Siemens SIPROTEC 7UT613 series Manual page 82

2 Functions
Further 1-phase
Protection Func-
tions
82
The same applies to the second overload protection that is assigned to a side under
address 444 THERM. O/L 2 AT.
The overexcitation protection (section 2.11) is only possible for devices with voltage
connection, and requires a measuring voltage to be connected and declared in the to-
pology (section „Topology of the Protected Object" under margin heading „Assignment
of Voltage Measuring Inputs"). It is not necessary to assign the protection function,
since it always evaluates the three-phase measuring voltage at the voltage input, and
the frequency derived from it. The same applies to the undervoltage protection, the ov-
ervoltage protection and the frequency protection.
When using the circuit breaker failure protection (section 2.17) (address 470
BREAKER FAIL.AT) please make sure that the assignment of this protection function
corresponds to that side or measuring location whose current actually flows through
the circuit breaker to be monitored. In the example shown in Figure 2-2, the assign-
ment must be set in address BREAKER FAIL.AT to Side 1 if you want to monitor
the circuit breaker of the high-voltage side, since both currents flow through the
breaker (via M1 and M2). If on the other hand you want to monitor the circuit breaker
of the cable feeder, you set address BREAKER FAIL.AT to Measuring loc.5.
When assigning the circuit breaker failure protection function, make sure that the
breaker auxiliary contacts or feedback information are correctly configured and as-
signed.
If you do not wish to assign any measuring location or side to the circuit breaker failure
protection because you want only the breaker position to be processed, set BREAKER
FAIL.AT to Ext. switchg. 1. In this case, the protection handles only the breaker
position but not any current flow for its operation. This allows even to monitor a circuit
breaker the current of which is not connected to the device. But you have to ensure
that the feedback information of this breaker is correctly connected and configured.
With the second circuit breaker failure protection an additional circuit breaker can be
monitored. The aspects regarding the assignment in address 471 BREAKER
FAIL2AT correspond with those for the first circuit breaker failure protection.
The 1-phase protection functions evaluate the 1-phase measuring current of 1-phase
additional measuring input. It is irrelevant in this context whether the connect current
belongs to the main protected object or not. Only the current connected to the addi-
tional measuring input is decisive.
The device must now be informed which current is to be evaluated by the 1-phase pro-
tection functions.
Address 424 DMT/IDMT E AT assigns the time overcurrent protection for earth
current (section 2.5) to a 1-phase additional measuring input. In most cases this will
be the current flowing in the neutral leads of an earthed winding, measured between
the starpoint and the earth electrode. In figure 2-2 the auxiliary measuring location X3
would be a good choice; so you set here AuxiliaryCT IX3. As this protection func-
tion is autonomous, i.e. independent of any other protection function, any 1-phase ad-
ditional measuring input can be used. This requires, however, that it is not a high-sen-
sitivity measuring input and, of course, that it is connected. Please note also that the
earth overcurrent protection will receive from the auxiliary measuring location as-
signed here not only its measured value, but also circuit breaker information (current
flow and manual-close detection).
The second earth overcurrent protection can be assigned to another single-phase
measuring location according to the same aspects under address 438 DMT/IDMT E2
AT.
7UT613/63x Manual
C53000-G1176-C160-2