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How to choose the right dry series core reactor

The dry series iron core reactor is one of the main components of the shunt capacitor device. It acts as a limiting capacitor combination shunt current, suppresses power harmonics, prevents damage to the capacitor, and avoids excessive amplification of the harmonics of the power grid by the access of the capacitor device. And the important role of resonance.
However, the iron core reactor and the capacitor cannot be combined arbitrarily. If the actual situation of the power grid connected to the capacitor device is not considered, the uniform configuration method is often counterproductive, resulting in serious amplification of the harmonics and even resonance, which jeopardizes the safety of the device and the system. Due to the universality, complexity and randomness of power harmonics, and the difference in the structure and characteristics of the power grid, the harmonic response of the capacitor device and the selection of the string resistance are becoming difficult problems.
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The "misunderstanding" of the dry reactor selection. In the early 1980s, in order to promote the improvement of the quality and production technology of domestic capacitor products, the state adopted major measures, including the import of a batch of capacitors from Western Europe and Japan by the former Ministry of Water Resources and Power, and allocated them to Northeast China and North China. And East China Power Grid is installed in 110kV and above substations, and the Japanese practice requires that all 6% string resistance be used. At one time, all parts of the country (except for Zhejiang Province and other provinces) form almost the same as "leading". Design mode. With the successive operation of large-capacity capacitor devices in various places, through field harmonic measurement, people gradually discover and realize that the facts are not as described in the textbook. Only the zero-order component of the third harmonic can be connected by the transformer Δ. The coil is looped, but is circulated everywhere. In addition to the electrified railway, the electric arc furnace load is a third harmonic source. According to a large number of test and analysis results, the dry transformer is also an important source of power harmonics. Its main component is 3rd harmonic. Due to the excitation current of the three-phase transformer plus the magnetic saturation of the core, and the asymmetry of the 3-phase circuit and the magnetic circuit prevalent in the power system, the three-phase power supply The voltage is not only different in amplitude, but also not 120° in phase. Therefore, even in the line voltage on the side of the transformer's delta winding, there are still 3rd harmonic components in the line current, which are positive and negative sequence components. Therefore, the third harmonic is spread throughout the power grid, especially when the load is low. As the grid operating voltage increases, the saturation of the transformer core increases, and the third harmonic content generated increases accordingly. According to Zhejiang Power Grid In recent years, the results of harmonic estimation of 165 measuring points in 10~500kV network at all levels, with the dominant harmonics of 3 times and the dominant harmonics of 3rd and 5th harmonics accounted for 92% of the total number of measured points. According to the Shaoxing regional power grid The monitoring results mainly accounted for 79% of the total number of points measured by the third harmonic, and 94% of the total of the three times and three or five times. Such background harmonics are universal in the national power grid. It turns out that China's national conditions are different from those of Japan. The latter's power grid does not have 3rd harmonics. It is correct that the capacitors are connected in series with 5%~6% string resistance to suppress the harmonics of the power grid 5 times or more, and we follow the latter. Anti-option introduces "misunderstanding". The situation of the 3rd harmonics in the grid is widespread, and there have been "misleading" to capacitors. Set and affect the operation of the grid connected arising should not be underestimated.
ZTELEC designs dry series core reactors to meet local usage according to different needs of customers.

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