SVC
Static Var Compensator
The key to better arc furnace economy
The key to producing
An electric arc furnace requires a stable and steady voltage supply for optimum performance. An SVC can instantaneously compensate the random variations of reactive power so characteristic of an arc furnace load. The net result is an overall
improvement in arc furnace utilisation.
2  The key to producing | Static Var Compensator
Static Var Compensator | ...at a lower cost per tonne (3)
...at a lower cost
...is a Static Var Compensator (SVC)
Reactive power compensation through an SVC helps you to obtain the following benefits:
A higher voltage level at the furnace busbar gives: –shorter meltdown times  –reduced energy losses
–reduced electrode consumption  –extended life of furnace lining
Improved power factor to:
–benefit from lower utility rates
–utilise existing electrical plant more effectively  –lower plant losses
Stabilisation of voltage and reduction of harmonics and phase unbalance to minimise:
–disturbances in nearby electrical equipment as well as in the feeding grid
–maloperation of protection devices
–
negative phase sequence currents in motor circuits
reactive toBy installing an SVC on the furnace busbar to instantaneously compensate the furnace’s large and continuously varying reactive power demand, troublesome voltage drops and
fluctuations can be avoided. The mean power input to the arc furnace is raised, and nearby electrical equipment can oper-ate as usual. The curves above show the furnace busbar’s voltage with and without SVC.
4  SVC provides a high and stable bus voltage  | Static Var Compensator
SVC provides a high and stable  bus voltage
Flexible system build-up enables optimum adaptation to customer needs
An electric arc furnace is a complex and heavy load in a
power grid. It is a large, unbalanced, and strongly fluctuating consumer of reactive power.
These reactive power fluctuations which are very marked, especially at the beginning of the melting operation, lead to voltage drops and fluctuations that reduce the active power to the arc furnace and also to other loads connected to the same feeding busbar. The furnace power varies with the square of the feeding voltage and it is thus very important to keep the voltage high and stable. With a Static Var Compen-sator the reactive power variations are compensated within a few milliseconds and also individually in each phase, providing a balanced and stable voltage.
The reactive power needed by the arc furnace is compensat-ed by a thyristor controlled reactor which i
n combination with harmonic filters on a cycle-by-cycle basis, produces almost a mirror image of the furnace current.
ABB can offer many features and options so as to provide the optimum solution for each customer.
Examples:
–Direct connection to the busbar that is to be compensated. No need for a stepdown transformer. This is valid for all existing EAF bus voltages up to 69 kV.
–Most often, the Bi-Directional Control Thyristor (BCT) is used. The BCT brings the advantage of locating two  thyristors in one housing, enabling more compact design. –  A fully computerized control system. High performance industrial standard buses and fibre optic communication links are utilized.
–The thyristor valves are of indoor type, water-cooled for efficiency and compactness.
Harmonic filters (FC) in combination with a thyristor-controlled reactor (TCR)Typical layout for an SVC plant
Thyristor valve
TCR reactors
Static Var Compensator | Unique experience from the steel industry  5
Unique experience from the steel industry
–Since 1972, ABB has been supplying Static Var Compen-sators to arc furnaces in steel mills all over the world. –We have been involved in design and manufacture of in-dustrial furnaces for almost a century and our metallurgists and engineers are specialists in the metallurgical process and the problems involved in arc furnace applications. –We have our own research, development and manufactu-ring facilities for both components and systems.
–We have a world-wide after-sales service organisation and local engineering and manufacturing companies in many countries.
ABB holds the key to the best reactive power compensation solutions. Consult us to find out exactly how much you will benefit by installing a Static Var Compensator – it’s usually a
very pleasant surprise!

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