Constructed from weather-resistant, flexible insulating materials and a reinforced, industrial-grade waterproof housing, Busbar-type coil current transformer is suitable for harsh environments such as outdoor distribution cabinets, photovoltaic plants, EV charging stations, and municipal outdoor power infrastructure. It supports applications including outdoor current monitoring, energy consumption analysis, and power quality assessment.
Market-leading accuracy: Class 0.5 precision with minimal positional error and low susceptibility to external electric fields; available in sensitivities of 22.5 mV/kA, 50 mV/kA, and 100 mV/kA.
IP67 fully sealed, waterproof, and dustproof: Professional sealing at the housing and cable exit points protects against rain, condensation, and dust ingress. It is ideal for harsh environments—such as open-air sites, underground utility tunnels, and humid workshops—ensuring no water entry or short circuits during long-term outdoor use.
Wide-temperature industrial design: Operates reliably across a range of -40°C to +80°C. Built with materials and processes resistant to temperature extremes, Busbar-type coil current transformer maintains stable performance and measurement accuracy despite significant fluctuations in ambient temperature, whether in the freezing cold of the north or the hot, humid conditions of the south.
Split-core structure for rapid, live-line installation: The snap-lock opening design allows for single-person on-site installation without modifying existing wiring or requiring power outages. It is particularly well-suited for upgrading legacy outdoor distribution equipment, helping to shorten project timelines and reduce construction costs.
Flexible coil for complex installation scenarios: The coil body offers slight flexibility, allowing it to fit around round cables, rectangular busbars, and irregular conductors. It is ideal for compact cabinet spaces and dense wiring layouts, overcoming the installation limitations associated with traditional rigid current transformers.
Outdoor PV Systems: Current monitoring on the AC/DC sides of PV combiner boxes, string inverters, and outdoor box-type substations.
New Energy Charging Piles: Current detection and metering for outdoor DC/AC charging piles and charging station distribution circuits.
Municipal Outdoor Power Distribution: Online monitoring for street light control cabinets, outdoor ring main units (RMUs), and power distribution systems in underground utility tunnels.
Outdoor Industrial Equipment: Operating current monitoring and fault early warning for outdoor fans, water pumps, and compressors in industrial zones.
Energy Storage Stations: Charge/discharge current acquisition for outdoor energy storage cabinets and battery clusters.
Field Power O&M: Portable measurement for temporary inspections, troubleshooting, and load testing on outdoor lines.
Humid/Corrosive Environments: Current detection for power distribution equipment at waterworks, sewage treatment plants, and coastal facilities.
Project Name: Low-voltage power distribution status monitoring upgrade and retrofit for the power utility compartment of the Sangtiandao underground utility tunnel, Suzhou Industrial Park.
Project Location: Underground utility tunnel within the Sangtiandao Science & Technology Innovation Belt, Suzhou Industrial Park, Jiangsu Province.
Retrofit Completion Date: May 2024.
Product Used: φ80mm IP67 wide-temperature split-core flexible Rogowski coil.
The Sangtiandao underground utility tunnel is a key municipal infrastructure project in the Suzhou Industrial Park. Spanning approximately 8.6 kilometers, the tunnel houses separate compartments for power utilities, general utilities, and gas pipelines. The power utility compartment supplies electricity to critical systems—including lighting, ventilation, fire protection, environmental monitoring, and emergency evacuation—classifying it as a "Level 1 Load" with extremely high requirements for power supply reliability.
The underground environment within the tunnel maintains a relative humidity exceeding 92% year-round, with localized short-term water accumulation occurring during the rainy season. The original current transformers (rated IP40) had been in operation for three years; during this time, twelve units suffered from terminal corrosion and degraded insulation resistance, while two units experienced signal acquisition anomalies due to condensation and water ingress, posing serious safety risks. Furthermore, due to the high load classification, prolonged power outages for the retrofit were not feasible, making traditional current transformer installation methods difficult to implement. Following extensive evaluation, the project selected an IP67-rated, flexible, split-core Rogowski coil as the core current-sensing component, enabling a monitoring system upgrade across all circuits without requiring any power outages.
High-humidity, water-prone underground environment; standard equipment lacks adequate protection. The underground utility tunnel is a confined space characterized by high humidity and severe condensation, with low-lying sections prone to temporary water accumulation during the rainy season. Standard current transformers (CTs) typically offer only IP40 protection; their poor sealing allows moisture and water vapor to penetrate the casing, leading to winding corrosion, insulation degradation, and signal drift. With an average service life of less than three years, frequent replacements drive up costs and introduce the risk of power outages.
Tier-1 power supply constraints; compliance issues regarding outage-based retrofitting. The power supply within the utility tunnel’s electrical compartment supports critical safety systems—such as fire suppression, ventilation, and surveillance—classifying it as a Tier-1 load where maintenance-related outages are prohibited except in extreme emergencies. Traditional solid-core CTs require cutting cables or dismantling busbars during installation, which violates operational management standards and poses significant safety risks; consequently, such proposals fail to secure approval from the outset.
