Thunderstorms caused the flow meter and pressure regulation system to fail, but what is the cause of the problem? How to solve it?
Thread Content
We have a gas transmission station in the mountains; a few days ago, during a thunderstormy night, a lightning strike caused the signal transmission module of the ultrasonic flow meter to be damaged. Other phenomena: The flow meter is connected to the cabinet via 2 sets of wires, powered by 24V and using RS485 signals. The on-site signal transmission module is damaged, but the measurement module is intact and can still perform counting; the pressure and temperature sensors from Rosemount at the site are working fine ； The traffic cabinet is equipped with a lightning protection module; the traffic counter is fine, and the lightning protection module is not damaged either. However, during the thunderstorm, the circuit breaker that supplies 24V power to the traffic counter tripped. The thunderstorms also caused a disruption in the communication of the voltage regulation system. The signal transmission cables have been shielded and grounded at the cabinet end, and the grounding of the cabinets is also satisfactory. The grounding tests in the processing area have passed as well, as have the tests conducted by the lightning protection department. Since there are many thunderstorms in the mountainous areas, I would like to ask everyone what the specific reasons for this phenomenon are In which areas should comprehensive protection be enhanced or equipment upgraded? Does the lightning protection inside the cabinet only protect the equipment in the cabinet? How to protect field devices?
Personally, I think the instrument should also be reliably grounded at the performance site.
The shield ground of the field panel should not be connected; it should be connected at the control cabinet. As for why it got damaged, that’s not clear
1. Have you checked for any issues with the wiring? 2. What is the rating of the circuit breaker? 3. Is the metering device within the range of lightning protection?
The enclosures of the field instruments must be grounded, as well as the shielding of the transmission cables; this grounding should be done at one end, with the control room serving as the grounding point. Also, pay attention to the waterproofing of the instrument enclosure – there is a risk of water entering and causing a power short circuit, which in turn may lead to the circuit breaker tripping
Check the lightning protection grounding at the site, as well as the coverage area of the lightning protection system; lightning-proof models can be selected for instruments installed at high heights
Surge protection, grounding, and lightning protection must all be added to the field instruments; none of them can be omitted
OP, do the lightning protection modules you use serve for signal protection or power protection? Their functions are different; based on your description, it is likely caused by induced lightning, as the signal line is not connected to a signal lightning protection module.
The overvoltage resistance of communication modules is generally low; it may be advisable to install external lightning protection grids. The poster should check all of their communication circuits. These are all the consequences of induced electricity; it completely ruins the lightning meters. Cables can be laid in trenches (burial is preferred), with separate conduits used for those that are located close to each other. In an environment like the one described by the poster, it is best to run the cables into the instrument room underground. Burial is the best method for lightning protection; shielding combined with grounding is also effective, while other methods are merely supplementary measures. Is the main incoming cable for your substation buried? Is it still routed into the distribution room? @jiaguoyun
The cables for the communication circuit are laid underground
Is the entire area covered by a comprehensive lightning protection system? If so, has it passed the lightning protection and grounding inspection? If it is qualified, the probability of a lightning strike directly hitting the instrument is almost 0. Even if the instrument is grounded at the site, the cable shielding is grounded, and surge protection devices are in place, the effect of these protections is minimal when the device is struck by lightning directly.