String data out of the combiner box
The RTU gathers string current, string voltage, and the surge-arrester state. It polls inverters and meters over RS485, then sends the plant control room a report over 4G or another link. A wide-range 110VDC/220VDC or AC supply matches the bus already in the combiner box.
High-temperature derating fits a cabin on a color-steel roof. SimtoLink supplies a string address table, a protocol map, and a batch commissioning script, so a failed string can be found without walking the array.
What the box has to survive
The ports are tested to the relevant items of IEC 61000-4 level 4, with surge and reverse-polarity protection. Ground is zoned so a loop or a common-mode hit is less likely to drop a string reading. Outdoor and coastal orders can take a higher ingress rating and a corrosion coating.
Parameters and thresholds load as a batch. Selected models store an event or a waveform. OTA carries settings and firmware. Accept the RTU with a power-on self-test, a time sync, and a sample of points. For metering or safety, SimtoLink helps with a third-party metrology submission and the type-test file.
Hardware figures
Typical order, for selection and for a bid schedule. For a wider range, a redundant supply, or an intrinsically safe explosion-proof variant, ask SimtoLink for the hardware specification and the installation guide. Order codes can differ slightly; the nameplate and the papers in the box decide.
| Item | Specification | Note |
|---|---|---|
| Telemetry / status | 64/128 | Configurable point table |
| Control / setpoint | 16/8 | Checkback |
| Uplink | BeiDou short message | Active/standby switchover |
| Downlink | Several RS485 channels | Isolated |
| Supply | DC 24V solar | Holds through a power loss |
| Clock | Timekeeping <2s/day | SOE 1 ms |
| Ingress | IP65 outdoor enclosure | Lightning protection class III |
| Safety | GB/T 13729 | Type test |
| MTBF | >80,000 hours | Room temperature |
| Installation | Wall mount | Anti-theft lock |
Where the RTU sits on a PV plant
Four plant types, so the uplink and the string map can be judged before the order.
Commercial rooftops
Several combiner boxes report to one cloud, and cleaning or an I-V diagnosis can be issued as a work order.
Ground-mounted plants
Array blocks are gathered where fiber has not been pulled, so those blocks are no longer a blind spot.
PV, storage, and charging on one site
PCS and BMS share the link and the timestamp, which is what an energy-management policy needs.
Village and livelihood PV
On a weak network the report resumes after a break, which settlement and the maintenance score both rely on.
Install, ground, and revisit
- Check the supply window and polarity before the RTU is powered. Measure the bus and the breaker if the combiner feed is uncertain.
- Shielded twisted pair, shield landed once, kept off long runs of power cable.
- Prove read, write, and one threshold against the host in the workshop, then take the RTU to the roof.
- Outdoors, let water leave and air move, inspect the gasket, and keep the lightning earth inside the local rule.
- Every 6 months, sample a set of strings and file the log.
Order, documents, and support
SimtoLink supplies the hardware specification, the outline drawing, a wiring table, and a sample project. Volume orders can include a sample review and a factory inspection. Warranty and calibration follow the contract and the papers in the box.