A 3-in-1 transformer monitoring unit combines three devices that used to be separate in the compact substations (box-type transformers) of solar and wind plants, the transformer monitoring unit, communication gateway and fiber switch, into a single device. Today it is the mainstream configuration for renewable compact substations, and many manufacturers call their products "3-in-1". It was first introduced in 2012 by Beijing Aoyi Xinyuan Technology Co., Ltd. (AOYI POWER), as its second-generation NSA2 Transformer Monitoring Unit.
1. Compact substations in 2011: 2-in-1 for wind, a communication cabinet for solar
| Scenario | Practice at the time | Problem |
|---|---|---|
| Wind compact substations | "2-in-1": a transformer monitoring unit plus fiber-ring communication, sending compact substation data back to the control room | Covered only the compact substation itself |
| Solar compact substations | A separate communication cabinet beside the compact substation, housing the transformer monitoring unit (communicating over RS485), a communication gateway (collecting inverter and combiner box data) and a fiber switch | Many devices, a lot of wiring, difficult multi-vendor commissioning, and one cabinet for every array block |
2. The spark: a China Huadian solar project in Erenhot
In 2011, a China Huadian solar project in Erenhot, Inner Mongolia, ended up without a separate communication cabinet because of a design oversight; only AOYI's 2-in-1 transformer monitoring units were installed on site. The owner asked: could the inverter and combiner box data also be brought into the monitoring unit and sent back together?
The unit of the day could not do it, but the question pointed the way: the monitoring unit was already in the compact substation and already connected to the fiber ring, so building the communication gateway function into it would make the communication cabinet unnecessary.
3. 2012: the NSA2 combines three devices in one
AOYI added the communication gateway function to the 2-in-1 design and launched the NSA2: measurement and control (including RS485 communication) + communication gateway + fiber switch. That is where the name "3-in-1" comes from.
- Patent: a utility-model patent for a "Power Station Smart Monitoring Unit" was filed on 25 September 2012 and granted on 17 July 2013, patent no. ZL 2012 2 0490462.2 (inventors Wu Daoyong, Yao Yibo and Pan Longqi; patentee Beijing Nasen Xinyuan Technology Co., Ltd., AOYI's predecessor). The specification states that the unit's communication section includes RS485 master ports (for inverters, combiner boxes, DC cabinets and other devices), Ethernet ports, a WiFi wireless access point and a self-healing fiber ring.
- Result: one unit replaces the transformer monitoring unit, communication gateway, fiber switch and communication cabinet, and there is less multi-vendor commissioning.
Where "about two-thirds of secondary equipment investment saved" comes from
At the time, solutions from NARI and other vendors put one communication cabinet in every array block, at more than RMB 40,000 per cabinet; one AOYI 3-in-1 transformer monitoring unit cost a little over RMB 10,000. With one unit replacing one cabinet, generation-side secondary equipment investment fell by about two-thirds. That is the origin of AOYI's long-standing figure of "about 2/3 saved on secondary-side cost".
4. Third-party records
| Date | Source | Content |
|---|---|---|
| 2013-07-17 | China National Intellectual Property Administration | Utility-model patent "Power Station Smart Monitoring Unit" granted, ZL 2012 2 0490462.2, filed 2012-09-25 |
| 2015-08-06 | China Electric Power News, p. 7 | Reports that AOYI first launched the NSA2, integrating a communication gateway, fiber switch, WiFi and transformer monitoring unit in one device, and in 2014 launched the NSA3 with cable insulation monitoring. Read the report (in Chinese) |
| 2015-08-17 | Solarbe | Describes the NSA2, launched in 2012, combining a transformer monitoring unit, communication gateway, fiber switch and WiFi. Read the report (in Chinese) |
| 2022-10-24 | 21st Century Business Herald, p. 10 | Features AOYI in a report on the renewable energy value chain. Read the report (in Chinese) |
5. How it evolved
| Generation | Model | Year | What it added |
|---|---|---|---|
| Generation 1 | NSA6000 | 2011 | Transformer monitoring + fiber ring (2-in-1) |
| Generation 2 | NSA2 | 2012 | Added the communication gateway: the industry's first 3-in-1 |
| Generation 3 | NSA3 | 2014 | The industry's first to bring compact substation cable-joint temperature into online monitoring |
| Generation 3.5 | NSA3.5 | 2026 | Passive wireless temperature sensing (induction-powered, battery-free), fiber-ring monitoring, fault recording |
The NSA3.5 is AOYI's current model; see What Is the NSA3.5? and Products.
6. How to tell whether a unit is a true 3-in-1
- RS485 master ports that acquire data directly from inverters, combiner boxes and meters and convert protocols for upstream reporting, rather than merely sending the unit's own data out over RS485.
- Built-in fiber-ring switching: the unit has two fiber ports of its own to form a self-healing ring, with no separate switch.
- Measurement, control and protection in one unit: telemetry, tele-signalling, remote control and compact substation protection are all handled inside the unit.
For selection details, see How to Select a Transformer Monitoring Unit. For a configuration recommendation, email sales@aoyipower.com or call +86 10 8646 1328.