Mobile Substations: A Comprehensive Guide

What Is Mobile Substation

Mobile substations are a type of power distribution system that can be transported and installed quickly and easily in different locations. They are used to provide temporary or emergency power supply to areas where the grid is unavailable or has been damaged, such as construction sites, disaster zones, remote areas, or events. They can also be used to test, maintain, or replace existing substations, or to integrate renewable energy sources into the grid.

Mobile substations consist of various components mounted on a trailer, a skid, or a container that can be moved by road, rail, sea, or air. The main components are:

mobile substation

A transformer that converts high voltage to low voltage or vice versa, depending on the application.
A cooling system that regulates the temperature of the transformer and prevents overheating.
A high-voltage switchgear controls and protects the high-voltage circuit and connects the mobile substation to the transmission line or the generator.
A low-voltage switchgear that controls and protects the low-voltage circuit and distributes power to the load or the grid.
A metering system that measures and records the electrical parameters of the power flow, such as voltage, current, power, frequency, etc.
A protection relaying system that detects and isolates faults and prevents damage to the equipment and personnel.
An AC and DC auxiliary power supply that provides power for the operation of the mobile substation and its accessories, such as lights, fans, pumps, etc.
A surge protection system that protects the mobile substation from lightning strikes and other voltage surges.
A cable connecting system that connects the mobile substation to the power source and the load using flexible cables and connectors.

Mobile substations are designed to meet the specific requirements of each customer and application. They can have different voltage levels, power ratings, configurations, features, and accessories. They are also designed to comply with state and federal road regulations, as well as the grid code and safety standards.

Benefits of Mobile Substations

Mobile substations offer several advantages over conventional substations, such as:

Mobility: Mobile substations can be transported and relocated easily and quickly to any place where they are needed. They do not require special permits or civil works for installation. They can also be rotated or repositioned to align with the existing power lines or equipment.
Flexibility: Mobile substations can be adapted to different voltage levels, power ratings, configurations, features, and accessories according to the customer’s needs and preferences. They can also provide multiple voltages for different loads or services simultaneously.
Reliability: Mobile substations are factory-tested and ready-to-connect units that ensure high-quality and high-performance power supply. They are equipped with state-of-the-art equipment and advanced control, protection, and communication systems that enable local and remote monitoring and control. They also have backup systems and redundancy features that enhance their availability and resilience.
Economy: Mobile substations are cost-effective solutions that save time and money for customers. They reduce capital expenditure (CAPEX) by avoiding permanent construction costs and land acquisition costs. They also reduce operational expenditure (OPEX) by minimizing maintenance costs and energy losses. They can also generate revenue by selling excess power to the grid or other customers.

Applications of Mobile Substations

Mobile substations can be used for various purposes in different sectors, such as:

Utility solutions: Mobile substations can provide power supply during emergencies or planned outages caused by natural disasters, accidents, maintenance, upgrades, or expansions of existing substations. They can also provide temporary power supply during peak demand periods or load-shedding events. They can also support grid stability and reliability by providing reactive power compensation, voltage regulation, frequency control, etc.
Renewables integration: Mobile substations can facilitate the integration of renewable energy sources into the grid by providing interconnection points for wind farms, solar plants, hydro plants, biomass plants, etc. They can also provide grid support services such as voltage regulation, frequency control, power quality improvement, etc.
Smart grid and urban substations: Mobile substations can support smart grid development by providing distributed generation, microgrid operation, demand response management, energy storage integration, etc. They can also provide compact and low-noise solutions for urban areas where space is limited and environmental concerns are high.
Datacenter electrification: Mobile substations can provide a reliable and secure power supply for data centers that require high availability.
Industrial power supply systems: Mobile substations can provide a reliable and secure power supply for industrial plants that require high power quality, availability, and efficiency. They can also provide backup power or load sharing for critical processes, such as oil and gas production, mining operations, chemical plants, etc. They can also support plant electrification projects, from feasibility studies to start-ups, by providing temporary power during construction or commissioning phases.
Shore-to-ship power: Mobile substations can provide green power supply for ships docked at ports or harbors, by connecting them to the local grid or renewable energy sources. This can reduce the emissions and noise from the ships’ engines and generators, and improve the air quality and environment for the port and nearby communities.

Types of Mobile Substations

Mobile substations can be classified into different types based on their design, size, and features. Some of the common types are:

Compact and modular mobile substations: These are mobile substations that have a compact and modular design, which allows easy mobility and fast relocation without the need for special transport permits. They are mounted on trailers or skids that can be towed by trucks or other vehicles. They can also be rotated or repositioned to align with the existing power lines or equipment. They are suitable for applications that require high flexibility and rapid deployments, such as emergency service, new service, or temporary service.
Skid-mounted substations: These are mobile substations that have a skid-mounted design, which allows fast and easy deployment, minimizing civil works as well as installation and commissioning efforts on site. They are mounted on skids that can be lifted by cranes or forklifts and placed on a flat surface. They are suitable for applications that require high reliability and low maintenance, such as industrial power supply systems, renewables integration, or smart grid and urban substations.
Containerized substations: These are mobile substations that have a containerized design, which provides shelter and protection for the components and accessories. They are mounted on containers that can be transported by road, rail, sea, or air. They are suitable for applications that require high durability and resilience in challenging environmental conditions, such as extreme temperatures, humidity, pollution, etc.
Rail-wagon substations: These are mobile substations that have a rail-wagon design, which allows them to be transported by railways. They are mounted on rail wagons that can be coupled with locomotives or other rail wagons. They are suitable for applications that require high mobility and accessibility in remote areas or difficult terrains.

