Definite Time Stages
The limit-value setting at address 4302 U/f > is based on the continuously permissible induction value
related to the nominal induction (B/B
N
) specified by the manufacturer of the object to be protected. This
setting determines the pickup of the warning stage as well as the minimum value for the thermal stage (see
below).
After the time T U/f > address 4303 has expired (approx 10 s) alarm is output.
Strong overexcitation endangers the protected object after short time. The high-set stage U/f >>, address
4304 should, therefore be only shortly delayed (approx. 1 s) by the time T U/f >>, address 4305.
The set times are additional time delays which do not include the inherent operating time (measuring time,
drop-out time) of the protection. If you set a time delay to , the associated stage does not trip; nevertheless,
a pickup indication is output.
Thermal Stage
[dwovexak-210313-01.tif, 1, en_GB]
Figure 2-102 Thermal tripping characteristic (with preset values)
The thermal characteristic is intended to simulate the temperature rise of the iron core due to overflux. The
heating-up characteristic is approximated by 8 time values for the 8 predefined induction values B/B
NObj
(reduced U/f). Intermediate values are gained in the device by linear interpolation.
If no instructions of the manufacturer are available, the preset standard characteristic should be used; this
corresponds to a standard Siemens transformer (Figure 2-102).
Functions
2.11 Overexcitation Protection
220 SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
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