The AcuCT Flex Pro Series Rogowski coil is engineered for modern protection relays, it delivers IEC 61869-10 Class 5P. a flexible current sensing protection relay for Intelligent Electronic Device (IED) applications where accurate, linear current signals are critical for protection and monitoring. Factory-calibrated for accuracy, delivering stable, low-distortion performance across a wide current range to support reliable fault detection in modern protection systems, while RJ45 connector enable simplified connection to protection relays.
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| Product Datasheet | Download PDF |
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| Utilizing Rogowski Coils for Protection Relaying | Application Note |
Protection-class current transformers ensure protection relays receive current signals during fault conditions. However, conventional iron-core current transformers are susceptible to magnetic saturation during high-magnitude fault currents. This phenomenon causes secondary waveform distortion and signal clipping, which can compromise the dependability of protection relays. The AcuCT Flex Pro utilizes an air-core architecture to inherently eliminate saturation, maintaining linear signal fidelity across the entire dynamic range.
IEC 61869-10 5P50kA standard defines the performance requirements for protection-class CTs used in relay protection systems. 5P specifies that the CT must limit composite error to 5% at its accuracy limit, while 50 indicates an accuracy limit factor of 50 times rated current, ensuring the current transformer delivers accurate and undistorted current signal during high-fault conditions.
Unlike iron-core CTs that saturate and distort waveforms at the "Knee Point," the AcuCT Flex Pro features an air core with constant permeability. It maintains perfect linearity even during short-circuit faults exceeding 40kA, ensuring relays receive accurate data for tripping decisions.
Traditional current transformers risk dangerous kV-level spikes if the secondary circuit opens. The AcuCT Flex Pro is a passive device outputting safe low-voltage signals (mV), eliminating open-circuit hazards and the need for shorting blocks during maintenance.
Beyond standard 50/60Hz monitoring, the AcuCT Flex Pro Rogowski coil captures high-frequency transients and harmonics up to 9kHz and beyond, providing critical data for advanced power quality analysis and traveling wave fault location.
Retrofitting protection systems often requires dismantling busbars—a costly and risky process. The AcuCT Flex Pro features a flexible, rope-like form factor designed to install around irregular conductors in tight spaces where rigid CTs cannot fit.
Versatile Sizing: Two standard window sizes, 106mm (4.17") and 178.0mm (7.01").
Rapid Integration: Native RJ45 (CAT-6) connectors allow for plug-and-play wiring, reducing installation time and errors.
Secure Mounting: Dedicated mounting brackets ensure the coil remains centered for optimal Class 5P accuracy.
 Zero Magnetic Saturation |
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Unlike iron-core CTs that saturate and distort waveforms at the "Knee Point," the AcuCT Flex Pro features an air core with constant permeability. It maintains perfect linearity even during short-circuit faults exceeding 40kA, ensuring relays receive accurate data for tripping decisions.
 Inherently Safe Design |
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Traditional current transformers risk dangerous kV-level spikes if the secondary circuit opens. The AcuCT Flex Pro is a passive device outputting safe low-voltage signals (mV), eliminating open-circuit hazards and the need for shorting blocks during maintenance.
 Broadband Frequency Response |
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Beyond standard 50/60Hz monitoring, the AcuCT Flex Pro Rogowski coil captures high-frequency transients and harmonics up to 9kHz and beyond, providing critical data for advanced power quality analysis and traveling wave fault location.
 Retrofit Advantage |
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Retrofitting protection systems often requires dismantling busbars—a costly and risky process. The AcuCT Flex Pro features a flexible, rope-like form factor designed to install around irregular conductors in tight spaces where rigid CTs cannot fit.
Versatile Sizing: Two standard window sizes, 106mm (4.17") and 178.0mm (7.01").
Rapid Integration: Native RJ45 (CAT-6) connectors allow for plug-and-play wiring, reducing installation time and errors.
Secure Mounting: Dedicated mounting brackets ensure the coil remains centered for optimal Class 5P accuracy.
The AcuCT Flex Pro is designed to be universally compatible with protection relays and IEDs featuring Low Energy Analog (LEA) inputs.
The AcuCT Flex Pro’s 225mV output aligns precisely within the relay's linear detection zone (Slot Z), ensuring optimal signal fidelity for protection logic.
Compatible with SEL-751 Feeder Protection.
Fully compatible with protection channels designed for low-power sensor inputs via standard termination methods.
Compatible with SIPROTEC 5 Series 7SY82 Universal Protection.
Compatible with devices accepting standard low-voltage analog inputs. AcuCT Flex Pro supports relays with generic LEA inputs.
Compatible with relay manufacturers such as ABB, GE, and Schnieder-Electric.
