At present, when designing petroleum instrumentation systems in China, lightning protection is basically not considered, but foreign countries have nearly 20 years of research and use experience in this area. Some domestic petrochemical plants often suffer from lightning strikes, which paralyzes the control system and causes the device to stop, resulting in huge economic losses. Therefore, some remedial lightning protection measures have been taken, mainly the shunt method, that is, the signal or communication circuit of the instrument system and the power supply part of the system adopt surge protector SPD(Surge ProtectiveDevice) to limit transient overvoltage and split surge current.
However, an SPD can only provide protection for a certain part of the loop; for example, an SPD installed in the DCS control room can only provide protection for the DCS card channel; an SPD installed in the field transmitter output can only provide protection for the transmitter. If all! The/0 channel is equipped with SPD, and the cost will be greatly increased. Moreover, if two SPD are added to each circuit, the failure rate of the instrument system will be greatly increased due to the failure of the SPD itself (which has been proved in production practice).
Therefore, some domestic petroleum instrument plants can only partially use SPD in some relatively important occasions, and the protection is limited to field instruments or control room DCS, PLC, etc., and there is no real realization of the overall lightning protection of the instrument system.