Abstract:
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. The logic system is connected to the interface and 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 directly present to the operator the breaker status indications and to directly operate the fault protection device in response to input received from the user through the interface in the event that the logic system experiences a failure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of a prior U.S. provisional application Ser. No. 60/202,074 filed May 5, 2000, and entitled “Controlling and Monitoring An Electrical System”, the entire disclosure of which is incorporated herein by reference. 
    
    
     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. 
    
    
     DESCRIPTION OF DRAWINGS 
     FIG. 1 is a block diagram of a conventional protection system that uses protective relays. 
     FIG. 2 is an operator interface used in the conventional protection system of FIG.  1 . 
     FIG. 3 is a block diagram of a protection system that offers more control and protection. 
     FIG. 4 is an improved operator interface used in the protection system of FIG.  3 . 
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a conventional microprocessor-controlled protection relay system  100  includes a circuit breaker  105  that isolates a faulted or damaged area in an electrical system  110  that includes a power supply and transmission line. To provide fault protection, a protective relay  115  is coupled to the transmission line through one or more current transformers  120  associated with the circuit breaker  105  and, if necessary, to one or more voltage transformers  125 . These transformers  120 ,  125  provide, respectively, electrical isolation and low-level secondary signals to the protective relay  115 . 
     The protective relay  115  typically includes an analog input section  130 , an interface  135 , a contact (binary) input section  137 , a contact (binary) output section  140 , and a data processing section  145 . 
     The analog input section  130  may perform the following functions. For example, the analog input section  130  may serve to reduce the current and voltage quantities to low voltages and provide first-level filtering. Additionally, the analog input section  130  may serve to receive output from the auxiliary transformers to remove high-frequency noise. The analog input section  130  may operate to sample and hold the analog signals from filters at time intervals determined by a sampling clock to preserve phase information. Furthermore, the analog input section  130  may operate to select one sample-hold signal at a time for subsequent scaling and conversion to digital through an analog-to-digital converter. 
     The output section  140  couples to a trip coil circuit  150  and a close coil circuit  155  that cause the circuit breaker  105  to, respectively, open or close accordingly. 
     The data processing section  145  includes a central processing unit (CPU) for controlling internal components of the system and for executing various computations on input data. The data processing section  145  may further include a RAM making up a work area and a data storage area for the CPU, and a ROM for storing a control program and an operation program of the CPU. Additionally, the data processing section couples to an input/output interface  160  that receives and sends signals to and from the analog input section  130 , the input section  137 , the output section  140 , and the interface  135 . Thus, the data processing section provides the output section  140  with control signals that are produced as a result of one or more computations. Additionally, the data processing section may receive information about the status (that is, open or close) of the circuit breaker  105  through the input section  137 , which receives information directly from a breaker status circuit  165  associated with the circuit breaker  105 . 
     The protection relay system  100  may be implemented in a single-phase electrical system or in a multi-phase system to provide phase-fault protection and/or ground-fault protection. 
     Referring to FIG. 2, a conventional interface  135  is shown in a rack-type mounting design. The setting interface  135  enables an operator to monitor and control the electrical system  110  when the protective relay  115  is in full service (that is, completely operational). Generally, the interface  135  includes various indicator lights  200  and a display  205  for viewing different quantities relating to operation of the electrical system  110 . The interface  135  also may include various pushbutton controls that enable an operator to perform various functional controls to the electrical system  110  to ensure proper operation of the electrical system. Input to the interface  135  is obtained from the operator or from the data processing section  145 . Furthermore, all output from the interface  135  is controlled by the data processing section  145 . Therefore, if the data processing section  145  fails to operate, the operator is unable to manually monitor and control the electrical system  110  using the interface  135 . 
     Conventionally, the operator could purchase and install at least several different auxiliary devices (for example, dedicated panel switches and annunciators) that could be operated in addition to the interface  135  to provide for emergency monitoring and control of the circuit breaker  105  and/or electrical system  110  in the event that the data processing section  145  fails to operate. Such auxiliary devices require additional set up considerations such as, for example, special interconnection wiring, and additional labor to wire and test the complete site installation. 
