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

1MRS759142 C
4.1.5.3
4.1.5.4
4.1.5.5
REX640
Technical Manual

Functionality

The three-phase thermal overload protection, two time constants, function T2PTTR
protects the transformer mainly from short-time overloads. The transformer is
protected from long-time overloads with the oil temperature detector included in its
equipment.
The alarm signal gives an early warning to allow the operators to take action before the
transformer trips. The early warning is based on the three-phase current measuring
function using a thermal model with two settable time constants. If the temperature
rise continues, T2PTTR operates based on the thermal model of the transformer.
After a thermal overload operation, the re-energizing of the transformer is inhibited
during the transformer cooling time. The transformer cooling is estimated with a
thermal model.

Analog channel configuration

T2PTTR has one analog group input which must be properly configured.
Table 407: 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 T2PTTR can be described using a module diagram. All the modules
in the diagram are explained in the next sections.
The function uses ambient temperature which can be measured locally or remotely.
Local measurement is done by the protection relay. Remote measurement uses analog
GOOSE to connect AMB_TEMP input.
Protection functions
Description
Three-phase currents
Section 4
367