Introduction to the technical principle of discharge coil

The discharge coil is a commonly used discharge element in capacitor cabinets. The outlet end of the discharge coil is connected in parallel to the two outlet ends of the capacitor bank. During normal operation, it bears the voltage of the capacitor bank. Its secondary winding reflects the primary transformation ratio, and the accuracy is usually 50VA/0.5 level. It can operate for a long time at 1.1 times the rated voltage. Its secondary winding is generally connected in an open triangle or phase voltage differential to provide protection for internal faults of the capacitor bank (PT on the busbar cannot be used). The open triangle voltage protection and unbalanced voltage protection of the capacitor bank are actually this kind of protection. And this kind of protection is widely used in 6kV~66kV single Y-connected capacitor banks according to the requirements of GB-50227.
Sometimes the discharge coil is replaced by a discharge PT. Whether the capacitor discharge uses a discharge coil or a voltage transformer depends mainly on the capacity of the capacitor. Generally, a small-capacity (<1.7Mvar) capacitor bank can be discharged with a voltage transformer, and a large-capacity capacitor bank (≥1.7Mvar) must use a discharge coil, otherwise it will cause the voltage transformer to burn or explode.