Thytronic SME70
Indoor detector for short circuits and directional earth faults in medium voltage substations.
The Thytronic SME70 is an indoor fault detector that signals short circuits and directional earth faults on medium voltage cable lines in secondary substations. 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
- 93, 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
- SME70 · SME70-C · SME70-M
- Last updated
Registers (93)
88 read, 51 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Phase Voltage V4 (% Un) | % | Read | |||
| Phase Voltage V8 (% Un) | % | Read | |||
| Phase Voltage V12 (% Un) | % | Read | |||
| Residual Voltage (% Un) | % | 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 Angle | ° | Read | |||
| Angle V4-V8 | ° | Read | |||
| Angle V8-V12 | ° | Read | |||
| Angle V12-V4 | ° | Read | |||
| Current Loop Output | mA | Read | |||
| Direction Inversion Input | Read | ||||
| Self-Test Level | Read | ||||
| Voltage Calibration Status | Read | ||||
| Oscillography Recorder State | Read | ||||
| Function Mode | Read and write | ||||
| Rated Frequency | Hz | Read and write | |||
| Input I8/IO Selection | 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 | |||
| 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 | |||
| 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 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 | ||||
| Set Clock Year | Read | ||||
| Oscillography Pre-Trigger | Read | ||||
| Voltage Calibration Result | Read | ||||
| Calibration Rated Voltage | kV | Read | |||
| Calibration Gain Rated Voltage | Read | ||||
| Calibration Gain Line Voltage | Read | ||||
| Calibration Gain V4 | Read | ||||
| Calibration Gain V8 | Read | ||||
| Calibration Gain V12 | Read | ||||
| Calibration Angle V4 | ° | Read | |||
| Calibration Angle V8 | ° | Read | |||
| Calibration Angle V12 | ° | Read | |||
| Voltage Calibration State | Read | ||||
| Current Calibration Result | Read | ||||
| Current Calibration State | 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 |
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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, 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
Close jumpers X21 and X22 of the SME70 and connect the 9-pin RS232 port behind the front cover to an RS232 to RS485 converter.
Wire A and B of the converter to the RS485 port of the ModbusCloud Gateway and terminate the bus at both ends with 120 Ω.
In ModbusCloud, add a Modbus device on the RS485 port of the Gateway at 9600 baud, 8 data bits, no parity and 1 stop bit, with the Modbus address that ThyVisor uses for the SME70.
Import the Thytronic SME70 template and check that the phase voltages and the self-test level come in.
Compare the voltages and currents with ThyVisor, and check the voltage calibration status if the voltages look wrong.
Things to watch for
The Gateway gets no answer from the SME70. What should I check?
The SME70 talks Modbus RTU on its RS232 port at 9600 baud without parity, so it needs an RS232 to RS485 converter. Jumpers X21 and X22 must be closed, otherwise reading and writing over the port is blocked. Also check the converter wiring, A and B, and that the address in ModbusCloud matches the address ThyVisor uses.
The voltages or currents do not match what I expect. Why?
The voltages come in percent of the rated voltage, measured through the capacitive dividers and corrected by the voltage calibration. The currents come from the Rogowski sensors; Input I8/IO Selection decides whether the second input measures the residual current or phase current I8. Check the calibration status and that setting, and compare again with ThyVisor.
I wrote a new setting, but it is gone after a restart. Why?
The SME70 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, 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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