outputs of any of the two other elements 11 that do not correspond to the pair of intact phases.

The device provides increased security protection.

Claims (1)

Claim A device for protection of a three-phase rectifier containing intermediate current transformers, the primary windings of which are connected in each phase to the secondary windings of protective current transformers, and sequential pulse formers of positive polarity and time delay elements connected to the ends of the secondary windings of intermediate current transformers security authorities included logical elements AND, OR, NOT, characterized in that, in order to increase reliability, the outputs of the elements you The time holders connected to the same ends of the secondary windings of intermediate current transformers of different phases are connected in pairs to the inputs of the AND elements of the first group, the outputs of each pair of which are related to a particular pair of phases are connected to the inputs of the OR elements, the outputs of which are connected to the first inputs of the AND elements of the second the groups whose outputs are connected to the executive bodies of the same pair of phases, with the outputs of each element of the second group being connected to the second and third inputs of two other elements of the second group of rez elements are NOT.