1 =>Dissolved Gas Analysis
(DGA)
DGA is a procedure that is used as an
oil-filled system diagnostic and repair tool. The dielectric fluid present in a
transformer won't decompose at a accelerated pace under normal conditions.
Thermal and electrical faults, however, can accelerate both the dielectric
fluid's decomposition and solid insulation. The gasses produced by this process
are all low molecular weight and include hydrogen, methane, ethane, acetylene;
carbon monoxide and carbon dioxide and these gasses will dissolve in the
dielectric fluid. Abnormal conditions can be detected early in a transformer by
analyzing the gases that accumulate inside it. While detecting defects, it is
important to examine the unique concentrations of each material. Processes such
as corona, flashing, overheating, and arcing can have faults identified in this
manner. If the appropriate countermeasures are taken early in the
identification of such gasses, equipment loss may be minimized.[2]
2 => SF6
Compressed SF6 gas has a high dielectric strength which results in its application to several AC power transmission apparatuses of 66 to 500 kV size. Nevertheless, the SF, gas-insulated DC power devices have only recently been developed and the Astoria Station in Con Edison has installed a 100 MW compact HVDC connector. Several dielectric properties of SF6 should be investigated to enable proper use for DC air insulation. The first of these is electrode area effect. The observed decrease of the breakdown voltages with increase in the electrode area was reported by Nitta, et al. But their approach does not appear to predict the DC failure voltages adequately accurately. Hence a more suitable solution is required. A second aspect is the dark currents awaiting the fall of the separating SF6gas. These currents are usually caused by high-field electron field emission, but in condensed SF, 6 gas at considerably low altitude, dark currents greater than the field emission currents are activated. Thirdly, because it is difficult to eliminate all metal particle particles from control systems, their impact on breakdown voltages along the spacer surfaces can be rendered easier. Finally, the effect of polarity reversal check must be calculated. This paper discusses certain characteristics and illustrates the capabilities of gas-insulated HVDC control systems.
0 Comments