Rectifier transformer group transverse bracing differential current protection method and apparatus

Abstract

The present invention discloses a rectiformer unit transverse differential current protection methode and device characterized in that: two sets of rectiformers at same capacity are adopted to provide DC electric supply for aluminum electrolysis series. The two sets of rectiformers respectively performs phase compensation to the aluminum electrolysis series through a current mutual conductor, and then produces a second current at same volume and consistent phase; the two second current is input into a current differential delay; while in normal running, the unbalance current obtained is close to zero; while in a breakdown occurs, unbalance current runs into the current differential relay, and the current differential relay exert effect onto the circuit breaker to perform a trip. The present invention forms a protection device by adopting transverse differential principle, utilizing the principle of the unbalance current at the primary side of the two sets of rectiformers, and has the advantages in that: simple structure, high sensitivity, hidden from the excitation flow, safe and efficient, reducing the times of adjusting the protection setting value etc. in such way, the present invention can provide a complete reliable protection for the rectiformer unit at convenient installation.

Description

technical field [0001] The invention relates to a rectifier transformer group cross-connected differential current protection method and device, and belongs to the technical field of rectifier transformer protection for electrolytic aluminum in electrolytic aluminum plants. Background technique [0002] The large-scale voltage regulating rectifier transformer group used to supply power to the electrolytic cell in a modern electrolytic aluminum plant is usually composed of a voltage regulating transformer and a rectifier transformer group. In order to reduce the harmonic components generated by the rectifier unit, each rectifier transformer group is usually composed of 2 rectifier transformers with a common oil tank, equal capacity, and connected in the form of wiring to form an equivalent 12-pulse rectifier circuit. Due to the requirements of the electrolysis process, an on-load tap changer OLTC is configured in the tap changer transformer to adjust the voltage UDN of the ou...

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Problems solved by technology

Carry out the sensitivity Klm (Klm=minimum fault current / protection device operating current) effect according to the lowest voltage regulation level of the voltage regulating transformer and the short-circuit current in the minimum operating mode of the system. Generally, Klm<2, the overcurrent protection may not operate when a fault occurs , loses the protective effect, and finally only the gas protection device can provide protection to the transformer group:

[0004] 2. It is impossible to avoid the excitation inrush current at the moment of power transmission of the voltage regulating rectifier transformer group, and the protection can only be put into operation after a delay until the excitation current is stable, and the protection is not timely;

[0005] 3. As the electrolysis series is put into production in stages, the setting value of overcurrent protection needs to be adjusted several times

In the production stage of the electrolytic aluminum plant, with the increase in the number of electrolytic cells in operation, the gear position of the on-load tap changer OLTC is gradually reduced, the DC series voltage UDN is gradually increased, and the impedance voltage of the voltage regulation rectifier transformer group is also gradually reduced, so the rectification The setting value of the second set of overcurrent protection relay protection of the transformer group needs to be adjusted in stages according to the production plan of the electrolyzer, and the work is cumbersome

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