Siemens 7UT51

6
Bus Differential Protection (87B)
7UT51 v3
80 PRIM-2330C
The relay can protect a three-phase bus with two
branches (7UT512 or 7UT513) or three branches
(7UT513 only). The protected zone is defined by the
location of the CTs (see Figure 6.1 and Figure 6.2).
The protected zone should not contain any series or
shunt reactors, or any other devices with significant
inductance.
A model 7UT513 is required if the protected bus has
three branches, or if the application includes
measurement of a ground (or neutral) current. A
7UT513 can also be used to protect simultaneously
both a two-branch bus and an additional protected
device.
6.2.2 System Frequency
The rated nominal frequency of the protected bus
must be specified in Address 7899.
Note:
The choice of frequency affects the availability
the auxiliary protection functions. With rated
frequency 60Hz, the backup overcurrent time
protection or the restricted earth fault
protection/tank leakage protection (dependent
on the ordered model) can be used besides the
differential protection for a bus. If the
three-branch bus protection is to be used, only
the backup overcurrent time protection is
available.
With rated frequency 50Hz, the backup overcurrent
time protection or the restricted earth fault protection/
tank leakage protection (dependent on the ordered
model) can be used in addition to the differential
protection for a bus.
With rated frequency 16 2/3 Hz, no restriction
concerning the additional functions are present.
If, during configuration, more functions have been
selected than the device is able to process, the relays
will give a corresponding message after configuration
has been finished. These messages can be read out
in the operational annunciations.
6.2.3 Rated Nominal Current
The rated nominal current of the bus, I
n
, which is used
as the unit of measure for all measured currents must
be programmed in the relay.
6.2.4 Normal Operational Status
The bus differential function can be set either to exist
or not exist. The choice is made in Address 7816.
Once the 87B function exists, it can be configured. Its
normal operational status is set in Address 1801.
7899 FREQUENCY
Rated nominal frequency of the protected bus.
Option Description
FREQ 50 Hz 50 Hertz
FREQ 60 Hz 60 Hertz (default)
FREQ 16 2/3 Hz 16
-
2/3 Hertz
1301 In TIE
-
PT
Nominal rated current of the protected bus.
Range: 1
–
100,000 A
Default: 2000
7816 87 STATUS
Choice of whether bus differential protection
function (87B) exists.
Option Description
EXISTENT 87 function exists (default).
NONEXISTENT 87 function does not exist.
1801 87 STATUS
Normal operational status of bus differential
protection (87B).
Option Description
OFF 87B function is inactive (default).
ON 87B function is active.
BLOCK
TRIPPING
87B function is active except that
trip contacts and signal contacts
will not respond to 87B events.