Siemens siprotec SJ62 User Manual page 137

2 Functions
Preparation of Mea-
sured Data
135
minimum current level (BkrClosed I MIN) is exceeded. Here, the largest of the
three phase currents is used. When the current decreases below the minimum current
setting after the circuit breaker has opened, undervoltage protection will drop out.
Note
Note: If parameter CURRENT SUPERV. is set to disabled in address 5120, the device
picks up when the undervoltage protection is enabled and no measured voltage is
present and the undervoltage protection function is in pickup. Apply measuring voltage
or block the voltage protection to continue with configuration. Moreover, you have the
option of setting a flag via device operation for blocking the voltage protection. This
initiates the reset of the pickup and device configuration can be resumed.
Using a Fourier analysis, the fundamental harmonic component of the three phase-to-
phase voltages is filtered out and forwarded for further processing. Depending on con-
figuration, either the positive sequence component V1 of the voltages is supplied to
the undervoltage protection elements (multiplied by √3 because the treshold values
are set as phase-to-phase quantities) or the actual phase-to-phase voltage Vphph.
The largest of the three phase–phase voltages iVphph is evaluated accordingly for ov-
ervoltage protection or the negative sequence voltage V2 is calculated, whereas in
that case the thresholds should be set as phase-to-ground voltages.
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015