Milesight · Three-phase current monitor
Milesight CT3xx integration with EpiSensor Edge
CT303, CT305 and CT310 combine three split-core current channels in one LoRaWAN device. Model choice sets aperture, rated current and the lowest self-powered current that the system can report reliably.
Connection design
Choose the path that matches the device
This is a protocol-compatible route, not a built-in Edge device mapping. Confirm the exact hardware generation, regional LoRaWAN parameters, phase assignment and network-server decoder. Hardware v2 energy values are estimates from configured voltage and power factor, not measurements of either input.
For a new or existing private LoRaWAN network
LoRaWAN network-server route
- CT3xx on the three phase conductors
- Compatible LoRaWAN gateway
- LoRaWAN network server and CT3xx decoder
- Supported MQTT or HTTPS integration
- Gateway running Edge
Provision the device for the site's region, decode the three phase channels at the network-server layer, and preserve the sensor timestamp and validity state when mapping data into Edge. A missing or failed channel is not a measured zero.
When LoRaWAN infrastructure is already managed centrally
Existing LoRaWAN estate
- CT3xx device identity
- Surveyed LoRaWAN coverage
- Network-server application output
- Authenticated IP handoff
- Edge phase data model
Agree phase naming, keys, decoder revision, timestamp rules and failure handling with the LoRaWAN operator. Edge consumes the decoded application stream and does not replace the network server.
Variant check
Match the exact model to its interface
Use the complete catalogue number, not the family name, when selecting an Edge connection.
| Models | Documented interface | EpiSensor route |
|---|---|---|
| CT303 · hardware v2 | 300 A rating · approximately 24.2 mm aperture · minimum reported current 3 A at a 1-minute interval or 2.5 A at 10 minutes | Three LoRaWAN current channels through a network server; best low-current visibility in the family |
| CT305 · hardware v2 | 500 A rating · approximately 36.5 mm aperture · minimum reported current 5 A at a 1-minute interval or 4.5 A at 10 minutes | Same LoRaWAN route with a larger conductor window and mid-range rating |
| CT310 · hardware v2 | 1000 A rating · approximately 51 mm aperture · minimum reported current 10 A at a 1-minute interval or 8.5 A at 10 minutes | Same LoRaWAN route for the largest conductors and highest currents in the family |
| Earlier hardware | Older manuals publish materially higher minimum reporting currents and a different feature set | Read the hardware and firmware versions and keep the matching documentation, decoder and acceptance payload together |
Data model
What Edge can exchange
The exact list depends on the model and its published data map. Start with the monitoring and control points the project will actually use.
- Independent RMS current for phase A, phase B and phase C, including per-phase minimum and maximum records
- Accumulated current for each phase, documented by Milesight as ampere-hours; preserve network receive timestamps and rollover behaviour
- Per-phase current threshold, over-current and sensor-status indications where enabled in the matching generation
- Optional cable-temperature value and temperature alarm states when the external NTC probe is fitted
- Hardware v2 per-phase estimated energy only when reporting type, nominal voltage and load power factor have been deliberately configured
- Hardware and firmware identity for choosing the matching base or v2 decoder
- Collection-failure sentinels and stale reports retained as invalid or missing, never converted to zero
- No measured voltage, measured power factor, active power, reactive power or revenue-grade energy value from the CT alone
Site acceptance
Commission it once, then preserve the map
A successful network connection is the start of the check, not the end.
- Confirm CT303, CT305 or CT310, record hardware and firmware versions, and select the matching base or v2 decoder before defining points. Retain representative raw and decoded payloads because current manuals and decoder code differ in some optional wire types.
- Have a qualified installer isolate the circuit as required, place each CT around one insulated phase conductor only, and verify that every split core closes fully.
- Map the labelled phase-A, phase-B and phase-C clamps to the site's phase references. Do not put a phase and neutral together through one CT.
- Connect phase A even when only a subset of channels is required: Milesight documents phase A as the self-power source, so its absence can power the device off.
- Check the lowest expected phase-A current and the other phase currents against the selected model's hardware-v2 reporting thresholds at the chosen interval.
- Provision the correct regional frequency plan, activation mode and unique LoRaWAN credentials; verify counters, timestamps and all three decoded channels at the network server.
- Compare each phase with a suitable reference instrument under representative load, deliberately swapping or interrupting one input to prove phase labels and failure handling.
- If using hardware v2 energy reporting, record nominal voltage and power factor as configuration assumptions and reconcile estimates with a true multi-function energy meter.
- If USB power is needed below the phase-A self-power threshold, confirm the approved accessory arrangement: the Type-C connection is also used by the optional NTC probe, and the reviewed documentation does not establish simultaneous USB power and temperature sensing.
- Test missed uplinks, the documented current collection-failure sentinel and stale timestamps. Alarms and dashboards must not present any of them as measured zero.
- If temperature is required, confirm that the optional NTC probe is installed and validate its position and plausible reading.
- Save the device configuration, decoder revision, phase map, reference readings and accepted raw/decoded payloads as the commissioning record.
Design review
Useful strengths and real constraints
These judgements are scoped to integrating this device family into an energy-data system. They are not a generic product award or a substitute for project design.
- Open integrationStrong
- LoRaWAN and published model codecs provide a standards-based route. The network server, exact decoder generation and downstream IP integration remain explicit project components.
- Three-phase contextUseful
- Three simultaneous current channels preserve phase loading and imbalance context that three unrelated single-channel devices can make harder to align.
- Power dependencyPhase A critical
- The product is current-derived and Milesight documents phase A as its power source. Loss or very low loading on that phase can affect the whole device rather than only one reading.
- Measurement scopeCurrent-led
- Hardware v2 kWh is estimated with configured voltage and power factor. It is not a substitute for a meter that measures voltage, phase angle and energy to a declared standard.
- SecurityShared responsibility
- Use unique LoRaWAN keys and protect network-server and integration credentials. Define operational ownership for key rotation, decoder changes and failed-device replacement.
- Evidence qualityRevision-sensitive
- Current product pages, older manuals and the vendor decoder corpus are not identical in every threshold or payload detail. Commission against the installed hardware and an observed payload.
Primary evidence
Sources
- CT3xx LoRaWAN Smart Current TransformerMilesight
- CT3xx configurable propertiesMilesight Development Platform
- CT3xx installation instructionsMilesight
- CT3xx uplink data definitionMilesight
- Milesight IoT device release notesMilesight
- CT-series codec source at the reviewed revisionMilesight IoT
Reviewed by EpiSensor technical review on . Revision 1. Product names and trademarks belong to their respective owners; this guide does not imply endorsement or a commercial relationship.