Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

Page: 144 / 706

3.64
SEL-351-5, -6, -7 Relay Instruction Manual
Date Code 20070117
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
Power Elements (Available in Firmware Version 7)
Make the following power element settings for the SEL-351(B):
EPWR = 2 (enable two power elements)
PWR1P =
24.0
(power element pickup; VA secondary [single-phase])
PWR1T =
+VARS
(power element type; lagging VARs)
PWR1D =
____
(power element time delay; cycles)
PWR2P = 96.0 (power element pickup; VA secondary [single-phase])
PWR2T = -VARS (power element type; leading VARs)
PWR2D =
____
(power element time delay; cycles)
To override transient reactive power conditions, set the above power element
time-delay settings equivalent to several seconds (or perhaps minutes).
Resulting single-phase power elements PWRA1, PWRB1, and PWRC1 assert
when the lagging VAR level exceeds the 0.3 per unit VAR level (lagging) for
each respective phase (see
Figure 3.40 and left-hand side of Figure 3.38 ).
These elements are used in close logic in the SEL-351(B) to automatically put
the 9600 kVAR capacitor bank on-line.
Resulting single-phase power elements PWRA2, PWRB2, and PWRC2 assert
when the leading VAR level exceeds the –1.2 per unit VAR level (leading) for
each respective phase (see
Figure 3.40 and left-hand side of Figure 3.38 ).
These elements are used in trip logic in the SEL-351(B) to automatically take
the 9600 kVAR capacitor bank off-line.
Settings for Three-Phase Power Elements
Following the single-phase derivation, the resulting power element setting
values need to be multiplied by three.
EPWR =
3P2
3PWR1P = 72.0
PWR1T = +VARS
PWR1D =
_____
3PWR2P =
288.0
PWR1T = –VARS
PWR1D = _____
The exact implementation of this capacitor close and trip logic in SEL
OGIC
control equations in the SEL-351(B) is not shown.