How do capacitive voltage transformers work in high-voltage power systems?

CVTs work in high-voltage power systems by dividing high voltage using a capacitive divider, then lowering it via an intermediate transformer for measurements.

Working of Capacitive Voltage Transformers in High-Voltage Power Systems

Capacitive voltage transformers (CVTs) are essential components in high-voltage power systems, providing accurate voltage measurements for metering, protection, and control purposes. This article discusses the working principle of CVTs in high-voltage power systems and their role in maintaining system stability and efficiency.

Construction and Components of a CVT

A CVT comprises three main components:

Capacitive Voltage Divider: Consists of a series-connected stack of capacitors housed in a porcelain insulator, responsible for reducing high voltage to a manageable level.

Intermediate Transformer: A magnetic, step-down transformer that further reduces voltage, providing isolation between the high voltage and low voltage sides.

Compensating Reactor: An inductor connected in series with the secondary winding of the intermediate transformer to compensate for capacitive current and ensure accurate voltage measurement.

Working Principle of a CVT

The CVT operates based on capacitive voltage division and electromagnetic transformation principles. The high voltage applied to the CVT is divided by the capacitive voltage divider, resulting in a reduced voltage that is proportional to the primary voltage. The reduced voltage is then further lowered by the intermediate transformer, producing a low voltage output suitable for metering and protection equipment.

The compensating reactor plays a critical role in the accuracy of the CVT. It compensates for the capacitive current drawn by the capacitive voltage divider, ensuring that the voltage transformation ratio remains constant over a wide range of load conditions and frequencies.

Applications of CVTs in High-Voltage Power Systems

CVTs serve several essential functions in high-voltage power systems, including:

Voltage Measurement: CVTs provide accurate voltage measurements, enabling assessment of power system performance, efficiency, and overall health.

Protection: The voltage output from a CVT is used as an input to protective relays, which monitor the power system for faults and initiate corrective actions when necessary.

Control: CVTs supply crucial voltage information for control systems in substations and power plants, allowing for precise regulation of voltage levels and system stability.

Synchronization: CVTs can be used to provide voltage signals for synchronizing generators and other power system equipment, ensuring proper coordination of power generation and distribution.

In summary, capacitive voltage transformers play a vital role in high-voltage power systems by providing accurate voltage measurements and contributing to the overall stability and efficiency of the system. Their unique construction and operating principle make them a preferred choice for high-voltage measurement tasks in modern power systems.