IL 44-751-1
Instruction Leaflet
Page 2 November, 2001
Scope
This guide contains general information for ordering and installing the type DTW de-energized tap
changer. This guide does not describe all possible contingencies, which may arise during
installation, operation, or maintenance of the tap changer, nor does it describe all details and
variations of the equipment. If you require additional information regarding the installation and
the operation or maintenance of your equipment, contact the local representative of ABB.
Safety Definitions
Safety notations are intended to alert personnel of possible conditions, which may cause personal
injury, property damage, or even death. They have been inserted into this instructional text prior
to the step in which the condition is cited.
The safety notations are headed by one of three hazard intensity levels, which are defined as
follows:
1.
DANGER-
immediate hazard that will result in severe personal injury, property damage, or
death.
2.
WARNING-
hazard or unsafe practice that could result in personal injury, property damage,
or death.
3.
CAUTION-
hazard or unsafe practice, which could result in minor personal injury, or property
damage.
Introduction
The type DTW de-energized tap changer is one of a family of ABB tap changers for power
transformers. A de-energized tap changer is a switch, which is connected to the winding taps of
the transformer. When the tap changer is moved from one position to another, the amount of the
tap winding connected into the circuit is changed. This permits the adjustment of the voltage ratio
of the transformer to best suit the voltage requirements at the transformer’s installation site. The
de-energized tap changer is usually installed into the high voltage circuit of the transformer and,
most of the time, it is used to adjust the primary voltage of the transformer within a 10 percent
range in 5 steps.
D A N G E R
The type DTW tap changer is a de-energized tap changer, and must, be operated only
when the transformer is completely de-energized. This type of tap changer must never be
operated when the transformer is energized. Operation when the transformer is energized
is dangerous and will result in severe personal injury, property damage, or death.
The type DTW tap changer is a modular, bridging-type (zigzag) tap changer with external
operating mechanism. It is most commonly available as a 5-position device. Other
configurations are available or can be designed; for these, please contact ABB. The type DTW
tap changer is made up of individual tap decks (one or two per phase). The phase tap decks are
connected to a common set of horizontal operating shafts through individual gear sets. The tap
changer is mounted in front of each phase coil, parallel to the side of the transformer tank. The
tap changer is supported by an insulating framework, which is part of and attached to the
transformer superstructure. See Figure 1 for a general view of a type DTW tap changer
installation.
The ability to locate the type DTW tap changer on the side of each phase coil permits very direct
tap lead routing with a minimum of bends.
