Abstract-This paper addresses the harmonic emission from a large off-shore wind farm. An overview is given of the issues, where a distinction is made between frequencies below and above 2 kHz. Three different approaches are presented: a simplified mathematical model; a more detailed mathematical model; and measurements and the point of connection for an off-shore wind farm. It is concluded from both models and measurements that the emission is small for frequencies above a few kHz. However, specific resonances at higher frequencies involving the power transformers, when coinciding with switching frequencies or harmonics of switching frequencies, could result in high emission even at these high frequencies.
The Customer Dissatisfaction Index (CDI) concept, developed in 2006 by Vattenfall and STRI [1], introduces the service level compliance put into figures in network planning. By using the performance in a load point and the probability that a preset "dissatisfaction" level of security of supply is not fulfilled, it presents a more understandable customer focus. This was presented in an earlier CIRED report. [4] A pilot network planning case in a rural network in Finland near Jyväskylä has been performed as a pilot. Two different levels of satisfaction criteria has been used one for domestic customers (max 8 hours or 3 interruptions) and one for preferred customers such as industry, hospitals, nursing homes, supermarkets etc. (max 1hour or2 interruptions) (fig 1
The paper describes the Submerged Turret Production System (STP) and a state of the art disconnectable FPSO. The STP technology is well proven in the North Sea, South China Sea and other offshore arenas worldwide for both disconnectable FPSO's and for permanent mooring configuration. Lately it is being used for turret mooring of one of the worlds largest FPSOs located in Mexican waters in Gulf of Mexico on the PEMEX KuMaZa field. The FPSO is scheduled for first oil April 2007 and a short update of this project is presented. The STP technology is built on the Submerged Turret Loading - STL technology used for Offshore Loading of Crude Oil, which is further developed for Discharge of Natural Gas and is the basis for the world's first Offshore LNG Receiving Terminal, Gulf Gateway - located in US Gulf of Mexico, Block WC 603. The paper presents this turret technology and how this technology can significantly reduce development risks in the Deep Water Fields in GoM and how it subsequently can have a positive impact on insurance premiums for the FPS/FPSO facility due to the ability to safeguard and sail away from Hurricanes. Introduction The ability to easily connect and disconnect a single point mooring and riser system in a safe way is attractive for a number of reasons. The most obvious reason in Gulf of Mexico is to be able to remove the vessel in case of a hurricane. The technology described, has been developed over a period of 15 years, starting in the North Sea with the STL loading system for shuttle tankers and the disconnectable STP mooring and riser system for FPSOs. Basically the technology is the same, utilizing a submerged buoy integrating riser buoy and turret in one compact module which all together is disconnected.
The top drive is designed to provide the highest level of instrumentation to ensure that the operator get total control of the drilling process. High accuracy sensors and actuators increase drilling efficiency due to better drilling data insight and the ability to respond quickly in a demanding drilling environment that ensures safer drilling operations for the rig crew. The top drive is suspended from the travelling block using 4 vertical tie rods with an innovative weight on bit (WOB) system. Redundant built-In WOB sensors in all the tie rods provide exceptionally accurate load readings over the entire top drive hoisting range. Accurate WOB measurements is important for the driller to be able to apply the correct downward force needed for the bit to efficiently break rock as well as extend bit lifespan. The top drive’s accurate WOB system decrease the number of time consuming bit runs as the lifespan of each bit is prolonged. Soft cushioning while doing spin in / spin out pipe connections are controlled using an active tread compensating system in hydraulic cylinders suspended between the travelling block and top drive gearbox. Stroke sensors provide the driller with additional control over actuators and top drive movement which in turn improve operational efficiency and rig safety. The top drive is powered by two high performance AC motors delivering one of the highest levels of torque and speed. The two 550 HP motors provide 51 000 ft-lb of continuous torque enabling deeper drilling both vertical and horizontal. The motor configuration is designed to be redundant allowing continuous operation at 100% speed and 50% torque if one motor is offline. The redundant individual driven traction AC-motors are crucial to ensure reliability and rig uptime.
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