What is a common use for capacitive coupled voltage transformers?

Capacitive coupled voltage transformers are primarily used in high voltage applications where it's essential to measure voltage safely and accurately. These transformers provide isolation and facilitate voltage measurement without directly connecting to high voltage lines, which helps protect instruments and operators from potentially dangerous levels of voltage.

The correct choice highlights their capability to manage and reduce the very high voltages found in transmission lines to a more manageable level that can be used for measurement or monitoring purposes. This is crucial for the design and operation of power systems, as it enables effective monitoring of electrical parameters without risking damage or safety hazards that would occur with direct connections.

Other options, while they speak to various functions related to voltage, do not accurately represent the purpose of capacitive coupled voltage transformers within high voltage systems. For example, disconnecting relay systems pertains more to circuit control than to voltage measurement, while measuring low voltage applications does not capture the primary context of capacitive coupled transformers which are primarily intended for high voltage settings. Operating mechanical systems also falls outside of the specific role that capacitive coupled voltage transformers play, focusing more on their electrical measurement capabilities.