Abstract:
A circuit protection system is provided in a circuit to protect power switches from fault conditions using the protective algorithms. The algorithms to control a response of said power switches to fault conditions to protect said circuit. The protective response of the power switches to a fault condition is displayed using the algorithms. The response enables the released energy from a fault condition to be minimized.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This disclosure relates generally to power distribution systems and more particularly, to a methodology using a protective algorithm for displaying a graphical representation of a protective response in the event of a fault condition for a circuit protection system. 
         [0003]    2. Description of the Prior Art 
         [0004]    In power distribution systems, power is distributed to various loads and is typically divided into branch circuits, which supply power to specified loads. The branch circuits can also be connected to other power distribution equipment. 
         [0005]    Due to the concern of an abnormal power condition in the system, i.e., a fault, it is known to provide circuit protective devices or power switching devices, e.g., circuit breakers, to protect the circuit. The circuit breakers seek to prevent or minimize damage and typically function automatically. The circuit breakers also seek to minimize the extent and duration of electrical service interruption in the event of a fault. 
         [0006]    It is further known to open and close these circuit breakers based upon statically defined zones of protection within the configuration of the power distribution system. The contemporary protection system applies algorithms based upon electrical properties of these statically defined zones and clears the fault through the use of circuit breakers disposed within the statically defined zones of protection. Such a contemporary system; however, does not have a mechanism for showing system operators how the zone will internally respond in the event of a fault to protect the system in the most efficient and safe manner. Such methods of showing protective scenarios are static, single protection cases that do not show the total scope of the adaptive process. Further contemporary systems do not have a way of minimizing potential harm to equipment or personnel by minimizing the released energy in the event of a fault. Additionally, contemporary systems do not have a way of providing a rapid backup when a component fails that minimizes released energy and the likelihood of injury within a zone. 
         [0007]    Accordingly, there is a need for a methodology using a protective algorithm to provide a graphical display of the adaptive protective response of the protective devices of power distribution system as they adapt to fault conditions. 
       SUMMARY OF THE INVENTION 
       [0008]    In one aspect, a method of displaying how a protective algorithm protects a power circuit having power switching devices is provided. The method comprises displaying the output/results of a protective algorithm during a fault condition or a series of fault conditions using the protective algorithm. 
         [0009]    In another aspect of the method, the user is able to define specific power device settings for the bus and load conditions and to cause the protective function characteristics to change using a protective algorithm. By changing bus and load conditions, the new trip curves will automatically be modified using the protective algorithm when load conditions are exceeded. 
         [0010]    In yet another aspect, in the event of a component fault, the protective algorithm trips the component and delays the main switch to let the component clear. 
         [0011]    In yet another aspect, a method of protecting a circuit having power switching uses a protective algorithm to provide more effective and timely backup of feeder and bus faults to protect equipment and personnel. 
         [0012]    In a further aspect, a method of reducing incident energy is also achieved by selectively tripping the breaker at a lower current level, than is possible when using a non-selective algorithm. 
         [0013]    A method of protecting a circuit having power switching devices is provided. The method has the steps of defining a set of characteristics representing threshold values for power switches in a circuit and inputting fault conditions that exceed the threshold values. The method uses algorithms to control a response of the power switches to the fault conditions to protect the circuit. The method displaying the response of the power switches to the fault condition, wherein a display represents a protective response of the switching devices controlled by the algorithms. 
