Thytronic SME-O
Fault detector for medium voltage substations with directional earth fault, overcurrent and voltage detection.
The Thytronic SME-O is a fault detector for remote controlled medium voltage secondary substations that detects short circuits and earth faults on the line and signals them to the control centre. This Modbus RTU template reads the phase voltages and currents, residual and sequence values, the earth fault angle and the fault records, and lets you change thresholds, times and modes from ModbusCloud.
- Protocol
- Modbus RTU
- Connection
- RS485, 9600 baud
- Registers
- 91, read and write
- Brand
- Thytronic
- Key readings
- Phase voltages · Phase currents · Residual voltage and current · Sequence voltages · Earth fault angle · Current loop output · Fault and event records
- Available commands
- Directional earth fault settings · Overcurrent thresholds · Voltage thresholds · Operating mode · Sensor calibration · Store, reset and test commands
- Compatible models
- SME-O · SMEO
- Last updated
Registers (91)
86 read, 64 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Phase Voltage V4 | % | Read | |||
| Phase Voltage V8 | % | Read | |||
| Phase Voltage V12 | % | Read | |||
| Phase Current I4 | A | Read | |||
| Phase Current I8 | A | Read | |||
| Phase Current I12 | A | Read | |||
| Residual Voltage | % | Read | |||
| Residual Current | A | Read | |||
| Positive Sequence Voltage | % | Read | |||
| Negative Sequence Voltage | % | Read | |||
| Earth Fault Angle Theta | ° | Read | |||
| Phase Angle Phi 4 | ° | Read | |||
| Phase Angle Phi 8 | ° | Read | |||
| Phase Angle Phi 12 | ° | Read | |||
| Current Loop Output | mA | Read | |||
| Input INV | Read | ||||
| Self-Test Level | Read | ||||
| Oscillography Recorder State | Read | ||||
| Faults Stored | Read | ||||
| Settings Command | Write | ||||
| Reset Command | Write | ||||
| Test Command | Write | ||||
| Restart Command | Write | ||||
| Recorded Data Default Command | Write | ||||
| Operating Mode | Read and write | ||||
| Nominal Voltage | kV | Read and write | |||
| Nominal Frequency | Hz | Read and write | |||
| LED Reset Enable | Read and write | ||||
| 67N1 Enable | Read and write | ||||
| 67N2 Enable | Read and write | ||||
| 67N Voltage Selection | Read and write | ||||
| 67N Voltage Threshold | % | Read and write | |||
| 67N Residual Current Threshold | A | Read and write | |||
| 67N1 Operating Time Mode | Read and write | ||||
| 67N1 Extended Operating Time | ms | Read and write | |||
| 67N2 Operating Time Mode | Read and write | ||||
| 67N2 Extended Operating Time | ms | Read and write | |||
| 51 Enable | Read and write | ||||
| 51 Threshold | A | Read and write | |||
| 51 Operating Time Mode | Read and write | ||||
| 51 Extended Operating Time | ms | Read and write | |||
| 51N Enable | Read and write | ||||
| 51N Threshold | A | Read and write | |||
| 51N Operating Time Mode | Read and write | ||||
| 51N Extended Operating Time | ms | Read and write | |||
| 59 Vo Enable | Read and write | ||||
| 59 Vo Threshold | % | Read and write | |||
| 59 Vo Operating Time | ms | Read and write | |||
| 59 Vi Enable | Read and write | ||||
| 59 Vi Threshold | % | Read and write | |||
| 59 Vi Operating Time | ms | Read and write | |||
| 27 Vd Enable | Read and write | ||||
| 27 Vd Threshold | % | Read and write | |||
| 27 Vd Operating Time | ms | Read and write | |||
| 59 Vss Enable | Read and write | ||||
| 59 Vss Threshold | % | Read and write | |||
| 59 Vss Operating Time | s | Read and write | |||
| Voltage Monitor Pulse Time | ms | Read and write | |||
| Voltage Monitor Delay Time | ms | Read and write | |||
| Endesa T1 Time | ms | Read and write | |||
| Endesa T2 Time | s | Read and write | |||
| Endesa T3 Time | min | Read and write | |||
| Relay 51 Normal State | Read and write | ||||
| Relay 59 Normal State | Read and write | ||||
| Relay 67 Normal State | Read and write | ||||
