Megger MTO210, Инструкция по эксплуатации

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Transformer Testing
AVTMTO210 Rev 7 Sept 2013
33
Testing Delta Configured Windings
Testing Delta winding resistance may be a very time consuming procedure, in
particular LV winding deltas the correct balance time can take up to 30-60
minutes for a large transformer, which far exceeds the time restriction of many
tests.
The method for quickly testing delta configurations requires that both the high
side and low side be connected in series with the MTO’s current source (see
connection Table 1). By using both HV and LV windings to magnetize the core,
the effective test magnetization current increases with the turn ratio. As an
example, testing the Low Voltage side of a 100/10 kV Yd transformer with dual
side injection at 10A is the same as testing only the Low Voltage side of that
same transformer 68 A. Even if only one side of the transformer needs to be
tested, connecting both high and low windings in series will speed the test up by
a factor of 10 or more.
DELTA WINDING RESISTANCE
Manufacturer’s winding resistance data are usually presented as per winding for
Y configurations and per terminal pairs for Delta windings. In the rare case that
manufacturer’s data is presented per winding also for a delta connection, the
recommendation is to recalculate the numbers to terminal pairs and compare
with the field measurement results.
Ravg = Average individual winding resistance
Rtp = Winding resistance between terminal pirs
Rtp=Ravg*0.6667