Siemens 6MD86 - Inrush-Current Detection; Overview of Functions; Structure of the Function; Function Description

Inrush-Current Detection
Overview of Functions
The function Inrush-current detection
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Recognizes an inrush process on transformers
•
Generates a blocking signal for protection functions that protect the transformer (protected object) or for
protection functions that are affected in undesirable ways when transformers are switched on
•
Allows a sensitive setting of the protection functions
The following protection functions evaluate the blocking signal
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Overcurrent protection with a pickup value below the maximum inrush current
•
Negative-sequence protection as sensitive backup protection for transformers
Structure of the Function
The function Inrush-current detection is not an individual protection function. In the connection process of a
transformer, it transmits a blocking signal to other protection functions. For this reason, the inrush-current
detection must be in the same function group as the functions that are to be blocked.
The following figure shows the embedding of the function. The setting parameter Blk. w. inrush curr.
detect. establishes the connection between inrush-current detection and the functions that are to be
blocked. If the parameter is set to yes, the connection is effective.
A jump detection or the threshold value exceeding of the functions to be blocked is used as trigger signal for
synchronization of the internal measurement methods.
The jump detection reacts to changes in the current. The threshold value exceeding is recognized due to an
internal pickup of the protection function that is to be blocked.
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Figure 7-127 Structure/Embedding of the Function
Function Description
The function Inrush-current detection analyzes the trigger signal of the jump detection or the threshold-
value violation of the function to be blocked in a start logic, and synchronizes the method of measurement. In
order to securely record the inrush processes, the function uses the Harmonic analysis method of measure-
ment and the CWA method (current wave shape analysis). Both methods work in parallel and link the results
through a logical OR.
If you wish to work with only one process, deactivate the other method by way of the parameters Blocking
with 2. harmonic or Blocking with CWA .
7.10
7.10.1
7.10.2
7.10.3
Protection and Automation Functions
7.10 Inrush-Current Detection
760 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017