Sparks Electrical News July 2019

CABLES AND CABLE ACCESSORIES

8

WIRED ANDWIRELESS SOLUTIONS FOR SMART HOMES

wiring, as it uses the existing electrical infrastructure. Legrand states that while there are switches that will work without a neutral, depending on the application, there are also switches that do require a neutral. This means, if there isn’t one in the box, a neutral will have to be added to the installation. To upgrade or extend an installation, ‘Arteor with Netatmo’ wireless connected controls can be paired with wired devices. Selected scenarios can be modified and upgraded at any time, according to chang- ing needs. By using wireless switches, users always have their controls exactly where they want them. If furniture needs to be re-arranged or small children need to be able to reach a switch, the wireless switches can be repo- sitioned easily at any time. All functions can also be used in the traditional way via switches on the wall. The Home + Control app is used by the installer for configuration of the entire system, based on individual requirements. Configuration is based on a set of simple steps, where each room and all functions are individually organised. This intuitive app allows the user to control all functions, while at home or remotely. ‘Arteor with Netatmo’ creates central con- trol of lights, curtains and roller blinds and also manages scenarios in and away from the home. A single press of a button turns off the lights and closes curtains and shutters, as the user leaves home. A scenario can be set to switch off lights and socket outlets when users go to bed and in the morning they can enjoy the ‘wake up’ scenario, where a soft light comes on and curtains automatically open. It is also possible to simulate presence when no one is at home.

LEGRAND has expanded the Arteor range of wiring devices with the addition of ‘Arteor with Netatmo’, to make connected homes effortless. With this system, automation is more efficient and easier for designers, in- stallers and users in homes, hotels and the professional environment. ‘Arteor with Netatmo’ is a collection of connected switches and socket outlets, designed to add comfort, simplicity, con- venience and safety to daily life. Further to this are energy savings, peace of mind and flexibility. It is a radio technology and Wi-Fi enabled solution which simplifies usage, by making complex functions in home auto- mation easy to use. The home automation system offers end-users and electricians the freedom to create a connected, customised home by combining controls and features to man- age scenarios, create centralised functions and allow remote-control of individual functions – to suit personal requirements. Using a few simple components, many useful functions can be implemented in the installation. The Gateway kit – consisting of the gateway and wireless master switch – is used to create the ZigBee radio network and Wi-Fi connection of the installation. This solution ensures easy and conveni- ent control of functions in the home, us- ing a smartphone or tablet via the Home + Control App. Users can control lighting, roller blinds and electrical appliances, from wherever they are. And by using voice con- trol with a voice assistant, the installation can be managed without having to lift a finger. As an example, lighting in the home can be switched on or off, with one word. This system is easily integrated into ex- isting installations, requiring no additional

Legrand’s Arteor range – with new functions, en- hanced operating concepts and updated designs – pro- vides flexible solutions to constantly changing trends in the modern world. Through ‘Arteor with Netatmo’, which is easy to install, configure and use, Legrand is committed to making smart homes a reality for South African home-owners and the professional environment.

In the event of a power failure, fire alarm signal or safety siren while users are away, the app gives an auto- matic alert so appropriate action can be taken. Greater energy efficiency is achieved by checking real-time en- ergy consumption and doing in-depth analyses. These functions are also controlled via voice com- mands, used in combination with Google Assistant, Amazon Alexa or Apple Siri. ‘Arteor with Netatmo’ can be integrated with other brands and platforms through the inter-operability programe ‘Works with Legrand’.

