Directional Test
The proper connection of the current and voltage transformer is checked with load current via the line to be
monitored or the monitored object. Switch the line off for this. A load current of at least 0.1 I
N
has to flow via
the line; it should be ohmic to ohmic inductive. The direction of the load current has to be known. In case of
doubt, meshed and ring systems should be unraveled. The line remains switched on the for the duration of
the measurements.
The direction can be derived directly from the operational measured value. First make sure that the power
measured values correspond to the power direction. Normally, it can be assumed that the forward direction
(measuring direction) goes from the busbar toward the line.
Using the power measured values at the device or DIGSI 5, make sure that it corresponds to the power direc-
tion:
•
P is positive if the active power flows in the line or in the monitored object.
•
P is negative if the active power flows to the busbar or out of the monitored object.
•
Q is positive if the lagging reactive power flows in the line or in the monitored object.
•
P is negative if the lagging reactive power flows to the busbar or out of the monitored object.
If the power measured values have a different sign than expected, then the power flow is opposite to the
current-direction definition. This can be the case, for example, at the opposite end of the line. The set of
current transformers then points in the direction of the monitored object (such as the line).
If the values are not as expected, it may be due to a polarity reversal at the voltage connection.
As a final step, switch off the system.
10.2
Functional Tests
10.2 Directional Test
SIPROTEC 5, Fault Recorder, Manual 425
C53000-G5040-C018-5, Edition 11.2017
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