ABB ret650, Technical Manual

Page: 181 / 670

8.5.6 Monitored data
Table 95: TRPTTR Monitored data
Name Type Values (Range) Unit Description
TTRIP REAL - - Estimated time to trip (in
min)
TTRIPCAL INTEGER - - Calculated time status to
trip: not active/long time/
active
TRESCAL INTEGER - - Calculated time status to
reset: not active/long
time/active
TRESLO REAL - - Estimated time to reset of
the function (in min)
HEATCONT REAL - % Percentage of the heat
content of the
transformer
I-MEASUR REAL - % Current measured by the
function in % of the rated
current
8.5.7 Operation principle
The sampled analogue phase currents are pre-processed and for each phase current the
true RMS value of each phase current is derived. These phase current values are fed
to the Thermal overload protection, two time constants (TRPTTR).
From the largest of the three phase currents a relative final temperature (heat content)
is calculated according to the expression:
2
final
ref
I
I
æ ö
Q = ç
÷
ç ÷
è ø
EQUATION1171 V1 EN
(Equation 49)
where:
I is the largest phase current
I
ref
is a given reference current
If this calculated relative temperature is larger than the relative temperature level
corresponding to the set operate (trip) current a start output signal START is activated.
The actual temperature at the actual execution cycle is calculated as:
1MRK 504 135-UEN A
Section 8
Current protection
175
Technical manual