85
Power Quality Analyzer Model 3945
Wh[3] = Wh[0] + Wh[1] + Wh[2] total active energy
VAh[3] = VA[0] + VA[1] + VA[2] total apparent energy
VARhC[3] = VARhC[0] + VARhC[1] + VARhC[2] total reactive capacitive energy
VARhL[3] = VARhL[0] + VARhL[1] + VARhL[2] total reactive inductive energy
8.1.14 Hysteresis
Hysteresis is a fi ltering principle, often used after the threshold detection has
occurred. A correct setting of hysteresis value will avoid repeated triggering when
the measure is varying close to the threshold.
The event detection is activate when the measure is going over the threshold but it
can only be deactivated if the measure goes under the threshold minus the value
of the hysteresis.
The default hysteresis value is 2% of the reference voltage but it may be set in the
range of [1%, 5%] depending of the voltage stability on the system.
Swell Detection
Hysteresis =
2% Uref
Swell duration
Threshold of swell =
120% Uref
Level to go back =
120% -2% = 118% Uref
Sag or Interruption Detection
Hysteresis =
2% Uref
Level to go back =
(x% -2%)Uref
Threshold = x% Uref
Duration
