Browsing by Author "Naiman, Shililiandumi"

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    Characterization of factors influencing electromagnetic interference and radiation in outdoor broadband power line communication systems: a case of Tanzania electrical supply company Ltd
    (Unversity of Dar es Salaam, 2015) Naiman, Shililiandumi
    The performance of BPLC technology suffers from various unsolved challenges including attenuation, reflection, radiation, noise, multipath, and notches affecting channel characteristics. This thesis identifies and characterizes factors contributing to BPLC radiation, formulates suitable model to characterize the radiation, and, lastly, devises suitable radiation mitigation mechanisms to minimize the emitted radiation. The contributions of number of nodes in the network, number of branches at the node and line length as well as load mismatch to radiation levels have been investigated culminating into a model to characterize the radiation behaviours based on Maxwell integral theory for scattering field on wire using MoM and validated using CST software as a modeling tool and live network measurements. The transmission line Bewley transient method has been used to obtain line current for different topologies. The characterization shows that an increase in line length from 100 m to 300 m results in a decrease in emitted radiation from 0.043 V/m to 0.035 V/m while an increase in the number of branches at a node and the number of nodes both increase the emitted radiation to the extent that, at a node with 4 branches the emitted field is 170 µV/m which increases to 330 µV/m when the branches increase to 10. Furthermore it has been shown that radiation increases due to mismatch at the load; for a matched load the radiated emission level was1.9 µV/m which increased to 28µV/m for short circuit load. The time reversal techniques have been applied as mitigation solution with time-reversal (TR) nulling and focusing filtering techniques showing the capability of reducing BPLC radiations by up to 20 dBV/m of emitted radiation with TR Nulling cancelling all the reflected signals.
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    Design of an intelligent energy meter with two-way communication
    (University of Dar es Salaam, 2004) Naiman, Shililiandumi
    Power utility companies have been facing a lot of problems in revenue collection such as improper energy measurement, meter tampering, delay in billing, huge costs of disconnection and reconnection of meters etc. Different techniques have been proposed to overcome these problems such as the use of metering system like computerized hand held recording devices, remote electronic meter reading, drive by or mobile radio-meter reading and full remote electronic meter reading. It has been identified that a remote monitoring system is a solution of such problems. Apart from that, the proper way of measuring consumed energy, power tampering identification and protection and the design of two way communication is essential. In this thesis the concept of an intelligent energy meter with two-way communication to solve the prevailing problem of revenue losses is introduced. Two kinds of solutions have been researched on and integrated as a single solution. These are tampering detection circuit design and real time monitoring using two-way communication facility. Also, accurate energy measurement has been discussed. In the tampering detection, the thesis explains different tampering techniques used and gives a simulated tampering detection algorithm to combat the problem, in addition, the thesis describes how a transceiver through powerline channel in combination with tampering detection circuit can be used to combat the tampering and revenue collection problem. Due to the nature of powerline communication channel, the transceiver parameters have been chosen carefully to enable communication at low cost Spread spectrums with BPSK modulation techniques has been chosen to effect communication through powerline. Results show that it is possible to detect all identified kinds of tampering for all tampering and theft conditions by monitoring the energy meter live and neutral currents and terminal voltage. The energy metering transceiver requires data rate of 10kbps, chip rate of 327.67Mchips/s, processing gain (PG) of 45dB or above and receiver signal-to-noise-ratio (SNR) of 28dB. Furthermore, the transceiver need receiver sensitivity and transmitting signal power of -110dB and 1 OmW respectively with channel bandwidth of 5 kHz.