External Rogowski Coils LEM

External Rogowski Coils by LEM – ARU Series

Overview and General Applications

The LEM ARU series consists of external (split-core), flexible Rogowski coils designed for AC measurements, providing galvanic isolation between the measured conductor and the measurement system. Thanks to the “Perfect Loop” technology, ARU coils minimize errors related to conductor positioning within the loop and reduce the influence of external magnetic fields.

Key Features and Benefits of Rogowski Coils

• Accuracy class 0.5 according to IEC 61869-10 and IEC 61869-6 – no need for additional resistors or calibration, eliminating potential calibration drifts.
• “Perfect Loop” and internal shielding – design ensures minimal errors due to conductor position and improved immunity to external magnetic fields.
• Flexible split-core with quick “Twist & Click” lock – enables fast installation without disconnecting the main conductor.
• Resistance to harsh environments – IP68 rating, UV, water, dust, ice; operating temperatures from –40 °C to +80 °C.
• Current range – from 1 A RMS up to 300,000 A RMS, depending on the model and measuring aperture diameter.
• No upper current limitation – thanks to the Rogowski design, saturation does not occur.
• Output voltage proportional to dI/dt – requires an external integrator (e.g., analog integrator or built-in in the measurement transducer). Standard sensitivity: ~100 mV/kA at 50 Hz.
• Wide range of loop diameters – available measuring apertures Ø 125 mm, 175 mm, 250 mm, 300 mm.
• High insulation voltage – CAT III 1 kV insulation voltage (PD2 – reinforced).
• Loop-open detection / legal protection – provision for a sealing plug on the loop closure.

Practical Applications of Rogowski Coils

• Outdoor installations in distribution networks, transformer substations, pole-mounted substations – current monitoring, distribution network diagnostics.
• Network automation, SCADA systems, phase current measurements in distribution networks.
• Large-scale monitoring – measurement of very high currents in transmission lines or transformers.
• Energy industry – short-circuit current measurements, overload monitoring, network protection.