Series compensation is defined as insertion of reactive power elements into transmission lines and provides the following benefits:

Reduces line voltage drops Limits load-dependent voltage drops Influences load flow in parallel transmission lines Increases transfer capability Reduces transmission angle Increases system stability

For these tasks, Siemens offers various solutions that have already been proven in numerous applications. Applications are the Fixed Series Capacitor (FSC), the Thyristor – Controlled Series Capacitor (TCSC) and the Thyristor - Protected Series Capacitor (TPSC).

The task of series compensation is to reduce the transmission lines inductivity. This means, that the line length is "virtually" shortened. As a consequence, the transmission angle is reduced and thus the power transfer can be increased without reduction of the system stability.

Series compensation makes use of capacitors, reactors or power electronic devices offering high flexibilty.

Depending on the application three different types of Series Compensation are provided. The most common application is the Fixed Series Capacitor (FSC). Thyristor-Valve Controlled Systems (TCSC) and Thyristor-Valve Protected Systems (TPSC) may also be installed

svcA SVC (Static Var Compensator) is a high voltage system that controls dynamically the network voltage at its coupling point. Its main task is to keep the network voltage constantly at a set reference value.

Some other control features are:

voltage control reactive power control damping of power oscillations unbalance control

The design and layout of a SVC system is always tailored to the specific project requirements.

The picture above shows the principle topology of a SVC coupled to the network via a high voltage transformer. On the secondary side there is an arrangement of usually 2 or more parallel branches. The following 3 principle branch types are available.

TCR : Thyristor Controlled Reactor for linear injection of inductive reactive power

TSC : Thyristor Switched Capacitor for stepwise injection of inductive reactive power

Filter: Tuned filter capacitor for fixed capacitive reactive power and harmonic filtering

Number and type of selected branches depend on the specific application and are project tailored. The most simple configuration is a TCR/Filter combination.

The reactive power is changed by switching or controlling these reactive power elements connected to the secondary side of the transformer. Thyristor valves act as extremely fast switches. Each capacitor bank is switched ON and OFF by thyristor valves (TSC). Reactors can be either switched (TSR) or controlled (TCR) by means of thyristor valves.

The system ratings of SVCs are:

Typical voltage levels: approx.  33 < kV < 800

Typical overall ratings: approx. 40 < MVAr < 800

Nowadays, power producers and providers throughout the world are faced with greater demands for bulk power flow, lower-cost power delivery, and higher reliability. Controlled technology started in the early 1970's with various applications of thyristor controlled booster magnets and arc furnace flicker control. Siemens´ first Static Var Compensator for utility application using tyristor controlled reactors (TCR) was commissioned in 1980

Svc plus

The SVC PLUS is an advanced STATCOM (Static Synchronous Compensator). By using the Voltage-Sourced Converter (VSC) technology based on the Siemens Modular Multilevel Converter (MMC) design (refer to Converter) it offers high economical and technical flexibility by its modular and containerized design.

Compact and adaptable, an ideal solution when space is limited and costly. Due to the MMC technology, the degree of harmonic generation emission is quite small. High frequency noise is absorbed by small standardized high-frequency blocking filters, resulting in an SVC design which is practically independent from individual network impedances.

It provides operational advantages like minimized maintenance and service requirements, network stabilization, excellent undervoltage performance and high dynamic performance by a very fast response time. It reaches a very high level of system availability, thanks to the redundancy of power modules.

From ± 25 MVAr to ± 50 MVAr, all of the main equipment, including the IGBT converter, the control and protection system and the converter cooling system of the SVC PLUS, is installed in a containerized solution and factory pretested, ready for grid connection at site. For indoor installations, converter modules with ± 100 MVAr are available. Parallel operation of converter modules is also possible, resulting in higher ratings.

The footprint of an SVC PLUS installation is smaller than a conventional SVC installation of the same rating, up to 50%

The SVC PLUS is an advanced STATCOM (Static Synchronous Compensator). By using the Voltage-Sourced Converter (VSC) technology based on the Siemens Modular Multilevel Converter (MMC) design (refer to Converter) it offers high economical and technical flexibility by its modular and containerized design.

Compact and adaptable, an ideal solution when space is limited and costly. Due to the MMC technology, the degree of harmonic generation emission is quite small. High frequency noise is absorbed by small standardized high-frequency blocking filters, resulting in an SVC design which is practically independent from individual network impedances.

It provides operational advantages like minimized maintenance and service requirements, network stabilization, excellent undervoltage performance and high dynamic performance by a very fast response time. It reaches a very high level of system availability, thanks to the redundancy of power modules.

From ± 25 MVAr to ± 50 MVAr, all of the main equipment, including the IGBT converter, the control and protection system and the converter cooling system of the SVC PLUS, is installed in a containerized solution and factory pretested, ready for grid connection at site. For indoor installations, converter modules with ± 100 MVAr are available. Parallel operation of converter modules is also possible, resulting in higher ratings.

The footprint of an SVC PLUS installation is smaller than a conventional SVC installation of the same rating, up to 50%.

SVC PLUS offers a multitude of benefits:

Improved dynamic stability of transmission systems Increased power quality; reduction in risk of voltage collapse and blackout Highly efficient flicker reduction in industrial applications Low harmonic generation and low noise emissions, thanks to the use of MMC (Modular Multilevel Converter) technology Minimized engineering efforts due to standardized component design Fast, efficient, modular, and cost-effective solution

Power producers and system operators all over the world are faced with increasing demands for bulk power transmission, lowcost power delivery, and high system security. At the same time, congestion and bottlenecks cause limitations in power transmission.

SVC PLUS provides a solution to such problems whenever they occur. SVC PLUS can be customized to individual reactive power demands: Three standardized pre-engineered configurations covering SVC PLUS S (+/-25 MVAr), SVC PLUS M (+/-35 MVAr), or SVC PLUS L (+/-50 MVAr) are available as containerized solutions, and up to four of these units can be configured as a system operating in a fully parallel manner. Transformerless solutions are available up to 36 kV. For higher system voltages, standard

AC transformers are used. This modular concept makes SVC PLUS uniquely adaptive without compromising on performance, construction time, and cost-effectiveness.

For indoor installations, converter modules with approximately ± 100 MVAr are available. In addition, hybrid solutions with mechanically switched capacitors (MSC) or reactors (MSR) are available, to expand the power range further.

It can be either used for utility applications, grid access, mobility applications and industrial applications.