Seeking the teacher’s help with issues related to interference in compressor control signals
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The compressors from Siemens were initially installed with dual-end grounding as specified by the manufacturer. Later, due to serious problems with cable overheating, extensive repairs were carried out: the insulation was repaired, the damaged cables were replaced, and dual-end grounding was changed to single-end grounding, which resolved the issue of cable overheating. However, an issue arose where the dry gas seal heater of the compressor could not be started. The dry gas seal heater is controlled from the substation MCC; when in standby mode, a current of 19.5 mA was detected on the temperature signal line returning from the field, and there was an alarm in the dry gas seal control box that could not be reset. I consulted the design institute, and it was determined that the issue was caused by electromagnetic interference from the cables; therefore, the wiring needs to be reconfigured. Because video surveillance signals that are also affected by electromagnetic interference have been shown to benefit from the use of up-converters to improve their resistance to such interference. I was wondering if the teachers have any methods, such as installing anti-interference modules, to solve this problem with the compressor.
Add an isolation safety barrier on the unit side.
It seems that the issue you’re facing is mainly caused by interference with the temperature signals. Whether the temperature cable is a shielded cable, whether the shielding wire is distributed separately, and whether it is installed in trays or ducts. An attempt to resolve this issue could be as follows: connect the signal shielding wire to the signal ground inside the single-ended cabinet, and connect the signal ground wire to the negative terminal of the 24VDC power supply for the controllers in the cabinet. Please resolve it when the machine is shut down; I hope this can help you.
1. Are all analog signal cables shielded, with a main shield and separate shields, and are they single-ended grounded, including the junction box? 2. Are all analog signal cables twisted pairs? 3. Was the cable laid in accordance with the noise level requirements? 4. Keep the exposed length of the shield on analog signal cables as short as possible, ideally less than 10 centimeters. By achieving the above 4 points, magnetic field interference can basically be overcome.
When carrying out construction, be sure to separate the power supply from the signals; generally, a partition is installed within the instrument enclosure to separate the power supply cables, signal cables, and intrinsically safe cables. The instrument tray is connected to the tray grounding cable.
:Handshake, thank you. How does this need to be fixed?