Flexible current sensors

Rogowski coils are a family of flexible current sensors that operate without a rigid ferromagnetic core. The principle relies on a flexible winding wound around the live conductor, generating a voltage proportional to the derivative of the current flowing through it. This architecture requires an electronic integrator to be systematically paired with it, such as compatible DIRIS units, to reproduce a faithful image of the measured current. Available models cover high currents and unusual geometric configurations, complying with the IEC 61869-2 standard for electronic current sensors.

Operating principle and architecture of Rogowski coils

Coreless winding structure and electrical properties

The flexible winding with no rigid ferromagnetic core is the technological heart of Rogowski coils. This absence of a saturating magnetic material gives the sensor extended linearity across the whole measurement range. Our installation experience confirms that this characteristic eliminates the saturation phenomena seen with conventional current transformers during high transient overcurrents.

Output signal and the need for electronic integration

The voltage delivered by the Rogowski coil is proportional to the time derivative of the primary current. An electronic integration step is therefore essential to obtain a directly usable image of the current. DIRIS units perform this function while offering standardised interfaces to electrical measurement and control systems.

Installation advantages and constraints of flexible sensors

Fitting without cutting or opening a rigid housing

Rogowski coils are installed without cutting or opening any existing rigid housing. Our installation feedback shows that this property significantly reduces intervention time on installations in service. Manual winding around the conductor removes the constraint of precise busbar-opening sizing imposed by traditional current transformers.

Adaptation to confined spaces and complex conductor geometries

The lightness and flexibility of the winding make fitting in confined spaces easier. In the field, we observe that this flexibility allows instrumentation of irregularly shaped busbars, grouped cable bundles or large-section conductors that are difficult for standard closed-core CTs to access.

Typical applications and use cases for Rogowski coils

Measurement on busbars and large-section conductors

Rogowski coils are mainly used on busbars and large-section conductors. Feedback from installers confirms their frequent use in tertiary and industrial panels where busbars do not allow a standardised-window current transformer to be fitted.

Instrumenting existing installations and reduced-space areas

In existing installation environments, the Rogowski coil avoids mechanically modifying cable or busbar routing. Our standard practice favours this type of sensor when installation downtime does not allow major work on the distribution bus.

Standards and certification of electronic current sensors

Compliance with the IEC 61869-2 standard guarantees the accuracy and stability of Rogowski coil performance under the declared operating conditions. This standard specifies the requirements applicable to electronic current sensors, including accuracy tests, influence-quantity effects and transient behaviour. Our commissioning tests show that meeting this normative reference ensures interoperability with measuring and protective equipment on the market.

Frequently asked questions

What is the fundamental difference between a Rogowski coil and a conventional current transformer?

A Rogowski coil relies on a flexible winding with no rigid ferromagnetic core, whereas a conventional CT uses a closed magnetic circuit made of ferromagnetic material. This absence of a core eliminates any risk of saturation and allows very high currents to be measured with no limitation linked to magnetic flux density.

Why does a Rogowski coil always require an associated integrator?

The output signal of a Rogowski coil is proportional to the derivative of the primary current. The electronic integrator, built into compatible DIRIS units, reproduces the current in its direct time-domain form. Without this step, no usable measurement or electrical monitoring function can be provided.

In which geometric configurations do Rogowski coils become essential?

Rogowski coils become essential as soon as the conductor has a non-circular shape, a section larger than standard CT windows, or is positioned in a confined space that prevents a magnetic core from being opened. Flat busbars, grouped cable bundles and crowded panel spaces illustrate these situations.

Does the IEC 61869-2 standard specifically cover Rogowski coils?

The IEC 61869-2 standard applies to electronic current sensors, a category that includes Rogowski coils associated with their processing electronics. It defines accuracy classes, test conditions and error limits across the temperature and frequency ranges specified by the manufacturer.