Themag (Brazil)

While searching for solutions to minimize environmental impact of substations and improve efficiency in services by optimizing costs, AES Eletropaulo promoted an RD the University researches and shapes solution proposals; the Manufacturer develops proposals and equipment and; finally, the Designer materializes the solution. This article presents the methodology and the results obtained, and describes solution implementation in a pilot area. Methodology involves an innovative method in the evaluation of substation alternatives, which contemplates objective issues in direct manner, and intangible issues through structured specialist analysis. Analysis of the grid, which functions as “distributed substation” “interconnection bus”, allowed for optimum location of re-connectors and maneuver switches, maximizing continuity and operational ease. The pilot project is being implemented in the region of Cotia, Sao Paulo, where strong environmental restrictions prevent penetration of high voltage lines within load center and 34.5kV power is available at neighboring substations.

A simplified method is presented to measure the grounding resistance of adjacent electrodes which can be of use in other situations, when ground electrodes are composed of many elements or when an existing electrode is extended. The opportunity of remeasuring electrode potential curves showed that local gradients can change, but in a relatively small range, +or-10%. For applications like the design of mitigation procedures or the prediction of corrosion currents, this range is deemed to be insignificant, not only because the verified range is small, but also because of the tendency of the changes to compensate. The tests in the irrigation system changed somewhat the formula previously used for evaluating touch potentials in irrigation pipes. The adopted mitigation criteria concerning electric shocks to immersed persons are explained together with suggestions for further work on evaluating body currents in the case of large DC gradients in water near energized metal parts. >

The authors describe an altered version of the borehole extensometer developed by the Building Research Station for observing ground displacements in foundation engineering. The original extensometer used a circular magnet as a marker and a reed switch as sensor. The same components are also used in the system described in this technical note, the distinction from the original one being related to the signal transmission when the reed switch is closed by the magnet. The new sensor system uses an oscillator as signal source and this simplifies the reading method, since electrical cables can be avoided. (TRRL)