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Advantages of Modular Electrical Substation

Updated: Aug 24, 2021

In oil and gas industry, the demand of modular units are increasing as it can be a unique solution for customization. A modular substation solution is traditionally an electrical power distribution substation or any other grouping of electrical equipment that is assembled on a self-supporting structural base, integrated and tested in a factory environment to enable energizing upon delivery. Modular substations offer many advantages to conventional substations including saving space and installation time while enhancing safety and aesthetics. After completing the construction and testing in accordance with client specifications, ambient conditions and limits on transport dimensions, it can be readily used at the final installation site. Its modular construction style can be utilized as plug and play solution. Every substation is subdivided into two or more modular structures specially developed and produced so that they can be disconnected and transported to the final installation site where they are reconnected and ready for use without the need for other systems. With this type of supply the local construction of buildings for substations and successive installation of panels and internal systems is no longer necessary. As it is tested before installation, the time and costs for modular substations are much lower and they operate reliably.

The electrical substation is a single structure which is installed in a predefined site in an installation for the distribution of electricity to other substations or final users. The electrical panels in a substation are the hub of the electrical power network. Switches are opened and closed locally or from outside the substation which must therefore have a secure communication system.

Due to severe ambient conditions, the substations are closed structures with outside connections using cables. All the rooms of the substations are equipped with HVAC system. The metallic structure of modules are insulated and fire resistant. It contains mechanical and electrical equipment, instruments, air ducts, cable ducts, lifting equipment necessary for maintenance. These all are connected to form the main and auxiliary systems of the substation.

Each equipment in the substation are manufactured by the supplier and installed to the module at the fabrication yard. Testing of the electrical substations after connecting modules are done at fabrication yard itself. The modules were then disconnected and transported with suitable measures and preservations to the final installation site. At the site, these modules are connected to form the entire substation and tested again. Finally, the substation was handed over to the final client.

Advantages of Modular Substations

The advantages of modularisation of electrical substations were:

  • Land acquisition and accessibility

When replacing unit substations where land is costly, such as urban areas, the site must have room for expansion for load growth or planned transmission additions. For voltage conversion, sufficient land area is required for installation of equipment with necessary clearances for electrical safety, which can be difficult in locations with tree line or building proximity. In addition, adequate space must be available for the accessibility to maintain or transport large apparatus such as transformers.

  • Minimum man-hours on site

Substations are constructed with concrete piles in which modules are positioned. After shipping the installation site, these modules are reconnected and installed as per the procedures agreed with the Client a few months before the modules were shipped. Then the cables of adjacent modules were connected and airducts were joints. Every cable to be reconnected had already been prepared before transport, placed in a wooden crate and with the ends wrapped in a sack and already prepared for reconnection by numbering each wire and attaching a cable-tag to the sheath of the cable. Before reconnecting the cables, they were first laid in the cable tray which was a natural continuation of the tray in the adjacent module. Also all cables wires shall be checked for continuity and insulation to ground following the same procedure and signing a test report. The wires of the cable were reconnected in the same terminal blocks from which they had been disconnected and therefore without any confusion. Similarly airducts are connected bolting together two flanges of the air ducts, which were already face to face, and replacing any insulation. In this way man hours on site can be considerably reduced as compared to local installation.

  • Reduction of peak labour force requirements

During the installation of units in the rooms of the substation there are specific periods of time when the size of labour force performing installation work peaks. In fact while the HVAC units are being installed it is possible to install the panels in other modules at the same time, or for example the lamps can be installed at the same time as the F&G sensors.

This peak will not occur in the final installation yard because with the modular substations system the work consists only of connecting cables and air ducts between adjacent modules and not installing all the equipment in the substation.

  • Increased productivity

Various facilities and materials for the construction of modules are easiliy accessible in the fabrication yard than installation site and this helps in higher productivity.

  • Reduced risk of falls on site

With modular substation units, the risk of falls to both equipment and personnel is reduced since the equipments are already installed and anchored. Risk of fall of peoples are reduced since they have only work of reconnecting cables at installation site and it does not require any ladders or mobile scaffolding.

  • Reduction of site congestion

The final installation yard occupied a smaller less congested area than a site in which the entire electrical substation is manufactured since all the equipments are pre installed and no requirement for lifting, inserting and anchoring of equipments arise. Furthermore, it is not necessary to build offices in the installation site.

  • Reduction of site security problems

Considerably very low security checks are required as the material handling outside the substation was reduced because the material is already installed. Site security was limited to checking the closure of the modules and containers of material supplied loose. Storage facilities and containers outside the substation were not needed to house installation material supplied in standard lengths which have to be cut to measure for installation, such as Unistrut, cable trays, cable spools, tubing, fittings etc.

  • Possibility of conducting QA / QC controls and acceptance of operations on completed parts of the module before mechanical completion

All the equipment was checked by QA/QC before the installation in the modules and installed only after passing the FAT (Factory Acceptance Test). This test for complex equipment such as the HVAC units, panels and PLC required several days at the manufacturer’s premises for testing. After passing the FAT procedure the equipment was ready to be installed in the modules without any problem.

  • Minimising risks that could affect the construction plans, costs and operations of the systems

The equipment control and acceptance operations were carried out before its installation in the modules, therefore the risk of having to remove faulty equipment was minimised.

  • Possibility of choosing the final installation site of the substation at a later time

The position where the substation is to be installed is normally decided at the beginning of the project, however, with modular substations this decision can be taken or changed if necessary even after the substation has already been assembled.

Universal Engineering services(UES) can do Engineering of modular substations. Our Structural Engineers can design offshore container modules, skids packages, cargo baskets, steel structural frames, lifting analysis of offshore structures,etc to clients all over the middle east countries like UAE, Oman, Qatar, Saudi and Kuwait for petrochemical, power and oil and gas industry. We also offers reliable offshore and onshore design of structures as per D.N.V. 2.7.1 and we are diversified into Structural Design, Engineering & Analysis for the Industrial, Offshore and Oil & Gas industry.

**The content of this article is taken from web open source. The blogs are intended only to give technical knowledge to young engineers. Any engineering calculators, technical equations and write ups are only for reference and educational purpose.

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