Created by: Glen Zhu | Updated Date: December 19th, 2023
Gas pressure control and measurement systems are designed to control and monitor gas flow and effective operation of gas distribution network. Gas pressure control and measurement systems regulate the pressure of gases throughout the distribution network, from the source to end-users.
Pressure is carefully managed at various stages, including pressure control stations and end-user connection points, ensuring safe and efficient delivery while monitoring pressure levels to meet industry standards and comply with safety regulations. Advanced monitoring systems and safety features contribute to the reliability and integrity of gas distribution networks.
However, its wide distribution and geographical location make it possible to be threatened by the effects of lightning strikes as well as the electromagnetic interference of modern measuring and control systems.
Incorporating electronics enhances the sensitivity of gas pressure control and measurement system to lightning, particularly. To this end, lightning and surge protection measures must be taken to address the risk of lightning strikes and potential loss of power failure.
A complete risk analysis is required to determine the effective protection measures for preventing destructive results of lightning strikes and power surges as the IEC 62305 standard stated.
Some of the risks associated with gas pressure control and measurement systems need to be taken into consideration.
Fire and Explosion: Malfunctions or damage to control valves, measurement devices, or pipelines can lead to gas leaks or releases. This poses a significant safety hazard, as natural gas is flammable and can result in fires or explosions.
Cybersecurity Threats: With the increasing use of digital control systems and communication technologies, there is a risk of cybersecurity threats. Unauthorized access or cyber-attacks could compromise the integrity of control systems, leading to potential safety and operational risks.
Over-pressurization and under-pressurization: If pressure control systems fail to operate correctly, over-pressurization or under-pressurization can occur which results in equipment damage or inadequate supply.
Environmental Impact: Gas leaks or releases can have environmental consequences, contributing to air pollution and potentially harming ecosystems. Methane, the primary component of natural gas, is a potent greenhouse gas.
External lightning protection has two forms: the isolated LPS and the bonded LPS. The main difference between isolated and bonded lightning protection system is the approach to safeguard structures and equipment from the destructive effects of lightning strikes.
Widely used bonded lightning protection system aims to provide a continuous and low-resistance path for lightning currents to follow safely to the ground, eliminating potentially devastating potential differences. A network of air terminals, down-conductors and grounding electrodes are installed and electrically bonded to the structure in a bonded lightning protection system.
Whereas, isolated LPS relies on creating a protective zone by using an appropriate “separation distance” between the LPS and the structure, preventing the risk of uncontrolled partial lightning. It is achieved either by installing air-termination rods or masts adjacent to the structure to be protected or by suspending overhead wires between the masts by the separation distance of IEC 62305-3, Section 6.3.
In certain cases, isolated and bonded systems are combined to provide comprehensive protection. This hybrid approach allows for the benefits of both systems, offering a layered defense against lightning-induced damage.
Figure 1 – Isolated LPS vs. Bonded LPS in the example for explosive atmosphere
Compared to traditional bonded lightning protection, isolated LSP protects specific structures or equipment from side-flashing because lightning energy is directed away from sensitive equipment.
That is the limitation of bonded LPS in the condition of rooftop electrical equipment, metallic items and the structure itself may carry a proportion of the discharged current.
Additionally, isolated lightning protection systems are preferred in scenarios where minimizing electromagnetic interference (EMI) is critical. The strategic placement of surge protection devices prevents disruptive electromagnetic fields generated by lightning from affecting sensitive electronic equipment.
An isolated LPS might be chosen to minimize the need for extensive bonding and reduce the risk of sparks or explosions. Certain applications, such as isolated structures, remote facilities, or buildings with specific design requirements, may benefit from isolated LPS due to its flexibility in adapting to diverse structural and functional needs.
According to IEC 62305-3, an isolated external lightning protection system should be used when the flow of the lightning current into bond internal conductive parts may cause damage to the structure or its contents.
Isolated lightning protection is employed for the gas pressure control and measurement system to prevent uncontrolled flashovers (dangerous sparking) caused by a significant potential difference between the LPS and other grounded metal bodies.
Isolating lightning protection system elements to provide separation distance from grounded metal bodies or increasing the number of down conductors to shorten the required bonding distances are options that can be used to overcome difficult installation problems for certain structures.
For the gas pressure control and measurement system, high-voltage-resistant, insulated (HVI) conductors offer effective and aesthetically pleasing solutions to keep separation distance. The HVI conductors can be installed directly next to conductive structural parts or electric lines or pipes. HVI conductor is installed on the roof without a lightning protection system (Figure 3).
Meanwhile, HVI conductors are suitable for hazardous areas. The gas pressure control and measurement system are the downstream process of gas industry, some factors that can contribute to the risk of explosions in certain environments or situations including the presence of flammable or explosive gases, inadequate safety measures, and equipment malfunctions.
The lightning protection system for a flat-roofed and gable-roofed gas pressure control and measurement system is described in Figure 3.
