Real time monitoring of distribution networks using internet based PMU
Pachpinde, Akanksha Eknath
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Measurement of synchrophasors can open up new avenues for improved control and stability of the power system. Phasor Measurement Unit (PMU) can measure positive sequence voltages and currents along with frequency and rate of change of frequency. They can directly measure the state of the system thus eliminating the need for state estimation altogether, if the system is completely observable. For this to become reality a large number of PMUs need to be deployed that would call for large upfront investments. Another possibility to ensure large scale deployment of PMUs, is to find ways to make the technology more affordable. Conventional PMUs which use global positioning system (GPS) for time synchronization have some limitations. This thesis proposes a novel concept of PMU using network time protocol (NTP) to synchronize the local oscillators of all the PMU. NTP is an attractive alternative as it uses existing LAN lines for internet communication and the existing infrastructure and has time accuracy in milli-seconds (lower than that of GPS). It does not require, however, any major infrastructural changes. It is thus suitable for monitoring systems that do not require very precise time stamping. We claim that a distribution network is an ideal candidate for such PMUs. Currently distribution networks have sparse monitoring by supervisory control and data acquisition (SCADA) system which has time synchronization window of 2-3 seconds. This conceptual PMU is elaborated in the following text and its feasibility is evaluated. Comparative measurement accuracy and cost of this PMU is discussed in detail in comparison with the conventional PMUs. The new PMU offers significant benefits in terms of monitoring and controlling the distribution network. One application considered in this study is fault-location detection.