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FITformer® REG
The adaptable distribution transformer
Main Features of
FITformer REG 2.0:
•Fluid-immersed distribution
transformer
•Power range up to 630 kVA
•Maximum operating voltage:
36 kV
•Low-voltage load regulation range
in three stages
•Operating characteristics
and dimensions correspond
to conventional distribution
transformers
•Additional high-voltage tapping
range for optimum operation
•Insulation possible using
alternative fluid
(ester or silicone oil)
Challenge: bidirectional power flow
Decentralized power generation from
renewable energies results in an
increasingly complex power flow in the
low-voltage distribution grid. Due to their
increasing cost-efficiency, wind turbines
and photovoltaic plants are becoming
more attractive, especially in rural areas.
Network operators are facing the growing
challenge of maintaining a constant
voltage.
An efficient, high-performance,
and exceptionally adaptable system
is required to create a high-efficient and
up-to-date grid infrastructure. It needs
to consider electricity producers and
consumers but also prosumers (electricity
consumers who double as producers),
as their load consumption, electricity
feed-in and storage abilities are subject
to considerable fluctuations.
Graphic 1:
The challenge lies in the maximum voltage difference
between heavy load and light load at a node
Graphic 2:
The regulated distribution transformer adjusts the voltage
at the infeed node, thereby reducing the voltage difference
Maximum voltage difference between heavy load and light load at a node: The challenge (graphic 1) and a solution using FITformer REG 2.0 (graphic 2)
Making the integration of renewable energies easy
For grid stability without having to implement expensive
measures for network expansion, use of the FITformer
REG 2.0 regulated distribution transformer is absolutely
sufficient.
The FITformer REG 2.0 regulated distribution transformer
from Siemens can change its transformation ratio under
load. In this way, it guarantees distributed infeed from
small generating plants while helping energy suppliers to
stay within the permissible voltage band without violating
the EN 50160 standard. This is achieved by the transformer’s three low-voltage taps, which are routed inside the
hermetically sealed corrugated tank to the control unit
directly on the transformer. All the usual connections as
well as the high-voltage tap area for load-free changing
of the transformation ratio remain unchanged. The operating characteristics and dimensions of the distribution
transformer correspond to those of commonly available
distribution transformers.
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As an alternative to traditional mineral oil, insulation
can also be provided using environmentally friendly,
biodegradable ester or silicone oils.
The voltage in the grid can vary considerably due to
different operating conditions. The extremes are known
as “heavy load without distributed infeed” and “light load
with maximum distributed infeed.” Voltages are considerably higher with high infeed, whereas they are reduced
in the case of a heavy load.
The challenge for network operators lies in the maximum
voltage difference between the two cases, that is, the
maximum difference at a node between a heavy load and
a light load (such as the difference caused by the use of
photovoltaic systems). In this case, the FITformer REG 2.0
distribution transformer adjusts the voltage at the infeed
node up or down, thus reducing the voltage difference
(see graphic 2).
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Regulation unit
1Cast resin bushing assembly
2Vacuum contactors
3Resistors
4Bypass contactor
5Overload relay
6Fuses
7Coupling relay
8Interface terminal blocks
Regulation unit
Reliability
• No replacement of substation thanks
to space-saving design
• No additional losses compared to conventional
fluid‑immersed distribution transformers
• Avoidance of regulation loops –
eliminates the need for safety measures
• Low maintenance need
(no moving components in the active part
of the transformer)
• Easy accessibility of the control cubicle
Thanks to the use of a combination of vacuum and
air-break contactors, the externally mounted regulation
and control unit, as well as the low number of switching
cycles, the maintenance requirement is low for the
FITformer REG 2.0. The transformer tank does not contain
any moving elements. This prevents oil contamination
as well as a greater need for maintenance.
The FITformer REG 2.0 ensures ease of use thanks
to separation of the regulation and control technology.
Electro-mechanical switching elements, placed in
a separate unit directly on the transformer tank
(see graphic), form the centerpiece of the regulated
distribution transformer.
A combination of vacuum and air-break contactors that
are characterized by high reliability, operating safety and
a compact design is used. With up to 5 million operating
cycles at rated operating current, the combination of
vacuum and air-break contactors offers a considerably
longer life span than their conventional counterparts.
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External structure of control cabinet
1Lock
2Switch for auto/manual/remote operation
3Switch for higher/lower regulation
4Indicator lamp for active tapping
5Status indication lamp
External structure of control cabinet
Intelligence and ease of operation
The control unit includes a programmable logic controller
(PLC) and enables easy accessibility as well as local operation. Having the regulation unit connected to the control
cubicle via a 10 m cable enables free installation inside
the substation.
