1. Field of the Invention
The present application generally relates to the detection of high-impedance faults in electrical power grids and, more particularly, to a new category of senor for deployment throughout an electrical grid and which is capable of detecting environmental conditions which are associated with a high impedance fault.
2. Background Description
High impedance faults are costly, dangerous to the equipment and a threat to human life. There is a huge diversity of phenomena classified as high impedance faults. These include, but are not limited to, a downed line, a tree branch touching a line, a broken insulator, and improper installation. As a result, there is no accepted scientific knowledge about the nature of high impedance fault detection.
Electrical power grids are extremely complicated, making the detection and localization of a high impedance fault difficult and problematic. Current methods of detection include circuit breakers tripping, readout from meters at the substation by human operators, and a telephone call from someone who noticed a fault. Interestingly, the last of these methods, e.g., a telephone call, is the most common method by which faults are detected and located. There have been attempts to use local sensors that automatically make a decision and either raise an alarm or disconnect a part of the grid. These attempts have proven to be unsatisfactory due to the lack the ability to flexibly adapt to the specifics of a particular environment. The sensors which have been used in the past have monitored electrical attributes, i.e., voltage and current, from the wires. However, such data “from the wires” may propagate a considerable distance, making localization of the actual fault difficult.
The inventors have correlated specific molecules in the environment, especially ozone, to high impedance electrical faults. Such faults are often accompanied by sparking and ionization. The corona discharge or ultraviolet light that occurs causes, for example, oxygen molecules to split into individual atoms which, upon recombining with another oxygen molecule, produce an ozone molecule. Also, some common high impedance faults are due to electrocuted animals (e.g., squirrels and birds) which can be detected by molecule detectors due to decomposition of the animal flesh.
According to the present invention, in addition to sensors that measure purely electrical (i.e., current and voltage), molecule sensors are provided in an electrical grid which sensors are sensitive to the surrounding environment. These sensors may detect one or more of a variety of molecules, such as ozone (O3), combustion gases (carbon monoxide (CO), carbon dioxide (CO2) and oxygen (O2) levels), and odor molecules (ammonia (NH3), sulfur dioxide (SO2), burned hair/feather, burned proteins, and the like), depending on the type of environmental phenomena that may be expected in a particular location of the sensor(s). The intensities of the molecules may be collected by Ion Selective Electrodes (ISE), e.g., diodes, or other specialized sensors. These sensors, in combination with conventional electrical sensors, provide a more complete set of data for evaluation and localization of a potential high impedance electrical fault. The use of such sensors is especially useful in confined areas like underground parking lots, substations, and the like.
The foregoing and other objects, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which:
Referring now to
Only those individual predictions from remote sensor units determined to be not typical are transmitted to the central processor unit. Several remote processor units may be aggregated for transmission of data to the central processor unit for the second stage of fault detection and analysis. This transmission can be by means of broadband power line technology (BPL) or wireless transmission or the combination of the two. For example, several remote processor units can be grouped into a wireless local area network (LAN) which communicates with a transmitter centrally located to that particular wireless local area network. If the technology used is limited to BPL, each remote processor unit would have a connection to the central processor unit to be able to be able to transmit the amount of data equivalent to two to five seconds or more of sampled readout of its associated sensor. Other technologies can be used to transmit the data.
Action can be initiated either locally or centrally, as generally indicated by block 17. For example, the local interpretation of the data from the sensors 10 and 11 by the processor unit 12 may result in one of three actions. First, if the interpreted data indicates a high impedance fault, an automated circuit breaker function can be initiated. If, however, the interpreted data, while identified as not typical, is inconclusive as to the occurrence of a high impedance fault, the data is sent to central processor 16 for further analysis. Finally, if the interpreted data is determined to be typical, the data is ignored and no further action is taken. At the central processor 16, the data sent by the remote processor is further analyzed, and this analysis may result in one of three actions. First, if the interpreted data indicates a high impedance fault an automated circuit breaker function can be initiated. At the same time, an alarm and a display is generated to alert a human operator of the action taken. If, however, the interpreted data is not conclusive as to indicating a high impedance fault, the central processing unit 16 may generate an alarm, either audibly, visually or both, and provide a display to a human operator with a prompt to take some further action. Finally, if upon further analysis it is determined that no high impedance fault has occurred, the data is ignored.
The process implemented of sensing of specific environmental molecules for the detection of high impedance faults is illustrated in
Although the invention has been described in terms of a two-stage detection system, it will be understood by those skilled in the art that the environment sensors, as well as any accompanying current/voltage sensors, may be configured to communicate directly with a central processor without the use of remote processors in a single stage detection system. Thus, while the invention has been described in terms of a single preferred embodiment, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims.