Siemens SIPROTEC 7UT613 series Manual page 215

Inverse Time
ElementI for IEC
2p
Characteristics
Definite Time Trip-
ping I
for ANSI
2p
Characteristics
7UT613/63x Manual
C53000-G1176-C160-2
I2>>
Setting
Delay T I2>>
The inverse curves (see below) permit a consideration of load imbalance per unit of
time. However, especially for generators and motors a better adjustment to the pro-
tected object can be achieved with the thermal stage (see below under „Thermal Trip-
ping Characteristic").
Having selected an inverse time tripping characteristic the thermal load of a machine
caused by unbalanced load can be simulated easily. Use the characteristic which is
most similar to the thermal asymmetrical load curve of the machine manufacturer.
With the IEC characteristics (address 140 UNBALANCE LOAD = TOC IEC) the follow-
ing options are available at address 4026 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).
The characteristics and equations they are based on are listed in the „Technical Data".
If an inverse-time 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 an unbalanced load of about 1.1 times the
setting value of I2p (address 4021 or 4022) is present.
The corresponding time multiplier is accessible via address 4023 T I2p.
The time multiplication factor may 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 inverse time stage
is not required, select 140 = UNBALANCE LOAD in address Definite Time when
configuring the protection functions.
If under address 4025 I2p DROP-OUT the Disk Emulationis set, dropout is thus
produced in accordance with the dropout characteristic, as described in the function
description of the asymmetrical load protection under margin heading „Dropout Be-
haviour".
The definite time stages as discussed above under „Definite Time Stages I
can be used in addition to the inverse-time stage as alarm and tripping stages.
The thermal behaviour of a machine can be closely replicated due to negative se-
quence by means of an inverse time tripping curve. Use the characteristic which is
most similar to the thermal asymmetrical load curve of the machine manufacturer.
With the ANSI characteristics (address 140 UNBALANCE LOAD = TOC ANSI) the fol-
lowing is made available in address 4027 ANSI CURVE:
• Extremely Inv.,
• Inverse,
• Moderately Inv., and
• Very Inverse.
The characteristics and the equations they are based on are listed in the „Technical
Data".
If an inverse-time 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.
2.8 Unbalanced Load Protection
= 0.55 · 545 A = 300 A primary or
0.55· 545 A · (1/600) = 0.50 A secondary
= 1 s
>>, I
>"
2 2
215