DC control battery system protection and coordination
Battery system failure jeopardizes a power system by eliminating the DC control power source for AC system circuit breakers and protective devices. The protection of control battery system components including the battery, battery charger and individual circuits is reviewed. Optimum battery system protective device coordination is discussed.<<ETX>>
Control and Auxiliary Power Systems for Industrial and Commercial Switchgear Installations
Protective relays for power systems are ineffective if no energy is available to actuate the circuit interrupter when a fault occurs. Therefore, control power systems deserve careful design attention. The design of both ac and dc control power systems is reviewed, and some design criteria for these systems are listed.
Damage initiation and propagation in composite shells subjected to impact
Abstract The paper investigates the impact-induced damage initiation and propagation for laminated composite shells under low-velocity impact. A three-dimensional eight-node non-conforming element is described to analyze interlaminar stress distribution, and progressive failure. The damage analysis is performed by using Tsai–Wu quadratic failure criterion, Tsai’s damage modes and an additional delamination formula at all Gaussian points. The damage modes considered are matrix cracking, fiber breakage and delamination. The progressive failure is expressed by reducing stiffness of the material at all failed Gaussian points. Special attention is centered on curved laminates. Impact energy threshold for the onset of damage and transient damage size are predicted for composite shells. The analyses of the flat and curved laminates are compared for discussing their different damage mechanism. In addition, the influence of the stacking sequence, the thickness and the radius of curvature on damage behavior of composite shells are studied.