Ferranti effect

Abstract: The direct current line feed for a telephone subscriber's line is derived from a variable voltage source connected to the line. In one case, the source is series connected in one leg of the line while in the other case it is connected across the line. In the first case there is a constant current source across the line while in the second case the voltage source is a constant current device. In both cases a pair of matching resistors is connected across the line with the center tap grounded to provide a high resistance balanced termination for the line. In both cases a high impedance monitor is connected across the line to monitor the voltage conditions on the line, and this, via a control circuit controls the voltage source and the separate constant current device if provided. This enables line voltage to be adjusted to take account of line length without introducing undesirably large dissipation.

Abstract: The invention provides a device for operative connection between a subsea step out cable far end and subsea loads such as pumps, compressors and control systems, distinctive in that the device is a rotating frequency stepper device, more specifically a rotating step up or step down device, and it comprises: a motor and a generator operatively connected so that the motor drives the generator, at least one gas and/or liquid filled vessel into which at least one of the motor and generator are arranged, and the step out length is long, which means long enough to cause problems due to the Ferranti effect at frequency and power levels feasible for subsea pump and compressor motors, and where the device via the step out cable receives input electrical power at a low enough frequency to have stable transmission and the device, operatively connected to the subsea motor, delivers an output electrical frequency, amperage and voltage feasible for operation of the connected motors Systerm for pressure boosting of hydrocarbon fluid or other fluid subsea, comprising the device

Abstract: For transmission of large amounts of electric power, AC in the overwhelming majority of cases is the established as well as the most cost effective option at hand. In cases of long distance transmission, care has to be taken for safeguarding of synchronism as well as stable system voltages, particularly in conjunction with system faults. With series compensation, the viable distances of AC power transmission become sufficiently large to eliminate altogether the issue of distance as a limiting factor for AC transmission in most cases. Thus, series compensated AC power interconnectors transmitting bulk power over distances of more than 1.000 km are a reality today. Series compensation, likewise, is an efficient means for minimizing the amount of transmission lines needed for a certain power transmission capability of an interconnector. With series capacitors, the capability of already existing power lines can be increased considerably, thereby decreasing the need for building of new lines in cases where the need for power transmission capability in a system is growing. Installing of series compensation, as a rule, is also less costly as well as less time consuming than building of new lines. The paper will present some basic mechanisms for series compensation in power grids, some salient design features as well as recent operational experience of series capacitors for improving of interregional power transfer in a cost-effective and environmentally friendly way.

Abstract: A signal transmission and receiving system. A transmission line is bidirectional along its length. An impedance element terminates each end of the transmission line. Line drivers each have an output circuit connected at a respective point on the transmission line. Each line driver has a first state presenting an open circuit and a second state for applying a current signal on the transmission line. A receiver has an input connected to the transmission line and responds to the presence or absence of a voltage signal exceeding a predetermined threshhold caused by any one of the line drivers for forming corresponding output signals. Each line driver is characterized in the second state for changing the current on the transmission line so as to change in a predetermined direction the voltage level, if any, on the transmission line caused by current from another line driver.