| Current Loop Mode | Read and write | ||||
| Current Loop Full Scale Mono | A | Read and write | |||
| Current Loop Full Scale Bi | A | Read and write | |||
| Theta Correction | ° | Read and write | |||
| V4 Gain Calibration | Read and write | ||||
| V4 Phase Calibration | ° | Read and write | |||
| V8 Gain Calibration | Read and write | ||||
| V8 Phase Calibration | ° | Read and write | |||
| V12 Gain Calibration | Read and write | ||||
| V12 Phase Calibration | ° | Read and write | |||
| I4 Gain Calibration | Read and write | ||||
| I4 Phase Calibration | ° | Read and write | |||
| I8 Gain Calibration | Read and write | ||||
| I8 Phase Calibration | ° | Read and write | |||
| I12 Gain Calibration | Read and write | ||||
| I12 Phase Calibration | ° | Read and write | |||
| Fault Record Select | Read and write | ||||
| Event Record Select | Read and write | ||||
| Oscillography Pre-Trigger | Read | ||||
| Selected Fault Number | Read | ||||
| Events Stored | Read | ||||
| Selected Event Number | Read | ||||
| Oscillography Records Stored | Read | ||||
| Clock Year | Read | ||||
| Device Identification | Read | ||||
| Product Code | Read |
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Show the phase voltages and currents of each substation on a dashboard and keep a year of history per value.
- Send an e-mail or webhook alert when the residual voltage or current rises above a threshold.
- Follow the number of stored faults to see how often a line sees short circuits or earth faults.
- Check the earth fault and overcurrent thresholds remotely and adjust them during commissioning.
- Get an alert when a phase voltage drops, for example after a line interruption.
Installation
Connect the RS232 port of the SME-O through an RS232 to RS485 converter to the RS485 port of the ModbusCloud Gateway, and terminate the RS485 bus at both ends with 120 Ω.
Check the Modbus address of the SME-O, for example with ThyVisor; the port works at 9600 baud without parity.
In ModbusCloud, add a Modbus device on the RS485 port of the Gateway with that address, 9600 baud, 8 data bits, no parity and 1 stop bit.
Import the Thytronic SMEO template and check that the phase voltages and currents come in.
Compare the voltages with the rated voltage set on the device and the currents with the line load.
Things to watch for
The Gateway gets no answer from the SME-O. What should I check?
The SME-O has an RS232 port, so it needs an RS232 to RS485 converter between the device and the Gateway. Check the converter wiring and power, the Modbus address of the device, 9600 baud and no parity in ModbusCloud, and that A and B on the RS485 side are not swapped.
Why are the voltages shown in percent?
The SME-O reports the phase, residual and sequence voltages as a percentage of the rated voltage in Nominal Voltage, and the currents in amps. If the values look off, check Nominal Voltage, Nominal Frequency and the gain and phase calibration of the sensor inputs.
I wrote a new threshold, but it is gone after a restart. Why?
The SME-O keeps changed settings in temporary memory until it receives the store command. After writing new values, write Store to the Settings Command register, or Clear to discard the changes. Read a setting first before you write it, so you know the current value.
Some values stay empty while the voltages come in. Is that normal?
The clock, the identification and the fault and event records are part of larger messages that the device may only send as a whole. The template fits SME-O devices with identification code 111; earlier versions place the measurements at other addresses.
Can a test command reach the control centre?
Yes. The test command switches output relay 51, 67 or 59 or drives the current loop to 20 mA, and the remote control unit sees that as a real signal. Warn the control centre first and end the test with Test off.
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