Which component is primarily used as a dynamic reactive resource to maintain system voltage?

The correct answer is that a Static Voltage Compensator is primarily used as a dynamic reactive resource to maintain system voltage. These devices are designed to provide real-time voltage support by dynamically adjusting reactive power. When system voltage levels drop or rise, the Static Voltage Compensator can inject or absorb reactive power as needed, thus helping to stabilize the voltage within the grid. This capability is critical during periods of variable load conditions or system disturbances, ensuring that voltage remains within acceptable limits.

In contrast, while series reactors and shunt reactors can influence system voltage, they typically have a more passive role. Series reactors primarily limit short-circuit currents and can help protect equipment but do not dynamically adjust voltage. Shunt reactors do provide reactive power but are usually fixed devices that only operate in a specific manner based on changes in voltage levels. Phase shifting transformers are used mainly to control power flow between different parts of a network rather than directly maintaining voltage stability.

Given the need for dynamic responsiveness to voltage fluctuations in a transmission system, the Static Voltage Compensator stands out as the component specifically engineered for this purpose.