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7SR11 & 7SR12 Commissioning and Maintenance Guide
2.12 Undercurrent (37)
I
L1
I
L2
I
L3
Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
Undercurrent Guard:
Undercurrent start:
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
©2017 Siemens Protection Devices Limited
37
(x2)
(I
)
A
37
(x2)
(I
)
B
37
(x2)
(I
)
C
46
BC
37G
(x2)
I
(I
)
4
G
27
V
(V
)
59
L1
A
(x4)
27
V
(V
)
59
L2
B
(x4)
27
V
(V
)
59
L3
C
(x4)
Figure 2-13
n/a
I
(I
), I
(I
), I
L1
A
L2
B
51N, 51G, 46, 60CTS, 46BC
37-n - Self Reset
As required
Any or ALL
67/
67/
50
49
51V
50
51
BF
(x4)
(x4)
67/
67/
50
49
51V
50
51
BF
(x4)
(x4)
67/
67/
50
49
51V
50
51
BF
(x4)
(x4)
46
67/
67/
60
60
NPS
50N
51N
CTS
VTS
(x2)
(x4)
(x4)
67/
67/
50BF
50
51
SEF
SEF
NOTE: The use of some
functions are mutually exclusive
47
81
59N
(x2)
(x4)
(x2)
Optional
79
Undercurrent
(I
),I4
L3
C
7SR12
81
HBL
51c
2
81
HBL
51c
2
81
HBL
51c
2
64H
Note:
Example shows
Voltage Config =
Van, Vbn, Vcn
74
T/
CCS
Chapter 6 Page 42 of 72
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