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FUNCTION CHARACTERISTICS
117
—
Directional reactive underpower - 37Q
Preface
The reactive power is calculated as:
Q
=
U
L1
I
L1
sin
f
L1
+
U
L2
I
L2
sin
f
L2
+
U
L3
I
L3
sin
f
L3
where:
• U
L1
,
U
L2
,
U
L3
are the fundamental components of the phase-to-neutral voltages
• I
L1
,
I
L2
,
I
L3
are the fundamental components of the phase currents
f
L1
,
f
L2
,
f
L3
, are the displacement angles of phase currents
I
L1
,
I
L2
,
I
L3
respect to the phase voltages
U
L1
,
U
L2
,
U
L3
, (positive when lag currents compared the phase voltages).
For the conventions on the active power sign is necessary to refer to the wiring diagram.
Operation and settings
The element is enabled for start and trip on the base of the direction setting for the two independent-
ly programmable thresholds.
User can disable the 37Q protection threshold from the keyboard. During this command, the trip
output relay (U <and / or U << thresholds) are forced to reset state, the message “Disabled 27-27V1-
37P-37Q” is displayed and all LEDs blink until the end of the command.
Q1< Tripping direction:
Q Forward
:
Q1< Tripping direction:
Q Reverse
:
Q1< Tripping direction:
Q Forward/Reverse
:
The element has two adjustable thresholds with time definite delay.
The active power is compared with the setting value (
Q
1
<
def
,
Q
2
<
def
) powers above the associated
P
Q
TRIP
Q
1
<
Q1< Tripping direction: Q Forward:
General operation time characteristic for the directional reactive underpower element - 37Q
P
Q
TRIP
Q
1
<
Q1< Tripping direction: Q Reverse:
General operation time characteristic for the directional reactive underpower element - 37Q
P
Q
TRIP
Q
1
<
Q
1
<
Q1< Tripping direction: Q Forward/Reverse:
General operation time characteristic for the directional reactive underpower element - 37Q
XMR-D EQUIPMENT MANUAL
Ed. 2.9 - 02/2021