A smart grid delivers electricity to consumers while leveraging digital communication and control technologies to minimize financial cost, save energy, and increase reliability. If designed properly, the smart grid will have a significant impact on improving a wide range of aspects in the electric power generation and distribution industry. Examples include self-healing, high-reliability, resistance to cyber-attack, accommodation of a wide variety of types of distributed generation and storage mechanisms, optimized asset allocation, and minimization of operation and maintenance expenses as well as high-resolution market control that incorporates advanced metering and demand-response.
An important component in operation of smart grids is fault detection, isolation, and restoration of the smart grid. Today, most distribution devices do not communicate with each other but operate and detect faults independently, unaware of the state of other protection devices and the condition of the grid beyond their own location. Furthermore, the protection settings of the distribution devices are configured manually and need to be coordinated precisely. The manual coordination is provided such that the distribution devices closer to the substation are required to wait longer compared to the distribution devices provided far from the substation. The physical effects of communication channels such as shadowing and multipath propagation for example leads to delay in detection of faults that occur at the distribution devices located nearer to the substation. The delay in detection of the fault results in less than optimal isolation of faults, undue equipment stress, and a larger than necessary number of consumers experiencing service outages during the faults.
For these and other reasons, there is a need for embodiments of the invention.
A self-organizing protection coordination system within a power network is provided. The self-organizing protection coordination system within the power network includes a plurality of distribution devices communicatively coupled to each other in a power network. The self-organizing protection coordination system also includes a protection device coupled to each of the plurality of distribution devices configured to transmit power in the power network. The self-organizing protection coordination system power network further includes a controller coupled to each of the plurality of distribution devices. The controller receives communication channel characteristics from a plurality of distribution devices in a power network at an interval of time. The controller subsequently computes a time delay based on the communication channel characteristics. The controller further determines a plurality of reliability indicators at each of the plurality of distribution devices. The controller adjusts tripping characteristics of the plurality of distribution devices to minimize the reliability indicators based on the computed delay.
These and other features and aspects of embodiments of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Embodiments of the present invention include a system and method for self-organizing protection coordination system within a power network. The power network includes a plurality of distribution devices communicatively coupled to each other that receive communication channel characteristics from each of the distribution devices in the power network. Each of the distribution devices includes a controller coupled to the distribution devices that computes a delay in time for receiving the communication channel characteristics from the plurality of distribution devices in the power network. The controller determines reliability indicators for each of the distribution devices and adjusts tripping characteristics of the distribution devices based on the delay to maximize reliability and minimize outage time and customers impacted.
Generally, power networks include multiple distribution devices electrically coupled to each other. Each of the distribution devices includes a protection device and a controller to control the protection device. The protection device switches between an open and a closed state to provide protection to human life and equipment, and minimize power distribution interruptions caused by temporary or permanent faults. Each of the protection devices operate based on tripping characteristics provided by the controller. The tripping characteristics include a time current characteristic curve that provides a time limit for a given level of current to flow from the protection device before the protection device switches from the closed state to the open state. All of the protection devices in the power network often have the same time current characteristic curve that results in undesirable switching of the protection devices from the closed state to the open state. For example, if a fault occurs at a particular protection device, the protection devices downstream of the above mentioned faulty protection device switch undesirably resulting in an undesired outage. A power network according to embodiments of the invention is described below.