Cramped space and dense cabling; installation difficulties with rigid CTs. Cable trays within the electrical compartment are tightly arranged, with passageways less than one meter wide. Large-cross-section power cables have large bending radii, leaving insufficient working space for rigid split-core CTs; installation is virtually impossible for circuits located at corners or featuring stacked cabling. Reorganizing the cables would exponentially increase both the workload and safety risks.
High manual inspection costs; significant delays in fault detection and resolution. Utility tunnels cover vast distances with widely dispersed monitoring points; a single inspection round requires over four hours. Hazards such as abnormal currents or circuit overloads are only detected during monthly inspections, resulting in delayed responses. Past incidents included undetected circuit overloads and overheating, which accelerated the aging of cable insulation. III. Equipment Configuration and System Design
To address the core requirements of underground utility tunnels—specifically high humidity/standing water, zero power interruption, confined spaces, and remote O&M—the project utilizes φ80mm IP67-rated, wide-temperature, split-core flexible Rogowski coils paired with waterproof data acquisition terminals. Data is transmitted via the tunnel's ring network to a surface monitoring center, enabling real-time, online monitoring of current across all circuits.
IP67 fully sealed protection; effectively resolves moisture and water ingress issues. The equipment housing employs ultrasonic welding for sealing, with reinforced waterproofing at cable outlets, achieving an overall IP67 rating. This ensures stable operation in environments with 100% relative humidity and condensation, as well as during brief periods of submersion in standing water. Following deployment, the system withstood Suzhou’s 2024 "Meiyu" (plum rain) season and summer torrential rains; despite repeated water accumulation in low-lying tunnel sections, none of the devices experienced water ingress, corrosion, or signal anomalies.
Live installation ensures zero power interruption and safety for critical loads. All 64 units were installed and commissioned while the system remained energized. Construction did not interrupt the power supply to the electrical compartment or affect the operation of safety systems such as fire suppression, ventilation, and monitoring. This fully complies with management standards for critical utility tunnel loads while eliminating safety and compliance risks associated with power outages.
Flexible structure adapts to confined spaces; installation efficiency doubled. The flexible coils can be bent easily, allowing for simple wrap-around installation even within narrow passageways and densely packed cable trays. The average installation time per unit is just 5 minutes—more than twice as efficient as installing traditional rigid current transformers. All 64 units were installed in just three days, significantly reducing the time spent working in confined underground spaces and lowering construction safety risks.
Stable performance across wide temperatures with no drift; highly adaptable to underground environments. Utilizing high/low-temperature resistant windings and sealing technology, the system maintains Class 1 measurement accuracy in the perpetually cool, humid underground environment. It exhibits no thermal drift or magnetic hysteresis, offering data stability far superior to conventional transformers. Remote monitoring replaces manual inspections, significantly reducing O&M costs. Current data is uploaded in real-time to a ground-based monitoring center, allowing O&M personnel to track the operating status of entire circuits without entering the utility tunnel, while automatic pop-up alerts notify them of anomalies. The frequency of tunnel inspections has dropped from twice a month to once a quarter, O&M labor costs have decreased by 60%, and the average fault response time has been cut from two hours to five minutes.
Zero equipment failures and compliant protection capabilities. As of January 2025, 64 units have operated stably for eight months. Having withstood various environmental challenges—including condensation during the rainy season, water accumulation from heavy storms, and low winter temperatures—there have been no instances of water ingress, corrosion, or signal drift. The equipment integrity rate stands at 100%, and the projected service life exceeds eight years, far surpassing the three-year average lifespan of the original equipment.
Zero power outages, zero risk, and successful compliance acceptance. Installation was completed without any power outages or impact on the safe operation of the utility tunnel. The project passed the specialized acceptance inspection by the Suzhou Industrial Park utility tunnel management authority on the first attempt, becoming a model project for the intelligent power distribution retrofit of underground utility tunnels in the park.
Significantly improved O&M efficiency and proactive handling of safety hazards. Real-time remote monitoring enables automatic early warnings for anomalies such as overloads, under-current conditions, and three-phase imbalances. Since commissioning, three instances of poor circuit terminal contact were identified and rectified before escalating into failures, effectively preventing safety incidents such as cable overheating and insulation damage.
Reduced total lifecycle costs. Although the procurement cost per unit is slightly higher than that of standard current transformers, the project's total lifecycle cost is 45% lower than traditional solutions—thanks to a longer service life, lower O&M and replacement costs, and the advantage of zero-outage installation—demonstrating significant economic benefits.
The IP67 busbar-type coil current transformer is ideally suited for specialized power distribution environments—such as underground utility tunnels, wastewater treatment plants, and underground substations—characterized by high humidity, a risk of water accumulation, and confined spaces. It fundamentally resolves three major industry pain points associated with traditional transformers: inadequate protection, the requirement for power outages during installation, and space constraints. Enabling the online monitoring upgrade of power distribution systems with minimal installation costs and negligible operational disruption, it serves as a highly reliable solution for the intelligent retrofitting of power distribution in underground municipal infrastructure and humid industrial environments.
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