Characteristic Value
Operate time accuracy ±1.0% of the set value or ±20 ms
Suppression of harmonics
Voltage: -50 dB at f = n × f
n
, where n = 2, 3, 4,
5, …
Current: No suppression
4.1.5 Three-phase thermal protection for feeders, cables and
distribution transformers T1PTTR (ANSI 49F)
4.1.5.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Three-phase thermal protection for
feeders, cables and distribution
transformers
T1PTTR 3Ith>F 49F
4.1.5.2 Function block
Figure 226: Function block
4.1.5.3 Functionality
The increased utilization of power systems closer to the thermal limits has
generated a need for a thermal overload function also for power lines.
A thermal overload is in some cases not detected by other protection functions,
and the introduction of the three-phase thermal protection for feeders, cables and
distribution transformers function T1PTTR allows the protected circuit to operate
closer to the thermal limits.
An alarm level gives an early warning to allow operators to take action before the
line trips. The early warning is based on the three-phase current measuring function
using a thermal model with first order thermal loss with the settable time constant.
If the temperature rise continues the function will operate based on the thermal
model of the line.
Re-energizing of the line after the thermal overload operation can be inhibited
during the time the cooling of the line is in progress. The cooling of the line is
estimated by the thermal model.
4.1.5.4 Analog channel configuration
T1PTTR has one analog group input which must be properly configured.
1MRS759142 F
Protection functions
REX640
Technical Manual
383
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