Thytronic SME71
Directional earth fault and short circuit detector for medium voltage secondary substations.
The Thytronic SME71 is a fault detector that signals short circuits and directional earth faults on medium voltage lines in secondary substations, in an indoor and an outdoor version. This Modbus RTU template reads the phase and residual voltages and currents, phase angles, fault records and self-test, and lets you change the earth fault and overcurrent settings and send store, reset and test commands from ModbusCloud.
- Protocol
- Modbus RTU
- Connection
- RS485, 9600 baud
- Registers
- 172, read and write
- Brand
- Thytronic
- Key readings
- Phase voltages · Phase currents · Residual voltage and current · Residual current angle · Current loop output · Fault and event records · Self-test status
- Available commands
- 67N earth fault settings · 51 and 51N current thresholds · Voltage element thresholds · Store and reset commands · Relay and current loop test
- Compatible models
- SME71-C · SME71-O
- Last updated
Registers (172)
161 read, 77 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Phase Voltage V4 | kV | Read | |||
| Phase Voltage V8 | kV | Read | |||
| Phase Voltage V12 | kV | Read | |||
| Phase Voltage V4 (% Un) | % | Read | |||
| Phase Voltage V8 (% Un) | % | Read | |||
| Phase Voltage V12 (% Un) | % | Read | |||
| Residual Voltage | kV | Read | |||
| Residual Voltage (% Un) | % | Read | |||
| Negative Sequence Voltage | kV | Read | |||
| Positive Sequence Voltage (% Un) | % | Read | |||
| Negative Sequence Voltage (% Un) | % | Read | |||
| Phase Current I4 | A | Read | |||
| Phase Current I8 | A | Read | |||
| Phase Current I12 | A | Read | |||
| Residual Current | A | Read | |||
| Residual Current Compensated | A | Read | |||
| Residual Current Angle | ° | Read | |||
| Angle V4-V8 | ° | Read | |||
| Angle V8-V12 | ° | Read | |||
| Angle V12-V4 | ° | Read | |||
| Angle V4-I4 | ° | Read | |||
| Angle V8-I8 | ° | Read | |||
| Angle V12-I12 | ° | Read | |||
| Current Loop Output | mA | Read | |||
| Direction Inversion Input | Read | ||||
| Self-Test Level | Read | ||||
| Voltage Calibration Status (MA) | Read | ||||
| Voltage Calibration Status (RJ45) | Read | ||||
| Operating Mode | Read | ||||
| Login Status | Read | ||||
| Failed Login Attempts | Read | ||||
| Oscillography Recorder State | Read | ||||
| 59 Vss Auto-Calibration State | Read | ||||
| Function Mode | Read and write | ||||
| Rated Phase Voltage | kV | Read and write | |||
| Rated Frequency | Hz | Read and write | |||
| Input I8/IO Selection | Read and write | ||||
| Voltage Input | Read and write | ||||
| Current Input | Read and write | ||||
| Current Sensor Secondary Voltage | Read and write | ||||
| Current Sensor Type | Read and write | ||||
| LED Reset Enable | Read and write | ||||
| 67N Reference Voltage | Read and write | ||||
| 67N Voltage Threshold | % | Read and write | |||
| 67N Residual Current Threshold | A | Read and write | |||
| 67N Residual Current Compensation | Read and write | ||||
| 67N1 Enable | Read and write | ||||
| 67N1 Operate Time Mode | Read and write | ||||
| 67N1 Operate Time | ms | Read and write | |||
| 67N2 Enable | Read and write | ||||
| 67N2 Operate Time Mode | Read and write | ||||
| 67N2 Operate Time | ms | Read and write | |||
| 51 Enable | Read and write | ||||
| 51 Phase Current Threshold | A | Read and write | |||
| 51 Operate Time Mode | Read and write | ||||
| 51 Operate Time | ms | Read and write | |||
| 51N Enable | Read and write | ||||
| 51N Residual Current Threshold | A | Read and write | |||
| 51N Operate Time Mode | Read and write | ||||
| 51N Operate Time | ms | Read and write | |||
