Abstract:
A system and methods that enable a restoration scheme for power distribution systems that is independent of power distribution system component configuration, the number of power distribution system components, and component settings are provided. In a power distribution system, a number of intelligent reclosers having restoration control modules are deployed that execute a restoration scheme. The intelligent reclosers constantly poll cooperating power distribution lines to determine changes in current or voltage provided by the power distribution lines. In the event of a power distribution system fault, the reclosers act in accordance to a predefined restoration scheme to reanimate the unaffected portions of the failing power distribution system.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to power distribution systems, and more particularly, to providing power distribution systems utilizing a restoration scheme to efficiently overcome power distribution system failures.  
         BACKGROUND OF THE INVENTION  
         [0002]    The basic function of a power system is to continuously maintain adequate and reliable supply of electric power. However, performing this function is not always possible because various types of failures occur randomly beyond the control of power system engineers. Power system planners, designers, and operators are generally concerned with the reliability of the power system and then calculate approximately the realistic availability of their system. Recently, this concern has been accentuated by increasing competition among utility companies due primarily to de-regulation of the electrical power industry. Now, utility companies that once shared information across a common electrical grid are competing against themselves to provide distinguishable services in an effort to sustain existing customers and attract new customers.  
           [0003]    Residential and business customers alike are increasingly dependent on power. From a simple switch to complex manufacturing equipment, power is required everyday. As a result of this new competition and the importance of power to customers, power systems are required to provide reliable, dependable, and more affordable power. Globally, power system engineers who maintain the operation and control of electrical power are challenged daily by consequences of electrical power being disrupted that translates directly to the quality, reliability and cost of electrical power. Utility companies have taken notice since the consequences of long-term unavailability and persistent interruption of electric power could directly translate to a loss of power customers.  
           [0004]    The techniques first used in practical applications of power system design were developed to account for random failures. These techniques were generally deterministic in nature. Their primary weakness was a lack of consideration for the stochastic nature of system behavior, customer demands, and equipment failures.  
           [0005]    In an effort to overcome power system limitations, power system equipment manufacturers developed devices, such as, power distribution protective relays and reclosers with control and operation schemes to achieve automated restoration of power systems. Existing restoration schemes, however, are rigid, requiring pre-defined configurations of power distribution system equipment and requiring pre-determined device settings.  
           [0006]    Presently, there exist power distribution equipment incorporating restoration schemes that assist in bringing a power distribution system online in the event of a fault or loss of voltage. However, these restoration schemes place inflexible limits on the power distribution system. Such limits include pre-defined quantity, configuration and operation settings of equipment used in a restoration scheme.  
           [0007]    From the foregoing, it is appreciated that there exists a need for a power system and method providing a robust restoration scheme that can be applied to power distribution systems, independent of power system equipment configuration or settings.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides automatic restoration of power distribution systems independent of power distribution system equipment, configuration and settings. A power distribution system has equipment in a variety of configurations; the present invention provides a solution such that in the event of a fault or loss of voltage, the equipment that are proximate to the fault, in a closed state, are all tripped to an open state. Subsequently, the equipment determines if there is voltage on either side of the equipment. If there is voltage on both sides, processing by the equipment ceases. However, if the contrary is true (e.g. one source of line voltage entering the equipment or the other source of line voltage leaving the equipment is de-energized), the equipment determines which source side is energized and initiates a close, such that current flows from the energized voltage source of the equipment to the de-energized source. In the event that the processing component is positioned in series to a power system circuit breaker the equipment is left open regardless.  
           [0009]    The invention permits the power distribution system to perform the automated restoration regardless of the number of equipment, configuration of the equipment, or equipment settings.  
