4.5.8.2 Function block
Figure 349: Function block
4.5.8.3 Functionality
The overexcitation protection function OEPVPH is used to protect generators
and power transformers against an excessive flux density and saturation of the
magnetic core.
The function calculates the U/f ratio (volts/hertz) proportional to the excitation
level of the generator or transformer and compares this value to the setting limit.
The function starts when the excitation level exceeds the set limit and operates
when the set operating time has elapsed. The operating time characteristic can be
selected to be either definite time (DT) or overexcitation inverse definite minimum
time (overexcitation type IDMT).
This function contains a blocking functionality. It is possible to block the function
outputs, reset timer or the function itself, if desired.
4.5.8.4 Operation principle
The function can be enabled and disabled with the
Operation
setting. The
corresponding parameter values are "On" and "Off".
The operation of OEPVPH can be described using a module diagram. All the
modules in the diagram are explained in the next sections.
Figure 350: Functional module diagram
1MRS757644 H
Protection functions
620 series
Technical Manual
673
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