Overtemperature Indication; Analog Channels; Scaling The Rated Values Of The Protected Unit - ABB REX 521 Technical Reference Manual, General

1MRS 751108-MUM
4.1.5.
4.1.6.
4.1.6.1.
Protection Relay
Technical Reference Manual, General

Overtemperature indication

The REX protection relay includes an internal temperature supervision function.
The CPU module issues an internal alarm signal when overtemperature has been
detected inside the relay enclosure. The alarm signal will be activated once the
temperature inside the relay enclosure increases approximately to +78
overtemperature indication can be seen on the HMI or as an event via serial
communication. The relay will go to the IRF (internal relay fault) state. See
Table 4.1.11.2-1, "Fault indications," on page 30.

Analog channels

The protection relay measures the analog signals needed for protection, measuring,
etc. via galvanically separated matching transformers. In addition, current sensors
(Rogowski coil) and voltage dividers developed by ABB can be used with REX 521.
The different versions of REX 521 are provided with the following matching
transformers and sensor inputs:
Version Matching transformers
Basic CT1, CT2, CT3, CT4
Medium CT1, CT2, CT3, CT4, CT5, VT1
High CT1, CT2, CT3, CT4, CT5, VT1, VT2, VT3, VT4 -
Sensor CT4, CT5, VT1
A letter in the order number specifies whether the protection relay is equipped with
basic, medium, high or sensor measuring input modules. (Refer to section "Ordering
information" on page 56).
Scaling the rated values of the protected unit for analog
channels
A separate scaling factor can be set for each analog channel. The factors enable
differences between the ratings of the protected unit and those of the measuring
device (CTs, VTs etc.) The setting value 1.00 means that the rated value of the
protected unit is exactly the same as that of the measuring device.
When scaling factors are used, it should be noted that they affect the
!
operation accuracy of the relay. The accuracies stated in the description of
each function block (in the CD-ROM Technical Descriptions of Functions)
only apply with the default values of the scaling factors. For example, a high
factor affects the operation of sensitive protection functions such as the
directional earth fault protection. To ensure the proper operation of the
function blocks, it must be checked that the analog scales (pu scales) of the
phase currents I
phase-to-phase voltages U
U , and U are identical.
2 3
, I , and I , and correspondingly, the analog scales of the
L1 L2 L3
, U , and U
12 23
REX 521
o
C. The
Sensor inputs
-
-
RS1, RS2, RS3, VD1, VD2, VD3
or phase-to-earth voltages U
31
,
1
19