Beijing Quartet CSC-221 digital capacitor protection and monitoring device functions: 1) unbalance protection. CSC-221A with unbalanced voltage protection element, CSC-221B with unbalanced current protection device, according to the situation unbalanced analog access can be used as a three-phase or single-phase imbalance protection. 2) over-current protection. Device is equipped with two-stage element and inverse definite time overcurrent element. Overcurrent Ⅱ segment can be set as inverse-time characteristics. 3) zero-sequence overcurrent protection. Device is equipped with two-stage element and inverse elements definite time zero sequence overcurrent. Zero flow Ⅱ segment can be set as inverse-time characteristics. 4) voltage protection. Device includes overvoltage protection element and under-voltage protection element. 5) Self-switching function. When not in use voltage and reactive power integrated automation system, the choice of self-administered or self-cutting function under the circumstances. To prevent the error from the cast to the fault, hand jump, jump or throw a protective action, the device can automatically withdraw "from switching," the soft platen. 6) Other functional descriptions. PT disconnection device having an alarm control mother and spring break warning alarm feature is not charged.