Modular Electrical Rooms: Engineering Criteria for Critical Oil & Gas Applications

An E-House concentrates electrical distribution, protection, automation, and auxiliary services into an integrated unit. Its true value lies not only in modularity but in reducing interfaces, controlling manufacturing quality, and shifting as many tasks as possible from the field to a testing environment.

A modular electrical room —also known as an E-House— should not be understood as a simple container equipped with switchboards. It is a functional unit designed to house, interconnect, and protect power, control, and auxiliary services systems. Its scope can range from a low-voltage room to a transportable substation with medium-voltage distribution, motor control centers, automation, and uninterruptible power supply. The architecture is integrated and tested at the factory before transport, reducing connections and field interventions. This definition aligns with that used by Schneider Electric for its E-House solutions, which encompasses engineering, integration, testing, validation, and delivery of the complete substation.

The design must begin with a clearly approved engineering basis: load list, voltage levels, grounding schemes, maximum and minimum short-circuit currents, operating philosophy, criticality of consumers, area classification, environmental conditions, and availability criteria. Based on these data, load flow, motor starting, short-circuit, protection coordination and selectivity, voltage stability, harmonics, reactive compensation, grounding, and arc flash risk studies are conducted. A common mistake is to select the container first and then attempt to accommodate the equipment; the correct practice is to define the electrical architecture, operating and maintenance needs, and only then size the enclosure.

The equipment may include medium-voltage switchgear, low-voltage main and distribution switchboards, motor control centers, variable speed drives, soft starters, transformers, capacitor banks, harmonic filters, direct current systems, chargers, batteries, and UPS. Protection relays, network analyzers, meters, auxiliary service panels, and transfer systems are also incorporated. Transformers can be installed inside or outside the room depending on their power, technology, thermal dissipation, fire risk, and transport strategy. Each assembly must be verified according to its corresponding standard: for example, IEC 61439-1 and IEC 61439-2 for low-voltage assemblies and IEC 62271-200 for medium-voltage metal-enclosed switchgear. The compliance of a switchboard does not automatically certify the entire room.

In a modern installation, the room also functions as an automation node. It can house PLCs, RTUs, a power management system, SCADA interfaces, industrial switches, protocol gateways, event recorders, and process control panels. Engineering must physically separate power, control, instrumentation, and communications; define shield handling; avoid ground loops; and use fiber optics when distance, electromagnetic immunity, or galvanic isolation justifies it. Critical trips and safety functions should not rely exclusively on a communication network. Furthermore, the architecture must address segmentation, access control, time synchronization, configuration backups, and a remote connection policy compatible with the plant's cybersecurity.

The container format is used because it offers a transportable, repeatable geometry compatible with industrialized manufacturing. However, an E-House should not be resolved through the improvised modification of a shipping container. Openings for doors, ventilation, and cables alter the structural load-bearing paths; additionally, switchboards, transformers, and cable trays introduce concentrated loads. Therefore, the total weight, center of gravity position, floor loads, resistance during lifting and transport, anchoring points, and expected accelerations must be verified. If the module must be handled as a container under ISO or CSC requirements, its suitability must be verified for the final modified configuration, not for the original structure.

In Oil & Gas, the location of the room is just as important as its equipment. Whenever possible, the goal is to install it outside the classified area and close to the load center, reducing cable runs without unnecessarily exposing it to a hazardous atmosphere. When it must be located within or adjacent to a classified zone, the design starts with the area classification document: zone or division, gas group, temperature class, and extent of the hazardous envelope. A pressurized room requires a comprehensive system compliant with the applicable criteria of the IEC 60079 series: safe air supply, initial purging, pressure control, door monitoring, alarms, and automatic actions upon loss of pressure. Maintaining positive pressure, on its own, does not make the interior a safe space.

Protection against arc flash requires studying the incident energy based on the fault current and the actual clearing time. The latter includes detection, processing, trip command, and breaker opening; it should not be confused with the response time of a sensor. Selectivity can be supplemented by differential protection, zone-selective interlocking, or optical arc detection when the analysis justifies it. In medium voltage, an internal arc classification of the switchgear also does not guarantee room safety if the gas exhaust is not coordinated with the ducts, raised floor, and enclosure. The Schneider Electric guide on arc flash protection also highlights the need to pre-power auxiliary protection circuits and record events with a consistent timestamp.

Safety is completed by an equipotential network linking the structure, skid, doors, panels, trays, and accessible conductive parts; normal and emergency lighting; signage; unobstructed exits; panic hardware where applicable; smoke, temperature, and gas detection; and an extinguishing system compatible with the equipment and the presence of personnel. The HVAC must result from a thermal balance that includes losses from switchboards, transformers, and drives, solar radiation, outdoor temperature, infiltration, and filter degradation. In critical services, cooling redundancy is analyzed. Batteries require a specific study of ventilation, temperature, and gases according to their chemistry; installing them inside the room without evaluating these factors can introduce a risk that did not exist in the original electrical design.

Factory acceptance must be planned from the beginning through a traceable FAT protocol. The usual scope includes dimensional and mechanical inspection, torque records, protective conductor continuity, insulation resistance, point-to-point verification, interlocking tests, breaker operation, secondary injection of protections, settings verification, transfer sequences, communications, alarms, HVAC, fire detection, and cause-and-effect logic. The integrated test allows for the detection of incompatibilities that do not appear when testing each switchboard separately. Delivery should include as-built drawings, single-line diagrams, cable and signal lists, configuration files, electrical studies, certificates, protocols, and a punch list. In the field, the SAT confirms grounding, external cabling, phasing, signals, protections, and system response in its final location.

In brownfield projects, modularity allows for the manufacturing and testing of the new room while the existing facility continues to operate. Field intervention is concentrated on foundations, grounding grid, duct banks, auxiliary services, positioning, and final connections. Migration can be split by feeders, busbars, or signal packages, using temporary links only when they have been calculated, protected, and approved. It is not technically responsible to promise an implementation with zero downtime: the final cutover may require a scheduled window, isolation, lockout, and verification of dead circuits. What can be achieved is a substantial reduction of work and uncertainty during that window. Due to its capability to design and integrate switchboards and rooms according to specific requirements, Equipel is positioned as a reference in this type of solutions for industrial and Oil & Gas projects.