ABB RELION REX640, Техническое руководство, Страница: 1391 / 1960

The total loss of life is the sum of the momentary loss of life and the total loss of life
until time, n-1.
L L DL
n n n
= +
−
1
(Equation 337)
The initial loss of life L
0
, is taken from the setting
Initial loss of life.
For new transformer installations, the
Initial loss of life setting should be
“0”. For previously installed transformers, the
Initial loss of life can be set
to the consumed transformer life in months.
The calculated value of the loss of life in years,
LOSS_OF_LIFE
, is given as an output
in the Monitored data view.
The calculated value of
LOSS_OF_LIFE
can be reset through the input
RESET
.
7.3.5.6 Level detector 2
This module compares the
ALM_AGE_RATE
output with the setting
Alarm level Age
Rte.
If the calculated
AVG_AGE_RATE
over the
Avg Age rate period setting is greater than
Alarm level Age Rte, the module activates the binary output
ALM_AGE_RATE
.
The binary input
RST_AVGAGING
can be used to reset the output
ALM_AGE_RATE
and
also the calculated value of
AVG_AGE_RATE
.
Once the
RST_AVGAGING
input is active, the average ageing rate values stored over
the
Avg Age rate period setting is erased and the calculation of
AVG_AGE_RATE
is
restarted.
If the
Avg Age rate period is set to "YEAR", the output
AVG_AGE_RATE
is
refreshed once in 30 days starting from the time the relay is installed or
since the last activation of binary input
RST_AVGAGING
.
The activation of the
BLOCK
input deactivates the
ALM_AGE_RATE
output.
7.3.6 Application
The insulation used in transformer windings is paper oil insulation that can
degrade over a period of time. The deterioration of insulation is a time function
of temperature, moisture and oxygen content. With modern oil preservation
systems, the moisture and oxygen contributions to insulation deterioration can be
minimized, leaving insulation temperature as the controlling parameter.
Since, in most of the transformers the temperature distribution is not uniform, the
part that is operating at the highest (hot-spot) temperature normally undergoes
the greatest deterioration. Hot-spot temperature of winding needs to be monitored
continuously in order to not exceed the flashover value of transformer insulation
oil. The first step in monitoring the insulation age is the calculation of hot-spot
temperature of the transformer.
A simplified representation of the variation of temperature inside the transformer is
shown in
Figure 790
(IEC 60076-7).
1MRS759142 F Condition monitoring functions
REX640
Technical Manual
1391