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Substations form powerful energy delivery hub.

As Qatar embarks on massive infrastructure development across the country, including extensions to the Hamad International Airport, seaport, metro, LRT, expressway, tunnels, stadiums, hospitals, schools, hotels and several other large mixed-use developments, demand for power has never been greater.

At the foundation of power generation and distribution are the substations, fueling infrastructure projects and coping with the ever-increasing domestic demand as Qatar's population swells.

Vasanth Kumar, CEO of Arabian MEP observes: "What we are now witnessing is large scale power transmission system expansion by the utility provider."

He explains that increased energy demand is driving expansion: "As part of the expansion program, hundreds of substations are presently being built across the state and, depending upon the location, both above and underground. In addition, several existing substations are being refurbished, upgraded and extended to suit the new requirements and growing demands of the country."

The type and capacity of these substations vary according to requirement and are built to various configurations, namely 33/11KV, 66/11KV, 132/11KV, 132/66/11KV, 220/66/11KV, 220/132/66/11KV and 400/200/66/11KV super-substations, Kumar informs.

As substations form the backbone of infrastructure projects, these mission-critical facilities have to be operational throughout the year on a 24/7 basis, coping with harsh desert conditions. "To keep a substation fully functional it is extremely important to have efficient and reliable MEP building services, with 100% standby systems equipped with auto-changeover controls for remote monitoring and control," he emphasises.

To achieve the required stringent design and performance criteria, MEP systems have to be of the highest quality and reliability for efficient operation and performance. Such high quality MEP installations can only be carried out by

highly professional and experienced MEP contractors.

In this niche market, Arabian MEP has clearly established itself as a market leader with an impeccable track record of successfully completing MEP services for hundreds of substations, having been involved in this highly specialised sector for almost two decades, ever since it was established in 1998, under the leadership of its chief executive officer, Kumar.

Arabian MEP carries out the complete scope of MEP building services, including heating, ventilation, air-conditioning system (HVAC), plumbing, drainage, electrical, small power distribution, fire alarm and firefighting systems.

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Kumar explains the intricacies of a 'typical substation building': "The building consists of a gas insulated switchgear (GIS) room, a switchgear room, a control and relay room, a LVAC and DC room, a battery room, a basement cable chamber, transformer yard, auxiliary transformer yard, a fire pump room, telecom room and ablutions etc," he outlines.

The building's HVAC component is considered to be the most important aspect of the MEP system as it is tasked with removing massive amounts of heat generated inside a substation, while keeping the building cool and safe at all times. "There is a need therefore, for custom-made, special purpose HVAC equipment. Only the highest quality HVAC equipment is used in all our substation projects," he adds.

The air distribution ductwork for HVAC and ventilation systems are installed to DW/144 standards and tested for air-leakage to DW/143 standards, recognised throughout the UK as the standard specification for ductwork manufacture and installation. The complete ductwork is made of high quality galvanized steel sheet.

The ventilation system ventilates excessive heat build-up mechanically "and also over-pressurises the area to avoid ingress of dust inside the building", Kumar explains.

"Battery rooms are provided with 100% exhaust duty/standby systems with explosion-proof bifurcated two-speed fans." Since charging of batteries results in the release of corrosive gases, battery room air is completely exhausted and never recycled.

The utility provider has laid out specifications, namely, under battery boost charge conditions, the design calls for a room ventilation system that gives a maximum residual hydrogen concentration in the room air of 1% by volume.

"Basement cable chambers are ventilated using several fresh air fans, electrically interlocked to differential temperature thermostats," he continues. These fans will operate only if the cable chamber's heat buildup exceeds 45?C and if the outside temperate is lower than inside. "If the ambient air temperature is high, then only the over-pressure supply fans will run, while the fresh air fans will be in off-mode," Kumar adds.

To avoid dust ingress into the substations, all HVAC and ventilation equipment is provided with a multi-stage air filtration system, using sand-trap louvers, washable pre-filter and high efficiency after filter to ASHRAE 52-76 standards.

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Smoke extraction systems are provided as per NFPA 72 (a US standard published by the National Fire Protection Association) for the basement cable chamber, GIS and switchgear rooms, along with the ventilation system. "In the event of a fire signal from the fire alarm control panel (FCAP), central air conditioning units will switch-off and all fire doors will close. Smoke extractor fans comply with NFPA 90A and 92A standards and the bifurcated fans are suitable for operation up to 400?C, for smoke extraction."

In addition to the HVAC and ventilation system, many other systems are provided under MEP building services, such as plumbing and drainage systems, internal lighting, external lighting, power cabling, earthing and bonding connections, the fire alarm and firefighting systems.

Whilst plumbing and drainage system requirements in substation projects are minimal, firefighting and fire protection systems are critical. Fire detection systems include fire alarm systems, FM 200 systems, deluge systems and hydrant systems.

Deluge and hydrant systems operate simultaneously in the event of activation. Fire hydrants with ring mains are provided all around the perimeter of the substation buildings. For the control and relay, LVAC and DC rooms, a waterless FM 200 fire suppression system - a synthetic/chemical fire suppression gas which extinguishes fire by removing oxygen - is dispensed via rechargeable cylinders. However, for the GIS room, control and relay room and other critical areas, fire alarm systems are used in addition to standard portable fire extinguishers.

"Passive fire protection is also required for substations. It includes fire coating for cables, cable tray, fire sealants for all wall openings and sleeves in fire zone walls , roof and floor slabs."

Building electrical systems include medium and low voltage power distribution to various MEP equipment, switches, sockets, lighting, earthing and control systems. "Lighting systems use high-pressure sodium luminaries for flood lighting, low pressure sodium luminaries for street lighting and security lighting and fluorescent light fittings for inside the building," Kumar expands.

In conclusion, Kumar says that the main challenges in substation projects are "finding and retaining highly skilled and experienced technicians to carry out installation to the highest quality.

"Also, various logistical bottlenecks associated with executing large numbers of substations projects simultaneously, at different remote locations scattered throughout the country, is a challenge".

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Publication:Construction Week
Date:Dec 2, 2015
Words:1130
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