What is LPCT? Benefits and Working principle
Definition :
- An LPCT (Low Power Current Transformer) is an instrument transformer defined by IEC 61869-10 that provides a low-power output signal proportional to the primary current. Unlike conventional current transformers that deliver standardized secondary currents (1 A or 5 A), LPCTs provide a standardized low-level voltage output suitable for modern digital protection, metering, and automation systems.
Working Principle :
- An LPCT operates by sensing the magnetic field generated by the primary current, typically using Rogowski coil technology or another low-power sensing method. The sensed signal is converted into a low-level voltage output proportional to the primary current. Due to its air-core or low-flux design, the sensor provides a wide linear measurement range and maintains accuracy without saturation under high short-circuit fault currents.
Benefits :
- Enhanced Safety : The low-level voltage output (millivolts) completely eliminates the dangerous high voltages associated with open-circuited conventional CTs.
- High Immunity to Saturation : Maintains accurate and linear current measurement under high fault-current conditions.
- Compact Design : LPCTs weigh and measure significantly less than traditional current transformers, enabling the design of ultra-compact and eco-friendly medium voltage switchgear.
- Ratio Standardization : Because a single LPCT covers a wide range of primary currents (measuring accurately from low loads up to massive faults), it standardizes switchgear design and reduces the need for multiple CT ratios.
Released for: Schneider Electric India