           [0010]    The invention further provides the power distribution system comprise power distribution components having microprocessors and logic capable of processing voltage levels and/or current levels along and/or across a cooperating power line and controlling the flow of current along and/or potential drop across said cooperating power line. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The system and methods providing a restoration scheme for power distribution systems in accordance with the present invention are further described with reference to the accompanying drawings in which:  
         [0012]    FIGS.  1  is a system diagram of a prior art power distribution system employing a prior art restoration scheme;  
         [0013]    [0013]FIG. 2 is a system diagram of an alternative prior art power distribution system employing a prior art restoration scheme;  
         [0014]    [0014]FIG. 3 is a system diagram of an exemplary power distribution system having exemplary power distribution components that are capable of realizing a restoration scheme in accordance with the present invention;  
         [0015]    FIGS.  3 A- 3 G are system diagrams showing the states of an exemplary power distribution system employing the restoration scheme in accordance with the present invention;  
         [0016]    [0016]FIG. 4 is a block diagram showing the elements of exemplary power distribution system equipment performing the steps of the restoration scheme of the present invention;  
         [0017]    [0017]FIG. 5 is a block diagram of a restoration control module configuration in accordance with the present invention; and  
         [0018]    [0018]FIG. 6 is a flowchart of the processing performed by the power distribution system to re-animate a power distribution system that has experienced a fault in accordance with the restoration scheme of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0019]    Power Distribution Systems Overview:  
         [0020]    Electrical transmission lines and power generation equipment must be protected against isolated faults and consequent short circuits, which could cause a collapse of the power system, serious and expensive equipment damage, and personal injury. It is the function of the protective relays, circuit breakers and reclosers, which monitor ac voltages and currents, to locate line faults and initiate isolation by the tripping of circuit breakers or reclosers.  
         [0021]    Reclosers are usually used to minimize power distribution interruptions caused by transient (e.g. temporary) and/or permanent faults. Typically, during a system disturbance, large increases in current occur. Sensing a current increase, the recloser will open thereby cutting off current flow in order to protect power distribution system equipment connected to the power distribution system. Since many fault conditions are temporary, the recloser is designed to close after a short period of time, thereby re-establishing normal current flow. For example, during a thunderstorm, if lighting were to strike the distribution system, the power to one&#39;s home may be disrupted for few seconds causing lights and appliances to turn OFF (recloser opening), then ON (recloser closing). Once the recloser closes, if it senses the continued presence of increased current, it will again open. Such cycling between open and closed may occur a number of times before the recloser remains open. In this case, lockout occurs, a state in which the temporary fault becomes a permanent fault.  
         [0022]    Comparatively, power distribution system protective relays and circuit breakers operate similarly to reclosers such that when circuit breakers open, they do not allow current to flow through, and when they are closed, allow current to pass.  
         [0023]    To capitalize on the functions of today&#39;s power distribution system equipment, power distribution operators have developed restoration schemes to automate the process of reanimating a failed power distribution system. These schemes exploit the intelligence found in power distribution system equipment. Specifically, power distribution system equipment, such as, control devices for reclosers comprise a central processing unit (CPU), memory storage means, a power supply module, a communication module, a digital input/output module, and PT/CT (Potential Transformer/Current Transformer) A/D (Analog-to-Digital) module. A set of instructions indicative of a power restoration scheme may be stored in the memory storage means of the control device for the recloser to perform. Accordingly, the restoration scheme may be active when the reclosers of a power distribution system act in accordance to roles pre-defined by the stored instructions. For example, a power distribution system may comprise a number of reclosers having a predefined configuration (e.g. configuration as defined by the restoration scheme) that allow the flow of current along the power distribution system. When a fault occurs in the power distribution system, the reclosers act in accordance to the pre-defined instructions to isolate the fault and attempt to energize the remaining undisturbed portion of the power distribution system. This, however, entails the use of specific control devices and reclosers performing very specific functions to realize the overall operation of the restoration scheme rendering such restoration schemes as extremely rigid.  
         [0024]    A more effective power distribution system would provide a power distribution system protection and restoration scheme that would be independent of power distribution system equipment providing fault protection and system restoration according to predefined set of rules realized through intelligent power distribution system circuit breakers, protective relays, and reclosers.  
         [0025]    As will be described below with respect to FIGS.  1 - 6 , the present invention is directed to power distribution systems and methods that provide a robust restoration scheme. In accordance with an illustrative implementation thereof, the present invention comprises systems and methods that employ power distribution system equipment capable of sensing voltage and current to employ a restoration scheme for reanimation of failed power distribution systems.  
         [0026]    In an illustrative implementation, described more fully hereinafter, the methods and apparatus of the present invention may be implemented as part of a power distribution system having reclosers with voltage sensing transformers. Although the depicted embodiment provides systems and methods employing exemplary power distribution components having a particular configuration, those skilled in the art will appreciate that the inventive concepts described herein extend to various types of power distribution components having varying configurations.  
