High-accuracy wideband LPCT for advanced grid automation and PQ metering

Design and testing of a Rogowski coil for the emerging metering and protection applications in the energy distribution system . The coil is the current sensing element of combined outdoor current and voltage Low-Power Instrument Transformers (LPITs) with rated insulation level 27/70/150 kV and rated current 630 A. Destined to global market, the LPIT must comply with a combination of IEC, IEEE and customer-specific standards. One design is intended to cover multiple applications thanks to its compatibility with different Intelligent Electronic Devices (IEDs): meters, protection relays, Power Quality (PQ) analyser, Capacitor bank control. The passive Low Power Current Transformer (LPCT) design is driven by a utility specification that refers to the pertinent IEC 61869-10 standard and adds special requirements for advanced measurement and protection functions. The coil and its electric shield have been studied to achieve the accuracy class 0.5 at power frequency and harmonics, but also to meet EMC class A requirements at IEC 61000-4-3 radiated immunity in the [80 MHz; 3.8 GHz] range, and special common mode voltage limit from customer. The LPCT bandwidth is investigated for PQ metering.