Cellulosic paper and oil insulation in a transformer degrade at higher operating temperatures. Degradation is accelerated in the presence of oxygen and moisture. Power transformers being expensive items need to be carefully monitored throughout its operation. Well established time-based maintenance and conservative replacement planning is not feasible in a current market driven electricity industry. Condition based maintenance and online monitoring are now gaining importance. Currently there are varieties of chemical and electrical diagnostic techniques available for insulation condition monitoring of power transformers. This paper presents a description of commonly used chemical diagnostics techniques along with their interpretation schemes. A number of new chemical techniques are also described in this paper. In recent times a number of electrical diagnostic techniques have gained exceptional importance to the utility professionals. Among these techniques polarisationr r r r rdepolarisation current measurement, return voltage measurement and frequency domain dielectric spectroscopy at low frequencies are the most widely used. This paper describes analyses and interpretation of these techniques for transformer insulation condition assessment.

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eer-to-peer (P2P) energy trading has emerged as a next-generation energy-management mechanism for the smart grid that enables each prosumer (i.e., an energy consumer who also produces electricity) of the network to participate in energy trading with other prosumers and the grid. This poses a significant challenge in terms of modeling the decisionmaking process of the participants' conflicting interests and motivating prosumers to participate in energy trading and cooperate, if necessary, in achieving different energy-management goals. Therefore, such a decisionmaking process needs to be built on solid mathematical and signal processing principles that can ensure an efficient operation of the electric power grid.

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Several studies on voltage stability analysis of electric systems with high photovoltaic (PV) penetration have been conducted at a power transmission level, but very few have focused on small area networks of low-voltage. As a distribution system has its special characteristics-high R/X ratio, long tap switching delay, small PV units and so on, PV integration impacts also need to be investigated thoroughly at a distribution level. In this paper, the IEEE 13 bus system has been modified and extended to explore network stability impacts of variable PV generation and the results show that a voltage stability issue with PV integration does exist in distribution networks. Simulation comparisons demonstrate that distribution networks are traditionally designed for heavily loaded situations exclusive of PVs, but they can still operate under low PV penetration levels without cloud induced voltage stability problems. It is also demonstrated that voltage instability can effectively be solved by PV inverter reactive power support if this scheme is allowed by the standards in the near future.