•
address 2421 for pickup value IEp,
•
address 2422 for time multiplier T IEp;
for inverse time overcurrent protection Ι
E
acc. to ANSI characteristics:
•
address 2423 for pickup value IEp,
•
address 2424 for time multiplier D IEp
User-Defined Curves
For inverse time overcurrent protection the user may define his own tripping and dropout characteristic. For
configuration in DIGSI a dialogue box appears. Enter up to 20 pairs of current value and tripping time value.
The procedure is the same as for phase current stages. See Section 2.4.2 Time Overcurrent Protection for
Phase Currents under margin heading “User-Defined Curves”.
To create a user defined tripping characteristic for earth current, the following has to be set for configuration
of the functional scope: address 124 DMT/IDMT Earth, option User Defined PU. If you also want to
specify the dropout characteristic, set option User def. Reset.
Inrush Restraint
In address2402 InRushRestEarth of the general settings, the inrush restraint can be enabled (ON) or disa-
bled (OFF). This inrush restraint is only sensible for transformers and if overcurrent time protection is activated
on the earthed feeding side. Function parameters of the inrush restraint are set in “Inrush”.
The inrush restraint is based on the evaluation of the 2nd harmonic present in the inrush current. The ratio of
2nd harmonics to the fundamental component 2.HARM. Earth (address 2441) is set to Ι2
fN
/Ι
fN
= 15 % as
default setting. It can be used without being changed. To provide more restraint in exceptional cases, where
energising conditions are particularly unfavourable, a smaller value can be set in the afore-mentioned address.
If the current exceeds the value indicated in address 2442 I Max InRr. E, no restraint will be provoked by
the 2nd harmonic.
Additional Overcurrent Protection Functions for Earth Current
In the aforementioned description, the first overcurrent protection is described respectively. The differences in
the parameter addresses and message numbers of the first and second overcurrent protection are illustrated
in the following table. The positions marked by x are identical.
Parameter
addresses
Dynamic
parameter
addresses
Message no.
1. Overcurrent protection for earth current 24xx 25xx 024.xxxx(.01)
2. Overcurrent protection for earth current 38xx 39xx 325.xxxx(.01)
Settings
Addresses which have an appended “A” can only be changed with DIGSI, under “Additional Settings”.
The table indicates region-specific presettings. Column C (configuration) indicates the corresponding secon-
dary nominal current of the current transformer.
Addr.
Parameter C Setting Options Default Setting Comments
2401 EARTH O/C ON
OFF
Block relay
OFF Earth Time Overcurrent
2402 InRushRestEarth ON
OFF
OFF InRush Restrained O/C
Earth
2.5.8
Functions
2.5 Time Overcurrent Protection for Earth Current
SIPROTEC 4, 7UT6x, Manual 169
C53000-G1176-C230-5, Edition 09.2016
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