| 59 Vo Enable | Read and write | ||||
| 59 Vo Threshold | % | Read and write | |||
| 59 Vo Operate Time | ms | Read and write | |||
| 59 Vi Enable | Read and write | ||||
| 59 Vi Threshold | % | Read and write | |||
| 59 Vi Operate Time | ms | Read and write | |||
| 27 Vd Enable | Read and write | ||||
| 27 Vd Threshold | % | Read and write | |||
| 27 Vd Operate Time | ms | Read and write | |||
| 59 Vss Enable | Read and write | ||||
| 59 Vss Threshold | % | Read and write | |||
| 59 Vss Operate Time | s | Read and write | |||
| 59 Vss Auto-Calibration | Read and write | ||||
| Relay 51 Normal State | Read and write | ||||
| Relay 59 Normal State | Read and write | ||||
| Relay 67 Normal State | Read and write | ||||
| Endesa Timer T1 | ms | Read and write | |||
| Endesa Timer T2 | s | Read and write | |||
| Endesa Timer T3 | min | Read and write | |||
| Voltage Monitor Pulse Time | ms | Read and write | |||
| Voltage Monitor Delay Time | ms | Read and write | |||
| Current Loop Mode | Read and write | ||||
| Current Loop Range (Monodirectional) | A | Read and write | |||
| Current Loop Range (Bidirectional) | A | Read and write | |||
| Fault Mask Time | ms | Read and write | |||
| Intermittent Fault Threshold | % | Read and write | |||
| Intermittent Fault Input Delay | ms | Read and write | |||
| Intermittent Fault Output Delay | ms | Read and write | |||
| Virtual DIP Switch | Read and write | ||||
| Theta Correction MA Rogowski | ° | Read and write | |||
| Theta Correction MA Direct | ° | Read and write | |||
| Theta Correction RJ45 Rogowski | ° | Read and write | |||
| Theta Correction RJ45 Direct | ° | Read and write | |||
| Current Calibration Input | Read and write | ||||
| Max Offset Standard | Read and write | ||||
| Max Offset Amplified | Read and write | ||||
| Fault Record Select | Read and write | ||||
| Event Record Select | Read and write | ||||
| Settings Command | Write | ||||
| Reset Command | Write | ||||
| Test Command | Write | ||||
| Recorded Data Default Command | Write | ||||
| Calibration Command | Write | ||||
| Operating Mode Command | Write | ||||
| Device Restart Command | Write | ||||
| Login Command | Write | ||||
| Logout Command | Write | ||||
| Password Confirm Command | Write | ||||
| Password Reset Command | Write | ||||
| Set Clock Year | Read | ||||
| Oscillography Pre-Trigger | Read | ||||
| Access User 1 | Read | ||||
| Access Password 1 | Read | ||||
| Phase Voltage V4 Direct (Test) | kV | Read | |||
| Phase Voltage V8 Direct (Test) | kV | Read | |||
| Phase Voltage V12 Direct (Test) | kV | Read | |||
| Residual Voltage Direct (Test) | kV | Read | |||
| Negative Sequence Voltage Direct (Test) | kV | Read | |||
| Residual Current IO_D (Test) | A | Read | |||
| Residual Current IO_A (Test) | A | Read | |||
| Calibration Angle V4-I4 (Test) | ° | Read | |||
| Calibration Angle V4-I8 (Test) | ° | Read | |||
| Calibration Angle V4-I12 (Test) | ° | Read | |||
| Angle V4-IO_A (Test) | ° | Read | |||
| Voltage Calibration Result (MA) | Read | ||||
| Calibration Rated Voltage (MA) | kV | Read | |||
| Calibration Gain V4 (MA) | Read | ||||
| Calibration Gain V8 (MA) | Read | ||||
| Calibration Gain V12 (MA) | Read | ||||
| Calibration Angle V4 (MA) | ° | Read | |||
| Calibration Angle V8 (MA) | ° | Read | |||
| Calibration Angle V12 (MA) | ° | Read | |||
| Voltage Calibration Aux State (MA) | Read | ||||
| Voltage Calibration Result (RJ45) | Read | ||||
| Compensation Gain V4 (RJ45) | Read | ||||
| Compensation Gain V8 (RJ45) | Read | ||||
| Compensation Gain V12 (RJ45) | Read | ||||
| Compensation Angle V4 (RJ45) | ° | Read | |||
