Process Engineering Division – Instrumentation and Automation Section – Daily Topics – Topic No. 2020-11-25

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To protect instruments from lightning strikes, it is first necessary to establish a proper grounding network: the instrument ground and the protection ground should both be connected to the electrical grounding network, with a grounding resistance of less than 4 ohms.

The issue may lie in the quality of the instruments, or the fact that instruments that have been in service for too long have reduced resistance to lightning interference； There is a poorly connected joint in the cable that connects the instrument ； The instruments are powered via a centralized power supply ； Power supply voltage fluctuations ； Fuse aging ； When input/output safety barriers are used for isolation for an extended period of time, the number of failure points undoubtedly increases, which reduces the instruments’ resistance to lightning strikes. To meet the requirements of production, when taking measures to protect instruments against lightning strikes, the following factors need to be considered based on the characteristics of lightning: (1) When selecting instruments, it is necessary to choose those with strong interference resistance, as well as those that have specialized lightning protection and grounding mechanisms built into them. The transmitter is equipped with a zinc oxide arrester, which provides protection against abnormal voltage surges generated by lightning-induced effects on the transmission cables. Zinc oxide arresters come in built-in types, field-installable types, and panel-mounted types. (2) When installing zinc oxide arresters, it is also possible to install online arrester monitors. When installing the instruments, all their fasteners must be fitted properly; the instrument box must be properly grounded. Additionally, the location of the instruments needs to be taken into consideration – instruments installed on tank tops or at high altitudes are prone to being struck by lightning, so lightning rods should be installed according to the actual conditions ； For instruments located far away from the production equipment and without any lightning protection devices in the vicinity, lightning rods must still be installed. The installation of instrument signal cables must be carried out by routing them into trunking as specified. When connecting the signals of the components on-site, the cable shielding must be grounded in accordance with the regulations; the cables should be laid inside galvanized metal conduits. In the event of a lightning strike at the point where the cable is enclosed in such conduits, a protection circuit is formed, allowing discharge to the ground. All metal components insulated from the ground should be bridged with metal wires.

To protect instruments from lightning strikes, it is first necessary to establish a proper grounding network: the instrument ground and the protection ground should both be connected to the electrical grounding network, with a grounding resistance of less than 4 ohms.

When protecting instruments from lightning strikes, several factors need to be taken into account based on the characteristics of lightning: (1) When selecting instruments, it is necessary to choose those with strong interference resistance, as well as instruments that have specialized lightning protection and grounding mechanisms built into them. The transmitter is equipped with a zinc oxide arrester, which provides protection against abnormal voltage surges generated by lightning-induced effects on the transmission cables. Zinc oxide arresters come in built-in types, field-installable types, and panel-mounted types. (2) When installing zinc oxide arresters, it is also possible to install online arrester monitors. When installing the instruments, all their fasteners must be fitted properly; the instrument box must be properly grounded. Additionally, the location of the instruments needs to be taken into consideration – instruments installed on tank tops or at high altitudes are prone to being struck by lightning, so lightning rods should be installed according to the actual conditions ； For instruments located far away from the production equipment and without any lightning protection devices in the vicinity, lightning rods must still be installed. The installation of instrument signal cables must be carried out by routing them into trunking as specified. When connecting the signals of the components on-site, the cable shielding must be grounded in accordance with the regulations; the cables should be laid inside galvanized metal conduits. In the event of a lightning strike at the point where the cable is enclosed in such conduits, a protection circuit is formed, allowing discharge to the ground. All metal components insulated from the ground should be bridged with metal wires.

To protect instruments from lightning strikes, it is first necessary to establish a proper grounding network: the instrument ground and the protection ground, which are ultimately connected to the electrical grounding network, with a grounding resistance of less than 4 ohms

Specifications are standards, and it is necessary to follow these specifications in both design and installation.

The issue may lie in the quality of the instruments, or the fact that instruments that have been in service for too long have reduced resistance to lightning interference； There is a poorly connected joint in the cable that connects the instrument ； The instruments are powered via a centralized power supply ； Power supply voltage fluctuations ； Fuse aging ； When input/output safety barriers are used for isolation for an extended period of time, the number of failure points undoubtedly increases, which reduces the instruments’ resistance to lightning strikes. To meet the requirements of production, when taking measures to protect instruments against lightning strikes, the following factors need to be considered based on the characteristics of lightning: (1) When selecting instruments, it is necessary to choose those with strong interference resistance, as well as those that have specialized lightning protection and grounding mechanisms built into them. The transmitter is equipped with a zinc oxide arrester, which provides protection against abnormal voltage surges generated by lightning-induced effects on the transmission cables. Zinc oxide arresters come in built-in types, field-installable types, and panel-mounted types. (2) When installing zinc oxide arresters, it is also possible to install online arrester monitors. When installing the instruments, all their fasteners must be fitted properly; the instrument box must be properly grounded. Additionally, the location of the instruments needs to be taken into consideration – instruments installed on tank tops or at high altitudes are prone to being struck by lightning, so lightning rods should be installed according to the actual conditions ； For instruments located far away from the production equipment and without any lightning protection devices in the vicinity, lightning rods must still be installed. The installation of instrument signal cables must be carried out by routing them into trunking as specified. When connecting the signals of the components on-site, the cable shielding must be grounded in accordance with the regulations; the cables should be laid inside galvanized metal conduits. In the event of a lightning strike at the point where the cable is enclosed in such conduits, a protection circuit is formed, allowing discharge to the ground. All metal components insulated from the ground should be bridged with metal wires.

To protect instruments from lightning strikes, it is first necessary to establish a proper grounding network: the instrument ground and the protection ground should both be connected to the electrical grounding network, with a grounding resistance of less than 4 ohms.