Functions
2.23 Auxiliary Functions
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
346
I
2
t-Procedure
During the I
2
t-procedure the squared fault current integral occurring per trip is added up phase-selectively. The
integral is derived from the squared instantaneous values of the currents occurring during arc time of the circuit
breaker. This results in:
T CB arc = (parameter 266 T 52 BREAKTIME) – (parameter 267 T 52 OPENING).
The three sums of the calculated integrals are represented as statistic values referred to the squared device
nominal current (I
nom
2
). As with the other procedures, a threshold logically combines the three sums via an OR
operation and evaluates them.
The calculated squared tripping currrent integrals are added to the existing statistic values. Subsequently,
threshold comparison is started using threshold „ΣI^2t>“, and the new statistic values are output. If one of
the values lies above the threshold, the message „Thresh. ΣI^2t>“ is generated.
Commissioning
Usually, no measures are required for commissioning. However, should the protection device be exchanged
(e.g. old circuit breaker and a new protection device), the initial values of the respective limit or statistical values
must be determined via the switching statistics of the respective circuit breaker.
2.23.2.3 Motor Statistics
General
There are two different types of statistical motor data:
• Operational information and
• startup information.
The statistical operational information contains the
• total number of motor startups
• total number of the motor operating hours (including startup conditions)
• total number of motor shutdown hours
• percentage of motor operating time and the total megawatt hours (if the device has a voltage transformer).
For every motor startup
• the duration
• the startup current
• and the startup voltage (if the device has a voltage transformer) are stored in the startup information.
Motor Operation Information
The motor operation statistic is newly calculated in a 600 ms cycle. In the statistics buffer, its image is de-
creased to a resolution of one hour.
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