1407-CGCM system process equipment in the presence of a large number of frequency converters, which produces the odd harmonic interference is very serious, coupled with the construction of the system during the laying of remote cables basically not in accordance with the norms of the construction, not only and power cables are laid in the same bridge in a bridge, and with the remote station connected to the branching, terminals, etc. are not specially shielded, which may lead to the odd harmonics of the frequency converter into the remote i/o system causing remote i/o communication errors. This may cause the odd harmonics of the inverter to enter the remote i/o system and cause communication errors in the remote i/o.

The plc system of 1407-CGCM requires separate grounding to avoid all kinds of interference from the electrical system entering the plc through the grounding line (Siemens’ control system does not require the grounding of the plc system to be strictly separated from the grounding of the electrical system, but according to the information I consulted, the prerequisite for doing so is that the transformer neutrals of the electrical system cannot be grounded). The system in the construction of plc grounding pole and electrical grounding pole is buried separately, but due to the long time electrical personnel daily maintenance of electrical wiring changes in the arbitrariness is too large, in fact, the two grounding poles have been in a number of nodes connected together. Due to the existence of a small potential difference between the two grounding poles, the resulting current between the grounding line also enters the plc system to form interference.

1407-CGCM In order to prevent interference caused by signal radiation, the branch should be installed away from the cabinet and shielded with a special metal shielding box. In fact, the branchers are installed in the plc cabinet, and no separate shielding measures are taken. The length of the substation cable requirements in the range of 2.5-50m, too short signal will be reflected in the branch, which will produce errors in the substation adapter; and too long will cause signal attenuation, the same will produce signal errors. In fact, since the branch is installed in the plc cabinet, the substation cable is only 1~1.5m long.