PCKN-OIL738
10
4 Functions
4.1 Protection
4.1.1. Undervoltage elements
Fig. 4.1 “Undervoltage element internal function block diagram” shows operation of the undervoltage
elements.
Undervoltage element compares input voltages of voltage circuit with the operation setting. If an input
voltage is less than the specified operation level, the element outputs an operation signal when the timer
expires.
Undervoltage element detected
(Operation indicator LED blinking)
Undervoltage element detected
(Operation indicator LED lit)
Operation signal
(Undervoltage element)
V
AB
Undervoltage element
Voltage comparison
Timer
(trip/reset)
AB-phase processing
BC-phase processing
Same as processing in AB-phase
V
BC
V
CA
CA-phase processing
Same as processing in AB-phase
Figure 4.1 Undervoltage element internal function diagram
4.1.2. Overvoltage elements
Fig. 4.2 “Overvoltage element internal function block diagram” shows operation of the overvoltage
elements.
Overvoltage element compares input voltages of voltage circuit with the operation setting. If an input
voltage is larger than the specified operation level, the element outputs an operation signal when the timer
expires.
Overvoltage element detected
(Operation indicator LED blinking)
Overvoltage element detected
(Operation indicator LED lit)
Operation signal
(Overvoltage element)
V
AB
Overvoltage element
Voltage comparison
Timer
(trip/reset)
AB-phase processing
BC-phase processing
Same as processing in AB-phase
V
BC
V
CA
CA-phase processing
Same as processing in AB-phase
Figure 4.2 Overvoltage element internal function diagram