Sparks Electrical News October 2017

MOTOR CONTROL CENTRES AND MOTOR PROTECTION

14

FIRE RATED SWITCH DISCONNECTORS

V entilation and smoke extraction systems are designed to assist building evacuation and fire rescue operations in the case of a serious fire. They do this by reducing roof temperatures and delaying lateral fire expansion in order to allow more effective attempts at extinguishing the fire, as well as to allow maximum time for people to escape the vicinity of the emergency. This is important in applications such as car parks, tunnels, warehouses, various industrial build- ings, workshops as well as any densely crowded public buildings. As a part of this system, the fire ratings of switch disconnectors play a pivotal role because, if power to the ventilation system is cut owing to conditions of great heat, the systems will be unable to fulfil their function, resulting in a more deadly fire. Certificate standard EN-1201-3 applies to these smoke and heat control systems, detailing the required specifications for powered smoke and heat exhaust fans. In order to guarantee complete safety under emergency conditions, all

of the ventilation system components (including the switch disconnector) must comply with the standard requirements. The Gave engineering team has developed a fire rated switch disconnector specifically for these stringent conditions and it has passed all the required laboratory tests. Testing The development of products rated to provide fire resistance in order to guarantee electrical function- al integrity under extreme circumstances requires the employment of specialist laboratories capable of reproducing, in a controlled manner, similar con- ditions to those present when a fire occurs. The recognised AFITI laboratory has facilities that allow constant pressure and temperature monitoring in the testing area, ensuring that the temperature curve is replicated as required by the standard. Under these conditions, the Gave range of fire rated switch disconnectors has been tested, and has passed to the full extent required by the EN-1201-3 standard.

enclosure with the other at the bottom. Handle: A safety/emergency handle with a pad- lockable facility (up to four padlocks) in the discon- nect position in order to guarantee safety during maintenance operations. Additionally, the handle can be padlocked in all positions. Enclosure: The enclosure is prepared to have di- rect contact with any external sources of heat and acts as a firewall diminishing heat from affecting the switch.

ponent lubricity even in high temperatures. IP65 protection: Sealing is injected in the enclo- sure lid, ensuring an IP65 degree of protection ac- cording to EN 60529. Surface finish: The enclosure is coated with epoxy polyester powder grey colour (RAL 7032 alumini- um – 7035 steel) with a semi-gloss textured fin- ish made using electrostatic projection and a high temperature oven dry. This treatment provides ex- cellent protection against chemical agents. Cabling: Connection to the switch is made through two threaded metric entries placed on the top of

Advanced material High performance polymers mixed with additives allow the fire rated switch dis- connectors to resist erosion while offer- ing stable dimensions and keeping com-

Enquiries: www.acdc.co.za

DRY-TYPE TRANSFORMERS IDEAL FOR TREND TO MODULAR SUB-STATIONS “O wing to various benefits and the cost effectiveness of modular substations – which are fitted into he says. Including the dry-type transformer inside the modularised substation has the cost saving benefit of eliminating the requirement for civils infrastructure that is needed for oil- filled transformers.

purposes, mounted near the auto reclosers. An added benefit – especially for remote sites in rural Africa – is that a dry-type transformer is virtually maintenance free, significantly lowering its operating cost.

a marine container or a specially fabricated E- house – dry-type transformers are becoming more popular,” says David Claassen, managing director of Trafo Power Solutions. “The Trafo dry- type transformer is ideal for this application as it can be mounted inside the modular structure; this cannot be done with the traditional oil-filled transformer.” Claassen says that safety is the prime concern in the design and construction of substations. Owing to its design and the absence of oil as a coolant, the dry-type transformer is simple and safe, allowing extensive test work to be conducted with the modular unit prior to the full solution being sent to site. This in turn reduces the costs associated with site installation, assembly work and commissioning. “There is an historical misconception that dry-type transformers are too large to be housed within a container, but this is not so,”

Sourcing dry-type transformers from Hammond Power Solutions (HPS) gives Trafo Power Solutions the flexibility to meet specific customer requirements. “In a recent E-house application that Trafo Power Solutions provided for a mining project in Sierra Leone, a 2000 kVA dry-type transformer was specified as part of the mobile mining unit,” says Claassen. “We supplied four dry-type transformers in total: two 800 kVA units, one 1600 kVA unit and one 2000 kVA unit. The unusual voltage levels required – 13,2 kV/480 V at 60 Hz – demonstrated our ability to meet specific customer requirements.” Parts of the substation, such as potential transformers are specifically designed and manufactured for outdoor use with a rating 13,2 kV/110 Vac, 500 VA, and, for protection

Enquiries: www.trafo.co.za

MCC AND DISTRIBUTION BOARDS MANUFACTURING FACILITY

MOTOR CONTROL CENTRE (MCC) is a common term in the electrical industry and in most aspects of flow based manufacturing concerns. The MCCs come in various designs depending on the end user’s requirements, which vary from basic starters mounted on a common chassis plate in an enclosure to individually compartmentalised (bucket) starters with PLC and SCADA control, arc detection equipment and arc containment com- partments at the higher end of the range. Electrahertz in Silverton, Pretoria, designs and manufactures MCCs using only approved brands of motor control equipment that conform to the relevant electrical safety standards and individual customer specifications. The company’s technical team is available to assist clients from preliminary design through to the completed product.

Enquiries +27 (0)12 804 0120

SPARKS ELECTRICAL NEWS

OCTOBER 2017