2.11 Overexcitation Protection
241
7UT613/63x Manual
C53000-G1176-C160-2
2.11.2 Setting Notes
General A precondition for use of the overexcitation protection is that measured voltages are
connected to the device and that a 3-phase protected object has been selected during
configuration of the protection functions. Additionally, the overexcitation protection
can only operate if it has been configured under address143 OVEREXC. PROT.
=Enabled.
In address 4301 OVEREXC. PROT., the overexcitation protection can be switched ON
or OFF. The option Block relay allows to operate the protection but the trip output
relay is blocked.
Definite Time
Stages
The limit-value setting at address 4302 U/f > is based on the continuously permis-
sible induction value related to the nominal induction (B/B
N
) specified by the manufac-
turer 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 4303 address T U/f > has expired (approx 10 s) alarm is output.
Strong overexcitation endangers the protected object after short time. The high-set
stage 4304 address U/f >> should, therefore be only shortly delayed (approx. 1 s)
by the time 4305 addressT U/f >>.
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
Figure 2-100 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.
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