You’ve likely seen the term “DEWA approval” more often than you’ve had cups of Arabic coffee, if you are thinking of an electrical substation or transformer installation in Dubai. And for good reason — not doing this is more than just a regulatory requirement, it’s a project killer that will cost you time, money, and a lot of awkward phone calls.
This guide explains all of the specifications that you need to know about when it comes to DEWA Approved Transformer foundation specifications in Dubai, UAE. This article is for developers, consultants, MEP engineers, contractors or anyone else embarking on their first substation project — before breaking ground.
What is DEWA and why is it controlling Transformer foundations?
Dubai Electricity and Water Authority (DEWA) is the only provider of basic utilities in Dubai. Any construction, renovation or fit-out project must have mandatory approvals and inspections by DEWA to ensure project safety, quality and fit-out into the city’s power and water networks.
Imagine that DEWA is the referee as well as the rules book. They don’t simply test the function of your transformer. Their testing measures are designed to determine where it is located, what supports it, how your civil work is designed, whether it meets their technical requirements or not and until a single cable is energised.
DEWA prescribes the sizes of electrical rooms, transformer specifications, metering arrangements, water supply connection sizing, power factor correction and cable sizing standards. Electrical and water designs for projects need to be approved by DEWA prior to construction.
In this context, what exactly is a Transformer Foundation?
A transformer foundation consists of the reinforced concrete unit on which the transformer unit rests in a transformer station or substation transformer room, which includes the plinth, base slab and associated civil works. It needs to accommodate the weight of the equipment, the expansion due to heat, the ability to retain oil, the routing of cables, and seismic or vibration loads.
This is not a civil works after thought in Dubai. It is a submission item of DEWA, and it will be reviewed in detail during the design approval.
The types of DEWA substations and their implications on the foundation
Different types of substations have different setups and the foundation requirements follow the substation type. DEWA Guidelines are applicable for the substations installed within the buildings on the ground level or basement level, either in one room or in split rooms (RMU room on one floor and transformer room on another floor). For substations outside buildings, either as regular, pocket or temporary substations, the requirements also apply.
There are civil works expectations for each type. The access and slab and drainage needs for an installation in a ground floor transformer room vary from a basement installation and an open air outdoor installation. There is no such thing as a one size fits all concrete specification that will be accepted by DEWA. They will not.
Here are the key Foundation specifications you should keep in mind:
Now, let’s get to the real stuff. These specifications are taken from DEWA’s published guidelines and regulations.
The level of transformer rooms on the floor of the building
The finished floor level (FFL) of the transformer room should be higher — between 0.075 metres and 0.15 metres — with respect to the ground level outside the transformer room. The cable trench/cable tray arrangement shall have a clear depth of at least 0.50 metres from FFL of the transformer room.
This isn’t some decorative floor level, it’s a functional one. It resists water from entering and provides a cable space that DEWA’s technical team can expect to find on your drawings.
Cable Trench Depth
Minimum depth of cable trench is 0.50 metres from the finished floor level as stated above. The size of this trench should clearly be shown on your drawings submitted and should fit the HV cable arrangement designed by DEWA. Don’t guess these numbers, they undergo a technical review!
Transformer Foundation Plinth
The plinth (foot) of the concrete transformer should be sufficiently strong to support the entire weight of the transformer, including the quantity of oil in the transformer. The plinth dimensions for 1000kVA and 1500kVA transformer, which are the most common transformer sizes utilized in Dubai commercial and residential constructions, are based on the transformer’s footprint dimensions provided by DEWA.
The owner is fully responsible for the transportation of transformers and other equipment from DEWA’s truck and placing it on the foundations in the substation. This requires that the foundation should be prepared, correct and completely cured prior to the delivery of DEWA equipment. Turn up with wet concrete and you’ve got a problem.
RMU Foundation Size
The size of the RMU foundation shall be 6.1 x 6.1 metres (37.21 sqm) while the FGRP Kiosk shall be supplied by DEWA. This is for 2 Nos. 11kV feeders.
The size (dimension) of the building room installation shall be approximately 29.16 sqm (5.4 x 5.4 metres RCC slab and Block work regular type RMU room). This is for 2 Nos. 11kV feeders.
These dimensions are not flexible. If you want to make the room slightly smaller to fit an architectural preference, don’t tell DEWA that you will do that. They will not.
The requirements for Concrete Attic Slabs in Wet Areas
This is one of the most neglected items in the construction of Dubai substations. If there is a wet area above a substation or RMU, a reinforced concrete attic slab must be installed above the entire substation or RMU. A clear space of 600mm should be provided between the attic slab and the floor slab above and a 1200 x 600 access aluminium louvred door should be provided to the void from the outside of the substation. There is also a requirement for waterproofing the attic slab and the floor slab above and the vertical side walls, and a 1.5″ diameter drain pipe protruding from the attic slab with a screed sloped towards the drain pipe.
It is not accepted to DEWA if there are wet areas above substations. Kitchens, baths or toilets above a substation with a wet area are not acceptable. This will be allowed only in the extremely rare circumstances where the situation is unavoidable and with the conditions as indicated in the relevant Annexure.
Ventilation Requirements for the Civil Design
The specification for foundations and civil works is not a stand-alone document. The structure for substation design is directly influenced by the ventilation system.
