Voltage Transformer: Function and Operation A voltage transformer (VT), also known as a potential transformer (PT), is a critical component in electrical power systems designed to step down high voltages to lower, measurable levels for metering, protection, and control purposes. It ensures safe and accurate voltage measurement while isolating secondary circuits from the high-voltage primary side. Working Principle Voltage transformers operate on the same principle as conventional transformers, utilizing electromagnetic induction. The primary winding is connected across the high-voltage line, while the secondary winding delivers a reduced voltage proportional to the turns ratio (e.g., 110V or 120V for standard measurements). The transformation ratio is fixed, ensuring precise scaling for instruments like voltmeters, relays, and energy meters. Key Features 1. Accuracy: VTs maintain high accuracy (typically within ±0.2% to ±3%) to ensure reliable readings for billing and protection. 2. Isolation: They provide galvanic isolation, protecting personnel and equipment from high-voltage hazards. 3. Burden Capacity: Designed to supply low power (usually <500VA) to connected devices without significant voltage drop. 4. Types: - Electromagnetic VTs: Common for indoor/outdoor AC systems. - Capacitive VTs (CVTs): Used in high-voltage transmission lines, combining capacitors and transformers. Applications - Metering: Feeds voltage signals to energy meters for billing. - Protection: Supplies voltage data to protective relays (e.g., over/under-voltage or distance relays). - Synchronization: Ensures phase-matching during generator or grid interconnection. Standards and Safety VTs comply with IEC 60044-2 or IEEE C57.13, covering insulation, thermal limits, and accuracy. Proper grounding of the secondary winding is vital to prevent floating voltages and ensure safety. Conclusion Voltage transformers are indispensable for safe, efficient power system operation, enabling precise voltage monitoring and control. Their robust design and adherence to standards make them a cornerstone of modern electrical infrastructure. (Word count: 500)