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  • Nadirsha Shahabudeen

Advantages of Modular Electrical Substation

Updated: Feb 10

There is an increasing demand by operators in the Oil & Gas sector for modular units to create unique solutions that can be completely customized and which are ready for use when transported to the final operating site ("plug and play" solutions). Complete electrical substations ready to be transported and put into service at the final installation site have been constructed and tested in accordance with Client specifications, ambient conditions and limits on transport dimensions. The distinguishing feature of these substations is their modular construction. Every substation is subdivided into two or more modular structures specially developed and produced so that they can be disconnected and transported on barges or lorries 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. Consequently the time and costs for modular substations are much

lower and they operate reliably since they have already been tested.

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.

Ambient conditions are severe, therefore the substations are closed structures with outside

connections using cables. All the rooms of the substations are equipped with HVAC system.

The modules supplied were metal structures, suitably insulated and fire resistant, containing mechanical and electrical equipment, instruments, air ducts, cable ducts, lifting equipment necessary for maintenance, all connected to form the main and auxiliary systems of the

substation.

The individual equipment items were manufactured in the factories of the supplier, transported to the fabrication yard, installed in the modules that form the entire electrical substation and connected to form part of the relative main or auxiliary system. The systems were tested at the fabrication yard. The modules were then disconnected, prepared for transportation with suitable preservation, loaded onto a barge and transported to the final installation site.

The modules were then reassembled and connected to form the entire substation. All the systems were tested again and the substation was handed over to the final Client.


Advantages of Modularisation

The advantages of modularisation of electrical substations were:

  • Reduction of man-hours on site

An important contribution to the reduction of time and costs was the reduction of man-hours at the installation site. The substations arrived on site which had already been prepared with concrete piles on which the modules were positioned. Installation took place following the procedures agreed with the Client a few months before the modules were shipped. After the installation and reassembly of all the modules the cables were reconnected between adjacent modules and the air ducts were joined. 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.

Before reconnections, 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 surprise or problem because this procedure was already tested previously. The air ducts were also connected without any surprise as this involved bolting together two flanges of the air ducts, which were already face to face, and replacing any insulation. All the work done by the labour force on site was therefore reduced considerably compared to the time necessary for complete or partial installation locally.

  • 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.


  • Reduction of the risk of falls on site

Reduction of the risk of falls concerns both the equipment and the personnel working on site. Since the equipment is already installed and anchored there is no risk of their falls. With regards to people, the risk of falling is reduced because the job of reconnecting cables for example is done mainly in junction boxes and panels that do not require ladders or mobile scaffolding to be reached.

  • Greater overall productivity

With installation in the fabrication yard a higher productivity is obtained compared to installation in the final installation yard. This is because the various facilities and materials for the construction of modules are easiliy accessible in the fabrication yard. Productivity is without doubt lower if installation takes place in a location not specialised in the production of modular substations

  • Reduction of site congestion

With the modular substation system the equipment arrives at the final yard already installed, so no plant is required for lifting, inserting and anchoring the equipment. The construction of storages for installation material is no longer necessary; the loose material is already supplied in containers accessible inside; furthermore it is not necessary to build offices in the installation site. For these reasons the Final installation yard occupied a smaller less congested area than a site in which the entire electrical substation is manufactured.

  • Reduction of site security problems

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. Material handling outside the substation was reduced considerably because the material is already installed and therefore requiring less security checks.

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

Before the installation in the modules, all the equipment was checked by QA/QC 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.


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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