         [0027]    Restoration Schemes Implementation:  
         [0028]    [0028]FIGS. 1 and 2 show prior art restoration schemes for power distribution systems. FIG. 1 shows a three-recloser restoration scheme for a power distribution system. As shown in FIG. 1, power distribution system  100  comprises a first source  110  and second source  120 . A circuit is completed from first sources  110  to second source  120  as first source  110  is connected to sectionalizing recloser  130 . In turn sectionalizing recloser  130  is connected to tie-point recloser  140  that is connected to sectionalizing recloser  150 . Lastly, sectionalizing recloser  150  is connected to second source  120  to complete the circuit. Further, as shown fault  160  may occur in power distribution system  100  such that current is interrupted between first source  110  and the rest of the power distribution system  100  circuit. The area where the fault occurs is referred to as the fault zone.  
         [0029]    Generally sectionalizing reclosers  130  and  150  have the characteristics of being placed close to the power station (e.g. first source  110  and second source  120 ). In operation, sectionalizing reclosers  130  and  150  trip and lock out (e.g. open) after a programmed time upon the loss of voltage from a sensing transformer (not shown) in the fault zone. Comparatively, a tie-point recloser is placed between cooperating circuits (e.g. between two power sources) and operates in an open state (e.g. not allowing current to flow through). In operation, the tie-point recloser closes (e.g. allowing current to flow through) after a programmed time.  
         [0030]    In the three-recloser scheme illustrated in FIG. 1, if the circuit is faulted between first source  110  and sectionalizing recloser  130  by fault  160 , first source circuit breaker recognizes the fault and locks out. Using a voltage-sensing transformer sectionalizing recloser  130  will recognize the loss of voltage and automatically open for a predetermined time period, isolating the faulted zone within the circuit. In conjunction, the tie-point recloser  140  will recognize a loss of voltage on the first source portion of the loop scheme. This, however, requires the presence of a tie-point recloser between the sectionalizing reclosers, thereby rendering this restoration scheme as inflexible. After a time delay, tie-point recloser  140  will close to establish service back to the sectionalizing recloser  130 .  
         [0031]    [0031]FIG. 2 shows a restoration scheme employing five reclosers. As shown, power distribution system  200  comprises first source breaker  210 , a second source breaker  220 , sectionalizing reclosers  230  and  270 , respectively; mid-point reclosers  240  and  260 , respectively, and tie-point recloser  250 . Sectionalizing reclosers  230  and  270 , and tie-point recloser  250  operate exactly as their counterparts in the three recloser restoration scheme described by FIG. 1. The five-recloser restoration scheme contemplates the use of an additional type of recloser that is, mid-point reclosers  240  and  260 . Mid-point reclosers  240  and  260  are placed between sectionalizing reclosers and tie-point reclosers. Further, during fault-free power distribution system operation, mid-point reclosers  240  and  260  stay closed. In operation, mid-point reclosers  240  and  260  monitor a voltage-sensing transformer (not shown). If there is dead voltage, mid-point reclosers  240  and  260  change their minimum trip value as it prepares to be back-fed from an alternative source (e.g. if a fault occurs between first source  210  and mid-point recloser  240 , mid-point recloser  240  will expect to be fed from second source  220 ).  
         [0032]    In the five-recloser restoration scheme described in FIG. 2, if the circuit is faulted between first source  210  and sectionalizing recloser  230  as indicated by fault  280 , first source breaker  210  will recognize the fault and lock out. Using a single voltage-sensing transformer, the sectionalizing recloser (e.g.  230  or  270 ) will recognize the dead voltage and open automatically isolating the faulted zone within the circuit. The mid-point recloser (e.g.  240  or  260 ) automatically changes its trip settings to allow proper operation during a back-feed condition from the tie-point recloser  250 . In addition, tie-point recloser  250  recognizes a dead voltage on the first source  210  portion of the loop scheme. After a predetermined time delay, tie-point recloser  250  closes to establish service back to the sectionalizing recloser (e.g.  230  or  270 ). Tie-point recloser  250  also changes its operation to one-shot to lockout in case it may be closing into a fault. After a programmed time, tie-point recloser  250  changes back to its original settings (e.g. three tries until lockout). Once again, the success of the restoration scheme is dependent on the configuration of the distribution system components.  
         [0033]    The above restoration schemes provide viable methods to restore power distribution systems having faults. However, these schemes present several shortcomings, such as, the need of manual resources to clear the fault, to close the sectionalizing recloser, and to open the tie-point recloser to its normal state. As such, two or three line crews, may be required to go out into the field and communicate with each other to repair the faulted line, to close the sectionalizing recloser to parallel the system and, lastly, to open the tie-point recloser.  
         [0034]    The present invention aims to ameliorate these shortcomings by providing automated restoration of power distribution systems. Specifically, the restoration scheme of the present invention automatically sets a new open point thereby eliminating the need to open the tie-point recloser. The recloser loop control scheme of the present invention employs a plurality of reclosers installed in series between two substation feeder circuits of a power distribution system. This provides isolation of any faulted section within a given distribution circuit while simultaneously re-establishing service to all customers unaffected by the faulted section within a short period of time. The details of which are described by FIGS.  3 - 5 .  
         [0035]    System Overview:  
         [0036]    [0036]FIG. 3 shows an exemplary power distribution system  300  employing the restoration scheme of the present invention. Power distribution system  300  comprises, source circuit breakers  305  and  310 , a plurality of standard reclosers (e.g.  315 ,  320 ,  325 ,  330 ,  335 ,  340 ,  345 ,  350 ), and sectionalizing recloser  355 . The reclosers are equipped with sensing transformers on the input and output sides enabling the recloser to monitor current and/or voltage levels at the input and output. In operation, power distribution system  300  allows voltage and current to flow from source circuit breakers  305  and  310  to power distribution nodes  360 ,  363 ,  365 ,  367 ,  370 ,  373 ,  375 ,  377 , and  380 .  
         [0037]    The power distribution system shown in FIG. 3 is shown to be operating in a fault-free state. In a fault-free state, power is distributed from source breaker  305  and through reclosers  315 ,  320 ,  325 ,  330 , and  335  such that power may be delivered to power distribution nodes  360 ,  363 ,  365 ,  36 ,  370 , and  373 , respectively. Similarly, power is distributed in the rest of power distribution system through source breaker  310 . Power passes from source breaker  310  to reclosers  350 ,  345 , and  340  supplying power to power distribution nodes  383 ,  380 ,  377 , and  375 . Sectionalizing recloser  355  serves an important role as it breaks up power distribution system into independent functioning sections. As such power distribution system is allowed to have two source circuit breakers  305  and  310  to service all of the power distribution nodes. In operation reclosers  315 ,  320 ,  325 ,  330 ,  335 ,  340 ,  345 , and  350  remain closed allowing power to pass through. Comparatively, sectionalizing recloser  355  remains open under normal operation such that power serviced from source breaker  305  does not interfere with power serviced from source breaker  310 .  
         [0038]    FIGS.  3 A- 3 G illustrate the operation of the restoration scheme on exemplary power distribution system  300  when power distribution system experiences a fault. Fault  385  (e.g. lightning, fallen tree, or sever ice) may afflict power distribution system such that power is interrupted along power distribution system. In the example provided, fault  385  strikes power distribution system between recloser  315  and recloser  320 . Upon the occurrence of fault  385 , recloser  315  trips from the closed state to the open state. In response the restoration scheme starts to take affect. The goal of the restoration scheme is to reanimate a failed power distribution system such that power may be delivered to as many power distribution nodes of the failed power distribution system as possible. Upon the occurrence of a fault, reclosers  315 ,  320 ,  325 ,  330 ,  335 ,  340 ,  345 ,  350 , and  355 , maintain instructions and logic that realize a power restoration scheme. Generally, if there is a drastic change in voltage and/or current at the input or output of a recloser, the recloser trips to its opposite state (e.g. if a recloser is closed it trips open or vice versa). Once tripped, the recloser will attempt to reclose after a set period of time so that power can pass from a voltage bearing side of the recloser to a non-voltage bearing side. In FIGS.  3 - 3 G the presence of the letter “V” indicates a voltage-bearing side of a recloser.  
         [0039]    Recloser  315  maintains logic such that it trips to an open state upon the detection (e.g. by the voltage sensing transformers) of a dead voltage at either of its input or output terminals. Reclosers  320 ,  325 ,  330 , and  335  maintain similar logic such that if there is change in the live or dead voltage at their input or output terminals they trip to an open state. Comparatively, sectionalizing recloser  355  maintains logic that trips recloser  355  to an open state upon the detection (e.g. by the voltage-sensing transformers) of a dead voltage at its input or output terminal.  
         [0040]    Accordingly and as shown in FIG. 3B, reclosers  320 ,  325 ,  330 , and  335  trip from their closed state to an open state in response to fault  385 . Further, in response to reclosers  320 ,  325 ,  330 , and  335  closing sectionalizing recloser  355  trips from its open state to a closed state as the voltage at its output level changes (e.g. recloser  335  opens). By having sectionalizing recloser  355  trip from an open state to a closed state power can be delivered from source breaker  310  to the rest of the failed power distribution system.  
         [0041]    FIGS.  3 C- 3 G show the states of reclosers of power distribution system as the restoration scheme continues to take effect. As shown in FIG. 3C, reclosers  315 ,  320 ,  325 , and  330  remain in their open position. However, recloser  335  is shown to be in a closed position. In response to sectionalizing recloser  355  tripping from an open to a closed state, recloser  335  now has live voltage at one of its terminals. As such, recloser  335  attempts to reclose. If successful, the recloser will close and allow power to pass through such that there is live voltage at both of its terminals (e.g. its input and output terminals). However, if unsuccessful (e.g. a condition exists such that the recloser is not allowed to reclose—e.g. the continuing presence of a fault, or if programmed to stay opened), the recloser locks out and remains open. In the example provided, recloser  335  is successful in its bid to close. Accordingly, power is allowed to pass through recloser  335 . Recloser&#39;s  335  success has impact on the rest of the system as recloser  330 , which is serially connected to recloser  335 , now has voltage at one of its terminals.  
         [0042]    Accordingly, and as shown in FIG. 3D, recloser  330 , now having voltage at one of its terminals, will attempt to reclose in a similar manner as to recloser  335 . In the example provided, recloser  330  is successful in its attempt to reclose thereby allowing power to flow through and providing power to a terminal of recloser  325 . As shown in FIG. 3E, recloser  325  will attempt to reclose in a manner similar to the operation of reclosers  330  and  335 . In the example provided, recloser  325  is successful providing power to recloser  320 . FIG. 3F shows that recloser  320  is successful in closing such that it may deliver power to recloser  315 . Unlike the other reclosers, recloser  315  will not attempt to reclose. The restoration scheme requires that reclosers connected closest to the source circuit breakers remain open upon the occurrence of a fault. This recloser will remain open regardless if a voltage is sensed at one of its terminals subsequent to the occurrence of the fault. At this point, power distribution system operators monitoring the power distribution system would deploy a ground crew to manually reset recloser  315 . As FIG. 3G shows, during the manual reset of recloser  315 , recloser  335  trips to an open state such to bring the power distribution system back to its originally operating state (as shown in FIG. 3).  
         [0043]    Power Distribution System Equipment:  
         [0044]    [0044]FIG. 4 depicts one presently preferred embodiment of a recloser employed by a restoration scheme in accordance with the present invention. As shown, the recloser comprises current and voltage transducers  10 , filters  12 , and a multiplexer  14 , the latter outputting an interleaved stream of analog phase current and voltage signal samples, as well as neutral current samples. The analog multiplex output by the multiplexer  14  is digitized by an analog-to-digital converter  16 . The output of the analog-to-digital converter  16  is fed to a digital signal processing block  18 . The digital signal processing block  18  employs a Fourier transformation to produce phasor data for each of the sampled channels. The phasor data is stored in a memory  20 . The phasor data in the memory  20  is fed via a  16 -bit data bus to a central processing unit (CPU) board  22 . The CPU board  22  includes a microprocessor  22 - 1 , random access memory  22 - 2 , and read only memory (ROM)  22 - 3 . The (ROM)  22 - 3  contains program code controlling the microprocessor  22 - 1  in performing fault typing, fault location, and reporting functions. Additionally, ROM  22 - 3  contains the instructions used by microprocessor  22 - 1  to perform the voltage sensing and tripping functions required by the restoration scheme. The random access memory  22 - 2  includes a pre-fault segment of memory, a post-fault segment of memory, and a circular array, which are employed as described below in performing the fault typing and fault location functions. Further, CPU board  22  outputs fault data to a protection/alarming block  24  that performs protection and alarming functions such as tripping a circuit breaker or sounding an alarm as appropriate such that power distribution system operators are placed on notice of the recloser&#39;s state.  
         [0045]    [0045]FIG. 5 depicts one presently preferred embodiment of a restoration control module configuration that may be employed in providing a restoration scheme in accordance with the present invention. As shown, restoration control module configuration comprises a first recloser  510  and a second recloser  520  having restoration control module (RCM)  515 , coupled by an electrical line  515 . Recloser  510  has an input  510   a  and an output  510   b  that denote a source side and load side, respectively. Similarly, recloser  520  has an input  520   a  and an ouput  520   b  that denote a source side and load side, respectively. Recloser  510  and  520  are part of power distribution system (not shown). When the power distribution system experiences a fault, it will generally occur between two reclosers, such as, recloser  510  and recloser  520 . In this scenario, on the upstream device (e.g. recloser  510 ) the fault is located on the load side (e.g.  510   b ) and on the downstream device (e.g. recloser  520 ), the fault is located on the source side (e.g.  520   a ). This condition generally holds true for the majority of faults presented to the power distribution system.  
         [0046]    In operation, RCM  515  will analyze and isolate the faults occurring on the hosting power distribution system. RCM  515  communicates with and receives information from the hosting recloser (e.g. recloser  510 ) and from upstream devices (e.g. recloser  520 ) via binary inputs and binary outputs. RCM cooperates with its host recloser to open or close the host recloser depending on various fault and non-fault conditions. Examples of such conditions are as follows: 1) if there is “dead voltage” (i.e voltage below a set threshold level) at both the source  510   a  of recloser  510  and source  520   a  of recloser  520 , recloser  510  RCM  515  residing in recloser  510  opens recloser  510 ; 2) if there is “dead voltage” at source  510   a  and “live voltage” (i.e. voltage above a set threshold level) at source  520   a  of recloser  520 , RCM  515  residing in recloser  510  closes recloser  510 ; and 3) if there is “dead voltage” at source  520   a  and “live voltage” at source  510   a  of recloser  510 , RCM  515  residing in recloser  520  closes recloser  520 . Using these exemplary rules, RCM  515  cooperates with power distribution equipment to effectively reanimate portions of (or entire) power distribution systems.  
         [0047]    Restoration Scheme Processing:  
         [0048]    [0048]FIG. 6 is a flowchart of the processing performed by power distribution system components employing the restoration scheme of the present invention to handle a fault along the power distribution system and the steps undertaken to reanimate the power distribution system. Processing begins at block  600  and proceeds to block  610  where a check is performed to determine if a fault has occurred along the power distribution system (PDS). A fault may be detected by checking power distribution system equipment for drastic changes in voltage or current. If there a fault has not been detected, processing reverts to block  600  and proceeds therefrom. However, if the alternative proves to be true, processing proceeds to block  620 , where all of the power distribution system equipment (e.g. reclosers) up until a sectionalizing recloser trips to an open state. Processing proceeds to block  630  where the sectionalizing recloser (e.g. sectionalizing recloser) is tripped to a close state. The power distribution system equipment closest to the sectionalizing power distribution source then attempts to close at block  640 . In this effort a check is performed at block  650  to determine if there exists a voltage or current at the input or output of the attempting power distribution equipment. If this check proves to be negative, processing proceeds to block  660  where the ground crew are notified to manually reset this power distribution equipment as it is deemed to be where the fault has occurred. Processing then proceeds to terminate at block  660 . However, if the alternative proves to be true at block  650 , the attempting power distribution equipment closes to allow current and voltage to pass at block  670 . A check is then performed at block  680  to determine if there are additional open power distribution system equipment. If there are additional open power distribution system equipment, processing reverts to block  650  and proceeds therefrom. However, if the results of this check indicate that there are additional open power distribution system equipment, processing reverts to block  660  and proceeds therefrom.  
       CONCLUSION  
       [0049]    In sum, the present invention provides a system and methods providing a robust restoration scheme for power distribution systems. It is understood, however, that the invention is susceptible to various modifications and alternative constructions. There is no intention to limit the invention to the specific constructions described herein. On the contrary, the invention is intended to cover all modifications, alternative constructions, and equivalents falling within the scope and spirit of the invention.  
         [0050]    For example, the present invention may be implemented in a variety of power distribution systems. The various techniques described herein may be implemented in a variety of hardware or software, or a combination of both. Preferably, the techniques are implemented in power distribution control devices having digital signal processors, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements) operating various computer programs. Program code is applied to perform the functions described above and to generate output information. The output information is applied to one or more of the power distribution components. Each program is preferably implemented in assembly or machine language. However, the programs can be implemented in a high level procedural or object oriented programming language to communicate with a computer system, if desired. In any case, the language may be a compiled or interpreted language. Each such computer program is preferably stored on a storage medium or device (e.g., ROM or magnetic disk) that is readable by a general or special purpose programmable computer for configuring and operating the computer when the storage medium or device is read by the computer to perform the procedures described above. The system may also be considered to be implemented as a computer-readable storage medium, configured with a computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner.  
         [0051]    Although exemplary embodiments of the invention have been described in detail above, those skilled in the art will readily appreciate that many additional modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of the invention. Accordingly, these and all such modifications are intended to be included within the scope of this invention as defined in the following claims.