         [0014]    The above-described and other features and advantages of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  illustrates a schematic representation of a power distribution system; 
           [0016]      FIG. 2  illustrates a schematic representation of a multiple source power distribution system; 
           [0017]      FIG. 3  illustrates a schematic representation of a portion of a power distribution system; 
           [0018]      FIG. 4  illustrates a static time trip curve representing the methodology of the static known algorithm to describe system behavior of the protection system of  FIG. 3 ; 
           [0019]      FIG. 5  illustrates a static trip time curve attempting to show the adaptive protective function of a bus fault, according to known algorithms; 
           [0020]      FIG. 6  illustrates the methodology that shows the adaptive protective function according to the present invention; 
           [0021]      FIG. 7  is illustrates the methodology that shows adaptive and multiple protective function according to the present invention; 
           [0022]      FIG. 8  illustrates the incident energy of static protective devices of known algorithms; and 
           [0023]      FIG. 9  is a illustrates incident energy of dynamic protective devices according to the methodology of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Referring now to the drawings and in particular to  FIG. 1 , an exemplary embodiment of a power distribution system generally referred to by reference numeral  10  is illustrated. System  10  distributes power from at least one power bus  12  through a number or plurality of power switching devices or circuit breakers  14  to branch circuits  16 . 
         [0025]    Power bus  12  is illustrated by way of example as a three-phase power system having a first phase  18 , a second phase  20 , and a third phase  22 . Power bus  12  can also include a neutral phase (not shown). System  10  is illustrated for purposes of clarity distributing power from power bus  12  to four circuits  16  by four breakers  14 . Of course, it is contemplated by the present disclosure for power bus  12  to have any desired number of phases and/or for system  10  to have any desired number of circuit breakers  14  and any topology of circuit breakers, e.g., in series, or in parallel, or other combinations. 
         [0026]    Each circuit breaker  14  has a set of separable contacts  24  (illustrated schematically). Contacts  24  selectively place power bus  12  in communication with at least one load (also illustrated schematically) on circuit  16 . The load can include devices, such as, but not limited to, motors, welding machinery, computers, heaters, air conditioners, lighting, and/or other electrical equipment. 
         [0027]    Power distribution system  10  is illustrated in  FIG. 1  with an exemplary embodiment of a centrally controlled and fully integrated protection, monitoring, and control system  26  (hereinafter “system”). System  26  is configured to control and monitor power distribution system  10  from a central control processing unit  28  (hereinafter “CCPU”). CCPU  28  communicates with a number or plurality of data sample and transmission modules  30  (hereinafter “module”) over a data network  32 . Network  32  communicates all of the information from all of the modules  30  substantially simultaneously to CCPU  28 . 
         [0028]    Thus, system  26  can include protection and control schemes that consider the value of electrical signals, such as current magnitude and phase, at one or all circuit breakers  14 . Further, system  26  integrates the protection, control, and monitoring functions of the individual breakers  14  of power distribution system  10  in a single, centralized control processor (e.g., CCPU  28 ). System  26  provides CCPU  28  with all of a synchronized set of information available through digital communication with modules  30  and circuit breakers  14  on network  32  and provides the CCPU with the ability to operate these devices based on this complete set of data. 
         [0029]    A protective algorithm  200  of the present invention is used to protect system  26 . The purpose of algorithm  200  is to protect devices, such as, but not limited to, motors, welding machinery, computers, heaters, air conditioners, lighting, and/or other electrical equipment in the event of a fault of a power device such as a bus, or a feeder on network  32 . When a load on a bus or a breaker is exceeded, protective circuit breakers  14  are activated. The protective algorithm  200  is configured to accept user defined settings for circuit breakers  14  to permit the protective functions enabled by algorithm  200  to occur. The CCPU  28  enables algorithms  200  to accept user defined inputs for settings for threshold values of time and/or current for circuit breaker  14 . These values are inputted by maintenance personnel or any other network operators to obtain a graphical representation of the protective action permitted by protective algorithm  200 . 
         [0030]    As shown in  FIG. 1 , each module  30  is in communication with one of the circuit breakers  14 . Each module  30  is also in communication with at least one sensor  34  sensing a condition or electrical parameter of the power in each phase (e.g., first phase  18 , second phase  20 , third phase  22 , and neutral) of bus  12  and/or circuit  16 . Sensors  34  can include current transformers (CTs), potential transformers (PTs), and any combination thereof. Sensors  34  monitor a condition or electrical parameter of the incoming power in circuits  16  and provide a first or parameter signal  36  representative of the condition of the power to module  30 . For example, sensors  34  can be current transformers that generate a secondary current proportional to the current in circuit  16  so that first signals  36  are the secondary current. 
