Rate Of Frequency Change Protection; Overview Of Functions; Structure Of The Function; General Functions (Undervoltage Test, Df/Dt Calculation) - Siemens 6MD85 Manual

Siprotec 5 high-voltage bay controller
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Protection and Automation Functions

7.21 Rate of Frequency Change Protection

7.21
Rate of Frequency Change Protection

Overview of Functions

7.21.1
The function Rate of frequency change protection is used to:
Detect a frequency change quickly
Prevent the system from not secure states caused by unbalance between the generated and consumed
active power
Network decoupling
Load shedding
7.21.2

Structure of the Function

The function Rate of frequency change protection can be used in protection function groups containing a
3‑phase voltage measurement.
2 function block types are available:
df/dt rising
df/dt falling
The function Rate of frequency change protection is preconfigured by the manufacturer with 1 df/dt rising
stage and 1 df/dt falling stage. A maximum of 5 df/dt rising stages and 5 df/dt falling stages can operate simul-
taneously within the function. Both of the function block types are similar in structure.
Undervoltage check and df/dt calculation are general functionalities and take place on the function level. All
stages use these general functionalities.
[dwdfdt01-160113-01.tif, 1, en_US]
Figure 7-166
7.21.3

General Functions (Undervoltage Test, df/dt Calculation)

7.21.3.1

Description

Logic
The following figure represents the logic of undervoltage check and df/dt calculation. It applies to all types of
stages.
846
Structure/Embedding of the Function
SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017

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