Electrical power for consumption at residences, offices and other structures is delivered by a power distribution system. A power distribution system may include numerous sections, which transmit power at different voltages. A section of high voltage power transmission lines forms a power distribution grid for transmitting power from a power plant to substations near populated areas. Various medium voltage (MV) power sections are coupled to the grid via substations to serve specific regions. An MV power section includes medium voltage power lines carrying power having a voltage in the range of 1,000V to 100,000V. Low voltage (LV) power sections are coupled to the MV power lines via distribution transformers to serve specific groups of structures such as homes. In the United States, the LV power lines typically carry voltages of approximately 120V phase to ground and 240V phase to phase.
The power distribution system includes transformers, switching devices, other devices, and miles of power lines. Maintaining the system in effective working order is imperative for the individual consumer and society. Maintenance is used to identify signs of potential failure and better manage distribution and redistribution of power to satisfy local needs. Even with such maintenance, however, faults occasionally occur, which often result in a power outage thereby preventing power delivery. Power outages also may occur due to other events, such as when inclement weather conditions or falling tree branches knock down power lines. It is desirable that the utility operator quickly identify and respond to such power distribution events to minimize the adverse impact to the power distribution system and to the consumers. In particular, it is desirable to determine that an adverse power distribution event is imminent, may occur, or has occurred, and the location of such an event.
As discussed, medium voltage power lines are typically connected to a plurality of distribution transformers, which supply power to the consumers. While the current (amperage) of the medium voltage power line varies according to the load, the impedance of the medium voltage power line will remain substantially constant between two locations on the medium voltage (MV) power line. Thus, a change in the impedance of the medium voltage power line may indicate an undesirable condition exists and/or that an adverse power distribution is imminent. As an example, if a tree limb intermittently touches an uninsulated overhead MV power line, the tree will provide a path to ground for power. This additional and intermittent electrical path to ground will change the impedance of the power line between two locations on either side of the tree limb. Consequently, measuring the impedance of the power line and monitoring the impedance over time to detect a change in impedance can be instrumental in identifying power distribution system events before they become more serious (e.g., the tree limb breaking the power line).
Accordingly, there is a need to measure the impedance of a medium voltage power line and to detect significant changes in the impedance in order to identify existing and/or imminent adverse power line distribution events. Another need is to obtain sufficient data to locate and respond to the existing or imminent power distribution event. Various embodiments of the present invention may satisfy one or more of these needs and/or others.