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Technical description
2 Protection functions
2.14 Inverse time operation
VM59.EN001
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89
Recorded values of the programmable stages PrgN (99)
Parameter
Value
Unit Description
yyyy-mm-dd
Time stamp of the recording, date
hh:mm:ss.ms
Time stamp, time of day
Flt
pu
Fault value
EDly
%
Elapsed time of the operating time
setting. 100% = trip
SetGrp
1
2
Active setting group during fault
2.14.
Inverse time operation
The inverse time operation - i.e. inverse delay minimum time
(IDMT) type of operation - is available for several protection
functions. The common principle, formulae and graphic
representations of the available inverse delay types are
described in this chapter.
Inverse delay means that the operation time depends on the
measured real time process values during a fault. For example
with an overcurrent stage using inverse delay a bigger fault
current gives faster operation. The alternative to inverse delay
is definite delay. With definite delay a preset time is used and
the operation time does not depend on the size of a fault.
Operation modes
There are three operation modes to use the inverse time
characteristics:
Standard delays
Using standard delay characteristics by selecting a curve
family (IEC, IEEE, IEEE2, RI) and a delay type (Normal
inverse, Very inverse etc). See chapter 2.14.1.
Standard delay formulae with free parameters
selecting a curve family (IEC, IEEE, IEEE2) and defining
one's own parameters for the selected delay formula. This
mode is activated by setting delay type to „Parameters‟, and
then editing the delay function parameters A ... E. See
chapter 2.14.2.
Fully programmable inverse delay characteristics
Building the characteristics by setting 16 [current, time]
points. The relay interpolates the values between given
points with 2nd degree polynomials. This mode is activated
by setting curve family to „PrgN‟'. There are maximum three
different programmable curves available at the same time.
Each programmed curve can be used by any number of
protection stages. See chapter 2.14.3.
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