5.2 Limit Switch :
Limit switch can be used to monitor upto three measured parameter (refer TABLE 3) with either ANDing/ORing or
no logic for tripping in relation with to a set limit.
The limit switch can be configured for Alarm-High or Alarm-Low, settable for each parameter and Energized or de-
Energized for the relay. The trip point, hysteresis, energizing delay and de-energizing delay are user-selectable.
High Alarm:
If Alarm - High and Relay - Energized or Alarm - High and Relay - De-Energized combination is configured then relay
will get Energized or De-energized, when selected parameter is greater than or equal to trip point.
Low Alarm:
If Alarm - Low and Relay - Energized or Alarm - Low and Relay - De-Energized combination is configured then relay will
get Energized or De-energized, when selected parameter is less than or equal to trip point.
# Note: For Alarm-Low configuration, set the values of trip point & hysteresis such that % trip point + % hysteresis
should be less than 100% Value.
Example for Phase angle:
If trip point is set 70% then maximum applicable hysteresis is 42.8%. i.e Trip point 70% (252 ) + Hysteresis 42.8% °
(107.8 ) = 359.8 If total value is greater than the 100% i.e. 360° ° ° then relay will not release.
0° (+1)
Relay De-energise
Relay Energise
0.4539(Trip point)
0.136(Hysterisis point)
180° (-1)
90° (0.00)
270° (0.00)
0.4539
0.136
Note: This function will work irrespective of +/-
sign. It depends only on value.
Trip point can be set in the range as specified in TABLE 3 of nominal value for Alarm - High & 10% to 100 % of
nominal value for Alarm - Low.
Trip point:
Example for PF:
For Alarm - High and Relay - Energized combination,
if trip point is 70% & hysterisis is 30%, then trip value
= 0.7x90°= 63°. Tripping PF = cos(63)=0.4539 &
hysterisis = 0.3 x 0.4539 = 0.136.
Hence, the relay will energize above 0.4539 and de-
energize below 0.3179.
Hysteresis can be set in the range of 0.5% to 50 % of set trip point. If Alarm - High & Relay - Energized or Alarm - High
& Relay - De-Energized combination is selected then relay will get Energized or De-energized respectively, if set
parameter value is less than Hysteresis. Similarly for the combinations of Alarm - Low & Relay - Energized or Alarm -
Low & Relay - De-Energized.
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