When maintenance staff find a box transformer monitoring unit misbehaving, the hardest part is knowing where to start. Experience shows that around 80% of problems lie in "external" factors such as wiring, power supply, optical cable and parameters; only a minority actually require a board replacement. We recommend troubleshooting outside first, then inside; software first, then hardware.
1. Rule out external factors first
- Power supply: confirm the unit's supply voltage (AC/DC 220V) is within tolerance and the miniature circuit breaker has not tripped.
- Wiring: check terminals for looseness or oxidation, and check that secondary wiring is not pinched by the enclosure door or cabinet.
- Optical cable and patch cords: check that fiber patch cords are firmly seated and not bent too sharply, and that ST connector end faces are clean; if necessary, measure received optical power with a power meter.
- External devices: check whether downstream devices such as inverters and combiner boxes are themselves online, and whether their addresses and baud rates match the unit's configuration.
- Parameters and point list: check whether the configuration, monitoring system or point list has recently been changed.
2. Identify the board by symptom
Once external factors are ruled out, use the table below to make a preliminary judgment of which board to inspect or replace (applies to the AOYI NSA series):
| Symptom | Check first |
|---|---|
| Communication lost with a single unit while others are normal | Communication board |
| Box transformer data normal, but one or more sub-devices (inverters, combiner boxes, etc.) not communicating | Communication board |
| No front-panel display, rear-panel indicators off, communication lost | Power supply board |
| No data shown on the front panel at all, monitoring system data not updating | Power supply board |
| No data shown at all on the monitoring system | Power supply board, fiber board |
| Communication lost with one or several adjacent units in the middle of the ring | Fiber board |
| No data or stale data on the monitoring system, but the front panel on site displays normally (units with optical ports) | Fiber board |
| Three-phase voltage or current unbalanced | CPU board |
| One or more voltage or current channels missing or reading abnormally | Analog input board (possibly CPU board) |
| Status signals do not match actual field conditions | Digital input board or CPU board |
| One or more remote control commands not executed | Digital output board |
| Temperature on the monitoring system does not match the field | Digital output board, or the terminals carrying the DC analog inputs |
3. Locating a ring communication failure
In a self-healing ring, a single fiber break normally does not interrupt communication. So when a contiguous section of units drops offline at the same time on the monitoring system, it usually means the ring is broken in at least two places, or a unit's fiber board has failed and split the ring in two. Start from the units at each end of the offline section and check the optical port indicators and received optical power unit by unit; the break point is quickly found.
4. When to contact the manufacturer
- When the table above indicates a board replacement, tell the manufacturer the unit model and board name, and a spare can be shipped directly.
- If the cause of a protection trip is unclear or SOE records look abnormal, export the event records and send them to the manufacturer for analysis.
AOYI provides after-sales service with 2-hour response and on site within 48 hours, with service centers in Beijing and Xi'an. Service hotline: +86 10 8646 1328. See Service & Support for details. The fault diagnosis table is also available on the Downloads page.