RCT16 | RCT24 | |
|---|---|---|
| Measuring Accuracy | +/- 0.5% | |
| Protection Accuracy | 5P50kA | |
| Rated Primary Current | 500A | |
| Rated Secondary Voltage | 225mV/270mV | |
| Short-Time Thermal Current | 50kA / 3 seconds | |
| Rated Burden | 2MΩ | |
| Frequency Range | 50/60 Hz (Rated) | |
| Operating Temperature | -25°C to 70°C (-4°F to 158°F) | |
| Extended Temp (Option) | -45°C to 125°C (-49°F to 257°F) | |
| Window Size | 4.17" (106mm) | 7.01" (178mm) |
| Length | 15.75" (400mm) | 23.62" (600mm) |
| Standard / Certifications | UL Recognized | UL Recognized |
| Form Factor | Flexible Rope-Like CT | |
RCT16 |
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| Measuring Accuracy | +/- 0.5% |
|---|---|
| Protection Accuracy | 5P50kA |
| Rated Primary Current | 500A |
| Rated Secondary Voltage | 225mV/270mV |
| Short-Time Thermal Current | 50kA / 3 seconds |
| Rated Burden | 2MΩ |
| Frequency Range | 50/60 Hz (Rated) |
| Operating Temperature | -25°C to 70°C (-4°F to 158°F) |
| Extended Temp (Option) | -45°C to 125°C (-49°F to 257°F) |
| Window Size | 4.17" (106mm) |
| Length | 15.75" (400mm) |
| Standard / Certifications | UL Recognized |
| Form Factor | Flexible Rope-Like CT |
RCT24 |
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| Measuring Accuracy | +/- 0.5% |
|---|---|
| Protection Accuracy | 5P50kA |
| Rated Primary Current | 500A |
| Rated Secondary Voltage | 225mV/270mV |
| Short-Time Thermal Current | 50kA / 3 seconds |
| Rated Burden | 2MΩ |
| Frequency Range | 50/60 Hz (Rated) |
| Operating Temperature | -25°C to 70°C (-4°F to 158°F) |
| Extended Temp (Option) | -45°C to 125°C (-49°F to 257°F) |
| Window Size | 7.01" (178mm) |
| Length | 23.62" (600mm) |
| Standard / Certifications | UL Recognized |
| Form Factor | Flexible Rope-Like CT |
Pair the mounting brackets with the AcuCT Flex Pro Series to securely center around the conductor, offering optimized accuracy and robust protection. The mounting brackets are available in two sizes with RJ45 connector for simplified installation and integration with protection relay systems.
The IP68 Rated option protects the CT’s electrical components from dust, dirt, and solid ingress and provides total water protection with the AcuCT Flex Pro Series’ waterproof enclosure, enabling robust performance under challenging environmental conditions.
The extended temperature rating allows the AcuCT Flex Pro Series to operate reliably under extreme temperature environments, from -45°C to 125°C (-49°F to 257°F), without compromising the measurement precision.
Yes. The AcuCT Flex Pro is fully compliant with IEC 61869-10 Class 5P standards. This certifies that it meets the rigorous linearity and accuracy requirements necessary for protective relaying decisions, ensuring zero saturation even at high fault currents.
Unlike iron-core CTs, which generate dangerous high-voltage spikes (arc flash hazards) if the secondary is opened, the Rogowski coil is inherently safe. It outputs a low-voltage mV signal, allowing for safe maintenance without the need for shorting blocks.
No. If your protection relay supports Low Energy Analog (LEA) inputs, the coil connects directly via the passive RJ45 interface, eliminating the need for external power or integrators.
Yes. Due to the high-impedance nature of LEA inputs, the signal leads can be extended up to 50 meters (approx. 164 ft) using shielded twisted pair cable without significant signal degradation.
Accuenergy offers an IP68-rated option that is fully waterproof and dustproof. Additionally, the Extended Temperature (ET) model operates reliably from -45°C to 125°C (-49°F to 257°F), making it suitable for extreme weather conditions.
Proper centering is critical for Class 5P accuracy. The AcuCT Flex Pro Series includes specialized mounting brackets designed to secure the coil perfectly around the conductor, preventing shifting or sagging over time.
Sensitivity is the ratio of the output voltage to the primary current. It is expressed in mV/A.
The AcuCT Flex Pro series measures the primary current and produces a proportional low voltage output signal to the protection relay. Sensitivity is important to ensure that the relays can accurately detect fault conditions in the system and respond accordingly.
The essential information includes:
| Serial Number | For proper identification and traceability. |
| Accuracy | The maximum allowable measurement error. |
| Protection class | Indicates accuracy of the AcuCT Flex Pro series in high-fault current events. |
| Rated Primary current (Ipr) | Input current measured by the AcuCT Flex Pro series. |
| Rated Secondary Voltage (Usr) | Proportional low output voltage to the rated primary current Ipr. |
| Rated Extended Primary Current Factor (Kpr) | A multiplier to the rated primary current Ipr to indicate the range of current handling capacity during fault conditions. For e.g.: If the Ipr is 500A and Kpr is 8, then the AcuCT Flex Pro series can accurately measure up to 4000A (500A x 8 = 4000A) without losing its accuracy. |
| Phase offset correction (Φo_Cor) | Used to compensate for the phase shift occurred inherently during measurement to avoid false alarms in the systems. |
| Coil Factor (CFI) | Coil specific multiplier applied to the relay settings to compensate for manufacturing tolerances, ensuring maximum precision. |
| Low Pass Integrator Time Constant (LPIT (di/dt)) | The time constant used by integrator to reconstruct current waveform from AcuCT Flex Pro series’ derivative output. This ensures an accurate transient response during fault conditions. |
AcuCT Flex Pro is designed for protection and control applications, which require a wide range of current where traditional iron core CTs may saturate and fail. They include:
| Arc Flash Protection | During high fault currents, traditional CTs might saturate and fail, AcuCT Flex Pro remains linear which helps relay to detect and respond to faults within milliseconds. This will reduce the arc flash energy and ensures personnel safety. |
| Generator Protection | Provides accurate measurement across a wide range of conditions including overloads, faults and transient events. |
| Transformer Protection | Traditional CTs may saturate during Inrush current events leading to nuisance trip. AcuCT Flex Pro series has an air core, so it does not saturate, which ensures that the system triggers trip state only during actual fault conditions. |
| Zero Export / Non-export scheme | Precise current sensing is necessary at grid connections (for e.g.: At solar and energy distributed sites) to maintain compliance and prevent unintended power export. |
No, AcuCT Flex Pro offers an RJ45 output at 225 mV at 50 Hz and 270 mV at 60 Hz.
Yes. Two mounting brackets are available with the AcuCT Flex Pro series and can be ordered separately to secure the coil to the busbar or transformer bushings, ensuring stable positioning and reliable measurement.
