Luiz F. Kawashita

Electrical and Thermal Effects of Fault Currents in Aircraft Electrical Power Systems With Composite Aerostructures

The upward trend for the use of electrical power on state-of-the-art aircraft is resulting in significant change to the design of power system architectures and protection systems for these platforms. There is a pull from the aerospace industry to integrate the electrical power system with the aircraft’s structural materials to form an embedded system, reducing the need for bulky cable harnesses. This directly impacts the fault response for ground faults and ultimately the development of appropriate protection systems. Such structural materials include composites such as carbon fiber reinforced polymer (CFRP). This paper presents the experimental capture and analysis of the response of CFRP to electrical fault current, which indicates the need for two distinct sets of electrical ground fault detection criteria for low and high resistance faults and identifies the threshold resistance for this distinction. By extrapolating these results to develop models of CFRP for use in transient simulation studies, the key electrical fault detection thresholds for speed, selectivity, and sensitivity for a dc system rail to ground fault through CFRP are identified. This provides the first set of key factors for electrical fault detection through CFRP, providing a platform for the design of fully integrated structural and electrical power systems, with appropriate electrical protection systems.

Electrical model of carbon fibre reinforced polymers for the development of electrical protection systems for more-electric aircraft

Carbon fibre reinforced polymers (CFRP) are increasingly used for structures on aircraft due to their superior mechanical properties compared to traditional materials, such as aluminium. Additionally, in order to improve aircraft performance, there is a continued trend for electrically driven loads on aircraft, increasing the on-board electrical power generation capacity and complexity of the electrical power system, including a desire to increase voltage levels and move towards DC distribution systems. Central to the reliable operation of an electrical power system is the development of an appropriate protection and fault management strategy. If an electrical earth fault occurs on a composite more-electric aircraft then the CFRP may form part of the route to ground. In order to develop an appropriate protection system and thus to understand the effects on engine generators it is necessary to investigate the fault response of this network. Hence a suitable electrical model of the CFRP material is required, which will enable CFRP to be included in a computationally-intensive systems-level simulation study of a more-electric aircraft (MEA) with fully switching power electronic converter models. This paper presents an experimentally validated impedance model of CFRP at an appropriate level of fidelity for use in systems level simulation platforms, enabling appropriate protection methods to be developed. The validated model considers the impact of the electrical bonding to ground, including the impedance added by a metallic frame that a CFRP panel may be mounted in. The simplicity of the model results in a less complex process to determine the expected impedance of the CFRP material, enabling a focus on the fault response of the system and subsequent development of appropriate protection solutions.