How does a Overhead Line Fault Passage Indicator work?
What is a Fault Passage Indicator?
Being outdoors, electrical networks are subject to the ravages of nature throughout the year. From lightning, heavy rain, dust, or even just local wildlife, these electrical networks become susceptible to faults forming over time.
When these faults occur, outages can take place which can affect large populations of end customers or industrial areas, causing dissatisfaction and revenue losses for the local utility. In our conversations with Utilities and Operations & Maintenance (O&M) firms, in the absence of a fault indicator, the standard practice involves the use of several technicians to walk or drive along the length of the line to find the exact location of the fault. In the case of a line such as an Aerial Bundled Cable (AB Cable) where the cables are bunched together, this practice becomes even more difficult according to our conversations as the technicians need to lower the line in order to find the fault. Additionally, if the fault occurs at night or in highly forested or hilly areas, this endeavor becomes increasingly difficult.
These large revenue losses for Utilities and the extra cost of O&M for fault detection have led to the development of products to aid utilities or the maintenance firms to quickly detect faults in their network. A Fault Indicator is a device that is placed on underground or overground electrical lines to provide utilities with either a visual or remote indication and location of a fault. These Fault Indicators also referred to as a Fault Passage Indicator (FPI), help the utility attain early information on the location of the fault, and take immediate action.
How does a Fault Passage Indicator work?
One Fault Passage Indicator is usually clipped onto each phase of the circuit allowing the utility or O&M firm to monitor current and faults in each phase. By placing the FPI’s at regular intervals along the line, the device can identify faults in the downstream section from its point of installation by monitoring the electromagnetic field surrounding the conductor. During the fault condition the magnetic field around the conductor increases rapidly as a high current will flow through that path for some fraction of time (di/dt) & than sudden breaks to zero as circuit breaker trips, this condition is sensed by the FPI & gives the alarm physically on-site & remotely to SCADA center.
In case of a non-communicable type, the FPI will give alarm physically on-site by blinking the RED Ultra bright LED & in case of a communicable type the FPI gives alarm physically on-site as well as send the data to the SCADA center through DCU over GSM/GPRS.
The illustration below provides a basic topology of a communicable system.
System Network Topology for the working of a Fault Passage Indicator System
The FPI product ultimately aims to reduce the time and effort taken by maintenance technicians to find faults by providing visual and/or remote cues.