During normal operation, when the power network 30 is first deployed and commissioned, the protection devices 132, 134, 136, 138 establish communication between each other via a preferred communication medium. In one embodiment, the preferred communication medium includes private and public wired and wireless systems, and any combination thereof. Examples of such networks include, but are not limited to power line carrier, land line telephony, electric utility radio, WiFi, WiMAX, and cellular telephony, for example. Each of the distribution devices 32, 34, 36, 38 automatically exchange information regarding their GPS location. These radio communications are also used to characterize the communications channel between devices. The devices store the data in their respective controller 232, 234, 236, 238. The distribution devices 32, 34, 36, 38 also communicate with the substations 42, 44 to determine the capacity of each substation. Initially, based upon the location of the distribution device relative to the substation, the controller automatically updates the tripping characteristics of the protection device at the distribution device. Furthermore, the controllers 232, 234, 236 and 238 automatically generate communication channel characteristics for each of the distribution device 32, 34, 36 and 38 respectively and exchange the communication channel characteristics between each other over a preferred medium of communication. In a particular embodiment, each of the controllers 232, 234, 236, 238 include a media access control (MAC) protocol based on a global positioning system (GPS) and a geographic information system (GIS). The GPS provides information about the location of the distribution device and the GIS provides environment information, terrain, foliage, and density information at the distribution device. The controllers 232, 234, 236, 238 aggregate all the information provided by the GPS, GIS and the protection device and distributes the communication channel characteristics among each other within the power network 30. In one embodiment, the GPS can be used to schedule transmissions to avoid collisions and to estimate the delay when provided with a density of the distribution device.
Each of the controllers 232, 234, 236, 238 receives the communication channel characteristics from others and determines a delay in time for receiving the communication channel characteristics from each of the controllers 232, 234, 236, 238. The delay in time is computed by calculating a difference between the send time and the received time at the distribution devices 32, 34, 36, 38 with respect to each other by their respective controllers as described above in detail. Consequently, the controllers 232, 234, 236, 238 calculate the reliability indicators at each of the distribution device 32, 34, 36, 38. In one embodiment, the reliability indicators include, but not limited to, system average interruption duration index (SAIDI), system average interruption frequency index (SAIFI), momentary average interruption duration index (MAIFI), customer average interruption duration index (CAIDI) and customer average interruption frequency index (CAIFI). The controllers 232, 234, 236, 238 calculate the reliability indicators based on the communication channel characteristics received from the distribution devices. Each of the controllers 232, 234, 236, 238 communicates with other controllers and exchanges the reliability indicators of each of the respective distribution devices 32, 34, 36, 38 via the preferred medium of communication. Furthermore, the controllers 232, 234, 236, 238 automatically adjust the tripping characteristics of the respective protection devices 132, 134, 136, 138 based upon the computed delay such that the protection devices of the distribution devices 32, 34, 36, 38 continue to operate and avoid tripping in case of fluctuations in the current levels flowing through the power network 30 to maximize the reliability of the power network and minimize the values of the reliability indicators.
However, the local conditions, density and environmental conditions are dynamic in nature and may cause unexpected delays in receiving the fault message during a fault resulting in false computations and inefficiency. Therefore, the controllers 232, 234, 236, 238 exchange communication channel characteristics at predefined intervals of time and continue to repeat the generation and exchange of communication channel characteristics till the computed delay is identical to the previous delay.
For a better understanding of the invention, assuming that each of the distribution devices 32, 34, 36, 38 serve an equal load and a fault occurs at the distribution device 34, the computed delay would be more for the fault message received at the distribution device 36 compared to the delay at distribution device 32. Furthermore, the delay in time is added to the tripping characteristics of the protection devices 136 and 132 that increases the time before which the protection devices 136, 132 switch from the closed state to the open state in case of an increase in the current levels. Accordingly, the time-current characteristic curve of the protection device 136 of the distribution device 36 is adjusted more compared to the protection device 132 of the distribution device 32. Furthermore, the time current characteristic curve is automatically adjusted in case of any changes in the communication characteristics, for example, addition of new distribution device or change in topology of the power network.
The various embodiments of the method described above provide a more efficient way to minimize the reliability indicators. Conventionally, the tripping characteristics of the protection devices were fixed manually resulting in less efficiency. The method described above automatically adjusts the tripping characteristics of the protection devices during operation in case of a permanent fault resulting in minimizing reliability indicators. This significantly increases the efficiency of the smart grids and reduces the number of customers that are affected by the fault.
It is to be understood that a skilled artisan will recognize the interchangeability of various features from different embodiments and that the various features described, as well as other known equivalents for each feature, may be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.