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There are over 150 HVDC systems now in operation around the world. Approximately more than 70 of these systems are 20 years and older. Earlier systems were realized with analog control systems. Some of those systems operated for over 30 years. Digital control systems were introduced in HVDC for a number of technical reasons. All systems that were installed in the last 30 years utilize digital controls. Digital controls typically have a much shorter life of 12- 15 years, with a Human Machine Interface (HMI) replacement about every 7 years. As a result, a number of systems are facing the challenge of replacing the digital control and protection systems. The control systems interact with other subsystems such as the valve base electronics (VBE), thyristor Gate Control Units, cooling controls as well as the measuring equipment. It is often challenging to decide which other related subsystems to replace (e.g. control and protection only or VBE and control and protection, or even to go further and include the cooling controls). This paper describes a process that can be followed to assist in making the decision to replace the control and protection systems, preparing the technical specification, bidding process, testing and commissioning. Even though the paper discusses Line Commutated Converters (LCC), the basic principles apply to Voltage Sourced Converters (VSC) as well}.

This paper discusses the impacts of large voltage drops on very long HVDC transmission lines, especially when operating in a monopolar mode. The effect of using dedicated metallic return (DMR) conductors is discussed. The main focus is on the potential rise at the neutral point of the converters and the need for an increased range for the converter transformer tap changers. Two grounding schemes for multiterminals transnational HVDC systems are presented: single point low impedance grounding and high impedance multi-point grounding. The advantages of the high impedance scheme are discussed. An innovative compensation method for voltage drop effects using a series HVDC converter is presented along with simulation results. The novel series converter can address both issues of neutral voltage rise and the impractical tap changer range. To put the ideas into the perspective, a realistic example of a transnational HVDC connecting China, central Asia, Russia and West Europe is presented.

BackgroundSecondhand smoke (SHS) in US casinos is common, but little is known about the residue of tobacco smoke pollutants left behind in dust and on surfaces, commonly referred to as thirdhand smoke (THS). We examined SHS and THS pollution and exposure before and during a casino smoking ban and after smoking resumed.MethodsA casino was visited nine times over a 15-month period to collect dust, surface and air samples in eight locations. Finger wipe and urine samples were collected from non-smoking confederates before and after a 4-hour casino visit. Samples were analysed for markers of SHS and THS pollution and exposure.ResultsExceptionally high levels of THS were found in dust and on surfaces. Although the smoking ban led to immediate improvements in air quality, surface nicotine levels were unchanged and remained very high for the first month of the smoking ban. Surface nicotine decreased by 90% after 1 month (PConclusionsLong-term smoking in a casino creates deep THS reservoirs that persist for months after a smoking ban. A complete smoking ban immediately improves air quality and significantly reduces exposure to SHS and THS. However, THS reservoirs contribute to continued low-level exposure to toxicants. To accelerate the effect of smoking bans, remediation efforts should address specific THS reservoirs, which may require intensive cleaning as well as replacement of carpets, furniture and building materials.

Most casinos owned by sovereign American Indian nations allow smoking, even in U.S. states such as California where state laws restrict workplace smoking. Collaborations between casinos and public health workers are needed to promote smoke-free policies that protect workers and patrons from secondhand tobacco smoke (SHS) exposure and risks. Over seven years, a coalition of public health professionals provided technical assistance to the Redding Rancheria tribe in Redding, California in establishing a smoke-free policy at the Win-River Resort and Casino. The coalition provided information to the casino general manager that included site-specific measurement of employee and visitor PM2.5 personal exposure, area concentrations of airborne nicotine and PM2.5, visitor urinary cotinine, and patron and staff opinions (surveys, focus groups, and a Town Hall meeting). The manager communicated results to tribal membership, including evidence of high SHS exposures and support for a smoke-free policy. Subsequently, in concert with hotel expansion, the Redding Rancheria Tribal Council voted to accept a 100% restriction of smoking inside the casino, whereupon PM2.5 exposure in main smoking areas dropped by 98%. A 70% partial-smoke-free policy was instituted ~1 year later in the face of revenue loss. The success of the collaboration in promoting a smoke-free policy, and the key element of air quality feedback, which appeared to be a central driver, may provide a model for similar efforts.

The capability and limitations of digital real-time simulators for the study of large HVDC systems and their interconnected AC systems is described. An example system model, based on the Nelson River HVDC System and its associated AC networks at the sending and receiving ends is included. Applications for the system model are discussed. (6 pages)

Background Nearly all California casinos currently allow smoking, which leads to potentially high patron exposure to secondhand tobacco smoke pollutants. Some argue that smoking restrictions or bans would result in a business drop, assuming > 50% of patrons smoke. Evidence in Nevada and responses from the 2008 California tobacco survey refute this assertion. The present study investigates the proportion of active smokers in southern California tribal casinos, as well as occupancy and PM2.5 levels in smoking and nonsmoking sections. Methods We measured active-smoker and total-patron counts during Friday or Saturday night visits (two per casino) to smoking and nonsmoking gaming areas inside 11 southern California casinos. We counted slot machines and table games in each section, deriving theoretical maximum capacities and occupancy rates. We also measured PM2.5 concentrations (or used published levels) in both nonsmoking and smoking areas. Results Excluding one casino visit with extremely high occupancy, we counted 24,970 patrons during 21 casino visits of whom 1,737 were actively smoking, for an overall active- smoker proportion of 7.0% and a small range of ~5% across casino visits (minimum of 5% and maximum of 10%). The differences in mean inter-casino active-smoker proportions were not statistically significant. Derived occupancy rates were 24% to 215% in the main (low-stakes) smoking-allowed slot or table areas. No relationship was found between observed active-smoker proportions and occupancy rate. The derived maximum capacities of nonsmoking areas were 1% to 29% of the overall casino capacity (most under 10%) and their observed occupancies were 0.1 to over 3 times that of the main smoking-allowed casino areas. Seven of twelve visits to nonsmoking areas with no separation had occupancy rates greater than main smoking areas. Unenclosed nonsmoking areas don’t substantially protect occupants from PM2.5 exposure. Nonsmoking areas encapsulated inside smoking areas or in a separate, but unenclosed, area had PM2.5 levels that were 10 to 60 μg/m3 and 6 to 23 μg/m3 higher than outdoor levels, respectively, indicating contamination from smoking. Conclusions Although fewer than roughly 10% of casino patrons are actively smoking on average, these individuals substantially increase PM2.5 exposure for all patrons in smoking and unenclosed nonsmoking areas. Nonsmoking areas may be too inconvenient, small, or undesirable to serve a substantial number of nonsmoking patrons. Imposing indoor smoking bans, or contained smoking areas with a maximum capacity of up to 10% of the total patronage, would offer protection from PM2.5 exposures for nonsmoking patrons and reduce employee exposures.