Siemens SIPROTEC 7SJ61, Руководство пользователя, Страница: 298 / 454

Mounting and Commissioning
3.3 Commissioning
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
298
3.3.6 Current and Phase Rotation Testing
≥
10 % of Load Current
The connections of the current and voltage transformers are tested using primary quantities. Secondary load
current of at least 10 % of the nominal current of the device is necessary. The line is energized and will remain
in this state during the measurements.
With proper connections of the measuring circuits, none of the measured-values supervision elements in the
device should pick up. If an element detects a problem, the causes which provoked it may be viewed in the
Event Log.
If current sum errors are found, check the matching factors.
Messages from the symmetry monitoring could occur because there actually are asymmetrical conditions in
the network. If these asymmetrical conditions are normal service conditions, the corresponding monitoring
functions should be made less sensitive.
Values
The currents can be seen in the display field at the front of the device or a PC via the operator interface. They
can be compared to the quantities measured by an independent source, as primary and secondary quantities.
If the measured values are not plausible, the connection must be checked and corrected after the line has been
isolated and the current transformer circuits have been short-circuited. The measurements must then be re-
peated.
Phase Rotation
The phase rotation must correspond to the configured phase rotation, in general a clockwise phase rotation. If
the system has an anti-clockwise phase rotation, this must have been considered when the power system data
was set (address
209 PHASE SEQ.
). If the phase rotation is incorrect, the alarm (FNo ) is generated. The
measured value phase allocation must be checked and corrected, if required, after the line has been isolated
and current transformers have been short-circuited. The measurement must then be repeated.
3.3.7 Test for High Impedance Protection
Polarity of Transformers
When the device is used for high-impedance protection, the current at I
N
or I
NS
is equivalent to the fault current
in the protected object. It is essential in this case that all current transformers feeding the resistor whose current
is measured at
I
N(S)
have the same polarity. The test currents used for this are through currents. Each CT must
be included in a measurement. The current at I
N(S)
may never exceed half the pickup value of the single-phase
time overcurrent protection.