ABB RELION REX640 Technical Manual page 1384

Condition monitoring functions
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.
7.3.5 Operation principle
The function can be enabled and disabled with the
corresponding parameter values are "on" and "off".
The operation of HSARSPTR can be described with a module diagram. All modules in
the diagram are explained in the next sections.
I3P
TOIL_TEMP
AMB_TEMP
BLOCK
RESET
RST_AVGAGING
Figure 789: Functional module diagram
7.3.5.1 Load factor calculation and parameter selection
The transformer top oil and hot-spot temperatures are dependent on the load
factor, the winding conductor properties and the cooling oil properties of the
transformer. This module calculates the load factor based on the measured phase
currents and selects the transformer parameters based on user defined settings.
Load factor calculation
Load factor is a ratio of the load current to the rated current. Since the thermal
content of all the three phase currents influence the temperature inside the
transformer, the load factor is calculated as a ratio of the root of sum of squared
phase currents to three times the rated current.
K
=
Where
1384
Load factor
I_A
calculation
and
I_B
parameter
I_C
selection
Top oil
Hotspot
temp temp
calculation calculation
2 2 2
I A _ I B _ I C _
+ +
2
3 I
⋅
rated
Operation setting. The
Level
detector 1
Ageing
and
Level
loss of life
detector 2
calculation
1MRS759142 F
ALARM
WARNING
ALM_AGE_RATE
HOTSPOT_TEMP
TOPOIL_TEMP
(Equation 321)
REX640
Technical Manual