In accordance with DEWA drawing specification the total minimum grill area is 1000 kVA transformer (14.9 square metres) and 1500 kVA transformer (18.6 square metres). If more than two transformers are proposed, then calculations to show the adequacy of the substation interior ventilation to keep the ambient temperature at a maximum of 55 degrees Celsius for an ambient temperature outside the substation of 48 degrees Celsius must be submitted.
It is important to the design of the foundation and walls that louvre openings, their placement and incorporation into the structure be designed into the civil works from the beginning, rather than cut in after the walls are up.
Access and Door Specifications That Impact Civil Works
There is no way to separate the foundation design from the access design. DEWA is quite particular about this.
The height and width of the doors in the substations are the following: Clear height 2.75 metres, clear width 3.05 metres or a minimum of 2.44 metres in exceptional cases per DEWA door detail drawings. The substation should be directly on a DM road or sikka. If it is on a sikka, the sikka needs to be at least 3.05 metres wide if the substation is only 10 metres from the main road. Otherwise the minimum clear width is raised to 6.1 metres.
Basement transformer rooms in particular: The ramp to the transformer room in the basement should be at least 3.05 metres wide and the clear space between the DM road and basement transformer room should be at least 3.05 metres.
In UAE Projects with Basement Substations, these requirements for the ramping of the concrete transformer foundation should be included in your structural and civil drawings from the beginning.
Learn about the DEWA Approval Process: What happens to your civil design?
If you know what to expect, you’ll ensure you have the proper documents in place and won’t experience delays. The application for DEWA approval will start by submitting an application with detailed project plans and specifications. DEWA will review the submitted documents and may require the documents to be amended or additional information provided if necessary. Afterwards, a site visit is carried out to ensure the installation is in line with the plans submitted and meets safety standards. Upon successful completion of the inspection, DEWA provides an Approval Certificate.
The documents needed entail completed DEWA application forms, comprehensive architectural and electrical plans (including layouts and schematics), detailed material and equipment specifications, copies of all relevant trade licenses and certifications for contractors and engineers, compliance certificates demonstrating adherence to safety and quality standards, a detailed site plan, and previous inspection reports (if applicable).
In general, demonstrate the work. In detail. On suitably drawn sketches. Engineered by a qualified engineer.
The following are some of the common mistakes that slow down DEWA approval process
Common errors that lead to headaches on Dubai projects are more or less the same. No particular order:
Contractors begin excavation prior to design approval. The civil works are executed based on the contractor’s assumptions and not DEWA’s requirements. The drawings then are not congruent with the site. Trigger revisions and re-inspections, and schedule slippage.
Cable trench is too small. It can be only a few centimetres less than the minimum depth of 0.50 metres. DEWA will flag it.
It is not possible to pour the transformer plinth without provision for oil containment bunding. DEWA anticipates that the foundation will contain a containment area (bunded plinth), to capture the entire volume of transformer oil in the event of an oil leak. This is not only required by DEWA but also for civil defence.
The floor level elevation is not done properly. A very common mistake is not having the finished floor elevated 75 to 150 mm above external ground level; a step-up which is often resisted by architects for aesthetic reasons.
UAE Substation Civil Works Concrete Grades and Standards.Civil works of Substation in UAE with Concrete Grades and Standards
Substation projects in Dubai are built according to structural concrete standards in UAE, although DEWA does not give any particular requirements for the concrete mix design (only dimensions and layout). Civil works specifications used for the construction of substations include relevant standards, design criteria, construction processes and civil design, materials, construction methods and codes and regulations.
Generally, the concrete grade for concrete transformer foundations is around C30 or above, as the soil in Dubai and UAE is normally quite aggressive with high numbers of sulphates in it. The soil aggressiveness of the region requires that foundations are often designed to be protected from chemical attack over the design life of the structure by the specification of sulphate-resistant cement or blended cements.
The hot and arid environment also demands longer curing times, typically at least seven days for regular cement and up to fourteen days for hot conditions, before equipment loads are applied to the product, in order to obtain the design strength. These are not DEWA specific numbers, but are those which are common to civil engineering practice in the UAE climate.
Who can submit drawings for DEWA transformer foundation?
Only qualified professionals, like engineers and architects, can prepare and submit electrical and civil drawings to DEWA. Contractors need to have a valid trade licence and be registered with DEWA in order to be awarded DEWA certification. Qualified engineers and technicians with understanding of DEWA’s standards and regulations are vital for the contractor to use. Experience in installation of electrical and water supplies in accordance with DEWA’s requirements is also required.
DEWA periodically revises their technical standards and MEP consultants should check that they are designing in compliance with the latest edition of relevant regulations.
This is important. The 1997 Regulations for Electrical Installations have been replaced by the 2017 edition of DEWA’s Regulations for Electrical Installations. Your submission may return to you with comments because the consultant you are using is referring to old documents.
Key Takeaway for Engineers and Developers
DEWA’s transformer foundation specifications are detailed, non-negotiable and fully embedded into the civil and electrical design disciplines. Concrete transformer foundations in UAE projects cannot be considered as common civil works. They have particular dimensional requirements, structural obligations, containment considerations and access mandates that are best addressed at design, not construction time.
Use a DEWA registered consultant. Submit early. Submit complete drawings. Wait until you have the design approval before pouring concrete.
Then DEWA is actually very easy to deal with. They want the same as you: a secure, dependable power supply system that will continue to provide Dubai with power for decades. Paperwork is a part of the job.
