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SCADA on the snow
Article taken from "Automazione Industriale", issue 111 - November 2003

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DEMAC, the snowfall plant

Thanks to Automa's SCADA, ELA supervises DEMAC, the snowfall plant in the ski resorts of Corviglia in St. Moritz..

By Helmuth Lardschneider - Titolare ELA and Elena Bertillo - Marketing Automa

In February 2003 the ski world championship took place in St. Moritz (Switzerland). The organization (organizzation) of the event required many years of work and thousands of people among voluntaries, military people and institutional organizers. Thanks to a total budget superior to 50 million €, as well as, to the expertise and professionalism of the organizers, they achieved in coordinating successfully all the plants and services to accomodate around 100,000 members of the audience, 400 athletes coming from 68 nations and 2,000 journalists.
In 1997 St. Moritz Council and FIS, the championship steering committee, entrusted the expansion and management of the plants of Corviglia ski resorts to SMBB (St. Moritzer Bergbahnen), a company supervised by the local council administration, in order to accomodate part of the ten expected ski specialities. Historically, this place never had snow scarcity thanks to the altitude (1,800m - 2,700m) even if located in south Switzerland. But for some years now, snow were not enough because of greenhouse effects and the increase of skiers attending every year. This problem drove SMBB to give the development and installation of a turn-key system to DEMAC, company from Alto Adige (Italy) specialized in planning and construction of technologically innovative snowfall plants, to solve successfully the problems regarding snow scarcity. The developed technical snowfall plant is composed of two groups of systems: those to supply and distribute water and pressurized air, and generators to convert water and air in crystals similar to flakes. The supplier and distribution system is composed of two submerged pumps picking water up needed for snow production from an old artesian well built in the sixties to satisfy in those times the big potable water requirements of St. Moritz council. The pumps carry 300m3/h of water on the whole up to the intermediate "Unteralpina" resort (1,900m) where a third pump of about 150m3/h is installed and connected to a tank, less used in low season. The 450m3/h of water on the whole are stored into an immense underground basin with a capacity of 4,800m3 created inside the rocks nearby the "Signal" resort (2,100m).A second cold basin picks the water up through four cooling towers to cold it to a temperature between 4°C and 1°C in order to obtain a profitable snow production. The main collector in the cold basin, to which four pumps of 400kw each are connected, starts working by introducing water in a pipes network of around 15,8km to feed 182 little underground wells connected to snow generators available even in remote areas and in almost prohibitive altitudes.

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Screen detail

The low-pressure snow generators built by DEMAC, use reduced-pressure air produced by a fan at the side of the machine in order to produce snow granules and carry them on the ski runs. Each generator is equipped with a PLC and conceived as an independent and intelligent machine. In order to save energy, it is in position to check climatic conditions, the activation status, the power, water and air feeding conditions, and to set/turn off independently or upon centralized controls. The electrical part of the plant is maintained by ELA, a company specialized in the development and management of electrical plants, and distinguished in an ingenious regulation system for electrical current load that allows to turn automatically off the less important snow generators in an emergency. The automation system of the water supplier plant is constituted of a complex of 21 panel controls PLC Saia-based. Each of them manages the functioning of pumps, valves, rolling shutters, fans and so on. The information exchange among PLCs is controlled by a master control panel.

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Main screen

Sporting Automation
The bus selected for the connection is a RS485-based with a Saia S-bus protocol which became the best solution to solve the problems concerning remote controls between two emplacements (a total of 5km of network) as well as the impossibility of inserting amplifiers and relays on the network given that the underground wells are neither reachable nor identifiable in winter season. For this reason they opted for using a bus rarely subjected to inconveniences with a protocol driving little information at a low-speed so as to eliminate the probability of malfunctionings and failures. A second system, still controlled by the main panel control and from the same PLC master, coordinates the communication network with all snow generators equipped with PLCs (Saia PCD1 or PCD2) connected to a palm display unit to allow end-users to set up all parameters needed to execute the various service operations and tests. The master panel control communicates sequentially with 82 snow generators transmitting possible parameters and controls and asking for the service status of each activation, the measure values and statistics. This RS485 network along with Saia S-bus is also developed on a vast surface with a total length of about 7km covering a difference in height of more than 1,000 meters in high mountains. Besides the two mentioned Fieldbus networks, a Profibus FMS network is installed to communicate with the supervision system. As a matter of fact the plant has two PC equipped with SCADA. The first one is in the ski resort located upstream the funicular railway in an always controlled place which is the departure point for authorized personnel for plant management. The other one is installed in the ski resort base connected to a modem for plant data transmission management. Both softwares are connected to a main PLC through a Profibus FMS network. The plant display units of both systems are identical but the upstream operator controls the entire energy-giving from the power supplier control panel.
Both softwares are developed with Super-Flash, Automa's development system for a generation of supervision applications, and are composed of numerous pages. In the main page the operator may carry out a first check-up of the system functioning status. The functioning status of the snow generators installed nearby the wells along the ski runs, the various resorts, pumps and compressors are displayed in the next pages.
From the main page it is possible to access to detailed displays of each single ski run. End-users may visualize and, if necessary, modify the functioning status of various snow generators; the snowfall features (snow quality, traverse, etc.); power and water consumption; pump functioning, power, speed and course; working status of other components such as compressors, fans, cooling towers, motovalves, unloaded solenoid and so on. In order to display all system processes, there have been used 34 graphic pages, around 1,800 variables, 37 Super-Flash programs, 25 MicroC programs, 61 system messages and around 600 different icons. As a result there is a plant setting automatically off in presence of favourable climatic conditions and reacting to temperature and wind variations positioning and/or turning off snow generators if snow is dragged over the edge of a ski run; guaranteeing resource savings by reducing costs thanks to the connection with a main power station directly coordinated from the local electric power company ( automatically) and managed by only 3-4 authorized persons thanks to the elevated automation level which allows a 80% saving in unskilled workers for management compared to traditional plants.
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