Data processing: generic control systems or specific application – Specific application – apparatus or process – Electrical power generation or distribution system
Reexamination Certificate
2002-09-19
2004-11-09
Gandhi, Jayprakash N. (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Electrical power generation or distribution system
C700S079000, C702S060000
Reexamination Certificate
active
06816757
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates power-distribution networks. More particularly, the invention relates to a control unit that identifies and isolates faults in a power-distribution network.
BACKGROUND OF THE INVENTION
Power-distribution networks typically deliver electrical power to consumers using an interconnected arrangement of transmission lines, distribution buses, distribution feeders, etc. Power-distribution networks are typically configured so that electrical power can be delivered over more than one path within the network. Moreover, power-distribution networks are often configured so that power can be delivered from two or more alternative sources (although only one source can supply the network at a given instant). Configuring a power-distribution network in this manner reduces the potential for a single-point fault to leave large numbers of users without electrical power.
Power-distribution networks are commonly equipped with sectionalizers that permit a section of the network to be isolated from its neighboring sections on a selective basis. The feature permits a faulted section of the network, i.e., a section of the network having a fault therein, to be de-energized and isolated so that other sections of the network can be re-energized after the occurrence of the fault.
Power-distribution networks are also commonly equipped with reclosers. Reclosers trip, or open, in response to an overcurrent condition, thereby interrupting the flow of electrical power and clearing the fault condition on at least a temporary basis. A typical recloser also closes after a predetermined interval to restore the flow of electrical power to the network. A reoccurrence of the fault upon closing will cause the recloser to once again trip. Transient-type faults can sometimes be cleared by repeated closings and openings of the recloser. Hence, the recloser may be closed several times following each trip until the fault clears, or until a predetermined number of closings have occurred. Reclosers can thus eliminate prolonged power outages and unnecessary service calls caused by a transient fault.
The reclosers and sectionalizers of a power-distribution network can be connected to a centralized communication unit that facilitates communication between the reclosers and sectionalizers. This feature permits the reclosers and sectionalizers to share operational information, via the communications unit, such as open-closed status, load condition, etc. The reclosers and sectionalizers can thus operate in a coordinated manner, i.e., each recloser and sectionalizer can open or close itself based on the operational status of the other reclosers or sectionalizers. Coordinating the operation of the reclosers and sectionalizers in this manner permits faulted sections of the power distribution network to be isolated, and allows power to be restored to sections in which a fault is not present (provided an alternative power source is available).
A centralized communication unit, however, merely facilitates the sharing of information among the reclosers and sectionalizers. The reclosers and sectionalizers must still perform the decision-making processes necessary to isolate faulted sections of the power distribution network, and to restore power to sections in which a fault is not present Hence, each of the reclosers and sectionalizers must be equipped with the hardware, firmware, and software to enable the recloser or sectionalizer to perform the required decision-making processes. This requirement can substantially increase the cost and complexity of the power distribution network.
Power-distribution networks that are not equipped with a centralized communications unit often rely on repeated closings and openings of a recloser to identify and isolate a faulted section. For example, the sectionalizers downstream of the recloser, i.e., the sectionalizers separated from the voltage source by the recloser, can be programmed to open on a sequential basis after the recloser has cycled through a predetermined number of closings and openings. More particularly, the sectionalizer located farthest from the recloser in the network can be programmed to open after the recloser has closed and reopened a predetermined number of times, e.g., two (this can be accomplished by programming the sectionalizer to open after a predetermined amount of time has elapsed following a drop in the voltage or current in the sectionalizer).
The sectionalizer located immediately upstream of the open sectionalizer can be programmed to open after the next closing and reopening the recloser. This process occurs for each subsequent upstream sectionalizer until the recloser remains closed, i.e., until the faulted section is no longer energized upon the closing of the recloser. This approach is time consuming in comparison to the use of a centralized communications unit to facilitate coordinated operation among the reclosers and sectionalizers. Moreover, power cannot be restored to un-faulted sections located downstream of the faulted section, i.e., to un-faulted sections separated from the voltage source by the faulted section, using this approach.
SUMMARY OF THE INVENTION
A preferred embodiment of control unit comprises a processor, a memory-storage device electrically coupled to the processor, a set of computer-executable instructions stored on the memory-storage device, and an input/output interface electrically coupled to the processor. The control unit receives data from a plurality of switching devices of a power-distribution network, and identifies ones of the switching devices located immediately up-line and down-line of a fault in a faulted section of the power-distribution network based on predetermined characteristics of the data. The control unit also generates and sends a first control input to at least one of the switching devices located immediately up-line and down-line of the fault to cause the at least one of the switching devices to open and thereby isolate the faulted section from another section of the power-distribution network.
Another preferred embodiment of a control unit for a power-distribution network comprises a central processing unit comprising a processor, a memory-storage device electrically coupled to the processor, and a set of computer-executable instructions stored on the memory-storage device. The control unit also comprises an input/output interface electrically coupled to the central processing unit
The input/output interface receives inputs from a first and a second switching device of the power-distribution network, the inputs being indicative of a load condition on each of first and second switching devices. The central processing unit detects the presence a fault in a first section of the power-distribution network located between the first and second switching devices by comparing the input from the first switching device with the input from the second switching device. The central processing unit generates a control input in response to the detection of the fault. The input/output interface sends the control input to at least one of the first and second switching devices, and the control input causes the at least one of the first and second switching devices to reconfigure itself to isolate the first section of the power-distribution network from a second section of the power-distribution network.
A preferred embodiment of a power-distribution network comprises a first switching device electrically coupled to a first voltage source and a first section of a first distribution feeder. The first switching device isolates the first section from the first voltage source in response to an overcurrent condition in the first distribution feeder. The power-distribution network also comprises a second switching device electrically coupled to the first section and a second section of the first distribution feeder. The second switching device isolates the first section from the second section on a selective basis.
The power-distribution network also comprises a third switching device elec
De La Ree Jaime
Fahey Timothy
LaPlace Carl J.
McElray Jeffrey L.
Stoupis James D.
ABB Technology AG
Gandhi Jayprakash N.
Woodcock & Washburn LLP
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