Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-06-05
2001-08-07
Lieu, Julie (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S638000, C307S1320EA, C361S001000, C361S100000, C361S101000, C700S292000, C700S293000
Reexamination Certificate
active
06271759
ABSTRACT:
TECHNICAL FIELD
This invention relates to protection and circuit breaker control relays.
BACKGROUND
Relays are electrical devices designed to respond to input conditions in a prescribed manner and, after specified conditions are met, to cause contact operation or similar abrupt changes in associated electric control circuits. Input conditions may be electrical, mechanical, thermal, or other quantities or combination of quantities. Electrical inputs include current, voltage, or a combination of current and voltage.
The Institute of Electrical and Electronic Engineers (IEEE) defines a protective relay as a relay whose function is to detect defective lines or apparatus or other electrical system conditions of an abnormal or dangerous nature and to initiate appropriate control circuit action. A protective relay operates when an electrical fault—an abnormal, intolerable situation—occurs on electrical transmission or distribution utility lines. A fault is caused by inadvertent, accidental connections between phase wires or from one or more phase wires to ground.
Some natural events that can cause faults include, by way of example, lightning strikes, wind, ice, earthquake, falling trees, or physical contact by animals. Some accidental events that can cause faults include, by way of example, vehicles hitting poles or contacting live equipment, people contacting live equipment, or work crews digging into underground cables. Many faults in an electrical utility system that uses overhead networked lines are one-phase-to-ground faults resulting primarily from lightning-induced transient high voltage and from falling trees and tree limbs.
Faults in an electrical system may provide significant changes in quantities that describe the electrical system. These changes may be used to indicate the presence of the fault and to distinguish between tolerable and intolerable electrical system conditions. Changing quantities include current, voltage or power, power factor or phase angle, power or current direction, impedance, frequency, temperature, physical movements, pressure, and contamination of insulating quantities.
Protective relays are used to sense or determine trouble in an electrical system. Distribution switches or fault protection devices such as circuit breakers and reclosers are used to open and/or isolate problem areas for fault isolation based on the trouble sensed by the protective relay or by their respective controller. Moreover, protective relays may be applied to all parts of an electrical system, including generators, buses, transformers, transmission lines, distribution lines and feeders, motors, capacitor banks, reactors, etc. Typically, protective relays are separate devices that are connected to the electrical system through current and voltage transformers from high system voltages (for example, around several hundred kiloVolts) down to service levels (for example, around several hundred Volts).
SUMMARY
In one general aspect, a system for controlling and monitoring operation of an electrical system is described. The system includes a fault protection device, for example, a circuit breaker, that is connected to the electrical system to provide fault isolation. The system also includes a protection system that includes an interface and a logic system connected to the electrical system. Moreover, the logic system is controlled by a processor to receive input from the electrical system and input from a user through the interface. The logic system operates the fault protection device when the received input from the electrical system indicates a fault event. Additionally, the logic system indicates information relating to operation of the electrical system through the interface. The system further includes one or more dedicated switches connected to the fault protection device and to the interface to operate the fault protection device in response to input received from the user through the interface.
Embodiments may include one or more of the following features. For example, the protection system may include one or more indicators connected directly to the fault protection device and to the interface to indicate information about the fault protection device. The interface may include a first interface area and a second interface area. The logic system may be connected to the first interface area to receive input from the user through the first interface area and to indicate information to the logic system through the first interface area. One or more dedicated switches may be connected to receive user input through the second interface area.
The protection system may operate the fault protection device in response to user-received input when the logic system fails to operate.
The fault protection device may include a circuit breaker. Likewise, the fault protection device may include a recloser.
The interface may include one or more pushbuttons. Each pushbutton may be coupled to a dedicated switch. Each pushbutton may include an indicator. Each indicator may be a light. The interface may receive input from the user through the one or more pushbuttons and may indicate information relating to operation of the electrical system through the one or more pushbutton indicators.
The interface may include a hot line tag control switch that, when actuated, blocks all commands that would otherwise close the fault protection device. The hot line tag control switch may be implemented in a first microprocessor-controlled interface or it may be implemented in a second hardwired interface.
In another general aspect, a system for controlling and monitoring operation of an electrical system includes a fault protection device connected to the electrical system to provide fault isolation, and a protection system that includes an interface. The protection system further includes a logic system connected to the electrical system and the interface. The logic system is controlled by a processor to receive input from the electrical system and input from a user through the interface. The logic system operates the fault protection device when the received input from the electrical system indicates a fault event. Moreover, the logic system indicates information relating to operation of the electrical system through the interface. The protection system also includes a dedicated system connected to the interface to directly receive input from the electrical system and indicate information relating to operation of the electrically system through the interface based on the directly received input.
The techniques and systems described here are advantageous when installing and operating a protection relay. For example, auxiliary devices that operated as dedicated switches are not required in the controlling and monitoring system. Thus, additional interconnection wiring is reduced. Moreover, a reduction in testing time and in cost is realized because of the reduction in devices. The techniques and systems permit an increase in reliability of the installation of the controlling and monitoring system because interconnection wiring, testing time, and number of devices are reduced. The enhanced tactile feedback provided by the dedicated switches coupled to the interface in addition to the hard-wired indicators reduces human error and therefore provides greater safety benefits.
The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
REFERENCES:
patent: 5428553 (1995-06-01), Chiba et al.
Schweitzer Engineering Laboratories, “SEL-351S Protection And Breaker Control Relay—Optimize Distribution Protection with Breaker Control, Monitoring and Fault Locating”, pp. 8-10, www.selinc.com.
Cooper Power Systems, “Putting A New Face On Relay Protection”, pp. 1-8, Cooper Industries, Inc. 1999; www.cooperpower.com.
Painchaud Henry W.
Skendzic Veselin
Weinbach David
Fish & Richardson P.C.
Lieu Julie
McGraw-Edison Company
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