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Basic description of the Transformer Monitor
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Inhaltsverz
4.
Basic description of the Transformer Monitor
Power transformers are key components of an electrical supply grid. The failure of a trans-
former not only has major economic consequences for the energy supplier, it can also lead
to serious losses for consumers. For this reason, it makes sense to monitor the transformer
as closely as possible, to record its 'temperature curve' (the thermal image) and to collect
information about the current load and the expected remaining service life as well as the
moisture content of the oil and the paper. This task can - based on IEC standards - be solved
by electronic measuring and computing facilities.
This operating manual describes the concepts and the measurement principles behind the
TMM functionality which is available for the REG-D
TM
and the REG-DA. lt also describes how
the software and the hardware of a REG-D(A) can be upgraded to enable TMM functionality
in addition to performing its role as a voltage regulator. Also the steps required to set up
the transformer monitoring functions are described in detail.
The winding's hot-spot temperature is determined by the current that runs through the
windings and the oil temperature. The latter can be fed into the REG-D(A) as a mA signal or
directly as a PT100 signal. Appropriate input modules are available for both types of signals.
The appropriate analogue input channels must be available in order to record the fill levels
and other quantities such as humidity, H2 or the oil's CO content.
These channels can be also added to the REG-D
TM
on side.
It is not possible to upgrade REG-DA at a later date therefore if TM is required this must be
specified at time of ordering. For safety and warranty purposes disassembly of REG-DA is
not permitted.
Monitoring consists of monitoring the transformer's main parameters. The oil temperature
is recorded in addition to the current. The hot-spot temperature is determined from the oil
temperature and the current in accordance to IEC 60354 or IEC 60076 and extrapolated to
the transformer's service life consumption. Up to six cooling stages can be activated de-
pending on the oil or winding temperature. The system monitors the operating times of the
fan and controls the individual fan groups so that as balanced an operating time as possible
is achieved over the whole operating life. If desired, individual fans can also be permanently
assigned to a specific cooling stage. Additional alarms such as Buchholz pre-warning and/or
Buchholz triggering can be fed into the monitoring system as binary signals, displayed and
sent to a SCADA system for further processing (see Figure 1).
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