Siemens 7SR18 Solkor - Page 339

7SR18 Commissioning & Maintenance Guide
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3.8 UNDERCURRENT (37)
46
BC
46
NPS
(x2)
37
(x2)
49
50
BF
I
L1
(I
A
)
81
HBL
2
37
(x2)
49
50
BF
I
L2
(I
B
)
81
HBL
2
37
(x2)
49
50
BF
I
L3
(I
C
)
81
HBL
2
I
4
(I
G
)
74
T/
CCS
NOTE: The use of some
functions are mutually exclusive
50
(x2)
51
(x2)
50N
(x2)
50
(x2)
50
(x2)
51
(x2)
51
(x2)
51N
(x2)
50G
(x2)
51G
(x2)
60
CTS-
I
50BF
51c
51c
51c
37G
(x2)
Figure 3.8-1 Undercurrent
Current Inputs: I
L1
(I
A
), I
L2
(I
B
), I
L3
(I
C
),I4
Disable: 51N, 51G, 46, 60CTS, 46BC
Map Pickup LED: 37-n - Self Reset
Undercurrent Guard: As required
Undercurrent start: Any or ALL
If two Undercurrent 37 elements are used with different settings, it is convenient to test the element with the
lowest setting first. The higher setting element can then be tested without interference from the other element.
Apply 3Phase balanced current or single phase current on the single pole relay models and earth fault function
37G/37SEF, at a level above the Undercurrent 37-n setting until the element resets. Check operation with start
option set to ANY phase and repeat with it set to operate for ALL phases.
If DTL setting is small, gradually reduce any phase current in turn until element operates.
If DTL is large apply 1.1x setting, check for no operation, apply 0.9x setting, check operation
Testing of this element phase by phase may cause inadvertent operation of the 46 NPS Overcurrent elements.
Apply 0.5x setting current and record operating time