Symmetrical, Primary Current Tests On The Protected Object - Siemens SIPROTEC 4 7UT6 Series Manual

Mounting and Commissioning
3.3 Commissioning

Symmetrical, Primary Current Tests on the Protected Object

3.3.8
If secondary test equipment is connected to the device, it must be removed; any existing test switches should
be in normal operating position.
NOTE
i i
It should be expected that tripping occurs if connections were wrong.
The measured quantities of the following tests can be read out from the PC using a web browser via the WEB
monitor. This provides comfortable read-out possibilities for all measured values with visualisation using
phasor diagrams.
If you choose to work with the Web-monitor, please note the Help files referring to the Web-monitor. The IP
address required for the browser depends on the port used for connecting the PC:
•
Connection to the front operator interface: IP address 192.168.1.1
•
Connection to the rear service interface: IP address 192.168.2.1
The transmission speed is 115 kBaud.
The following descriptions refer to read-out of measured values with DIGSI. All measured values can be read
out from the device.
Preparation of Symmetrical Current Tests
At first commissioning, current checks must be performed before the protected object is energised for the first
time. This ensures that the differential protection is operative as a short-circuit protection during the first exci-
tation of the protected object with voltage. If current checks are only possible with the protected object under
voltage (e.g. power transformers in networks when no low-voltage test equipment is available), it is impera-
tive that a backup protection, e.g. time overcurrent protection, be commissioned before, which operates at
least at the feeding side. The trip circuits of other protection devices (e.g. Buchholz protection) must remain
operative as well.
If more than 2 measuring locations are present for the main protected object, the test must be repeated such
that each possible current path through the protected object has been part of a test. It is not necessary to test
every possible current path. Thus, it is advised to start with measuring location M1 of the main protected
object and to check this measuring location against all others. If a side has more than one measuring location,
each location must be included in a test. The other measuring locations remain current-free.
If further three-phase protected objects are present, these are tested individually according to their topology.
The test setup varies dependent of the application.
!
DANGER
Operations in the primary area must be performed only with plant sections voltage-free and earthed!
Perilous voltages may occur even on voltage-free plant sections due to capacitive influence caused
by other live sections!
²
On network power transformers and asynchronous machines a low-voltage test is preferably used. A
lowvoltage current source is used to energise the protected object, which is completely disconnected from the
network. A short-circuit bridge, which is capable of carrying the test current, is installed outside the protected
zone and allows the symmetrical test current to flow. On transformers, the test source is normally connected
at the primary side, and the short-circuit bridges are on the lower voltage side.
372 SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016