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Sensor networks are deployed for real-time monitoring of large objects and systems such as volcanoes, bird nesting habitats, chemical plants, bridges and civil structures. A network consists of a large number of sensor nodes, each of which consists of a CPU with memory, a battery, one or more sensors and a radio trans-receiver. The nodes are deployed randomly over the terrain associated with the application. The topology of the network is irregular, and the nodes communicate with the base station through multi-hop paths. In many cases, the environment is hostile, so node failure is significant, occasionally a node is temporarily unavailable, and communication incurs significant packet loss. Once the energy of a node is depleted, it can no longer contribute to the operation of the sensor network; after a significant number of nodes fail, the life of the network is over. All aspects of sensor network design have to take into account the unreliability and unavailability of nodes, the limited available energy at each node, the irregular nature of the network and the packet losses during communication. In this presentation, we will look at some aspects of sensor network topology, communication mechanisms, task allocation, mode localization and other interesting problems. All algorithms that we look at are decentralized, since frequent node failures would make any centralized algorithm unviable. The algorithms also need to be robust, and to take into account the redundancy in the network. Message latency is not a major consideration in most cases, and response times are not critical. The most important consideration is energy usage, since the network life-time is critically dependent on how rapidly the battery power is depleted. The purpose of the talk is to provide an overview of the principles and challenges of wireless network implementation, rather that attempting to provide a specialized state-of-the-art presentation of one or two topics of relevance.

Micromobility protocols have been proposed to provide seamless local mobility support. There are several micro mobility protocols such as HMIP, Cellular IP and HAWAII. This paper focuses on the performance of single stream forwarding scheme of HAWAII . An analytical model is developed for the evaluation. The aim of the paper is to investigate the impact of the buffering at the old base station on the handoff and to introduce a buffer at the cross over router to eliminate the packet loss at the mobile host for a given play out delay and also show by means of simulation the packet loss at the mobile host dependent on the router service rates and link propagation delays.

It is becoming increasingly important for power system planning and operating engineers to be capable of performing comprehensive voltage stability analyses of the systems. This need is largely due to recent trends towards operating systems under stressed conditions as a result of increasing system loads without sufficient transmission and/or generation enhancements. This paper discusses effect of the on-load tap changing transformers (OLTCs) on voltage stability and identifying critical OLTCs to avoid possibilities of voltage instability conditions. The developed approach has been tested on sample systems. Results obtained on an equivalent system of 24-node practical power system are presented.

Distribution networks, unlike in transmission system, may not be provided with protective devices or circuit breakers in each branch of the feeder. For any fault in the feeder, a large part of the feeder, may be isolated depending on the circuit breaker installation. For the purpose of speedy repair work and maintenance, it is important to find the exact fault location and type of fault. This paper presents an algorithmic approach for finding the location and type of fault based on the three phase measurements obtained for state estimation. Results of the simulated fault conditions on practical distribution systems are presented.

Electric power systems are exposed to various contingencies. Network contingencies often contribute to overloading of network branches, unsatisfactory voltages and also leading to problems of stability/voltage collapse. To maintain security of the systems, it is desirable to estimate the effect of contingencies and plan suitable measures to improve system security/stability. The paper presents an approach for selection of UPFC (unified power flow controller) suitable locations considering normal and network contingencies after evaluating the degree of severity of the contingencies. The ranking is evaluated using composite criteria based fuzzy logic for eliminating masking effects. The selection of UPFC suitable locations uses the criteria on the basis of improved system security/stability. The proposed approach for selection of UPFC suitable locations has been tested under simulated conditions on a few sample power systems and the results for a real life 36-node equivalent EHV power network are presented for illustration purposes.