Siemens 7SJ85 - I2 T-Method Stage; Description

I2t-Method Stage
Description
Logic of the Stage
[LoCBWI2t, 1, en_US]
Figure 10-38
Logic of the I
2
t-Method Stage
Calculation of the Wear
The I
2
t method evaluates the wear of a circuit breaker based the sampled measuring values of the phase
currents during the arc time. The duration of the arc time is defined by the difference between the 2 settings
of parameters CB break time and CB opening time (see also Figure 10-32). The stage determines the
ending point of the arc time by searching backward the zero-crossing point of the phase currents after it
receives the logic release signal. Then, the squared fault currents during the arc time are integrated phase-
10.12.6
10.12.6.1
Measured Values, Energy Values, and Supervision of the Primary System
10.12 Circuit-Breaker Wear Monitoring
SIPROTEC 5, Overcurrent Protection, Manual 1365
C53000-G5040-C017-8, Edition 07.2017