Eastron and Acrel CTs and Rogowski Coils for Retrofitting Energy Monitoring in Industry
- Aug 5
- 10 min read
Retrofitting energy monitoring used to mean disruption, shutdown planning, and awkward compromises inside crowded switchboards. That is no longer the case. With the latest Eastron and Acrel current transformers and Rogowski coils now supported and distributed by ProSense Instruments, industrial sites have more practical options for adding metering to machines, circuits, panels, and whole-site supplies without rebuilding their electrical infrastructure.
For factories, process plants, engineering workshops, food production sites, warehouses, and utilities, this matters. Energy is no longer just a monthly bill. It is a production input, a maintenance signal, and a way to find waste before it becomes accepted as normal.
Current transformers, often called CTs, and Rogowski coils sit at the centre of that change. They allow industrial energy meters to measure current safely and accurately without placing the meter directly in the main power path. When matched correctly to the application, they make energy monitoring easier to install, easier to scale, and more useful over time.
Why retrofit energy monitoring instead of replacing panels
Most industrial sites already have the electrical distribution they need. Main incomers, sub-distribution boards, motor control centres, and machine panels are already feeding production. Full replacement is rarely attractive unless the switchgear is at end of life.
Retrofitting is different. It adds visibility to what is already there.
A good retrofit project can answer practical questions such as:
Which machines draw the most power during normal production?
Which circuits remain loaded outside working hours?
How much energy does one production line use per batch?
Are compressors, chillers, kilns, pumps, or extraction systems running when they should be idle?
Is the site close to a supply limit during peak operation?
Which areas should be targeted first for energy reduction work?
CTs and Rogowski coils make this possible because they can often be installed around existing conductors. In many cases, split-core CTs and flexible Rogowski coils reduce the need to disconnect large cables. That can lower installation time, reduce downtime, and make monitoring projects easier to stage across a live industrial site.
ProSense Instruments’ support and distribution of the Eastron and Acrel range gives installers, energy managers, and system integrators access to a broad set of sensing options for different circuits and retrofit conditions.
How CTs and Rogowski coils work with industrial energy meters
Industrial energy meters measure voltage and current, then calculate values such as kWh, kW, power factor, current, voltage, and demand. The meter usually takes voltage references directly, through appropriate fusing and protection, while current is measured through a CT or Rogowski coil.
The current sensor does not simply “accessorise” the meter. It has a direct effect on accuracy, safety, installation method, and long-term reliability.
Current transformers suit defined circuits and repeatable loads
A current transformer is a magnetic device that produces a smaller, proportional current from a larger primary current. For example, a CT may represent a high current circuit with a lower secondary signal that the meter can read.
CTs are widely used because they are familiar, accurate when selected properly, and well suited to fixed circuits. Eastron and Acrel CT options typically cover common industrial needs, including metering at distribution boards, machine panels, sub-mains, and individual loads.
CTs are often the right choice when:
The cable or busbar size is known
The current range is reasonably predictable
The installation has enough physical space
The application needs strong measurement stability
The meter input is designed for CT use
Solid-core CTs are common in new builds or planned shutdowns where cables can be passed through the CT. Split-core CTs are especially useful for retrofit work because they can be opened and fitted around an existing conductor.
Rogowski coils suit large conductors and awkward retrofit spaces
A Rogowski coil is a flexible current sensor that wraps around a conductor. Unlike a conventional CT, it does not use an iron core. This makes it light, flexible, and easier to fit around large cables, busbars, mixed cable routes, or tight switchboard spaces.
Rogowski coils are particularly useful where a conventional CT would be too large, too difficult to install, or impractical without major disruption.
They are often selected for:
Main incomers
Large sub-mains
High-current busbars
Temporary energy surveys
Retrofitting in crowded panels
Sites where shutdown time is limited
A Rogowski coil normally works with an integrator or compatible meter input, so correct matching matters. When specified as a system, it provides a practical way to monitor high currents without heavy metering CTs.
Where Eastron and Acrel sensing products fit in industrial monitoring
The latest Eastron and Acrel CTs and Rogowski coils for retrofitting energy monitoring in industry are best understood by application level. Most sites need more than one type of measurement.
A plant rarely gets enough value from a single main meter. Whole-site data shows the total, but it cannot explain what caused the total. Machine-level data gives detail, but it may miss demand peaks across a building. The strongest systems use layered metering.
