Compensation system FSC

Overview
Siemens Energy fixed series capacitor (FSC) systems increase the transmission capacity of new and existing high-voltage AC transmission lines and contribute to improved power quality and system stability. Fixed series compensation is a cost-effective measure to optimize power flow and support grid resilience without constructing extensive new transmission corridors.

What is fixed series compensation?
Series compensation uses capacitor banks placed in series with overhead transmission lines to partially offset the line inductive reactance. This reduces load-dependent voltage drops and the transmission angle, raises voltage at the connection point and increases usable transfer capability of long-distance AC lines.

Key benefits of Siemens Energy fixed series capacitors

• Increased transmission capacity: compensates line impedance to improve usable transfer capability without building new lines.
• Improved grid stability and reliability: reduces voltage drops at connection points and supports stable bulk power transfer over long distances.
• Cost-efficient and scalable: modular approach enabling tailored capacity and phased deployment.
• Serviceability: designed for maintainability and lifecycle support with available global service network.

How the FSC works
An FSC connects a capacitor bank in series with the transmission conductor to partially cancel the inductive reactance. The result is a higher voltage at the connection point, a reduced transmission angle and improved transfer capability. Protection and fault handling include metal-oxide varistors (MOV) and bypass arrangements: on fault detection the FSC is tripped and the bypass breaker closes. For fast transient protection a triggered spark gap can bypass capacitors and MOVs in under 1 ms; gap-less protection schemes are available where applicable.

Applications

• Bulk power transmission corridors
• Long-distance high-voltage AC lines
• Grid modernization and stability enhancement projects
• Integration of renewable generation requiring voltage support and reactive power management
• Industrial transmission systems requiring reliable, efficient long-distance transfer

Why choose Siemens Energy for FSC solutions

• Sector expertise: decades of experience in series compensation and FACTS technologies.
• Customized designs: engineered solutions matched to grid topology and site constraints.
• Quality control: major components manufactured in-house to ensure supply security and consistent quality.
• Global support: installation, commissioning and lifecycle services available worldwide.

Market trends and future developments
Fixed series compensation remains a proven solution while demand grows for more flexible schemes such as thyristor-controlled series compensation. Trends include improved protection concepts, advanced control algorithms and deeper integration with grid automation to support resilient and sustainable transmission networks.

Technical characteristics / specifications

• Product type: Fixed series capacitor (FSC) — series-connected capacitor bank for transmission lines.
• Primary function: Partial compensation of line inductive reactance to increase transfer capability and improve voltage regulation.
• Protection components: Metal-oxide varistors (MOV); bypass breaker for faulted conditions.
• Fast protection option: Triggered spark gap capable of bypassing capacitors and MOVs in under 1 ms; gap-less solutions available when acceptable locally.
• Operational effects: Increases voltage at the connection point, reduces transmission angle and line voltage drops.
• Applications: Bulk corridors, long-distance HV AC lines, grid modernization, renewable integration, industrial transmission.
• Manufacturing: Major components produced in-house for quality control and supply security.
• Customization: Individually engineered solutions tailored to grid and site conditions.