Application And Setting Notes - Siemens 7SJ82 Manual

Protection and Automation Functions
6.34 Underfrequency Load Shedding
Blocking the Stage
In the event of blocking, the picked up stage will be reset. The following blocking options are available for the
stage:
•
Via the binary input signal
•
Via the Inactive input from the function block General
Behavior on Leaving the Operating Range
The sampling frequency tracking makes a wide frequency-operating range possible. If the stage has picked up
before leaving the frequency-operating range, the pickup is maintained. The Pickup signal is reset when a
blocking condition becomes active.
6.34.4.2

Application and Setting Notes

Parameter: Threshold
•
Default setting (_:18151:3) Threshold = 49.00 Hz for f
With the Threshold parameter, you define the underfrequency pickup value of the stage. The specific value
depends on the application and the total number of the stages applied in parallel.
Parameter: Operate delay
•
Default setting (_:18151:6) Operate delay = 0.10 s
Set the Operate delay parameter for the specific application.
Parameter: Dropout differential
•
Default setting(_:18151:5) Dropout differential = 20 mHz
With the Dropout differential parameter, you define the dropout threshold. For example, if you set the
Threshold to 49.00 Hz and the dropout differential to 20 mHz, the stage drops out at 48.98 Hz.
Due to the high-precision frequency measurement, the setting value can remain at the default value of
20 mHz.
Parameter: Operate & flt.rec. blocked
•
Default setting (_:18151:2) Operate & flt.rec. blocked = no
With the Operate & flt.rec. blocked parameter, you can block the operate indication, the fault
recording, and the fault log.
Parameter: f< stabilization counter
•
Default setting(_:18121:113) f< stabilization counter = 6
You can configure the f< stabilization counter parameter in the function block General.
With the f< stabilization counter parameter, you set the number of measurement cycles in which the
measured frequency value must be lower than the frequency threshold to meet the pickup condition. With
this setting, you can optimize the pickup-condition reliability versus the pickup time.
The measuring cycle time is 10 ms. With the default setting of 6, the pickup time is the sum of the inherent
frequency measuring time (approx. 10 ms to 30 ms) plus the 6 times measuring repetition of 60 ms, which is
70 ms to 90 ms in total.
In order to avoid a wrong pickup in case of a phase jump, Siemens recommends setting the value of the f<
stabilization counter parameter not below 5.
782
>Block stage from an external or internal source
= 50 Hz
rated
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017