The core element of the control cubicle is the PLC based
on the universally applicable SICAM CMIC.
It offers technical and mechanical advantages including
the following:
• Temperature range from –40°C to +70°C
• High EMC resistance
• Small compact dimensions
As a result, this universal automation and remote terminal
unit is especially suitable for distribution substations.
SICAM CMIC
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Internal structure of control cubicle
1SIMEAS P55 power meter
2Power supply
3SICAM CMIC
4Thermometer
5External power supply (optional)
6Voltage measurement
7Current measurement
8Fuses
9MTC connection
10Fault indication relay
11RS 232/RS 485 media converter (optional)
Internal structure of control cubicle
Versatility of SICAM CMIC
• Nodal functionality for use as subordinate remote
terminal unit with serial and Ethernet connection
• Coupling of additional devices over Modbus RTU
• Freely programmable user programs for local
control, interlocking or regulation tasks, according
to IEC 61131-3
• Remote maintenance, remote diagnostics
and remote parameterizing
• Configuration, diagnostics and test through
a web browser
Intelligence of SICAM CMIC:
If all possibilities offered by SICAM CMIC are retrieved,
the unit can be integrated into an intelligent transformer
substation in three steps:
1. Supervision/monitoring
2. Tele control
3. Automation and load flow control
In this way, the SICAM CMIC enables the integration
of the FITformer REG 2.0 into a Smart Grid.
The communication interface and protocol as per
IEC 60870‑5‑104 is available as standard.
The following protocols are available as options:
Modbus RTU, IEC 608705101, IEC 608705103,
IEC 61850 and DNP 3.0.
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N
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A
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N
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B
N
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C
A control unit clocks the switching of the air break contactors:
A A bypass is activated by closing the bypass contactor
B Faultless switch-over of the mechanical contactor with no unwanted voltage peaks
C Bypass is opened and the transformer is in the target position
The principle of regulation in the low-voltage grid
Adaptable control in the low-voltage grid
The circuit basically consists of vacuum or air-break
contactors, resistors, and a control unit. All components
are reliable and have been used for many years in various
electro-technical applications. A cable establishes the
connection to the control unit.
The regulation principle is based on activating a bypass
by closing a contactor (A). The current then flows over the
bypass so that the mechanical contactor can be switched
without unwanted voltage peaks or dips (B). The contactor for the bypass is not opened and therefore deactivated
until the target position is reached (C).
Control possibilities
• Standard: voltage controlled in two stages based on
measurements in the substation (parameter for slow
and fast switchover as well as delay times)
• Remote: voltage regulation and monitoring with serial
or TCP/IP-based communication
• Manual: manual voltage regulation via respective
control elements on the control cubicle
• Optional: additional ammeter (enables more accurate
assessment of the network condition in terms of the
amount of power fed in and the load and thus increases
control accuracy)
• Optional: control based on decentralized measurements
in the low-voltage grid (SICAM product portfolio
including a master control unit)
• Alternative: external signals
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In the event of a supply interruption, the FITformer REG 2.0
automatically starts up (wired program control to nominal
position). All set parameters are stored on a micro memory
card (MMC) so that no data is lost even without the use of
a maintenance-intensive backup battery.
Efficient operation ensured
The costs of replacing key components in the power
­distribution grid play a major role besides the functionality.
Especially in the event of new developments or specialized
products reconstruction necessitated by the replacement
and increasing operating costs often need to be taken into
account in addition to a higher purchasing price. Thanks
to its space-saving design, the FITformer REG 2.0 can be
integrated into existing substations. Additional constructional modifications are not required.
Furthermore, the FITformer REG 2.0 is the only regulated
distribution transformer on the market that has the same
load and no-load losses as conventional non-regulated
distribution transformers. In this way, the loss-optimized
FITformer REG 2.0 compensates for its higher purchasing
price in a shorter period of time than comparable regulated distribution transformers with additional losses.
The 3-stage voltage regulation on the low-voltage side
keeps the number of switching cycles at a low level.
This prevents additional costs for suppressing regulation
loops in the switching process.
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Published by
Siemens AG 2015
Energy Management Division
Freyeslebenstrasse 1
91058 Erlangen, Germany
Siemens AG
Transformers
Katzwanger Strasse 150
90461 Nuremberg, Germany
Article No. EMTR-B10007-00-4A00
Dispo 19200
TH 101-150669 WÜ WS 12151.0
Subject to changes and errors.
The information given in this document only contains general
descriptions and/or performance features which may not always
specifically reflect those described, or which may undergo
modification in the course of further development of the products.
The requested performance features are binding only when they
are expressly agreed upon in the concluded contract.
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