SPA-bus Protocol
SPA-bus (Substation Protection Acquisition bus) is a proprietary protocol used in ABB protection relays and substation automation products.
The protocol is used in substation automation with one master and multiple slaves configuration.
Physical Layer
Usually a RS232 (V.24) serial connection with the following characteristics:
- 1 start bit
- 8 data bits
- 1 parity bit (even)
- 1 stop bit
Protocol Features
- Master-slave communication
- Channel-based data organization
- Time synchronization (Channel 0 only)
- Event logging and retrieval
- Data validation and acknowledgement
Data Channels
| Channel | Data Type | Description |
|---|---|---|
| 0 | Time | Time synchronization (Channel 0 only) |
| 0 | Last events | Event logging (Channel 0 only) |
| Various | Protection data | Protection relay measurements and status |
Acknowledgement Codes
| Code | Description |
|---|---|
| 2 | Overflow |
| 6 | Slave does not contain all data requested in the message |
| 7 | Addressed data is impossible to write or read |
| 8 | Data in write message not validated |
| 9 | Undefined negative acknowledgment |
Checksum
The checksum is calculated using hexadecimal digits of data XOR:ed together. If unused, the checksum field contains 'XX'.
SerialMon Support
- Frame parsing and validation
- Protocol decoding
- Data tracking and monitoring
- Acknowledgement code interpretation
- Channel-based data organization