Monitoring level | Typical sensor choice | What it helps reveal |
Machine monitoring | Split-core CTs or compact CTs | Energy per machine, idle consumption, abnormal load patterns |
Circuit monitoring | CTs or Rogowski coils | Lighting, HVAC, compressed air, process circuits, distribution loads |
Whole-site monitoring | Large CTs or Rogowski coils | Main demand, total kWh, supply loading, peak periods |
Temporary surveys | Split-core CTs or Rogowski coils | Short-term load studies before permanent metering |
Retrofit panel upgrades | Split-core CTs and compact meter-compatible sensors | Energy data without major rewiring |
Machine monitoring finds waste at source
Machine-level metering is useful where production assets have different operating profiles. A CNC machine, hydraulic press, packaging line, oven, or injection moulding machine may all behave differently.
With CTs feeding an industrial energy meter, the site can compare actual energy use with production output. This supports simple but valuable findings. A machine may draw significant power while waiting for material. A motor may run continuously during breaks. A heater bank may cycle more often than expected.
The goal is not only to measure. The goal is to identify patterns that operators and maintenance teams can act on.
Circuit monitoring makes services visible
Many industrial energy savings come from services rather than production equipment. Compressed air, chilled water, extraction, lighting, pumps, and HVAC systems often run across multiple areas.
Circuit-level metering helps separate these loads from process consumption. This is especially useful when a production site wants to understand base load, weekend use, or demand spikes.
For example, a distribution board feeding compressors can be metered with CTs. If the data shows high overnight consumption, the maintenance team can investigate leaks, control settings, or unnecessary running. The meter does not fix the issue, but it gives the evidence needed to find it.
Whole-site monitoring supports demand control and reporting
Whole-site metering gives the main energy picture. It helps show total consumption, load peaks, and changes after projects are completed.
For high-current incomers, Rogowski coils can be especially practical. Their flexible construction can make them easier to place around large conductors or busbars, especially where the switchboard layout leaves little room for large CTs.
Whole-site data is useful for:
Checking maximum demand trends
Verifying utility bill data against site metering
Tracking energy use by shift or production period
Supporting energy management systems
Measuring the effect of efficiency projects
The main benefits for retrofit projects
The value of CTs and Rogowski coils is not limited to measurement. Their installation method can affect the success of the whole project.
Improved accuracy when sensors are correctly specified
Energy data only earns trust when people believe it. CT ratio, accuracy class, burden, cable length, phase matching, and meter compatibility all affect the result. Rogowski coils also need compatible inputs or integrators.
A well-specified Eastron or Acrel metering package can help reduce common problems such as poor low-load accuracy, incorrect CT ratios, or mismatched sensor outputs.
Accuracy matters most when data is used for:
Cost allocation between departments or tenants
Energy performance tracking
Measurement before and after efficiency work
Machine benchmarking
Demand management
Good installation practice is just as important as product choice. CT orientation, phase order, secure connections, and correct meter setup all need attention.
Easier installation in existing panels
Retrofit installers often face limited space, limited access, and limited shutdown windows. Split-core CTs and Rogowski coils directly address these problems.
Split-core CTs can clamp around conductors without pulling cables through a closed core. Rogowski coils can bend around large or awkward conductors. These features reduce physical disruption and can make phased monitoring projects more realistic.
That is especially useful when metering must be added to older panels that were never designed with energy monitoring in mind.
Better energy efficiency decisions
Meters do not save energy by themselves. They show where energy goes, when it is used, and whether changes have worked.
With reliable current sensors and meters in place, sites can make decisions based on measured load rather than estimates. That can support:
Switching schedules
Production planning
Compressed air improvements
Motor and drive assessments
Load balancing
Preventive maintenance
Capital planning for upgrades
The best results come when energy data is reviewed regularly and compared with production, operating hours, weather, or process conditions.
Practical examples from real industrial scenarios
The following examples are based on common retrofit applications seen across industrial sites. They are anonymised and illustrative, but they show how CTs and Rogowski coils can create practical value.
A packaging line reveals high idle consumption
A manufacturer wanted to understand why one production area had a higher energy cost than expected. The main site meter showed the total load, but it could not separate the packaging line from nearby process equipment.
Compact split-core CTs were fitted to the line’s supply and connected to a multi-function energy meter. After several operating cycles, the data showed a clear pattern. The packaging line used a steady amount of power during production, but it also kept several auxiliary systems running during long gaps between batches.
The fix was operational rather than expensive. The site adjusted shutdown procedures, trained operators to use standby settings, and reviewed the control sequence. The metering then confirmed that idle load had fallen during breaks and shift changes.
