Siemens SIPROTEC 4 7UT6 Series Manual page 387

[webmon-diff-messwertprim-zeig, 1, en_GB]
Figure 3-46
•
Open the miniature circuit breaker of the feeder voltage transformers. The measured voltages in the
operational measured values appear with a circuit close to zero (small measured voltages are of no
consequence).
– Check in the Event Log and in the spontaneous annunciations that the VT mcb trip was noticed
(annunciation
of the VT mcb is connected to the device via a binary input.
•
Close the VT mcb again: The above indications appear under the "going" operational indications, i.e.
>FAIL:Feeder VT "OFF".
– If one of the annunciations does not appear, the connection and allocation of these signals must be
checked.
– If the "ON" and "OFF" messages are exchanged, then the breaker auxiliary contact type (H-active or
L-active) should be checked and corrected if necessary.
•
Finally, the protected object or the voltage measuring location is switched off.
Allocation and Direction Test
Voltages are also used for calculation of powers and metering of energy. Therefore, it must be checked
whether the connected voltages have correct relationship with respect to the currents which are to be used
for power calculation. When using power protection functions (reverse power protection, forward power
supervision) the correct allocation and polarity are prerequisite for the correct function of this protective func-
tion.
Primary tests are preferred as secondary tests cannot prove the correct polarity.
A load current of at least 5 % of the rated operational current is required. Any direction is possible but must be
known.
•
In a first step, check whether power measurement is carried out at the desired measuring location, i.e.
that the assignment of the 3-phase voltage transformer set is made correct. The powers are always calcu-
lated from the connected voltages and the currents of that measuring location to which the voltages are
assigned. If the voltage inputs are assigned to a side of the protected object with more than one meas-
uring location, the sum of the currents flowing into the protected object is decisive.
Address is relevant 261 VT SET. Refer to Section
"Assignment of Voltage Measuring Inputs".
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
Phasor Diagram of the Primary Measured Values — Example
>FAIL:Feeder VT , No 361 "ON"). Beforehand it has to be assured that the position
2.1.4 Power System Data 1
Mounting and Commissioning
3.3 Commissioning
under margin heading
387