Siemens – Highlights & Innovations in Transmission and Distribution
version >> please,
SVC Systems for E.ON in Lübeck-Siems
The Static Var Compensator (SVC) is supplied by Siemens with
new control and protection equipment
PTD is supplying transformers and a Static
Var Compensator system for the German utility company E.ON Netz GmbH,
in order to stabilize the supply voltage in the Lübeck area.
The HVDC Baltic Cable (with a transmission capacity of +/-600 MW) was
constructed more than ten years ago to link the power systems of
Germany and Sweden. To ensure optimum dynamic operation of the
transmission line it was originally planned to connect the converter
station to the 380 kV grid of E.ON. Changes in the European power
market meant that this connection, along with other grid expansion
projects, was abandoned. The HVDC transmission link was consequently
connected to the Lübeck district’s existing 110 kV net-work, which is
inadequately dimensioned in terms of necessary system impedance. Only
a short 380 kV link was ever installed between the HVDC converter
station Herrenwyk and the Siems transformer substation (380/110 kV).
Fig. 1: Network
Based on a network study,
ref. fig.1, performed by E.ON, various extensions to the
existing grid will be completed by the end of 2004. For instance, a 10
km long cable will connect the Siems substation to the 220 kV
transformer substation in Lübeck. Siemens has already received an
order from E.ON to supply the 380/220 kV transformer (rated at 350 MVA)
destined for the Siems substation. A Static Var Compensation system
will additionally be installed to ensure voltage quality.
According to the highly dynamic behavior of the central component (i.e. the
HVDC converter station), the power factor correction must meet similar
requirements at a very minimum. To stabilize system voltage it must respond
to any variations in the amount of power being transmitted through the HVDC
cable by supplying an equivalent amount of reactive power. To ensure fast
control processes, the power factor correction equipment must be designed
using high-speed electronics. E.ON placed an order for the SVC (Static Var
Compensator) with Siemens on November 1, 2003.
SVC is to be installed on a 3,600 m2 plot on the former
site of the Lübeck-Siems power plant (Fig. 2 shows the future location
as little more than a waste dump at present).
Once completed, the electrical components of the SVC will essentially
comprise a three-phase transformer (400/18 kV) for connection to the
transmission network at the Siems substation and four branches (2
thyristor controlled and 2 filter branches) to be installed on the 18
kV secondary side. The SVC’s reactive branches are designed to provide
a control range of +200 to -100 MVar. The layout of the SVC - system
is shown in fig. 3.
One of these four branches is a Thyristor
Controlled Reactor (TCR). The TCR provides linear reactive power
control through its entire reactive power range. Therefore the SVC has
linear reactive power control through the entire reactive power range
from +200 to -100 MVar.
The second branch is a Thyristor Switched Capacitor unit (TSC) which
can be switched in and out using thyrsitors for stepwise control of
The two other branches are fixed filter banks which are also a source
of capacitive reactive power. The filter banks are designed to absorb
harmonic currents produced by the TCR so that they are not allowed to
enter the network.
Fig. 2: Aerial View:
Site of the new SVC
3: Overview of SVC System
A service building will house the thyristor
equipment and the control and protection system required for SVC
operation. This is provided with the first-ever implementation of the
new highly reliable control and protection system from Siemens based
on SIMATIC TDC, a proven industrial hardware design. It is remarkable
to consider the entire project time, scheduled from signing of
contract to PAC, of only 14 months.
For noise damping reasons, the components
most likely to “offend” will be enclosed in suitable noise reducing
enclosures. In particular, these are the power transformer and the
reactors for inductive current control.
The project is timed so that the system will be
ready to enter full service by the end of 2004. Essential foundation
and construction work is scheduled to commence in spring of 2004 as
soon as the building and environmental authorities have approved the
documentation. Although sections of the existing power plant
foundations are suitable for the new structures, the ground works
nevertheless pose a challenge. Due to the site’s proximity to the
River Trave, some of the foundations will have to be reinforced with
piles to a depth of up to 18 meters.
On completion of commissioning, the SVC and the
revised subnetwork of the E.ON grid will be put through their paces
when they are in normal operation in conjunction with the Baltic Cable
HVDC (starting on January 1, 2005).