Direction Test of the Phase Quantities (Current and Voltage
Connection)
The proper connection of the current and voltage transformer is checked with load current over the line to be
protected. For this, the line must be switched on. A load current of at least 0.1 I
rated
has to flow over 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 meas-
urements.
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 protected object.
•
P is negative if the active power flows to the busbar or out of the protected object.
•
Q is positive if the inductive reactive power flows in the line or protected object.
•
Q is negative if the inductive reactive power flows to the busbar or out of the protected object.
If the power measured values have a different sign than expected, then the power flow is opposite the
current-direction definition. This can be the case, for example, at the opposite end of the line . The current-
transformer neutral point then points in the direction of the protected object (for example 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.
11.2
Functional Tests
11.2 Direction Test of the Phase Quantities (Current and Voltage Connection)
SIPROTEC 5, Overcurrent Protection, Manual 1373
C53000-G5040-C017-8, Edition 07.2017
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