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Page 17
Basic description of the Transformer Monitor
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Inhaltsverz
If the voltage transducer is installed close to the bus bar, the controller will still measure a
voltage if the secondary voltage of transformer T1 is switched off because the bus - and
thus the voltage transducer - is supplied through the second active transformer T2.
Figure 8 displays the secondary control voltage, while the voltage for the operating hour
count is tapped from the primary voltage transducer. This version records the operating
hours correctly.
The value I
2
t is used to estimate the contact erosion in the tap changer. Two parameters
are needed to determine this value. One is the current in the electric arc and the other the
time 't' during which the arc is discharged. Current 'I' is the current that is flowing at the
time of the changeover, whereas time 't' can be entered for a specific tap changer. It should
be noted that the changeover time is very difficult to determine accurately and is also not
constant over the life of the changer. But the accumulation of I
2
t provides a way to capture
the qualitative condition of the tap changer. If time 't' is set to 1, the sum of product I
2
t is
only I
2
.
If the oil pumps are controlled by the controller, the operating time of the pump is summed
up and displayed in the menu.
Figure 7: secondary voltage measurement
Figure 8: primary and secondary voltage
measurement
Operating hours (2)
4.3.2
The operating times of the fan and the oil pumps are listed under 'Operating hours (2)'.
The fans are controlled according to an algorithm that always activates the fan with the
smallest total operating time. This ensures that all the fans are more or less evenly loaded
over time. It’s also possible to assign a certain cooling stage to a certain relay output (no
operating hour equalisation).
The oil pumps are fixed assigned to a digital output (no operating hour equalisation)
Summary of Contents for REG-D
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