ABB RELION REX640 - Page 1058

Measurement mode setting Power calculation
P S=
( )
Re
PhsC
S U I
c c
= ⋅ ⋅3
*
P S=
( )
Re
If all three phase voltages and phase currents are fed to the protection
relay, the positive-sequence alternative is recommended (default).
Depending on the set Measurement mode , the power calculation calculates active
power, reactive power and apparent power values from the available set of
measurements. The calculated powers S, P, Q and the power factor angle, PF_ANGL,
are available in the Monitored data.
Directional calculation
Directional calculation determines the direction of the measured power. The
measured power is considered to be in the forward direction if the active power
is positive, else it is considered to be in the reverse direction.
A typical error is, for example, that the VT or CT poles are wrongly
connected. This is seen as a power flow opposite to that of the intended
direction. The Pol Reversal setting can be used to correct the situation.
By setting the value to "True", the measured apparent power is turned
180 degrees.
Level detector
Level detector compares the calculated value of the active power with a set Start
value . If the calculated value of the active power falls below Start value in the
forward direction or if the measured power is in the reverse direction, Level detector
enables the Timer module.
Protection functions
1MRS759142 F
1058 REX640
Technical Manual