FUNCTION CHARACTERISTICS
121
Operation and settings
The resistive
R
L1
and reactive
X
L1
components and the cos
f
ZL1
power factor, concerning the
Z
L1
impedance (phase voltage
U
L1
phase current
I
L1
ratio) are calculated:
Z
L1
=
U
L1
/
I
L1
R
L1
=
Z
L1
cos
f
ZL1
X
L1
=
Z
L1
sin
f
ZL1
where
Z
L1
and
f
ZL1
are the impedance module and displacement
Z
L1
,
U
L1
is the L1 phase-to neutral
voltage,
I
L1
is the L1 phase current phasor.
Convention:
f
ZL1
positive with current
I
L1
lagging the voltage
U
L1
.
Setting for GENERATOR mode
Reference: connection diagram shown in fig. 1 and 2.
The start of the alarm element is issued when both the following conditions are filled:
• X
L1
≤
KR
L1
• R
L1
≤ 0
or when both the following conditions are filled:
• X
L1
≤ -
KR
L1
• R
L1
> 0
where
K
is the adjustable angular coefficient (10° ≤
a
≤ 75°,
K
= tan
a
).
After expiry of the associated operate time (
t
40AL
) a trip command is issued.
The start of the first element is issued when both the conditions concerning the alarm element are
filled and the
R
L1
and
X
L1
computed values are placed inside the circle with equation:
R
L1
2
+(
X
L1
+
X
C1
)
2
≤ (
X
D1
/2)
2
1)
where the absolute coordinate of the center is
X
C1
and the diameter
X
D1
are adjustable.
After expiry of the associated operate time (
t
XC1XD1
) a trip command is issued.
X
L1
(p.u.
Z
nf
)
α
α
R
L1
(p.u.
Z
nf
)
TRIP
TRIP
ALARM
X
D2
X
C1
X
D1
NO TRIP
NO TRIP
NO TRIP
X
C2
General operation R-X characteristic for the loss of field element - 40 in the RL1-XL1 plane with
Mode40 = GENERATOR setting
Loss of field (40) protection for a synchronous machine normally working as generator (fig.1 and 2) or motor (fig. 3)
Fig. 1
Fig. 2
Fig. 3
SYSTEM
U
L1
U
L2
U
L3
VOLTAGE
INPUTS
CURRENT
INPUTS
SYSTEM
U
L1
U
L2
U
L3
I
L1L
I
L2L
I
L3L
I
L1L
I
L2L
I
L3L
I
L1L
I
L2L
I
L3L
VOLTAGE
INPUTS
CURRENT
INPUTS
XMR-x
XMR-x
XMR-x
VOLTAGE
INPUTS
CURRENT
INPUTS
SYSTEM
U
L1
U
L2
U
L3
40
40
40
CTs star side
CTs line side
XMR-D EQUIPMENT MANUAL
Ed. 2.9 - 02/2021
