Functionality; Analog Channel Configuration; Operation Principle - ABB RELION REX640 Technical Manual

Section 4
Protection functions
4.1.4.3
4.1.4.4
4.1.4.5
360

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.

Analog channel configuration

T1PTTR has one analog group input which must be properly configured.
Table 398: Analog inputs
Input
I3P
See the preprocessing function blocks in this document for the
possible signal sources.
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings. For
troubleshooting, check the contents of this chapter and also the preprocessing blocks
in this document. The configuration can be written to the protection relay once the
mismatch is corrected.

Operation principle

The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of T1PTTR can be described using a module diagram. All the modules
in the diagram are explained in the next sections.
Description
Three-phase currents
1MRS759142 C
REX640
Technical Manual