MV Current and Voltage Transformers
MV Current Transformers
Instrument Transformers Overview
Instrument transformers are specialized devices designed to supply measuring instruments, meters, protection relays, and similar apparatus. They isolate measurement and protection circuits from the high-voltage primary side, ensuring safety and accuracy in electrical systems. These transformers comply with international standards, including IEC 61869, and are widely used in both measuring and protective applications.
Types of Instrument Transformers:
1. Current Transformers (CTs):
– Transform primary current into a proportional secondary current, with minimal phase difference.
– Isolate measurement and protection circuits from high-voltage primary systems.
– Can feature multiple secondary windings with identical or different characteristics, all fully isolated from each other.
2. Measuring Current Transformers:
– Designed to supply indicating instruments, integrating meters, and similar devices.
– Ensure accurate measurement of current for monitoring and energy management.
3. Protective Current Transformers:
– Intended to supply protective relays.
– Provide reliable current data for fault detection and system protection.
Key Components and Terms:
– Primary Winding: The winding through which the current to be transformed flows.
– Secondary Winding: The winding that supplies current to measuring instruments, meters, relays, or similar devices.
– Secondary Circuit: The external circuit connected to the secondary winding.
– Rated Primary Current: The primary current value on which the transformer’s performance is based.
– Rated Secondary Current: The secondary current value on which the transformer’s performance is based.
– Rated Transformation Ratio: The ratio of rated primary current to rated secondary current (e.g., 100/5 A).
– Current Error (Ratio Error): The error introduced by the transformer due to the difference between the actual and rated transformation ratios, expressed as a percentage.
Applications:
– Measurement: Accurate current measurement for energy monitoring and management.
– Protection: Reliable current data for fault detection and system protection in electrical networks.
– Isolation: Safely isolates low-voltage measurement and protection circuits from high-voltage systems.
Compliance and Standards:
– Manufactured in compliance with IEC 61869 and other applicable national and international standards.
– Ensures high accuracy, reliability, and safety in diverse electrical applications.
MV Voltage Transformers
Voltage Transformers Overview
Voltage transformers (VTs) are specialized instrument transformers designed to accurately step down high primary voltages to lower, measurable secondary voltages. They isolate high-voltage primary circuits from connected instruments and protection devices, ensuring safety and precision in electrical systems. These transformers are essential for measurement, monitoring, and protection applications in medium-voltage (MV) networks.
Key Features and Functions:
– Proportional Voltage Transformation: The secondary voltage is substantially proportional to the primary voltage, with minimal phase difference.
– Isolation: Safely isolates high-voltage primary circuits from low-voltage measurement and protection systems.
– Accuracy: Converts primary voltage into a measurable secondary voltage that is true in both magnitude and phase.
Key Components and Terms:
– Primary Winding: The winding to which the primary voltage is applied.
– Secondary Winding: The winding that supplies voltage to measuring instruments, meters, relays, or similar devices.
– Rated Primary Voltage: The primary voltage value on which the transformer’s performance is based.
– Rated Secondary Voltage: The secondary voltage value on which the transformer’s performance is based.
– Rated Transformation Ratio: The ratio of the rated primary voltage to the rated secondary voltage.
– Voltage Error (Ratio Error): The error introduced by the transformer due to the difference between the actual and rated transformation ratios, expressed as a percentage.
– Accuracy Class: A designation indicating that the transformer’s errors remain within specified limits under prescribed conditions.
– Burden: The admittance of the secondary circuit, expressed in siemens and power factor (lagging or leading).
– Rated Burden: The burden value on which the transformer’s accuracy requirements are based.
– Rated Output: The apparent power (in volt-amperes) that the transformer can supply to the secondary circuit at the rated secondary voltage and with the rated burden connected.
– Rated Insulation Level: The combination of voltage values that define the transformer’s ability to withstand dielectric stresses.
Applications:
– Measurement: Accurate voltage measurement for energy monitoring and management.
– Protection: Reliable voltage data for fault detection and system protection in electrical networks.
– Isolation: Safely isolates high-voltage systems from low-voltage measurement and protection circuits.
Compliance and Standards:
– Manufactured in compliance with international standards, ensuring high accuracy, reliability, and safety.
– Suitable for both indoor and outdoor applications in medium-voltage systems.