Electrical transmission or interconnection systems – Plural supply circuits or sources – Substitute or emergency source
Reexamination Certificate
1999-04-23
2001-11-20
Fleming, Fritz (Department: 2836)
Electrical transmission or interconnection systems
Plural supply circuits or sources
Substitute or emergency source
C307S068000
Reexamination Certificate
active
06320279
ABSTRACT:
OBJECT OF THE INVENTION
The present invention refers to a system to allow the electric energy supply to be maintained in the case of variations or interruptions of the electric power supply in a public or private electric supply network, the system also including means to compensate overloads.
BACKGROUND OF THE INVENTION
Spanish patent applications ES-A-8900495 (corresponding to British patent application GB-A-2229329) and ES-A-9102561 (corresponding to British patent application GB-A-2261778) describe systems that comprise a synchronous machine that comprises electric motors and alternator means. Normally, the motor means are fed from the network. The systems also comprise an internal combustion engine, for example, a diesel engine, that serves to provide power to the synchronous machine in the event of failure in the network, so that the alternator means can continue feeding a load. Besides, the systems described in said applications comprise a hydraulic motor, that serves to provide energy to the synchronous machine during the time that passes from the detection of a failure in the network until the internal combustion engine can provide necessary power to the synchronous machine. Likewise, the hydraulic motor can serve to start the diesel engine. In ES-A-9102561, the hydraulic motor also serves to compensate overloads.
A disadvantage of the systems described in the above patents, is that the hydraulic motor needs a certain amount of time to start to function and provide the desired power to the synchronous machine, since in an idle state the hydraulic motor remains off in order not to endure any unnecessary wear and to reduce energy consumption. This implies that it may become necessary or convenient to include relatively large inertia flywheels, to ensure that the frequency at the output of the alternator means may be maintained within some specific limits, corresponding to the established tolerance level. These inertia flywheels imply high costs and diverse practical problems, known by an average expert in the field.
DESCRIPTION OF THE INVENTION
The system of the invention is basically comprised of a synchronous machine that carries out the functions of a synchronous electric motor and alternator, coupled by means of coupling means to an internal combustion engine, preferably a diesel engine. Likewise and in addition to the internal combustion engine, the system of the invention includes means to supply energy to the synchronous machine, these means comprising a turbine. Said turbine includes a shaft, a plurality of nozzles, means to convey pressurized fluid from the pressurized fluid accumulation means to the nozzles, and means to release pressurized fluid in such a way that the fluid is expelled through the nozzles. The nozzles are placed in such a way that the expulsion of fluid through them provides turning torque to the shaft. Besides, the system includes the pressurized fluid accumulation means and control means (preferably, electronic means). The control means include means to control the expulsion of fluid by the nozzles. The pressurized fluid may be liquid or gaseous, for example, compressed air.
Preferably, all the elements of the system are mounted on a frame.
Preferably, the synchronous machine is coupled to a inertia flywheel or to a plurality of inertia flywheels.
The power of the internal combustion engine can correspond to the nominal power of the system. The synchronous machine may comprise one or several alternators, each one corresponding to a galvanically independent circuit that is to be kept fed.
In the case that there are several alternators, they are mechanically connected to one another and, optionally, to an inertia flywheel. The alternators may be connected by means of rigid couplings between their shafts, or by means of flexible couplings. As to the inertial flywheel, it may have reduced dimensions in comparison to flywheels of previous systems, due to the inclusion of the turbine. The flywheel may be coupled to the synchronous machine by means of higher speed gears.
The coupling means between the internal combustion engine and the synchronous machine are preferably comprised of a freewheeling type clutch.
As to the turbine, it corresponds to a reaction turbine, which seems to be especially advantageous when very powerful systems (typically of more than 800 kVA) are involved. In this case, the nozzles turn with the shaft of the turbine and they serve to accelerate the pressurized fluid to maintain the turning speed of the synchronous machine within the established limits. These nozzles that are positioned radially to the tangential output of the pressurized fluid, receive the flow from the pressurized fluid accumulation means through the above mentioned duct means. In the case of operation by reaction or by reaction/action, the nozzles accelerate the pressurized fluid that can be supplied to the turbine by the radial ducts from a central part that surrounds the shaft of the turbine and that comprises a ball joint. The shaft of the turbine can be integral to the shaft of the synchronous machine or it may connected to it by means of rigid or elastic couplings or even by gears at different speeds. The central part may receive a flow of pressurized fluid when the pressurized fluid release means are activated, for example, upon a series connected valve between said central part and the pressurized fluid accumulation means being electrically activated.
Above all when the linear speeds of the rotating nozzles are high, the reaction effects suffice in principle. This may correspond to systems with a diameter in the range of 1.5 to 2 meters. (The diameter corresponds to the diameter of the imaginary circle passing through the nozzles).
Normally, the diameters are proportional to the powers of the systems.
The pressurized fluid release and accumulation means (for example, compressed air) are essentially comprised of at least one high pressure compressor, at least one high pressure accumulation tank, at least one fluid flow control valve, as well as ducts that connect the valve, compressor, as well as the high pressure fluid tank(s) together.
Operation of the pressurized fluid release valve, although electrically controlled, can be carried out by means of a servomechanism that receives pressurized fluid from a low pressure drum, that communicates with the high pressure fluid tank through a pressure reducer.
As to the control means, preferably electronic control means, two aspects, namely, power and control are distinguished.
With regard to power control, when the public or private network correctly supplies electric energy, the system, namely, the synchronous machine, receives electric energy through reactor means, that may be comprised of an inductance. Advantageously, the reactor means may be connected between first switching means, located between the reactor means and the network, and third switching means, located between the reactor means and the synchronous machine. The synchronous machine may be connected by said third switching means and through the second switching means, to the load, the second switching means being located in series between the reactor means and the load. If the system includes a plurality of alternators, they may be coupled by means of the corresponding switching means to the respective loads, namely, the respective electric energy consumers that are to be protected. The voltage to the load is the correct one produced by the corresponding alternator, for example by the synchronous machine. This absorbs energy from the network, through the reactor means, and acts as a rotating autotransformer, using the same winding, thanks to the voltage that drops in said reactor means.
Preferably, so that the system can be disconnected from the network, when revision, maintenance or repair work of the system in the absence of electric current must be carried out, fourth switching means by means of which the load can be connected directly to the network, when the system is disconnected from the network by means of third switching means, ar
Fleming Fritz
Klauber & Jackson
LandOfFree
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