Siemens SIPROTEC 7UT613 series Manual page 164

2 Functions
Definite Overcur-
rent Stages I>
Overcurrent Stage-
sI with IEC charac-
p
teristics
164
< I>> < I
1.6 · I
startup k 2pol
The potential increase in starting current caused by overvoltage conditions is already
accounted for by the 1.6 factor. The I>> stage can trip instantaneously (T I>> =
0.00 s), since there is no saturation of shunt reactance for motors, other than for
transformers.
The set time T I>> is an additional delay time and does not include the operating time
(measuring time, etc.). The delay can be set to ∞. If set to infinity, the pickup of this
function will be indicated but the stage will not trip after pickup. If a pickup threshold is
set to ∞, neither a pickup annunciation nor a trip is generated.
The setting of the I> stage (address 2014 or 2015) is mainly determined by the
maximum operating current. A pickup caused by an overload must be excluded, as
the device operates in this mode as fault protection with correspondingly short tripping
times and not as overload protection. For lines or busbars a rate of approx. 20 %
above the maximum expected (over)load is set, for transformers and motors a rate of
approx. 40 %.
The time delays to be set (address 2116 T I>) are derived from the coordination chart
of the network.
The set times are purely additional time delays that do not include the operating time
(measuring time, etc.). The delay can be set to ∞. If set to infinity, the pickup of the
corresponding function will be signaled but the stage will not issue a trip command. If
a pickup threshold is set to ∞, neither a pickup indication or a trip will be triggered.
The inverse time stages, depending on the configuration („Functional Scope", address
120 (see section 2.1.3.1), enables the user to select different characteristics.
With the IEC characteristics (address 120 DMT/IDMT Phase = TOC IEC) the follow-
ing options are available at address 2026 IEC CURVE:
• Normal Inverse (inverse, type A according to IEC 60255-3),
• Very Inverse (very inverse, type B according to IEC 60255-3),
• Extremely Inv. (extremely inverse, type C according to IEC 60255-3), and
• Long Inverse (longtime, type B according to IEC 60255-3).
The characteristics and the equations on which they are based, are listed in the „Tech-
nical Data".
If the inverse time trip characteristic is selected, it must be noted that a safety factor
of about 1.1 has already been included between the pickup value and the setting
value. This means that a pickup will only occur if a current of about 1.1 times the
setting value is present.
The current value is set under address 2021 Ip or2022 Ip. The maximum operating
current is of primary importance for the setting. Pickup due to overload should never
occur, since the device, in this modem, operates as fault protection with correspond-
ingly short tripping times and not as overload protection.
The corresponding time multiplier is accessible via address 2023 T Ip. It must be co-
ordinated with the time grading of the network.
The time multiplier can also be set to ∞. If set to infinity, the pickup of this function will
be indicated but the stage will not trip after pickup. If the
select address 120 DMT/IDMT Phase = Definite Time when configuring the pro-
tection functions.
stage is not required at all,
p
7UT613/63x Manual
C53000-G1176-C160-2