Abstract-Harmonic analysis of motor current has been used to track the speed of motors for sensorless control. Algorithms exist that track the speed of a motor given a dedicated stator current measurement, for example [1][2][3][4][5]. Harmonic analysis has also been applied for diagnostic detection of electro-mechanical faults such as damaged bearings and rotor eccentricity [6][7][8][9][10][11][12][13][14][15][16][17]. This paper demonstrates the utility of harmonic analysis for fault detection and diagnostics in non-intrusive monitoring applications, where multiple loads are tracked by a sensor monitoring only the aggregate utility service. An optimization routine is implemented to maintain accuracy of speed estimation while using shorter lengths of data.
I. SMART MONITORINGAt any point in the life of a system, mechanical and electrical equipment may be poorly operated. For example, as buildings age, both the electro-mechanical actuators and associated mechanical components wear, cease to function properly, and eventually fail, via myriad processes that are often undetected. Valves do not close fully, filters clog, airconditioning system dampers stick, refrigerant leaks, heating and cooling coils -from the smallest refrigerator to the largest building air-conditioning system -become fouled with dirt and debris, and belts slip. Energy waste and excessive plant wear are often exacerbated by closed-loop control. Under active control, damaged but still functioning equipment will operate by extending run times or operating points to meet user commands, leaving few obvious signs of compromised operation.For example, a number of surveys of airflow faults in buildings hint at the range and extent of these problems. One compendium of fault surveys [18], which examined 503 rooftop air-conditioning units in 181 buildings in five states in the Western U.S. from [2001][2002][2003][2004], found that the airflow was out of the specified range in approximately 42% of the units surveyed. A separate study [19] of 4, 168 commercial airconditioners in California reported that 44% of the surveyed units had airflow that was out of specifications. Studies of 29 new homes in Washington State [20] found that average duct leakage rates to the exterior ranged from 687 to 140 cubic feet per minute (CFM). Extrapolating from such fault surveys, one estimate for the total energy consumed by duct leakage is $5 billion/year [21].When "failure is not an option," the performance of important electro-mechanical loads on mission-critical systems like warships or power plants is often tracked by dedicated monitoring equipment [22]. An extensive sensing network can provide obvious advantages for fault detection, diagnosis, and prognosis. However, a large sensing network can be expensive and difficult to maintain.Smart Grid and Smart Meter initiatives hope to allow energy providers and consumers to intelligently manage their energy needs through real-time monitoring, analysis, and control of electrical power usage. The U.S. Department of Energy has i...