         [0031]    Module  30  sends and receives one or more second signals  38  to and/or from circuit breaker  14 . Second signals  38  can be representative of one or more conditions of breaker  14 , such as, but not limited to, a position or state of separable contacts  24 , a spring charge switch status, a lockout state or condition, and others. In addition, module  30  is configured to operate or actuate circuit breaker  14  by sending one or more third signals  40  to the breaker to open/close separable contacts  24  as desired, such as open/close commands or signals. 
         [0032]    System  26  utilizes data network  32  for data acquisition from modules  30  and data communication to the modules. Accordingly, network  32  is configured to provide a desired level of communication capacity and traffic management between CCPU  28  and modules  30 . In an exemplary embodiment, network  32  can be configured to not enable communication between modules  30  (i.e., no module-to-module communication). 
         [0033]    In addition, system  26  can be configured to provide a consistent fault response time. As used herein, the fault response time of system  26  is defined as the time between when a fault condition occurs and the time module  30  issues a trip command to its associated breaker  14 . In an exemplary embodiment, system  26  has a fault response time that is less than a single cycle of the 60 Hz (hertz) waveform. For example, system  26  can have a maximum fault response time of about three milliseconds. 
         [0034]    The configuration and operational protocols of network  32  are configured to provide the aforementioned communication capacity and response time. For example, network  32  can be an Ethernet network having a star topology as illustrated in  FIG. 1 . In this embodiment, network  32  is a full duplex network having the collision-detection multiple-access (CSMA/CD) protocols typically employed by Ethernet networks removed and/or disabled. Rather, network  32  is a switched Ethernet for preventing collisions. 
         [0035]    CCPU  28  can perform branch circuit protection, zone protection, and relay protection interdependently because all of the system information is in one central location, namely at the CCPU. In addition, CCPU  28  can perform one or more monitoring functions on the centrally located system information. Accordingly, system  26  provides a coherent and integrated protection, control, and monitoring methodology not considered by prior systems. For example, system  26  integrates and coordinates load management, feed management, system monitoring, and other system protection functions in a low cost and easy to install system. 
         [0036]    Referring to  FIG. 2 , an exemplary embodiment of a multi-source, multi-tier power distribution system generally referred to by reference numeral  105  is illustrated with features similar to the features of  FIG. 1  being referred to by the same reference numerals. System  105  distributes power from at least one power feed  112 , in this embodiment a first and second power feed, through a power distribution bus  150  to a number or plurality of circuit breakers  14  and to a number or plurality of loads  130 . CCPU  28  can include a data transmission device  140 , such as, for example, a CD-ROM drive or floppy disk drive, for reading data or instructions from a medium  145 , such as, for example, a CD-ROM or floppy disk. 
         [0037]    Circuit breakers  14  are arranged in a layered, multi-leveled or multi-tiered configuration with a first level  110  of circuit breakers and a second level  120  of circuit breakers. Of course, any number of levels or configuration of circuit breakers  14  can be used with system  105 . The layered configuration of circuit breakers  14  provides for circuit breakers in first level  110  which are upstream of circuit breakers in second level  120 . In the event of an abnormal condition of power in system  105 , i.e., a fault, protection system  26  seeks to coordinate the system by attempting to clear the fault with the nearest circuit breaker  14  upstream of the fault. Circuit breakers  14  upstream of the nearest circuit breaker to the fault remain closed unless the downstream circuit breaker is unable to clear the fault. Protection system  26  can be implemented for any abnormal condition or parameter of power in system  105 , such as, for example, long time, short time or instantaneous overcurrents, or excessive ground currents. 