This type of project works well because the measurement point is close to the behaviour that needs to change.
Rogowski coils make main incomer monitoring possible in a crowded panel
A process site needed whole-site visibility but had very little spare room around the main incoming conductors. Large conventional CTs would have been difficult to fit without major shutdown planning.
Flexible Rogowski coils were selected for the main incomer. Their shape allowed the installer to route them around the conductors inside the available space. Once connected to compatible metering, the site could monitor total load, demand profile, and daily consumption.
The data helped the facilities team see when the site approached peak load and which production periods created the strongest demand. That information supported better scheduling of large loads and helped assess whether future equipment could be added without supply changes.
Circuit metering exposes compressed air waste
Compressed air is one of the most common sources of hidden energy waste in industry. One site added CT-based metering to the compressor distribution circuit to compare production and non-production periods.
The data showed the compressor circuit remained active for long periods when production demand was low. That prompted a review of leak rates, local isolation, timer settings, and control strategy.
After changes were made, the same meter provided before-and-after evidence. This gave the maintenance team a clear way to verify improvement and keep watching for drift over time.
Temporary metering supports a permanent monitoring plan
A multi-building industrial site wanted permanent metering but did not know where to start. Rather than meter every panel at once, the team used portable or temporary measurement points with split-core CTs and Rogowski coils to survey key supplies.
The survey identified the largest and most variable loads. It also showed which areas had stable consumption and did not need detailed metering straight away.
The permanent system was then designed in stages. Whole-site metering came first, followed by high-value circuits, then selected machines. This reduced waste in the metering budget and focused attention where data would be used.
Choosing between CTs and Rogowski coils
There is no single best sensor for every retrofit. The right choice depends on current range, conductor size, installation space, accuracy needs, and the meter being used.
Requirement | CTs are often suitable when | Rogowski coils are often suitable when |
Physical access | Conductors are accessible and space is available | Space is tight or conductors are large |
Retrofit speed | Split-core CTs fit the cable size | Flexible coils can route around awkward geometry |
Current level | Loads are within available CT ratios | High-current mains or busbars need flexible sensing |
Measurement detail | Stable circuit monitoring is needed | Broad operating range and retrofit access are priorities |
Metering setup | The meter accepts CT secondary inputs | The meter supports Rogowski input or integrator output |
For many industrial projects, the answer is a mix. CTs may be used for machines and sub-circuits, while Rogowski coils handle mains and large distribution points.
Installation points that protect data quality
A retrofit project should not treat current sensors as a quick clamp-on task. Small installation errors can create confusing readings.
Good practice includes:
Confirming the meter input type before selecting sensors
Matching CT ratio or Rogowski output to the expected load
Checking conductor size and panel clearance
Fitting each sensor in the correct direction
Keeping phase voltage and current references aligned
Labelling circuits clearly for future maintenance
Recording setup values in the meter schedule
Testing readings against expected load after installation
Safety also comes first. Work inside electrical panels should be carried out by competent people under site procedures, with suitable isolation and risk control.
Why ProSense Instruments support matters
Product choice is only one part of a successful retrofit. Matching the sensor, meter, current range, physical layout, communications needs, and installation method is where many projects succeed or fail.
With ProSense Instruments now supporting and distributing Eastron and Acrel CTs and Rogowski coils, industrial customers have a practical route to source metering hardware for new and retrofit energy monitoring projects. That support can help with product selection, application fit, and building a metering approach that suits real site conditions.
For system integrators, this can simplify specifying hardware across different monitoring levels. For maintenance and energy teams, it provides access to components that suit both small machine meters and larger whole-site monitoring projects.
A clear path to better industrial energy data
Industrial energy monitoring works best when it starts with a specific question. Measure a machine to understand production cost. Meter a compressor circuit to find waste. Monitor a main incomer to track demand. Add sub-metering to explain where the total load goes.
Eastron and Acrel current transformers and Rogowski coils give sites the sensing options needed to do this without unnecessary disruption. CTs bring accurate, familiar measurement to machines and circuits. Rogowski coils make large and awkward retrofit points easier to monitor. Together, they support a practical, layered approach to energy visibility.
For industrial sites planning an energy monitoring upgrade, the most useful next step is to map the main supplies, key circuits, and priority machines, then match each point to the right sensor and meter. With the right design and installation, retrofit metering can turn existing electrical infrastructure into a reliable source of energy intelligence.
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