Siemens SIPROTEC 4 User Manual page 130

Functions
2.6 Voltage Protection 27, 59
[stoerfallverlauf-ohne-stromkriterium-260602-kn, 1, en_US]
Figure 2-49
Figure 2-50shows a fault profile for a load side connection of the voltage transformers. When the circuit
breaker is open, the voltage disappears (the voltage remains below the pickup setting), and current supervi-
sion is used to ensure that pickup drops out after the circuit breaker has opened (BkrClosed I MIN).
After the voltage has dropped below the pickup setting, tripping is initiated after time delay 27-1 DELAY.
When the circuit breaker opens, voltage decreases to zero and undervoltage pickup is maintained. The current
value also decreases to zero so that current criterion is reset as soon as the release threshold (BkrClosed I
MIN) is exceeded. Pickup of the protection function is also reset by the action of the AND-combination of
voltage and current. As a consequence, energization is admitted anew when the minimum command time
elapsed.
130
Typical fault profile for source side connection of the voltage transformer (without current
supervision)
SIPROTEC 4, 7SJ62/64, Manual
C53000-G1140-C207-8, Edition 08.2016