Function Block; Functionality; Operation Principle - ABB RELION 611 Series Technical Manual

1MRS757454 D
4.1.6.2
4.1.6.3
4.1.6.4
611 series
Technical Manual

Function block

GUID-1EEED1E9-3A6F-4EF3-BDCC-990E648E2E72 V4 EN
Figure 65: Function block

Functionality

The thermal overload protection for motors function MPTTR protects the electric
motors from overheating. MPTTR models the thermal behavior of motor on the basis
of the measured load current and disconnects the motor when the thermal content
reaches 100 percent.
Thermal overload conditions are the most often encountered abnormal conditions in
industrial motor applications. The thermal overload conditions are typically the result
of an abnormal rise in the motor running current, which produces an increase in the
thermal dissipation of the motor and temperature or reduces cooling. MPTTR
prevents an electric motor from drawing excessive current and overheating, which
causes the premature insulation failures of the windings and, in worst cases, burning
out of the motors.

Operation principle

The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of MPTTR 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.
If the quality of remotely measured temperature is invalid or
communication channel fails the function uses ambient temperature
set in Env temperature Set.
Section 4
Protection functions
145