Method for preventing differential protection from failing due to faulty inrush current on converter transformer valve side
A technology for differential protection and converter transformers, which is applied to emergency protection circuit devices, power transmission AC networks, electrical components, etc., and can solve problems such as false blocking of converter transformer differential protection
Inactive Publication Date: 2019-12-31
NORTH CHINA ELECTRIC POWER UNIV (BAODING) +1
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Problems solved by technology
[0004] Aiming at the above-mentioned problem that the conversion failure on the valve side of the converter converter leads to false blocking of the converter converter differential protection, the present invention proposes a new solution
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Embodiment Construction
[0014] The present invention proposes a method for preventing the failure of the inrush current on the converter transformer valve side from causing the differential protection to refuse to operate, which is described below with reference to the accompanying drawings.
[0015] Based on the identification of the polarity transition of the DC component of the current on the valve side of the fault phase, the present invention proposes a method for preventing the failure of the converter transformer valve side from causing the failure of the differential protection to fail. After the single-phase ground fault on the converter valve side, the short-circuit current flows through the converter valve. Due to the single-phase conductivity of the valve, the short-circuit current is biased to the time axis side and has a DC component. Therefore, the ground fault on the valve side of the converter transformer is judged according to the characteristics of the DC component of the fault current...
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The invention proposes a method for preventing differential protection from failing due to faulty inrush current on the converter transformer valve side. The differential current of a fault phase is greater than the starting current 0.2IN (IN is the rated current), and the second harmonic percentage content thereof is calculated after one cycle. If the second harmonic content is less than 15%, theprotection operates. If the second harmonic content is greater than 15%, and the current of the valve side of the converter transformer fault phase has direct component polarity reversal after the fault, the protection operates. If the harmonic content is greater than 15%, but the current of the valve side of the converter transformer fault phase does not have direct component polarity reversal after the fault, the protection does not operate. According to the invention, the feature of polarity inversion of the direct component of the current of the valve side of the fault phase after the occurrence of a switching fault is used; based on the principle of second harmonic braking, new criteria for preventing differential protection rejection caused by faulty inrush current caused by the ground fault of the converter transformer valve side is prevented; the problem of blocking of converter transformer differential protection caused by the fault in an area outside the converter valve sidegenerating area is effectively solved; and the reliability of converter transformer differential protection is ensured.
Description
Technical field [0001] The invention belongs to the technical field of power system relay protection, and particularly relates to a method for preventing the failure of a converter transformer valve side from causing a differential protection to refuse to operate. Background technique [0002] With the completion and development of HVDC power transmission projects, AC and DC hybrid systems have gradually formed in my country. In the UHV DC transmission system, as one of the most important equipment, the converter transformer is located between the AC system and the converter bridge. It can adjust the AC voltage in a larger range to make the system run in the best condition. , Whether the converter transformer can operate reliably and stably directly affects the reliability of the entire DC transmission system. The converter valve directly connected to the converter valve side has unidirectional conductivity, so that after the converter valve side fails, the fault current is bias...
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IPC IPC(8): H02H7/045H02J3/36
CPCH02H7/045H02J3/36Y02E60/60
Inventor 郑涛罗美玲国兴超吴建云郑现州于晓军寿海宁杨鑫慧赫嘉楠
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)