     As discussed above, circuit breaker indicator lights are typically microprocessor-controlled, such that, whenever the CPU fails to operate (such as during a loss of power), the indicator lights would fail to operate. Therefore, indicator lights may be installed as auxiliary devices apart from the microprocessor and apart from the interface  135  in a separate interface. For example, the indicator lights may be connected in series with respective open and close coil circuits of the circuit breaker. 
     Referring also to FIG. 3, an improved relay system  300  is shown in which a circuit breaker  305  isolates a faulted or damaged area in an electrical system  310  that includes a power supply and transmission line. To provide fault protection, protective relay  320  is coupled to the transmission line through one or more current transformers  325  and, if necessary, to one or more voltage transformers  330 . 
     As discussed above, the protective relay  320  includes an analog input section  335  for receiving electrical signals from the electrical system  310  and converting the electrical signals to digital signals, a data processing section  340  that includes a microprocessor or CPU, and a contact (binary) output section  345 . The contact (binary) output section  345  drives to a trip coil circuit  346  and a close coil circuit  348  that activate the circuit breaker  305  based on information from the data processing section  340 . Also, the protective relay  320  includes a contact (binary) input section  350  that receives information relating to the circuit breaker  305  through a breaker status circuit  355  associated with the circuit breaker  305 . 
     The protective relay  320  further includes various controls, readouts, and/or indicators  360  on a first interface; the controls, readouts, and indicators  360  being controlled by the data processing section  340 . 
     The protective relay  320  also couples directly to the electrical system  310  and/or circuit breaker  305  through a second interface that includes direct-wired breaker status indicators  365  and/or direct-wired breaker control switches  370 . 
     Thus, the first interface, which includes controls, readouts, and indicators  360 , receives information relating to the electrical system  310  from the data processing section  340 . Likewise, all information output from the controls, readouts, and indicators  360  of the first interface are directed through the data processing section  340 . Therefore, operation of the controls, readout, and indicators  360  of the first interface depends on the operation of the data processing section  340 . 
     In contrast, the second interface receives information relating to the electrical system  310  directly from the circuit breaker  305  and/or the breaker status circuit  355  associated with the circuit breaker  305 . All information output from the second interface to the electrical system  310  is directed through the one or more control switches  370  that are directly connected (that is, hardwired) to the circuit breaker  305 . 
     The one or more control switches  370  may be connected to the circuit breaker  305  in a fashion identical to previously designed auxiliary devices. In this way, setup and installation of the second interface and control switches  370  may be simplified. For example, in a traditional design, auxiliary switch devices are placed in circuit breaker trip and close coil circuits  346 ,  348 . Therefore, control switches  370  may be coupled to the circuit breaker trip and close coil circuits  346 ,  348 , respectively. 
     Referring also to FIG. 4, an interface panel  400  is used with the protective relay  320 . The panel  400  includes the first interface  405  and the second interface  410 . The first interface includes  25  light indicators arranged across a top  415  of the first interface  405 . The light indicators provide the operator with information about the electrical system  310 . For example, an indicator  420  that is illuminated indicates that the circuit breaker  305  is open, whereas an indicator  425  that is illuminated indicates that the circuit breaker  305  is closed. 
     The first interface  405  includes eight programmable push buttons arranged in two vertical groups along outer edges  430 ,  432  of the first interface  405 . The programmable push buttons may provide access to functions such as metering  435 , breaker status  437 , reset targets  440 , and lamp test  442 . 
     The first interface  405  further includes a display  445  such as, for example, a liquid crystal display (LCD). The display  445  provides feedback about the electrical system  310  to the operator. For example, the display  445  may indicate one or more phase currents and/or a ground current. Information on the display  445  is controlled using context sensitive function keys F1 through F4  450  located directly below the display  445 , navigation buttons  455  located below the function keys  450 , and cursor movement buttons  460  located below the function keys  450 . 
     One or more communication ports  465  may be accessed to connect the protective relay  320  through the first interface  405  with another component such as a personal computer or control system. 
     The first interface  405  also includes nine programmable feature push buttons  467  with integral indicating lights. These push buttons  467  may provide instant access to ground trip block, reclose block, supervisory block, and one touch access to six of the protective relay&#39;s eight setting groups or other functions the user may designate. For example, as mentioned above, the operator may disable supervisory control by pushing the supervisory off button. 