| Compensation Angle V8 (RJ45) | ° | Read | |||
| Compensation Angle V12 (RJ45) | ° | Read | |||
| Calibration Gain V4 (RJ45) | Read | ||||
| Calibration Gain V8 (RJ45) | Read | ||||
| Calibration Gain V12 (RJ45) | Read | ||||
| Calibration Angle V4 (RJ45) | ° | Read | |||
| Calibration Angle V8 (RJ45) | ° | Read | |||
| Calibration Angle V12 (RJ45) | ° | Read | |||
| Voltage Compensation Aux State (RJ45) | Read | ||||
| Sensor Voltage Calibration Result | Read | ||||
| Sensor Voltage Calibration State | Read | ||||
| Current Calibration Result | Read | ||||
| Current Calibration State | Read | ||||
| RJ45 Voltage Swap 4-12 (App) | Read | ||||
| RJ45 Voltage Swap 4-12 (Smp) | Read | ||||
| RJ45 Current Swap 4-12 (App) | Read | ||||
| RJ45 Current Swap 4-12 (Smp) | Read | ||||
| Faults Stored | 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 | ||||
| Serial Number Setting | Read and write | ||||
| Debug Value 1 | Read | ||||
| Debug Value 2 | Read | ||||
| Debug Value 3 | Read | ||||
| Debug Value 4 | Read | ||||
| Debug Value 5 | Read | ||||
| Debug Value 6 | Read | ||||
| Debug Value 7 | Read | ||||
| Debug Value 8 | Read |
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Use cases
- Show the phase voltages, phase currents and residual values of each substation on a dashboard with a year of history.
- Get an e-mail or webhook alert when the number of stored faults changes or the self-test level rises above zero.
- Follow the residual voltage and current over time to see how the earth fault level of a line develops.
- Check the 67N and overcurrent settings remotely and adjust them during commissioning.
- Watch the voltage on the three phases to see when a line section goes dead and when it comes back.
Installation
Connect the RS232 port of the SME71 to an RS232 to RS485 converter and wire A and B of the converter to the RS485 port of the ModbusCloud Gateway. Terminate the bus at both ends with 120 Ω.
Look up in ThyVisor which Modbus address the SME71 answers on; the port runs 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 SME71 template and check that the phase voltages and the self-test level come in.
Compare the voltages and currents with ThyVisor, and set the rated phase voltage on the SME71 if the kV values look wrong.
Things to watch for
The Gateway gets no answer from the SME71. What should I check?
The SME71 talks Modbus RTU on its RS232 port at 9600 baud without parity, so it needs an RS232 to RS485 converter. Check the wiring and power of the converter, that A and B are not swapped, and that the address in ModbusCloud matches the address ThyVisor uses for the device.
The voltages or currents do not match what I expect. Why?
The voltages come both in percent of the rated voltage and in kV; the kV values depend on the rated phase voltage setting and on the voltage calibration. The currents depend on the sensor type, input and secondary voltage set on the device. Check those settings and the calibration status, and compare again with ThyVisor.
I wrote a new setting, but it is gone after a restart. Why?
The SME71 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, the access codes and the fault, event and calibration records are part of larger messages that the device may only send as a whole. When one of those stays empty, the voltages, currents, angles and settings are still read as normal.
Can a test command signal a fault to the remote control unit?
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. Only use it during commissioning or maintenance, after informing whoever operates the remote control system, and end the test with Test off.
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