The ac voltage protectors provide continuous surveillance of the monitored circuit. When the measured voltage moves outside the set point limit, the relay will operate giving an alarm or initiation signal. The protector can be used for under and over-voltage detection, start standby generators, operation of mains failure units and switching standby supplies. An illuminated LED indicates when the relay is energised. The three-phase, three or four-wire models, protect each phase independently.
Description
AC voltage protectors offer user adjustable trip point (set point) and differential (hysteresis) settings. The set point adjustment range is 25%, operating between 75% and 100% of the nominal supply for under-voltage units and between 100% and 125% for the over-voltage units. The differential setting adjustment range is 1% to 15% and it can be used to reduce nuisance tripping if the measured signal is noisy or unstable.
When the measured voltage moves outside the set point limit, the relay will operate, giving an alarm or initiation signal. As soon as the monitored signal moves outside of the set point limit, a trip will occur.
A fixed time delay is available as a factory option, preventing the relay from tripping for a predetermined period to prevent nuisance tripping. The units draw their operating power from the measuring inputs, although a separate auxiliary supply input option is available on some models. Three-phase products monitor the voltage level for each phase and
are not phase sequence sensitive. Combined units offer under and over-voltage trips in one compact unit. Single function units are also available.
Over-Voltage Models
When the monitored voltage exceeds the set point, the relay will energise and the red LED will illuminate to indicate the trip condition. The relay will automatically reset once the monitored voltage falls below the set point minus the differential. When reset, the LED will extinguish and the relay de-energises.
Under-Voltage Models
When the monitored voltage falls below the set point, the relay will de-energise and the red LED will extinguish to indicate the trip condition. The relay will automatically reset once the monitored voltage rises above the set point plus the differential. When reset, the LED will illuminate and the relay energises.
Options
250 series protector relays offer various customised options to suit individual requirements. Please consult factory.
- Time delay – internal fixed time delay before a trip occurs.
- Separate auxiliary supply – sometimes required to maintain a time delay or energised relay when the monitored signal fails.
- Adjustment ranges – different adjustment ranges are possible for the set point and
differential controls.
- Relay operation – standard models are fail safe, but the relays can be customised to energise or de-energise on trip.
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