Damage To Electrical Equipment Research Articles

Effectiveness and limitations of two drop studies to explain emulsion dehydration under modulated electric fields

AbstractElectrocoalescence has long been known for the separation of a water‐in‐oil emulsion. An associated challenge with electrocoalescers is the undesired noncoalescence and consequently chain formation of aqueous phase droplets. This leads to low separation efficiency and damage of electrical equipment. Recently Hasib et al. proposed an electric field modulated scheme that showed significant improvement in dehydration of water‐in‐oil emulsions. They investigated the range of modulation parameters when the scheme is most effective. The fundamental process in electrostatic dehydration of an emulsion is the interaction between a pair of water droplets. In the present study, two suspended aqueous drops in insulated oil experiments are compared for their behavior under unmodulated and modulated electric fields. Further, a model is developed and the experimental behavior under unmodulated and modulated electric fields is compared with numerical solutions. The model predicts the experimental observations accurately by balancing electrostatic, electrophoresis, dipolar, and resisting viscous drag forces, ignoring the end (bridge) effect during the contact. The study shows that the increase in the rate of dehydration of a water‐in‐oil emulsion under modulated electric fields with an increase in duty ratio and its near independence on the modulation time period can be explained by the two‐drop studies. However, several other processes such as multidrop interactions as well as scavenging of fine droplets by charged droplets created as intermediates in the interaction of two droplets cannot be explained by the two‐drop studies.

Electromagnetic Shielding Effectiveness of Physical Property PET/Stainless Steel Composite Fabrics

The electronic appliance is capable of emitting electromagnetic waves that will cause the damage of electrical equipment and influence peoples health. In this study, stain steel filament (SS filament) and 75D PET filament were used to manufacture SS/PET composite yarn The SS/PET composite yarn were made by the wrapping machine, which the core yarn is stain steel filament, wrapped yarn is 75D PET filament and the wrapping layers is varied as one and two. After that, the composite yarn is fabricated by the automatic sampling loom into composite woven fabrics. The composite SS/PET woven fabrics were under the tests of electromagnetic shielding effectiveness (EMSE) and air permeability. The test results revealed that the EMSE of the one-layer composite woven fabric is 9.5 dB at 900 MHz, but the EMSE decreases as test frequency increases. When laminating layer added to three layers, the EMSE raise up to 12.6 dB. The EMSE of composite woven fabric reached at 29.9 when the laminated angle is 45°. And the air permeability decreases as the laminate layer increases, which the thickness of sample affect air to pass through the sample.

Countermeasures for controlling lightning‐caused overvoltage on indoor wiring with communication line

AbstractOvervoltage generated by lightning is a threat to indoor electrical equipment in our information‐oriented and computerized society. Countermeasures for preventing overvoltage on indoor wiring are demanded. Therefore, we have investigated the effectiveness of some countermeasures, such as low‐voltage arresters, communication line arresters, SPDs, and a common grounding wire, for reducing the overvoltage on indoor wiring with a communication line. In particular, we have studied the effect of the combination of these countermeasures and their layout on controlling the overvoltage, using a full‐scale test distribution line with a customer's facility. The main results are as follows: A common grounding wire installed along the low‐voltage indoor wiring is more effective for reducing the overvoltage on the indoor wiring with a communication line than is one installed under the floor, when the arresters are installed at the panel board. Combination of an SPD and other countermeasures, such as low‐voltage arresters and a common grounding wire, is effective for controlling the overvoltage on the indoor wiring, and the effectiveness of these countermeasures for preventing damage of electrical equipment has been verified by an experiment using actual electrical equipment. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 37–45, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10223

通信線を含む屋内配線における雷過電圧抑制策の検討

Overvoltage generated by lightning is a threat to indoor electrical equipment in our information-oriented and computerized society. Countermeasures for preventing overvoltage on indoor wiring are demanded. Therefore, we have investigated the effectiveness of some countermeasures, such as low-voltage arresters, communication line arresters, SPDs, and a common grounding wire, for reducing the overvoltage on indoor wiring with a communication line. In particular, we have studied the effect of the combination of these countermeasures and their layout on controlling the overvoltage, using a full-scale test distribution line with a customer's facility. The main results are as follows: (1)A common grounding wire installed along the low-voltage indoor wiring is more effective for reducing the overvoltage on the indoor wiring with a communication line than is one installed under the floor, when the arresters are installed at the panel board. (2)Combination of an SPD and other countermeasures, such as low-voltage arresters and a common grounding wire, is effective for controlling the overvoltage on the indoor wiring, and the effectiveness of these countermeasures for preventing damage of electrical equipment has been verified by an experiment using actual electrical equipment. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 37–45, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10223