A digitally controlled voltage window discriminator controls operation and delay of the voltage low/high alarm relays. The unit measures the zero point crossing and the true r.m.s. voltage value, and accuracy is independent of any wave form distortion.

The auxiliary voltage is supplied from the unit voltage inputs. A DC or AC auxiliary voltage input is optionally available. A green LED indicates POWER on. Start of monitoring function is delayed when the power is switched on (default 2 secs delay). In this way false tripping during power up is avoided.

The voltmeter and the triple-zone status LEDs give the clear safety message:

• HIGH ALARM
• NORMAL
• LOW ALARM

Red alarm lamps LOW (under voltage) and/or HIGH (over voltage) flash instantly (approx. 1 flash per second) on passing the lower and/or upper voltage differential set points. The lamp changes state and the trip relay operates after the pre-set delay. If a fault condition ends during the delay interval, the timer will automatically reset.

The voltage differential set points can be user-adjusted to suit most applications. Trip levels and delays are settable on unit rear. Operation of the status trip relay is inverted (fail safe), i.e. the relays are energized during normal conditions.

If one phase voltage is below the low trip level and, simultaneously, another phase voltage exceeds the high trip level then both relays will operate.

The class 1,5 moving iron DIN96 voltmeter must be connected directly to any phase or via a selector switch to read all three phases. The unit has low-reflection glass to ease reading at a distance.

The “Pathfinder” function identifies the phase(s) causing the trip by flashing pattern of the relevant LED(s).

The F-versions have an isolated output proportional to the at any time highest measured voltage.

KEV233x – Three Phase 3-wire system
KEV234x – Three Phase 4-wire system