Sensorless load monitoring and management in electric power grid through energy harvesting
The article shows a possibility to measure the instant value of the consumed current in electrical devices or in branches of the electric power grid, without specialized sensors. As it is demonstrated, in some types of electrical networks the neutral conductor could be used as a current sensing device and as an energy source. The measuring of the voltage difference between the neutral conductor and the protective conductor can supply convenient information about the load.
Electric Secondary Distribution System Design
As energy prices and the costs of building new generating facilities continue to increase, electric utilities have started looking for ways to reduce system losses. The secondary distribution system is under scrutiny due to the large number of distribution transformers and high secondary load currents. A companion paper (Gibson et al., 2007) presents a new method of secondary distribution system modeling and load characterization. The secondary distribution system is modeled in terms of a few secondary circuit archetypes. The power demand of each load is derived from actual energy consumption. A computer software using Microsoft Excel has been developed to calculate the losses for all transformer secondary circuits in the pilot area, including energy losses in the service drops, secondary lines, and transformers; thus, the circuits with the greatest losses are identified for further study. The applications of the proposed secondary distribution model and load characterization on the economic analysis and design of secondary circuits are also presented.
THE PERFORMANCE OF STEADY DETONATION ENGINES
Propulsion systems driven by steady normal detonations are studied. The practical di‐culties associated with stabilizing a detonation wave are highlighted. The requirement on the freestream total enthalpy is considered in parallel with efiects such as condensation or auto-ignition of the fuel-air mixture and limitations associated with fuel sensitivity to detonation. A criterion for detonation stabilization is formulated and applied to an analytical treatment of a detonation ramjet and a detonation turbojet, which are the respective analogs of the ramjet and the turbojet using detonative combustion. The performance of these engines is evaluated and compared to the ideal ramjet and turbojet models for hydrogen and JP10. A limitation is placed on the maximum total temperature allowed in the combustor, based on material considerations. The results show that steady detonation engines have a small thrust-producing range, due to the requirements for detonation stabilization. Their performance is always lower than that of the conventional ramjet and turbojet because of the total pressure loss across the detonation.