This paper discusses die goals of routine maintenance testing for protective relays. The paper advances a Markov Probability model diat predicts die optimum test interval for protective relays widi and widiout self-testing capabilities. The model uses known system transition rates and relay failure rates. The probability model shows diat die optimum test interval for a relay widi self-tests is quite long.Digital relay failures can also cause relay misoperations and prevent operation for faults. However, relay characteristics are typically not affected by failures. Failures tend to be significant enough to eidler generate a self-test failure indication or cause dIe user to recognize dIe problem during nonnal operation of dIe relay.

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Mobile commerce and location based services (LBS) are some of the fastest growing IT industries in the last five years. Location update of mobile clients is a fundamental capability in mobile commerce and all types of LBS. Higher update frequency leads to higher accuracy, but incurs unacceptably high cost of location management at the location servers. We propose RoadTrack -- a road-network based, query-aware location update framework with two unique features. First, we introduce the concept of precincts to control the granularity of location update resolution for mobile clients that are not of interest to any active location query services. Second, we define query encounter points for mobile objects that are targets of active location query services, and utilize these encounter points to define the adequate location update schedule for each mobile. The RoadTrack framework offers three unique advantages. First, encounter points as a fundamental query awareness mechanism enable us to control and differentiate location update strategies for mobile clients in the vicinity of active location queries, while meeting the needs of location query evaluation. Second, we employ system-defined precincts to manage the desired spatial resolution of location updates for different mobile clients and to control the scope of query awareness to be capitalized by a location update strategy. Third, our road-network based check-free interval optimization further enhances the effectiveness of the Road-Track query-aware location update scheduling algorithm. This optimization provides significant cost reduction for location update management at both mobile clients and location servers. We evaluate the RoadTrack location update approach using a real world road-network based mobility simulator. Our experimental results demonstrate that the RoadTrack query aware location update approach outperforms existing representative location update strategies in terms of both client energy efficiency and server processing load.

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