         [0038]    In order to provide the circuit breaker  14  nearest the fault with sufficient time to attempt to clear the fault before the upstream circuit breaker is opened, the upstream circuit breaker is provided with an open command at an adjusted or dynamic delay time. The upstream circuit breaker  14  is provided with an open command at a modified dynamic delay time that elapses before the circuit breaker is opened. In an exemplary embodiment, the modified dynamic delay time for the opening of the upstream circuit breaker  14  is based upon the location of the fault in system  105 . Preferably, the modified dynamic delay time for the opening of the upstream circuit breaker  14  is based upon the location of the fault with respect to the circuit breakers and/or other devices and topology of system  105 . 
         [0039]    Protection system  26  can provide open commands at modified dynamic delay times for upstream circuit breakers  14  throughout power distribution system  105  depending upon where the fault has been detected in the power flow hierarchy and the modified dynamic delay times for the opening of each of these circuit breakers can preferably be over an infinite range. Protection system  26  has CCPU that is configured with algorithm  200  of the instant invention to provide adaptive circuit protection for circuit breakers  14 . Protection system  26  reduces the clearing time of faults because CCPU  28  provides open commands at modified dynamic delay times for the upstream circuit breakers  14  which are optimum time periods based upon the location of the fault. It has been found that the clearing time of faults has been reduced by approximately 50% with the use of protection system  26 , as compared to the use of contemporary systems. 
         [0040]    CCPU  28  coordinates protection system  26  by causing the circuit breaker  14  nearest to the fault to clear the fault. Protection system  26  variably adjusts the dynamic delay time for opening of the upstream circuit breakers  14  to provide backup protection for the downstream circuit breaker nearest the fault. In the event that the downstream circuit breaker  14  nearest the fault is unable to clear the fault, the next upstream circuit breaker will attempt to clear the fault with minimal additional delay based upon its modified dynamic delay time. This reduces system stress, damage and potential arc energy exposure of operating and service personnel while maintaining selectivity. 
         [0041]    Referring to  FIG. 4 , a static representation of two protective device trip time curves representing a protective function are shown, and generally referred to by reference numeral  100 . Graph  100  represents the response of a power system to a feeder fault as shown in  FIG. 3 . Graph  100  of  FIG. 3  illustrates a system substantially similar to the system of  FIGS. 1 and 2 . Graph  100  the shows curve  105  representing the protective response of main breaker and curve  110  representing the response of feeder breaker. Both curves  105  and  110  are static and respond to all fault conditions in an identical fashion. Graph  100  represents a main breaker  415  and a feeder breaker where the feeder breaker is intended to trip while the main breaker  415  remains closed. Because these curves are static, if there is a bus fault in the equipment or the feeder breaker  420  compartment, the main breaker  415  will trip at the static delay time, and not earlier, thus releasing more energy than necessary. Should the feeder breaker  420  not activate, the main breaker  415  would trip at a much higher energy level because it has to be set above the delays of the slowest feeder and cannot adjust to dynamic conditions. 
         [0042]    Referring to  FIG. 5 , a graph representing a static trip time curve of an adaptive protective function in the event of a bus fault, is shown and generally represented by reference numeral  120 .  FIG. 5  represents the scenario in which there is a bus fault as opposed to a feeder fault of  FIG. 3 . Main curve  125  and feeder curve  130  are shown at their default delays. The main breaker is shown as tripping more rapidly than the feeder thus showing the devices to be non-selective. This graph gives the impression that the main and feeder are not selective. 
