Technical Support

Effect of arc suppression coil in practical application
Publisher: Administrator Release time: 2019-3-27
Setting the detuning degree during the arc suppression coil operation: The setting of the detuning degree is directly related to the compensation effect of the system. If the setting is not correct, the ground signal may not disappear after the fault disappears, and the regulator reflects the neutral point. The displacement voltage is abnormally high, and the system will run at resonance.
Pre-fault state: the arc suppression coil is running in L position, the inductor current compensation value is IL, the reactance is XL, and the detuning degree is ε%.
In case of phase A ground fault: U0 is the asymmetric voltage of the system, U0 = UA, the damping resistance is shorted, and the system loop impedance is XL-XC = ε% · XL. The moment after the fault disappears: zero-sequence loop current I0 = U0 / (ε% · XL), displacement voltage Un = I0XL. At this time, if the detuning preset is too small, the zero-sequence loop current I0 may be greater than the current setting protection value, the displacement voltage Un is greater than the voltage setting value, and the CPU control circuit mistakenly believes that the grounding has not disappeared, making the vacuum circuit breaker unbreakable. On, the system runs almost near the resonance point.
Adjustment of neutral point displacement voltage:
In coastal areas, the asymmetric voltage is low, sometimes only about 10V, and the limited displacement cannot meet the requirements of the signal voltage of the auto-tuning device.The adjustment sensitivity and accuracy of the regulator are reduced, and the system is subject to transient fluctuations caused by voltage fluctuations and external factors. The large size makes the device malfunction, and the arc suppression coil frequently adjusts gears, which is not conducive to safe and stable operation. Therefore, in actual operation, the adjustment of the neutral point displacement voltage should be considered.
Protection of arc suppression coil damping resistance:
The damping resistor is protected by two short-circuit vacuum circuit breakers operated by AC and DC power supply at the same time.According to the neutral point voltage U0, the neutral point current I0, and the bus opening triangle voltage UL, it adopts voltage and current dual protection, independent In the microcomputer tuner circuit. The principle is: when U0 > 15V, I0 > 10A, UL > 25V, the relay will act and short the resistance.
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