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Under/Over Frequency (81); Figure 2-18 Under/Over Frequency - Siemens 7SR21 Manual

Overcurrent relay
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2.13.8 Under/Over Frequency (81)

I
L1
(I
A
I
L2
(I
B
I
L3
(I
C
I
4
(I
G
I
5
(I
SEF
V
L1
(V
)
A
V
L2
(V
)
B
V
L3
(V
)
C
V
4
(V
)
X
Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
This function can be tested by application of 1P or 3P voltage. For Over-frequency, the elements with the highest
setting should be tested first and for Under-frequency the elements with the lowest settings should be tested first.
The elements with other settings can then be tested without need to disable the elements already tested. Note
that the relay is designed to track the gradual changes in power system frequency and that sudden step changes
in frequency during testing do not reflect normal system operation. Normal 'instantaneous' operation of the
frequency element is 140-175ms in line with the Performance Specification. Application of sudden step changes
to frequency can add additional delay which can produce misleading test results.
Gradually increase/decrease applied voltage frequency until 81-n operation occurs. Elements set for more
extreme frequency fluctuation should be tested first with lesser elements disabled.
If the 81-n Delay setting is long it will be advantageous to map the function to temporarily drive the relevant
Pickup output in the Pickup Config sub-menu in the Output Config menu as this will allow the Pick-up led to
operate for the function. If the delay setting is short the operation of the element can be easily checked directly.
©2010 Siemens Protection Devices Limited
37
50
49
(x2)
BF
)
37
50
49
(x2)
BF
)
37
50
49
(x2)
BF
)
46
46
60
NPS
BC
CTS
(x2)
)
)
functions are mutually exclusive
27
59
(x4)
27
47
59
(x2)
(x4)
27
59
(x4)
27
59
Optional
79

Figure 2-18 Under/Over Frequency

V
(V
), V
(V
L1
A
L2
B
n/a apply zero current to stabilize other functions
81-n - Self Reset
7SR21 & 7SR22 Argus Commissioning and Maintenance
67/
67/
51V
50
51
(x4)
(x4)
67/
67/
51V
50
51
(x4)
(x4)
67/
67/
51V
50
51
(x4)
(x4)
60
67/
67/
60
CTS-
50N
51N
VTS
I
(x4)
(x4)
67/
67/
81
50G
51G
HBL
(x4)
(x4)
2G
67/
67/
64
50S
51S
H
(x4)
(x4)
NOTE: The use of some
Note:
Example shows
81
Voltage Config =
(x6)
Van, Vbn, Vcn
59N
74
(x2)
TCS
), V
(V
)
L3
C
7SR22
81
HBL
51c
2
81
51c
HBL
2
81
HBL
51c
2
81
HBL
2N
37G
(x2)
37S
(x2)
Chapter 6 Page 55 of 69

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