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7SR12 Functional Diagrams
67/
37
50 G
(x2)
I1
(x4)
(I
/I
)
G
SEF
27
VL1
59
(x 4)
27
VL2
59
(x 4)
27
VL3
59
(x 4)
Fig 3. Single Pole Directional Relay
37
49
(x2)
IL1
37
49
(x2)
IL2
37
49
(x2)
IL3
46
46
NPS
BC
(x2)
50
37
BF
I4
27
VL1
59
(x4)
27
VL2
59
47
(x4)
27
VL3
59
(x4)
Optional
79
Fig 4. Four Pole Directional Overcurrent Relay
Notes
1.
Items shown dotted are only available in some
models; please refer to the Ordering Information
Section.
2.
The use of some functions are mutually exclusive
Siemens Protection Devices Limited
7SR12
67/
67/
67/
81 H
51 G
50 SE
51 SE
BL 2
(x4)
F (x2)
F(x2)
47
59 N
(x2)
(x2)
74
T/
CCS
7SR12
67/
67/
50
81HBL
51V
50
51
BF
2
(x4)
(x4)
67/
67/
50
81HBL
51V
50
51
BF
2
(x4)
(x4)
67/
67/
50
81HBL
51V
50
51
BF
2
(x4)
(x4)
67/
67/
60
50
50N
51N
CTS
BF
(x4)
(x4)
67/
67/
67/
67/
50SEF(
51SEF(
50G
51G
64H
x2)
x2)
(x4)
(x4)
59N
Description of Functionality
27/59 Under/Over Voltage
Each element has settings for pickup level, drop-off level and
Definite Time Lag (DTL) delays. Operates if voltage exceeds
64 H
setting for duration of delay.
37 Undercurrent
Each element has settings for pickup level and Definite Time
Lag (DTL) delays. Operates if current falls below setting for
duration of delay.
46BC Phase Unbalance/Broken Conductor
Element has settings for pickup level and DTL delay. With the
circuit breaker closed, if the NPS:PPS current ratio is above
setting this could be due to a broken conductor.
46NPS Negative Phase Sequence Overcurrent
Each element has user settings for pickup level and IDMTL or
DTL delay, operates if NPS current exceeds setting and delay.
NPS current elements can be used to detect unbalances on
the system or remote earth faults when a delta-star
transformer is in circuit.
51c
47 Negative Phase Sequence Voltage
Each element has settings for pickup level and Definite Time
51c
Lag (DTL) delays. Operates if NPS voltage exceeds setting for
duration of delay.
51c
49 Thermal Overload
60
The thermal algorithm calculates the thermal states from the
VTS
measured currents and can be applied to lines, cables and
transformers. Alarm outputs are given for thermal overload
81HBL
and thermal capacity.
2
50BF Circuit Breaker Fail
74
The circuit breaker fail function may be triggered from an
T/CCS
internal trip signal or from a binary input. Line currents and
earth currents are monitored following a trip signal and an
output is issued if any current is still detected, above setting,
after a specified time interval. Alternatively, if the trip is
from a mechanical protection the circuit breaker position can
be used to determine a failure. A second time delay is
available to enable another stage to be utilized if required.
An input is also available to bypass the time delays when the
circuit breaker is known to be faulty.
4
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