1 2 3 4 A - SIPROTEC

Functions
2.4 Time Overcurrent Protection for Phase and Residual Currents
Inrush Restraint
178
At address 2202 InRushRest. 3I0 of the general settings, the inrush restraint can be enabled (ON) or disabled
(OFF). Especially for transformers and if overcurrent time protection is activated on the earthed supply
side, this inrush restraint is required. 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. 3I0 (address 2241) is set to I 2fN/I 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 above-mentioned address.
If the current exceeds the value indicated in address 2242 or 2243 I Max InRr. 3I0, no restraint will be
provoked by the 2nd harmonic.
Additional Time Overcurrent Protection Functions for Residual Current
In the aforementioned description, the first overcurrent protection for zero sequence current is described. The
differences in the parameter addresses and message numbers of the first, second and third overcurrent protection
are illustrated in the following table. The positions marked by x are identical.
1st time overcurrent protection for residual
current
2nd time overcurrent protection for residual
current
3rd time overcurrent protection for residual
current
Note
Addresses of the
parameters
Addresses of the
dynamic parameters
Message no.
22xx 23xx 191.xxxx(.01)
34xx 35xx 321.xxxx(.01)
36xx 37xx 323.xxxx(.01)
If the time overcurrent protection is assigned to a side of the main protected object, the current values are set
referred to the rated current of that side II/I NS .
SIPROTEC, 7UT6x, Manual
C53000-G1176-C230-2, Release date 06.2012