This project included four unusual and complex problems, the solution of which required innovative applications of technology: hurricane survivability, corrosion and pest control, communications across rugged terrain, and the challenge of communicating alarms to a mobile workforce with varying needs and capabilities.
When this project started in 1999, there was still abundant evidence of the damage caused by the Category 5 Hurricane Iniki that devastated Kauai in 1992. Consequently, it was imperative that SCADA system design consider the impact of tropical storm and hurricane damage. This requirement dictated that control of the system be decentralized. Then if some of the system was destroyed, the remainder would continue to operate. The requirement was met by installing submaster programmable logic controllers (PLCs) in each hydraulic zone, or group of neighboring hydraulic zones, that operate independently of the other submasters and the SCADA host computers. A wide area network was designed to allow high speed access between the submaster PLCs and the SCADA host computers via frame relay (high speed leased telephone data circuits) under normal operation and lower speed connectivity over either dial-up or cellular telephone in the event of frame relay failure. These concepts allow the SCADA system to maintain control of functioning aspects of the water distribution system even after complete failure or loss of communication to the SCADA servers.
With regard to the physical installations, it was determined that SCADA remote terminal units (RTUs) and associated antenna masts at individual sites should be able to withstand 115 MPH winds and that the monopoles supporting four submaster antennas withstand 150 MPH winds. Timberline engaged Boyle Engineering of Albuquerque, New Mexico to perform a structural analysis/review of Timberline’s standard design to ensure the design met this graded approach. (Boyle Engineering was the only subconsultant engaged by Timberline for this project.)
Finally, in consideration of the loss of power that invariably accompanies storms, all sites have been provided with battery backup systems (duration of operation depends on the importance of the site), and a sophisticated power management scheme that shuts-down non-critical RTU loads based on the duration of the outage. Key sites have also been equipped with solar powered battery charging systems to allow (weather permitting) for indefinite loss of utility power.
Corrosion and Pest Control
Corrosion and damage by pests is more subtle than a hurricane, but no less serious. Because of Kauai’s humid, rainy climate, equipment installed in unconditioned environments will rust very quickly. Even cabinets made of Type-316 stainless steel will show significant rust less than two years after being installed on the island. Submaster Cabinet with Separate Battery CabinetSince this project involved installing electronics in cabinets outdoors and in unconditioned buildings throughout the island, it was important that Timberline determine the best possible design to limit corrosion.
Timberline’s research into corrosion led to the finding that applying heat to stainless steel, through actions such as drilling, welding, and punching, caused the material to lose much of its corrosion resistance. To mitigate this problem, Timberline specified high-quality Type-316 stainless steel cabinets with a polyester powder coat finish. The specifications also called for all drilling, welding, and punching to be conducted in the factory before the cabinets were coated. No field modifications were allowed. In addition to equipment cabinets, a combination of epoxy painted steel, stainless steel, and non-metallic material were used as appropriate for the specific component and particular application. As a result of these carefully considered measures, cabinets and material installed in the early phases of the multi-phase installation process show little effect from the environment after nearly ten years.
Because of the temperature and humidity in Kauai, it was necessary to use ventilated cabinets. However, equipment is plagued by damage due to those “cute but pesky” geckos that are so prevalent in Kauai. Geckos find equipment cabinets to be an irresistible habitat, and they are capable of entering through very small openings. Almost every electrical cabinet that Timberline entered during field investigation contained geckos and their “droppings,” both of which cause problems to the components in the cabinets. The solution to the gecko problem was to specify cabinets with tight fitting, gasketed doors with multi-point rolling latches and ventilation louvers with filters and stainless steel insect cloth. The result is cabinets that have proven to be generally free of gecko infestation.
Communications Across Rugged Terrain
Kauai’s rugged terrain required a sophisticated application of radio and wired telemetry. Generally, SCADA systems communicate between master and remotes over multiple address system (MAS) radio. Photosim of Monopole at Princeville Tank In a typical system, the master station will communicate to all the remote sites over one or two MAS master radios situated to provide coverage over the entire system. In the case of Kauai, Timberline performed detailed radio path analysis followed by on-site radio testing to allocate the 19 hydraulic zones to nine submasters, each equipped with spread-spectrum MAS masters. In addition, four spread-spectrum end-link repeaters were needed to extend coverage to 11 outlying RTUs, and three of the sites required leased telephone service; two because their remoteness made radio communication impractical and one because of its proximity to an explosives storage, where radio transmissions were prohibited.
In addition to rigid-galvanized-steel (RGS) conduit antenna masts at most project sites, the radio system also required the installation of four monopoles ranging in height from 40 to 100 feet. For use in the permitting process and discussions with the public about project impact, Timberline prepared photosimulations for each of the monopole sites and some representative RGS antenna mast sites.
Communicating Alarms to a Mobile Workforce
The nature of KDOW’s workforce required sophisticated, flexible interfaces to the SCADA system. KDOW did not want a system requiring personnel to monitor SCADA screens on a 24/7 basis, as their existing operation staff works a standard Monday-Friday day-time schedule and are often located far from the main offices where the SCADA master station is located. Therefore, it was important that the SCADA system be able to deliver alarm information on a 24/7 basis to the operation staff, regardless of their location, in a clear, efficient manner. Furthermore, the maintenance staff has varying levels of technological sophistication, so a solution was needed that would work for everyone.
Timberline’s solution to this issue is a SCADA system that can analyze an alarm and contact the appropriate person (based on area of responsibility, time of day, and day of week), by the method that is most convenient for that person. Choices include voice synthesized telephone calls, e-mailed text messages, and pager messages. In addition, when a maintenance person receives an alarm message, he can call the SCADA system from a land-based or cellular telephone and interrogate it for more detail or log on to the SCADA system from his office, home, or mobile computer to look at the system in detail before responding to the alarm. This approach used sophisticated technology to make operation of the system readily accessible and remarkably transparent (given the complexity of the system) to KDOW’s mobile workforce.