Detail KRK KAD 04 Under & Over Voltage Protection Relays
Under & Over Voltage Protection Relays are used for 3 phase systems, to protect systems from: Phase loss, phase sequence failure, Under voltage, Over voltage.These functions are shown below. 1) Under & Over Voltage Protection: Under and Over voltage tolerances can be adjusted seperately. If the phase- neutral voltage values are between the adjusted levels ` ` out` ` led is on( 2-3 contacts are closed) .otherwise device close the output( 1-2 contacts are closed) .During normal operation any of phases voltage value decreases under the adjusted value ` ` under` ` led is on, increases over the adjusted value ` ` over` ` led is on.If one of the phases is over the limit and one of the under the limit both ` ` under` ` and ` ` over` ` leds are on.If these condition continues more than adjusted delay time ` ` out` ` led is off( 1-2 contacts are closed) .Related warning leds remain on.If these condition continues less than adjusted time, warning leds are off.Device operating normally. 2) Phase Loss: If the system has lost one of the phases , the output s closed without delay( ` ` on` ` and ` ` under` ` leds are lighted) . In case of supply voltage loss, all leds are off. 3) Phase Sequence Failure: If the squence of the phases are wrong the output is closed without delay. Any case if the sequence is changed during normal operation the output is closed without delay.` ` Under` ` and ` ` over` ` leds are flashing. 4) If any of phases values increases over 1.5XUn or decreases under 0.5XUn device will closed the system without delay. Warning leds will light on accordingly. 5) If phase sequence control is not desired in KAD 04: S1-S2 should be short-cut; SKAD 04: S-N should be short-cut.