Siemens SIPROTEC 7UT613 series Manual page 165

Overcurrent Stages
I
with ANSI char-
p
acteristics
Dynamic Cold Load
Pickup
7UT613/63x Manual
C53000-G1176-C160-2
2.4 Time Overcurrent Protection for Phase and Residual Currents
If under address 2225 TOC DROP-OUT the Disk Emulation are set, dropout is pro-
duced in accordance with the dropout characteristic, as set out in the functional de-
scription of the inverse time overcurrent protection in section „Dropout Behaviour".
The inverse time stage, depending on the configuration of the functional scope
enables the user to select different characteristics.
With the ANSI characteristics (address 120 DMT/IDMT Phase = TOC ANSI) the fol-
lowing is made available in address 2027 ANSI CURVE:
• Definite Inv.,
• Extremely Inv.,
• Inverse,
• Long Inverse,
• Moderately Inv.,
• Short Inverse, and
• Very Inverse
The characteristics and the formulas 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 of the
setting value is present.
The current value is set under address 2021 Ip or 2022 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 set at address 2024 D Ip. It must be coordinated
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 I
select address 120 DMT/IDMT Phase = Definite Time.
If disk emulation is set in address 2025 TOC DROP-OUT, dropout is produced accord-
ing to the dropout characteristic. For further information refer to section „Dropout Be-
haviour" (see section 2.4.1, margin heading „Dropout Behaviour").
An alternative set of pickup values can be set for each stage. It may be selected au-
tomatically in a dynamic manner during operation (see section 2.6).
stage is not required at all,
p
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