Out Of 3 Logic - Siemens Argus 7SR21 Technical Manual

7SR210 & 7SR220 Commissioning & Maintenance Guide
Lag (point C)
Pick-up
MTA MTA-85
Phase A
Phase B
Phase C
B
b
0
+180
0
+210
V
C
Figure 2.1-1
4. With the instrument reading 'Fwd' or 'Rev', reduce the voltage until the element resets. Record the
minimum phase-phase operate voltage.
Minimum Voltage Setting
2.1.1

2 out of 3 logic

Ensure that at least 1 Phase Overcurrent element is set to Directional. Apply balanced nominal voltage. Apply
current at a level above on phase A only at the characteristic angle for forward operation, normally 45º lagging.
Ensure no Directional Phase Overcurrent element operation occurs. Note that non-directional Phase Overcurrent
and Non-direction Earth Fault elements may operate unless disabled.
Repeat the test with Phase A current as above but also with equal current in the B phase at 180º to that in the A
phase.
1 phase current
No 50/51-n Operation
Page 16 of 82
Forward
Lead (point A)
Drop-off Pick-up Drop-off
MTA+85
V
A
0
+90
a
0
+60
A
I
A
FWD
+30
V
BC
C
REV
D
0
+240
d
0
+270
Directional Phase Fault Boundary System Angles
Lead(point B)
Pick-up Drop-off
MTA-85
With balanced 3-phase system quantities:
Adjust the phase angle of the currents
relative to the voltages:
0
Verify directional pick-up and drop off at
points A, B, C and D
0
0
Alternatively,
Verify correct directional indication at points
c
0
a, b, c and d (C.A +75 , +95
V
B
Measured
2 phase current
50/51-n operation
© 2013 Siemens Protection Devices Limited
Reverse
Lag (point D)
Pick-up Drop-off
MTA-85
0 0 0
, -75 , -95 )