Download SVC Light® enabling strong flicker reduction from a steel plant in the

SVC Light® enabling strong flicker reduction from a steel
plant in the UAE
An SVC Light® rated at 33 kV, 0-164 Mvar capacitive has
been installed by ABB at Emirates Steel in the United Arab
Emirates for reduction of flicker emanating from the operation of an electric arc furnace (EAF), rated at 130 MVA, and a
ladle furnace (LF) rated at 24 MVA. Flicker mitigation is called
for due to the considerable size of the EAF in relation to the
limited fault level of the feeding grid. The SVC Light came on
line in 2010.
The steel plant takes its power from a 220 kV grid. The fault
level varies between 4.800 MVA and 10.000 MVA, depending
on grid conditions and winter/summer variations. Considering the substantial rating of the EAF, unless proper measures
were taken, strong flicker could have been expected as a
result of the operation of the EAF, particularly at minimum fault
level of the grid. With the SVC Light operated on the 33 kV
EAF bus, efficient flicker mitigation is attained, and the Grid
Code of the feeding grid is fulfilled for all operating conditions.
A flicker reduction factor of 7 is achieved with the SVC Light
in operation.
As a matter of fact, the flicker level at the 220 kV point of
common connection (P.C.C.) is influenced by two additional
steel plants situated in the same region and operated from the
same grid. Consequently, the flicker measured is an aggre-
gated value arising from the operation of all three plants.The
main purposes of the SVC Light installation are to mitigate the
flicker emission produced by the EAF, reduce the harmonic
pollution, compensate the reactive power and stabilize the
furnaces’ bus voltage.
EAF grid impact
The EAF generates several kinds of disturbances, which,
unless remedied, result in more or less severe deterioration
of power quality. The melting process inside an EAF is erratic in its nature, from time to time resulting in an “electrical
short” within the furnace’s electric circuit. As a consequence,
the consumption of reactive power strongly fluctuates in a
stochastic manner. The fluctuation of reactive power flowing
through circuit reactances results in voltage fluctuations.
Furthermore, the EAF acts as an asymmetrical load on the
three-phase feeding grid, giving rise to current and voltage
imbalance in the grid. Normally, only very limited levels of grid
asymmetry can be allowed without causing deterioration of
the power quality for other consumers connected to the same
grid. And last but not least, the EAF generates harmonics,
odd and even, as well as inter-harmonics.
−− A flicker reduction factor of 7
− − Acceptably low levels of harmonic distortion
−− A high and constant power factor, with no back-feed of
reactive power into the grid
− − Voltage variations as well as voltage imbalance kept at
acceptable levels
−− Grid reinforcements kept to a minimum
Main circuit design
The compensated load is a joint operation of the EAF and LF.
The type of charge of the EAF is 100% DRI (Direct Reduced
Iron), continuously charged. For optimal flicker damping, the
dynamic range of the SVC Light needs to be higher than the
maximum reactive load power. For this application and taking
into account the needed flicker reduction, a dynamic rating of
164 Mvar has been chosen.
220 kV
Harmonic filter yard
Main performance features of the SVC Light
Flicker reduction factor at the 220 kV P.C.C.7
Compensated power factor at the 220 kV P.C.C.0.996
Voltage fluctuations, voltage imbalance and harmonic content
at the P.C.C. are all within the values required by the grid
owner.
150/180 MVA
Main technical data
33 kV
Supply grid voltage
Furnace bus voltage
Rated EAF power
Rated LF power
SVC Light rating
LF
24 MVA
EAF
130 MVA
VSC
-/+ 82 Mvar
11th
2 Mvar
2nd
30 Mvar
3rd
25 Mvar
220 kV
33 kV
130 MVA + 20%
24 MVA + 20%
33 kV, 0-164 Mvar capacitive
4rth
25 Mvar
Single-line diagram, SVC Light and electric arc furnaces
The SVC Light is based on a Voltage Source Converter (VSC),
built up of IGBT (Insulated Gate Bipolar Transistors). A single
converter is utilized, thereby avoiding all paralleling of devices. The converter is directly connected to the 33 kV EAF
bus, without any need for a step-down transformer or other
complex magnetic interfaces. As DC link, DC capacitors are
utilized. The SVC Light control scheme is based on pulsewidth modulation (PWM), thereby ensuring minimum need for
harmonic filtering.
The VSC is rated at ±82 Mvar. In addition, the SVC Light
comprises a 2nd harmonic filter rated at 30 Mvar, a 3rd
harmonic filter (25 Mvar), a 4th harmonic filter (25 Mvar) and
a 2 Mvar high-pass filter. The 33 kV bus is connected to the
220 kV grid by a 150/180 MVA power transformer. The VSC
together with the harmonic filters give the SVC Light a total
operating range from zero to 164 Mvar capacitive reactive
power, continuously controllable.
For more information please contact:
ABB AB
FACTS
SE-721 64 Västerås, SWEDEN
Phone: +46 (0)21 32 50 00
Fax:
+46 (0)21 32 48 10
www.abb.com/FACTS
Application Note 1JNS017105, 2014-04
Benefits of the SVC Light installation
With the SVC Light in operation, the following benefits are attained at the 220 kV P.C.C.: