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1)Human errors may produce power-system outages. Switches may be opened unintentionally, cutting off loads; temporary grounding electrodes may be put on energized circuits by mistake; equipment handled by hotline devices may be dropped. Such occasions, although rare, must be considered as hazard possibilities in power-system design.
The Long Island Lighting Co. provides service to over a million customers via 750 plus distribution feeders, comprised, mainly, of overhead lines. These feeders are subject to the usual storm-related problems involving damage due to thunderstorms, lightning, tree contact, ice storms and hurricanes. Compared with other New York State electric utilities, on average, LILCO provides the fastest restoration, although customers have in the past experienced more frequent sustained interruptions.
An analysis of customer outages determined that about 78% of interruptions were due to faults on main there-phase lines. A fault on the main line would cause, on average, 2000 customers to lose power. In order to reduce these outages, the company has instituted reliability programmers that include trimming trees, installing lightning arresters, installing covered wire and replacing obsolete armless insulators. These programmes reduced outages, but were not sufficient to reach the desired level of service continuity. To further improve reliability, LILCO has installed an advanced distribution automation system, developed jointly by LILCO and Harris Distributed Automation Products, Calgary, Alberta, Canada. This system isolates faults and restores non-damaged portions of the main line circuit based on real-time parameters of voltage, current, breaker status and supervisor-controlled switch positions. Since this project was initiated in 1993, more than 240,000 customers have avoided a sustained interruption of service.
2) The third stage of the project required the development of an advanced algorithm for the automatic restoration of power reaching the non-faulted feeder zones. This algorithm was written to run on the Harris D-200, which serves as the front end processor for communications with the RTUs.
The Harris D-200 receives information from the Autosectionalizing switches reporting loss of voltage and fault location. In addition, the Harris D-200 receives substation breaker status and loading from the affected circuit as well information from the adjacent tie circuit. Finally, based on real-time voltage, load, breaker status, switch positions and safety interlocks, the algorithm calculates and reports corrective measures to restore service. The autorestoration algorithm is designed to restore up to 12 feeders simultaneously and will support as many as seven switches arranged in an open loop arrangemeng. In addition, the operators can set the level of automation for each circuit loop. The levels include:
The manual. The PC SCADA system will not issue a recommendation to restore service. The operators have full supervisory control and indication of switches.
Operator Acknowledgement. The Harris D-200 will determine the faulted zone and then based on real-time information will issue to the PC SCADA a simulation screen and the switching steps required to restore service. If the operator agrees with the algorithm’s recommendation, the operator “issues an acknowledgment” enabling the PC SCADA to perform the necessary switching steps. A failure of any switching step aborts the restoration and places the circuit loop into manual.
Full Automation. Based on the algorithm the faulted zone is determined and the switching is automatically performed to restore the non-faulted zones. All automatic switching steps are based on real-time information, and operator procedures(interlocks) prevent the energizing of work areas. No operator intervention is required.
On April 30, 1996, LILCO received a patent for the advanced restoration algorithm. While many utilities are using supervisory switching to isolate faults, most use operator remote control to restore service. This procedure is time consuming and inefficient, particularly during storm conditions when multiple faulted circuits occur
3)Distribution Automation Increases Reliability
The operation of electric power systems may be disturbed as the result of a number of causes. The troubles on the electric circuits are usually in the form of broken conductors or circumstances in which conductors are temporarily (or permanently) connected to each other or to ground. Regardless of the cause of the disturbances, such troubles seriously interfere with the flow of power and require corrective action.
Overhead lines are vulnerable to troubles caused by lightning. When lightning strikes a line or a nearby object, a transient voltage is created on the line. High-voltage circuits have large spacings between conductors and from conductors to grounded objects, such as towers. Direct strokes to such lines are usually diverted to ground through overhead ground wires and may cause no interference with operation. Occasionally strokes terminate directly on the power conductors and introduce into them transient voltages of such magnitude that arcover across insulator strings may result. Once an arc is established, power current flows through it until the circuit is deenergized. Lightning voltages may be of high magnitude but are of very short duration; their time is measured in microseconds. As a result, their effects are most noticeable at the point where the stroke occurs. Distribution lines, which operate at perhaps 12kv or less, are mounted on relatively small insulators which may be flashed over by the voltage induced in a line even though the lightning stroke does not contact the line. Such resulting arcs interfere with operation and usually are eliminated by deenergizing the line. When the line is deenergized, the arc is extinguished and, very commonly, the line may be reenergized immediately.