Enquiries: +27 (0)11 444 7971

SILICONE ELASTOMERS AND AUXILIARYMATERIALS FOR CABLE ACCESSORIES

T he first silicone cable accessories were developed in the late 1960s and appeared together with in- troduction of extruded XLPE cables. The main fo- cus at the time was on a design with field-grading and insulating parts in a prefabricated body that allowed easy assembly and helped avoid errors in mounting. The first terminations and joints were still rather massive since the excellent electrical behaviour of silicone was not yet fully understood. Still, test results and initial service experience compared to the then state-of-the-art polyurethane and other solutions proved encouraging. The basic concept of a prefabricated silicone elastomer body remained and has since been further refined to the point that today users benefit from a broad portfolio of different silicone elasto- mers and auxiliary materials for both medium and high voltage cable accessories. Types and tasks for cable accessories The majority of all power cables are extruded XLPE insu- lated cables. These consist of a conductor, an inner con- ductive layer, the main insulation layer, an outer conductive layer, an outer conductor and an outer insulation/jacket. At places where two cable sections are connected, theses layers have to be re-built in the same way by applying a cable joint or splice. At the cable termination, the layers have to be treated such that they can withstand all result- ing electrical and environmental stresses. This is done by mounting a cable termination. Besides these main cable accessories, there are sev- eral combinations and modifications such as connec- tors and pluggable systems. The main resulting tasks include: • Electrical connection. • Field grading. • Sealing. • Withstanding weathering. Medium voltage plug-in systems are a good example for the first task. A rather soft silicone elastomer cone is pressed by a metallic spring into the male resin part and provides for a perfect electrically insulated interface. Apart from the low hardness of the silicone elastomer, its high gas permeability is another advantage since any gas trapped in the interface diffuses out shortly after mount- ing. As mentioned, one of the main goals during early development of silicone accessories was to pre-fabricate a ready-to-use part consisting of all insulating and field grading parts. Other solutions applying silicone elasto- mers with high permittivity are also possible. Silicone elastomers, especially liquid silicone elastomers, have been found to be an ideal material for all necessary step- moulding processes since they are low in viscosity and allow for good flow into the mould and towards the triple- points located between mould and pre-inserted conduc- tive parts. Proper sealing is another important task of a silicone cable accessory. The outstanding mechanical proper- ties of soft silicone elastomers facilitate slip-on mount- ing while the perfect and lasting ability to shrink to orig- inal dimensions, even after long expansion time, allows for cold-shrink technology. Both mounting technologies also benefit from the high gas permeability of silicones.

Proper mounting and sealing are supported as well by special silicone pastes available for transmission and distribution applications. Pastes can be modified so as to allow easy dismantling even after long time or of a migrating type that disappears from the interface in a short time. Most important in the case of outdoor ap- plications is the general capability of silicone elasto- mers to withstand weathering. Nevertheless, silicones for these applications are specially modified to ensure lasting stability against weathering stresses as well as the possibility of resulting electrical and erosive stress- es during service. Experience and formulating know- how allow for silicones that can withstand the rather short-term stresses encountered during type tests (e.g. salt fog) as well as long-term stresses during service. It is important to consider pollution affecting outdoor cable accessories. In this regard, the ability of suitable silicone elastomers not only to remain hydrophobic but also to show good hydrophobicity transfer to the pollu- tion layer is important. Types of silicone materials The principal materials used in silicone cable accessories are silicone elastomers. The early years of their produc- tion were characterised by two component, low viscosity elastomers designed to cure at low temperatures and parts were mainly cast or vacuum cast. Production output at the time was low compared to the sophisticated tech- nologies available today. Nevertheless, these materials are still available, e.g. for prototyping or for manufacturing of small series of products. State-of-the-art materials for ca- ble accessories are either low hardness, high-consistency silicone rubber (HCR), available as peroxide curing types or as one or two component addition curing materials for fast and very fast injection moulding applications or ex- trusion respectively. Press moulding is not recommended since state-of-the-art accessories require a high accuracy of moulds. The other option is using liquid silicone rubbers (LSR) that usually come as 1 to 1 two component systems. These materials are now used to manufacture all types of cable accessories. Silicone pastes are also available in a variety of modi- fications. Extremely soft silicone elastomers, i.e. silicone gels, first saw application in the low voltage area below 1000 V. So-called ‘gel-joints’ allowed proper electrical installation and sealing just by closing shell-like parts pre-filled with soft silicone gel. Thanks to special fillers, new potential applications for silicone gels are becom- ing evident to manufacturers.

Enquiries: www.inmr.com

SPARKS ELECTRICAL NEWS

JULY 2019