Design Considerations of Mobile Substations

Mobile substations have to meet various design considerations to ensure their functionality, performance, safety, and environmental compatibility. Some of the main design considerations are:

Transformer: The transformer is the main component of a mobile substation that converts high voltage to low voltage or vice versa. The transformer has to be designed to optimize its size and weight for transportability and required electrical parameters. The transformer has to have a hybrid Nomex insulation system for higher ratings (>20 MVA) or a cellulose insulation system for lower ratings (<20 MVA). The transformer has to have a high impedance (up to 30%) to reduce its size and weight, but this may affect its voltage regulation and losses. The transformer has to have a low noise level (<65 dB) to comply with environmental standards. The transformer has to have multiple voltages (up to 5) to provide flexibility and versatility for different applications. The transformer has to have external de-energized switches for star-delta re-connection.
Cooling system: The cooling system is the component of a mobile substation that regulates the temperature of the transformer and prevents overheating. The cooling system has to be designed to dissipate the heat produced by the load losses and auxiliary cooling losses of the transformer. The cooling system has to have an aluminum cooling system for weight reduction. The cooling system has to have a forced-air cooling system (ONAF) or a forced-oil forced-air cooling system (OFAF) for higher ratings (>20 MVA) or a natural-air cooling system (ONAN) or a natural-oil natural-air cooling system (ONAN) for lower ratings (<20 MVA).
High voltage switchgear: The high voltage switchgear is the component of a mobile substation that controls and protects the high voltage circuit and connects the mobile substation to the transmission line or the generator. The high-voltage switchgear has to be designed to comply with the voltage class (up to 420 kV) and the interrupt.
Low voltage switchgear: The low voltage switchgear is the component of a mobile substation that controls and protects the low voltage circuit and distributes power to the load or the grid. The low-voltage switchgear has to be designed to comply with the voltage class (up to 1 kV) and the current rating (up to 2000 A) of the application. The low voltage switchgear has to have various components, such as low voltage switches, earth leakage circuit breakers, HRC fuses, electrical isolators, air circuit breakers (ACB), molded case circuit breakers (MCCB), and miniature circuit breakers (MCB). The low voltage switchgear has to have different mountings, such as chassis, DIN rail, panel, or 19″ rack mounted. The low-voltage switchgear has to have different enclosures, such as open-frame, enclosed, or IP-rated.
Metering system: The metering system is the component of a mobile substation that measures and records the electrical parameters of the power flow, such as voltage, current, power, frequency, etc. The metering system has to be designed to provide accurate and reliable data for monitoring and billing purposes. The metering system has to have different types of meters, such as analog meters, digital meters, smart meters, etc. The metering system has to have different communication modes, such as wired or wireless, local or remote, etc.
Protection relaying system: The protection relaying system is the component of a mobile substation that detects and isolates faults and prevents damage to the equipment and personnel. The protection relaying system has to be designed to provide fast and selective tripping of the faulty circuit or equipment. The protection relaying system has to have different types of relays, such as electromechanical relays, solid-state relays, microprocessor-based relays, etc. The protection relaying system has to have different protection functions, such as overcurrent protection, overvoltage protection, differential protection, distance protection, etc.
AC and DC auxiliary power supply: The AC and DC auxiliary power supply is the component of a mobile substation that provides power for the operation of the mobile substation and its accessories, such as lights, fans, pumps, etc. The AC and DC auxiliary power supply has to be designed to provide stable and sufficient power for the required load. The AC and DC auxiliary power supply has to have different sources, such as batteries, generators, converters, inverters, etc. The AC and DC auxiliary power supply has to have different voltages and frequencies, depending on the application.
Surge protection system: The surge protection system is the component of a mobile substation that protects the mobile substation from lightning strikes and other voltage surges. The surge protection system has to be designed to divert or limit the surge current and voltage to a safe level. The surge protection system has to have different types of devices, such as surge arresters, surge suppressors, surge filters, etc. The surge protection system has to have different locations, such as at the input or output terminals of the transformer or switchgear.
Cable connecting system: The cable connecting system is the component of a mobile substation that connects the mobile substation to the power source and the load using flexible cables and connectors. The cable connecting system has to be designed to provide easy and secure connection and disconnection of the cables. The cable connecting system has to have different types of cables, such as high-voltage cables, low-voltage cables, control cables, communication cables, etc. The cable connecting system has to have different types of connectors, such as plug-in connectors, clamp connectors, bolted connectors, etc.

Conclusion

Mobile substations consist of various components mounted on a trailer, a skid, or a container that can be moved by road, rail, sea, or air. The main components are a transformer, a cooling system, a high voltage switchgear, a low voltage switchgear, a metering system, a protection relaying system, an AC and DC auxiliary power supply, a surge protection system, and a cable connecting system.

Mobile substations offer several advantages over conventional substations, such as mobility, flexibility, reliability, and economy. They can be used for various purposes in different sectors, such as utility solutions, renewables integration, smart grid and urban substations, data center electrification, industrial power supply systems, shore-to-ship power, etc.

Mobile substations have to meet various design considerations to ensure their functionality, performance, safety, and environmental compatibility. Some of the main design considerations are transformer design, cooling system design,

high voltage switchgear design, low voltage switchgear design, metering system design, protection relaying system design, AC and DC auxiliary power supply design, surge protection system design, and cable connecting system design.

Mobile substations are a comprehensive and convenient solution for power distribution and control in various situations and locations. They are a valuable asset for utilities and industries that need to ensure high-quality and high-performance power supply for their customers and operations.

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