以上论文仅供参考（三段）
The Long Island Lighting Co. provides service to over a million customers via 750 plus distribution feeders, comprised, mainly, of overhead lines. These feeders are subject to the usual storm-related problems involving damage due to thunderstorms, lightning, tree contact, ice storms and hurricanes. Compared with other New York State electric utilities, on average, LILCO provides the fastest restoration, although customers have in the past experienced more frequent sustained interruptions.
An analysis of customer outages determined that about 78% of interruptions were due to faults on main there-phase lines. A fault on the main line would cause, on average, 2000 customers to lose power. In order to reduce these outages, the company has instituted reliability programmers that include trimming trees, installing lightning arresters, installing covered wire and replacing obsolete armless insulators. These programmes reduced outages, but were not sufficient to reach the desired level of service continuity. To further improve reliability, LILCO has installed an advanced distribution automation system, developed jointly by LILCO and Harris Distributed Automation Products, Calgary, Alberta, Canada. This system isolates faults and restores non-damaged portions of the main line circuit based on real-time parameters of voltage, current, breaker status and supervisor-controlled switch positions. Since this project was initiated in 1993, more than 240,000 customers have avoided a sustained interruption of service.
2) The third stage of the project required the development of an advanced algorithm for the automatic restoration of power reaching the non-faulted feeder zones. This algorithm was written to run on the Harris D-200, which serves as the front end processor for communications with the RTUs.
The Harris D-200 receives information from the Autosectionalizing switches reporting loss of voltage and fault location. In addition, the Harris D-200 receives substation breaker status and loading from the affected circuit as well information from the adjacent tie circuit. Finally, based on real-time voltage, load, breaker status, switch positions and safety interlocks, the algorithm calculates and reports corrective measures to restore service. The autorestoration algorithm is designed to restore up to 12 feeders simultaneously and will support as many as seven switches arranged in an open loop arrangemeng. In addition, the operators can set the level of automation for each circuit loop. The levels include:
The manual. The PC SCADA system will not issue a recommendation to restore service. The operators have full supervisory control and indication of switches.
Operator Acknowledgement. The Harris D-200 will determine the faulted zone and then based on real-time information will issue to the PC SCADA a simulation screen and the switching steps required to restore service. If the operator agrees with the algorithm’s recommendation, the operator “issues an acknowledgment” enabling the PC SCADA to perform the necessary switching steps. A failure of any switching step aborts the restoration and places the circuit loop into manual.
Full Automation. Based on the algorithm the faulted zone is determined and the switching is automatically performed to restore the non-faulted zones. All automatic switching steps are based on real-time information, and operator procedures(interlocks) prevent the energizing of work areas. No operator intervention is required.
On April 30, 1996, LILCO received a patent for the advanced restoration algorithm. While many utilities are using supervisory switching to isolate faults, most use operator remote control to restore service. This procedure is time consuming and inefficient, particularly during storm conditions when multiple faulted circuits occur
3)Distribution Automation Increases Reliability
The operation of electric power systems may be disturbed as the result of a number of causes. The troubles on the electric circuits are usually in the form of broken conductors or circumstances in which conductors are temporarily (or permanently) connected to each other or to ground. Regardless of the cause of the disturbances, such troubles seriously interfere with the flow of power and require corrective action.
Overhead lines are vulnerable to troubles caused by lightning. When lightning strikes a line or a nearby object, a transient voltage is created on the line. High-voltage circuits have large spacings between conductors and from conductors to grounded objects, such as towers. Direct strokes to such lines are usually diverted to ground through overhead ground wires and may cause no interference with operation. Occasionally strokes terminate directly on the power conductors and introduce into them transient voltages of such magnitude that arcover across insulator strings may result. Once an arc is established, power current flows through it until the circuit is deenergized. Lightning voltages may be of high magnitude but are of very short duration; their time is measured in microseconds. As a result, their effects are most noticeable at the point where the stroke occurs. Distribution lines, which operate at perhaps 12kv or less, are mounted on relatively small insulators which may be flashed over by the voltage induced in a line even though the lightning stroke does not contact the line. Such resulting arcs interfere with operation and usually are eliminated by deenergizing the line. When the line is deenergized, the arc is extinguished and, very commonly, the line may be reenergized immediately.
以上论文仅供参考（三段）
参考资料： http://bbs.newenergy.com.cn/Announce/announce.asp?BoardID=2&ID=3633
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