Effectiveness of Shunt FACTS Controllers in Varying Fault Current Scenarios

Selvakumar S Author

Discover how shunt FACTS controllers improve stability and manage fault currents in power systems under different operating scenarios.

Effectiveness of Shunt FACTS Controllers in Varying Fault Current Scenarios

Introduction

In modern power systems, voltage stability is a non-negotiable requirement for maintaining power quality and reliability.

Shunt Flexible AC Transmission System (FACTS) controllers—including Static Var Compensators (SVC) and Static Synchronous Compensators (STATCOM)—are widely deployed for dynamic voltage regulation.

However, their effectiveness is not the same in all conditions. One of the most important factors influencing their performance is the short-circuit strength of the system, often measured through available fault current levels at a given bus.

Understanding System Strength

The concept of system strength refers to how resilient a grid is to voltage fluctuations.

• Strong System: High fault current (e.g., 10 kA), low source impedance.
• Weak System: Low fault current (e.g., 3 kA), high source impedance.

The effectiveness of Shunt FACTS controllers is inversely proportional to system strength:

• In weak systems, voltage is highly sensitive to reactive power changes, meaning SVCs and STATCOMs can significantly improve voltage profiles.
• In strong systems, the inherent voltage stability makes reactive compensation less impactful.

Impact of Transmission Line Parameters on Fault Current

Transmission line length and impedance directly influence fault current levels:

• Longer lines → Higher impedance → Lower fault current → Weaker system.
• Shorter lines → Lower impedance → Higher fault current → Stronger system.

This is why remote or radial network sections, often fed through long lines, are more prone to voltage fluctuations and require targeted reactive power support.

Role of Shunt FACTS Devices in Voltage Stability

Shunt FACTS controllers' function by providing dynamic reactive power compensation:

• SVC (Static Var Compensator): Uses thyristor-controlled capacitors/reactors for stepped voltage regulation.
• STATCOM (Static Synchronous Compensator): Uses voltage source converters for smooth and rapid compensation.

In weak grids, these devices have a pronounced effect, reducing voltage dips during faults and stabilizing the system during load changes.
 In strong grids, while still beneficial, their relative impact is significantly lower.

Practical Applications for Grid Operators

To optimize system performance:

• Deploy SVCs and STATCOMs in areas with low short-circuit strength.
• Consider alternative stability solutions (e.g., series compensation, synchronous condensers) for strong network sections.
• Integrate with renewable projects in remote areas to counteract voltage fluctuations caused by weak grid conditions.

Key Takeaways

• Weak grids benefit most from Shunt FACTS controllers due to higher voltage sensitivity.
• Fault current level is the key indicator of system strength and compensation effectiveness.
• Line impedance and length directly affect grid strength, influencing where reactive power devices should be installed.

Categories: : Insulation Coordination