21-06-2013, 03:07 PM
DISTRIBUTION TRANSFORMERS - READY FOR THE SMART GRID
DISTRIBUTION TRANSFORMERS.pdf (Size: 278.47 KB / Downloads: 80)
ABSTRACT
For the past hundred years the definition of the term distribution
transformer has been closely connected to its function:
to transform and distribute electric power to end users.
The direction of energy flow was clearly defined: from
medium voltage network to low voltage network. All controls,
protective measures and other considerations were
based on this fact.
Today, all players in the energy sector who sense a responsibility
for our common future are taking steps to reduce
CO2 emissions.
• Utilities attempt to reduce losses in their distribution network,
consequently impelling leading transformer producers
to reduce the losses inherent in their products.
• Energy producers develop and introduce green, renewable
energy sources, convert this energy into electric power and
offer it to utilities. In several countries such as Germany,
the state subsidizes this activity starting with the smallest
solar panels, though biogas and geothermic energy, all the
way up to wind generators. This activity has spawned a new
trend: the diversification of power generation.
Development of amorphous transformers
Siemens has extended its portfolio of single-phase and
three-phase liquid-immersed distribution transformers designed
with amorphous steel cores.
Our Canadian factory is already set to produce single-phase
amorphous steel core transformers in the 10 to 100 kVA
power range.
Our European factories have developed and successfully
tested three-phase units in the 100 to 630 kVA range. Table
2 shows typical comparative data for 250 and 400 kVA
transformers (Ck/A0 category according to EN 50464-1).
New concept
The new approach uses a distribution transformer with taps
on the low-voltage side of the transformer and a combination
of low-voltage switchgear with contactors, breakers,
solid-state relays (thyristor-based) and an appropriate control
unit (Figure 3). The solid-state relay acts to ensure
continuous current flow by conducting the current during
the mechanical switching operations. This principal solution
is under legal protection (Patent No. WO/2010/072622).
SUMMARY
Power supply in the future will present our infrastructure
with major challenges. Demographic dynamics, resource
scarcity and a strong environmental focus will keep the
power industry busy. Intelligent energy management within
the grid will allow more efficient use of the power produced
by integrating and bundling small power generation plants.
In the future, power generation surpluses will have to be
stored in bulk, in such stores as heat pumps or e-cars.
All parties involved will need to follow this trend and think
of intelligent solutions tailored to the so-called Smart Grid.
For distribution transformers, the challenges in the areas of
increased energy efficiency, on-load voltage regulation and
higher utilization must be taken on.
Siemens is well prepared to face these challenges, and has
provided here an overview of one possible future concept
for distribution transformers used in the Smart Grid.