     The second interface  410  includes a trip button  470  and a close button  472  connected to the installed control switches  370  to, respectively, open and close the circuit breaker  305 . When the operator pushes the trip button  470 , the respective control switch  370  opens the circuit breaker  305  and when the operator pushes the close button  472 , the respective control switch  370  closes the circuit breaker  305  if various other conditions are met. For example, a close circuit disable link may be removed (discussed below) to prevent a closing of the circuit breaker  305 . Or, a hot line tag function (discussed below) may prevent a closing of the circuit breaker  305 . Thus, the operator can manually control the circuit breaker  305  when the protective relay  320  fails to operate, such as, for example, when the power source fails or when internal components in the protective relay  320  fail. 
     The trip and close buttons  470 ,  472  may be illuminated by underlying lights that serve as the direct-wired breaker status indicators  365  to indicate the open or close status of the circuit breaker  305  as driven by the breaker status contacts  355 . When the operator pushes the trip button  470 , the underlying light illuminates to indicate that the circuit breaker  305  is open. Likewise, when the operator pushes the close button  472 , the underlying light illuminates to indicate that the circuit breaker  305  is closed. Thus, when the operator pushes an un-illuminated button, the circuit breaker  305  changes its state. A successful change of state is indicated by the loss of illumination of the previously illuminated button, and the illumination of the recently pressed button. 
     The underlying lights may be hardwired to the circuit breaker  305  through the breaker status circuit  355  to provide status indication even when the protective relay  320  fails to operate, such as, for example, during a loss of power from the power source. 
     A red light may be used to indicate a closed circuit breaker (power line is energized) and a green light may be used to indicate an open circuit breaker (power line is de-energized). 
     The circuit configuration that includes the underlying lights may be designed to support traditional wiring configurations used when installing auxiliary indicator lights as discussed above. For example, the underlying lights may be connected in series with the respective open and close operation coil circuit  346 ,  348  associated with the circuit breaker  305 , to provide continuous indication of the status of the circuit breaker  305 . Such multi-configuration design provides continuity and consistency to the operations personnel because personnel are able to use the previous wiring configuration during connection of the underlying lights to the circuit breaker. 
     The second interface  410  may include a close circuit disable link  480  that, when removed, places a physical open in the circuit breaker&#39;s circuit, thus making it impossible to close the breaker using the protective relay  320  or the close button  472  under any condition. A hot line tag (HLT) control switch  485  may be implemented in either the first interface  405  or the second interface  410  (as indicated by dashed line  490  in FIG. 4) to interrupt the ability of the protective relay  320  to issue a close command to the circuit breaker  305  by preventing the contact (binary) output  345  and/or pushbutton  472  from issuing a close operation to the circuit breaker  305 . In particular, the HLT control switch  485  signals an internal relay to block all circuit breaker close commands. 
     If the HLT control switch  485  is implemented in the first interface, the HLT control switch  485  may be a center off, spring-loaded toggle switch supervised by the CPU  340 . When enabled, the HLT control switch  485  further prevents remote operations through supervisory control, that is, from control switches  370  or communication ports  465 . When the HLT control switch  485  is switched on, an HLT light  487  begins flashing on and off if supervisory control is still in operation or the HLT light  487  flashes on continuously if supervisory control is turned off. 
     If the HLT control switch  485  is in the second interface  410 , the HLT control switch  485  may be a two position toggle switch. In this case, operation through the HLT control switch  485  is independent of the CPU  340 . 
     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, advantageous results still could be achieved if steps of the disclosed techniques were performed in a different order and/or if components in the disclosed systems were combined in a different manner and/or replaced or supplemented by other components. Accordingly, other embodiments are within the scope of the following claims. For example, the second interface  410  may include audio devices coupled to the trip and close buttons  470 ,  472  to indicate the open or close status of the circuit breaker  305 . The direct-wired breaker status indicators  365  may be designed at a location on the second interface  410  apart from the trip and close buttons  470 ,  472 . 
     For simplicity, the first and second interfaces  405 ,  410  have been shown in separated areas. However, the second interface  410  may be within or may include the first interface  405 . Thus, there may be no demarcation between the first and second interfaces  405 ,  410 .