The implementation of this system is a tall, isolated support mast through which the isolated down conductor is run. Isolated LPS is more flexible to unique architectural designs or structures where traditional down-conductors and bonding might be visually intrusive or impact the aesthetics of the building.
Figure 2 – Gable-roofed and flat-roofed gas pressure control and measurement system
The isolated down conductor provides the material and cross-sectional area equal to a conventional down conductor, but with a highly insulated covering. The advantage is to against side flashing and reduces the risks of partial lightning currents being carried by galvanic coupling.
Electrical insulation between the air-termination or the down-conductor and the structural metal parts, the metal installations and the internal systems can be achieved by providing a separation distance, between the parts.
When considering a lightning protection system, the calculation of separation distance is the most challenging problem to determine. Even sometimes, it is not easy to achieve the ideal separation distance as guidelines in the actual practice. Special problems may occur when plants and equipment are installed on roofs and are especially vulnerable to direct lightning strikes.
The ways to achieve the required separation distance could be:
Figure 3 – Separation distance concept
The separation distance calculation is also used within the IEC 62305 series standards to determine the need for equipotential bonding for non-isolated systems. Metallic items, such as wall vents or window frames, located beyond the separation distance from the closest down-conductor do not require bonding to the Lightning Protection System (LPS).
Items within the separation distance must be bonded to the LPS to ensure proper protection against lightning-induced effects. Internal metallic items, including electrical circuits and plumbing. These items must either be bonded to the LPS or located at a greater distance than the separation distance.
Equipped with an isolated lightning protection system, all metallic conductors or components are required to bond together to form equipotential bonding. The bonding should be established as close as possible to the entry point (from LPZ 0 to LPZ 1 or higher) to reduce high potential differences and dangerous sparks over in potentially explosive atmospheres and to prevent partial lightning currents from entering the structure.
Figure 4 – Lightning equipotential bonding for incoming lines
The power supply provides electric energy to various elements of the system, including sensors, controllers, actuators and communication devices. The safety of power source is the top priority of the well-operation of the system due to its sensitivity to lightning strikes and connectivity of complex systems.
Figure 5 – Surge protective devices installed in the gas pressure control and measurement systems
Voltage fluctuations can compromise the precision and dependability of measurement and control processes, leading to potential instances of unexpected downtime and equipment damage.
For the power side, Type 1 surge protective device is installed in the main distribution boards, as well as the supply of control and monitoring systems. Specific configurations should be consistent with right network and function request.
Figure 6 – The structure of gas pressure control and measurement
Control valves and pressure regulators are commonly employed to precisely regulate gas flow and maintain desired pressure levels in various applications.
The control valve is used for regulating gas flow by changing the size of the flow passage according to the controller and enabling control over the flow rate. A “controller” receives pressure signals and compares them with the desired flow. If the actual flow varies from the desired flow, the control valve adjusts to overcome the difference.
Pressure regulators operate by maintaining a consistent outlet pressure irrespective of fluctuations in the inlet pressure. The device typically consists of a diaphragm or a piston that responds to changes in pressure. When the outlet pressure deviates from the set point, the regulator modulates the flow area, allowing the required amount of fluid to pass through and stabilize the outlet pressure.
Today, electrical control often includes a smart communication signal that can be superimposed over the 4-20mA control signal, allowing the controller to monitor and signal valve health and position back to the controller.
To prevent the lightning implications for the signal and data transmission, surge protectors are usually installed for protecting 4-20mA signals, field bus systems and safe measuring circuits.
Buried pipelines and other underground utilities are exposed to corrosion which occurs when metals, such as steel, react with environmental factors like moisture and oxygen, forming rust or other corrosion products.
To prevent that costly equipment from being destroyed by corrosion, active and passive corrosion protection measures must be taken. The way to deal with the corrosion is impressed current cathodic protection.
Impressed Current Cathodic Protection (ICCP) employs an external power source, or rectifier, to generate a controlled direct current that flows from non-consumable anodes to the metal structure to be protected. By continuously adjusting the protective current based on measurements from a reference electrode, ICCP shifts the electrochemical potential of the metal structure, effectively preventing corrosion and ensuring long-term protection, particularly in large structures and high-resistance environments.
However, due to the large interception areas of the pipelines and their direct galvanic connection to the cathodic protection rectifier, lightning and surge protection measures are required to promise the well-operation of the cathodic protection rectifier.
Isolating spark gaps for use in hazardous areas are placed aboveground and underground to protect insulating joints. It is helpful to prevent the direct flow of electrical currents and mitigating galvanic connections.
Combined surge protective devices protect the anode and cathode side of cathodic protection systems. The surge protectors are installed to protect the rectifiers in the protective circuit and sensor circuit.
LSP’s reliable surge protection devices (SPDs) are designed to meet the protection needs of installations against lightning and surges. Contact our Experts!
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