Creative Technology Provider Neutral Voltage Detection Method (NVS : Neutral Voltage Sensor) NVS(Neutral Voltage Sensor) is the one of protection method that makes at outside in double Y connection with single capacitor and insert a NVS(Neutral Voltage Sensor) to the neutral point and detect a differential voltage when capacitor is broken. If capacitor occurs failure during operation, it will give an operation signal to circuit breaker used first pulse power from first output and separate from power supply and neutral voltage becomes extinct. There are single star method(single capacitor 3unit + spare resistor 3unit) and double star method (single capacitor 6unit) for composition of circuit. Both of method are used a voltage detection of neutral point when failure occurs. The good point of NVS(Neutral Voltage Sensor) protection method is as follows. ◆ Easiness of maintenance & repair Broken capacitor can be replaced only when capacitor occurs failure. ◆ Malfunction of relay There is no malfunction of grounding relay because neutral point is from insulated resistor (non-grounding). ◆ No effect from inrush current There is no effect from inrush current and harmonics because of voltage detection method. ◆ Regular inspection It can check a capacitor defect or not through regular inspection of NVS(Neutral Voltage Sensor). ◆ Reducing generate heat of capacitor It can make a generate heat for capacitor because whole capacitor capacity separate 3unit or 6unit. Film Capacitor Division -1- Technical Engineering Team Creative Technology Provider 1 Vn = Vp 3P(S-1)+1 = 4054 Series Reactor 직렬리액터 3 × 1 × ( 3 -1 ) + 1 방전코일 Discharge Coil = 579 V Auxiliary 보조저항 Resister Vn : Neutral point voltage when failure occurs P : Capacitor external parallel circuit no. 전력용콘덴서 Capacitor S : Capacitor inner series circuit no. Vp : Phase voltage Film Capacitor Division -2- Technical Engineering Team