The construction of a containerised switchroom involves more than simply installing the electrical equipment inside a shipping container. There are many considerations that need to be made in order to design a switch room safely, efficiently, and according to Australian standards. A good design process at the outset means that installation will be quicker and commissioning easier.
Why is thermal management critical?
Heat is one of the most serious problems associated with containerized switch rooms. Unlike the conventional switch rooms constructed using concrete or masonry, the containers have enclosed spaces. The electrical equipment used in the switch room, such as switches, transformers, and motors, produce heat when running. Failure to manage the heat produced will lead to excessive increase in temperature inside the enclosure.
Active cooling is generally necessary in most systems. The process includes the use of air conditioners, which may be industrial grade, depending on the total heat load within the enclosure. The heat load is estimated based on losses in the system, surrounding temperature, solar gain, and diversity factor. Some cooling systems also include ventilation, where the design may have filtration air inlets and outlets. Ventilation alone is not adequate in cases with dense electrical systems.
Redundancy is another important consideration. For critical applications, an N+1 cooling configuration ensures that if one unit fails, the system continues to operate safely.
How is cable routing and segregation managed?
Containerised switchroom cable management requires efficiency and compliance. Space limitations necessitate proper cable routing that is to be considered during the design stage of the project. Cables can be routed using cable trays and conduits which are usually attached to the ceiling or walls to save space. Segregation is essential. Control and power cables must be segregated to avoid interference from one another. Likewise, different voltage levels must be separated based on AS/NZS requirements. Proper entry point consideration is crucial. Usually, bottom entry is done via a cable trench but sometimes it is made via the sides. Proper sealing is required to ensure that the ingress protection rating of the container remains intact. Efficient cable management does not only ensure safety but also makes future installation and maintenance tasks easier.
What IP rating is required?
IP rating is an important factor in the design process, more so if the switchroom is to be located outside. A containerised switch room will likely have to be used in an extreme environment such as in mining areas, construction zones, and even in coastal areas. This makes environmental protection an important concern in such designs. The type of IP rating needed will depend on the application. In some designs, a very high degree of sealing is sought to protect the equipment from environmental intrusion. This requires careful design for doors, cable entry points, and ventilation points among other features. In some designs, there may be total sealing of the switchroom with air conditioning providing ventilation instead of natural airflow through the switchroom. This protects the switchroom from environmental hazards but leaves it dependent on mechanical systems. Other considerations include protection against corrosion.
How is structural design handled?
Even though containerized switchrooms use standard shipping containers, structural changes are usually necessary. The cutouts for doorways, cable access, and ventilation may compromise the integrity of the container unless appropriate reinforcements are applied. The engineers have to make sure that the structure will maintain its stability during handling, transport, and erection. Handling points are critical because the prefabricated units are usually transported as-is; thus, they must be able to sustain the forces exerted during craning and transport. Normally, special lifting points and foundation structures are developed. Weight is an issue. There may be several pieces of heavy equipment inside the enclosure, such as transformers or switchboards. Reinforcements are required to make sure that the load will not cause any distortions of the floor. Sometimes, additional supports called skids may be attached.
What safety systems need to be included?
Safety is the primary concern in the design of any type of switchroom, even when containerised. Another critical consideration is arc fault containment. Switchgear should be selected and installed to reduce the risk of arc fault occurrences; in certain instances, it may be advisable to specify arc-resistant equipment. A further important factor to consider is fire protection. Depending on the nature of the project, this can take the form of fire-rated walls, fire detection equipment, and even fire-suppression systems using gases. Emergency evacuation is also a very important issue. Despite the confined space in which the switchgear will be located, there should always be an appropriate means of safe exit from the container. Emergency lighting and signage are additional safety factors. These can be relatively minor elements, yet they play an important role during normal operations.
How do you ensure compliance with Australian standards?
Compliance is not an option but a necessity when designing. The containerised switchroom design must comply with AS/NZS 3000 (Wiring Rules) and AS/NZS 61439 switchgear assembly designs. Standards impact aspects such as cable separation and clearance, right through protection and installation considerations. On top of that, there may be site-specific standards that must be met – especially in cases where a utility company, mining company or large infrastructure company may require this. Factory Acceptance Testing (FAT) is usually done prior to delivery on-site to make sure that the system operates as expected and does not run into problems upon commissioning. Planning for compliance up-front avoids costly changes and unnecessary delays at inspection time.
Why does layout planning matter so much?
Layout is where all the pieces fit together. Proper design layout would guarantee accessibility, safety during operations, and ease of maintenance of the equipment. Switchboard clearances would meet all required standards, while adequate room would be available for cable termination and future extensions. Minor changes in layout would make a huge difference. This is because cable entries and switchboard locations coincide. Moreover, proper layout takes into account the ergonomic aspects. This means that technicians will be able to test and maintain equipment safely.