         [0043]    Referring to  FIG. 6 , a graph representing a protective mode of the present invention is called Zone Selective Interlock (ZSI), a protective function in low voltage equipment, is shown and generally referred to by reference numeral  150 . According to the present invention, the ZSI mode is selected from a user interface that permits selective functioning depending upon whether or not the fault is a feeder or a bus fault. In an exemplary embodiment, the ZSI routine is performed at CCPU  28  and interacts with the individual protection functions for each module  30 , which are also determined at the CCPU. The ZSI routine could also use pre-set clearing times for circuit breakers  14  or the clearing times for the circuit breakers could be determined by CCPU  28  based on the physical hardware, which is known by the CCPU. The CCPU  28  effectively knows the topology of power distribution system  105 , which allows the CCPU to open the circuit breakers  14  at an infinite range of times. 
         [0044]    In  FIG. 6 , graph  150  shows the scenario when a feeder fault occurs. The main delay is automatically adjusted to allow the feeder to clear the fault first as shown by curve  155 . Should the fault not be cleared by the feeder, the main breaker is automatically tripped to ensure that the feeder breaker is backed up, immediately thereafter, as shown by curve  160 . ZSI is a protective function that reduces the time delay of the main breaker in the event of a bus fault to minimize the released energy. Additionally, ZSI provides a more rapid response of the main breaker thus protecting the bus and the associated equipment. The ZSI function behaves in a selective manner if the fault is in the feeder in comparison to the fault existing in the bus, to minimize the released energy and respond as soon as possible. 
         [0045]    The protective function the instant invention shown the protective action immediately and graphically for both feeder and bus fault events. 
         [0046]    Referring to  FIG. 7 , the method of the present invention is also described with respect to a bus differential protective function, and is generally referred to in graph  170 . Graph  170  displays a scenario with a bus fault, where bus differential is represented by curve  175  is clearing the bus fault. Should the fault beat a higher magnitude, the main represented by curve  180  will clear the bus fault. The curve of the feeder remains unchanged  185  because the fault is at a higher level than the feeder breaker. 
         [0047]    In addition to modifying the response of circuit breakers, the protective function of the instant invention also displays how released incident energy can be reduced in the event of a fault. Referring to  FIG. 8 , the instant energy of a static protective device is shown and generally referred to in graph  190  at curve  195 , during a bus fault. Graph  190  shows incident energy that is being released during the fault event shown at graph  100  of  FIG. 4 . The incident energy is the amount of energy that is released until the fault is cleared. In the first approximately two seconds of a fault event, the energy is being released and there is no fault protection. Accordingly, the energy at the start of a fault for a static device is high at approximately 48 C/cm 2 . After approximately 2 seconds when the fault is being cleared, the available current is approximately 20K amperes, a relatively high value which correlates to a high class of energy. When the fault is cleared (begins to be cleared) approximately 18 C/cm 2  is being released. A high level of energy is being released because the current at the time of clearing is very high, due to the lack of adaptively of the static protective system. 
         [0048]    Referring to  FIG. 9 , the incident energy being released is shown in graph  205  by curve  210  for the adaptive multiple protection function of  FIG. 5 . Comparing graph  205  of  FIG. 9  to graph  190  of  FIG. 8 , the initial incident energy is identical. However, the current when the fault is being cleared is substantially lower in  FIG. 6  than in  FIG. 4 . In  FIG. 6  the current is approximately 3000 amps. In  FIG. 4 , the current is approximately 14K amps when the fault is being cleared. In  FIG. 9 , because the current is so much lower when the fault is cleared, the amount of incident energy released is substantially lower as well. The benefit of the bus differential (a fault protection algorithm) is that it provides substantial protection against high energy releases by tripping the bus differential at a low current. 
         [0049]    In addition to the system being able to adapt and to provide a protective function in the event of a location fault, the system also adapts to other conditions. For example, the system provides different adaptive responses based on different scenarios such power flow topology and the states of the breakers. The “on” or “off” status of the breakers provides a different condition that would also enable different protective functions and cause different curves to be drawing that are representative of the protective function based upon the algorithms. Further, user selected inputs such as maintenance mode would change the protective response for the specific fault condition. 
         [0050]    While the instant disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope thereof. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.