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Protection & Prevention

Skin Effect

An area of power transmission that we have not talked about in any Lectromec article thus far is the impact of skin effect. While this is an area that is well documented and understood for signal/data cables, the impacts in the area of power cables have been generally ignored. However, as power systems embrace new power technologies, skin effect starts to creep in to have a noticeable and measurable impact. In this article, we discuss what skin effect is and its impact.

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Partial Discharge at Altitude

PD is not a simple phenomenon to model as there are many environmental factors that have influence. Factors such as heat, humidity, pressure, are some that can change the voltages required to initiate and extinguish PD within a wire/cable’s insulation. This article specifically discusses the influence of altitude on partial discharge events. The consideration of the operational altitude effect on partial discharge is particularly necessary for aerospace applications as aircraft tend to spend a lot of operating time at high altitudes.

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Addressing the Big Questions of Partial Discharge

In this high-voltage present, wires and cables must address new challenges, perhaps the most notable is partial discharge (also referred to as corona). This article discusses the fundamentals of partial discharge, its impacts on wiring design, and test methods used to assess a component’s partial discharge performance. The PD may occur between (1) the conductor and insulation, (2) within void in the insulation, (3) between insulation layers, or (4) between the insulation surface and shield. Read more

Impact of Secondary Wire Harness Protection on Heating

If you are standing outside on a cold winter day, would you be warmer in a T-shirt or in a jacket? The answer is obvious, but somehow that ‘obvious answer’ is obscured when thinking of aircraft wire harness design. A common question of OEMs and aftermarket modifiers is: how much of an impact (if any) does secondary harness protection have on wire harness heating?

Lectromec took time this last week to put together a representative harness and run tests to generate data on the thermal impact of three secondary wire harness protection schemes. While this data is not representative of every wire harness configuration, it does provide a basis for determining if additional testing (or simulation) are needed for your application.

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Getting the Right Bonds

Things were so much easier with aluminum aircraft structures. The structure acted as an EMI shield, electrical grounding could be done right to the structure without additional effort, and the electrical mating of the structure was straight forward. Now, with composite structures, aircraft design concepts such as electrical bonding, particularly in the case of handling lightning strikes, becomes more important.

When done right, the impact of a lightning strike should have a limited impact.

In this article, we review the concepts around primary aircraft bonding, its requirements, and the implementation as they relate to lightning strike.

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Shield Grounding and EMI Protection

The push for more electric aircraft is driven by weight savings and the availability of reliable electrical components. This is made possible with greater power generating capacity, however, this comes with an increased challenge of ensuring reliable data transmission. More power flowing through the aircraft means higher levels of electromagnetic interference (EMI). Aerospace environmental test […] Read more

Evaluating Secondary Wire Harness Protection Performance

There are several reasons to deploy secondary harness protection (SHP): chafe protection, maintenance protection, fire protection, harness cable management and, in some cases, arc protection. The EN6059-502 test examines secondary harness protections and the potential damage from arcing. This article runs through the test method and problems that could occur if the results are misinterpreted. […] Read more

Fuel System Protection Part II

Lectromec has written multiple articles on fuel system safety as it relates to SFAR88, AC 25.981, and AC 25.1701. In this article, we continue the discussion by reviewing some of the recommendations that came out of the NTSB report on TWA 800 and subsequently influenced AC 25.981. Some of these recommendations may not apply to […] Read more

Signs of an Aging Wiring System

All components wear out over time, but the rate at which they degrade will vary depending on the quality of the product, how is it handled, and the environmental conditions in which the component is installed. To consider all the potential ways that an EWIS can fail, it can be overwhelming. As a brief list […] Read more

Nuisance Trips

Circuit protection devices are primarily responsible for protection of electrical circuits from low impedance faults. These device types may be thermal, arc fault circuit breaker (AFCB), or integrated within a solid-state power distribution. Regardless of type, their role remains the same. But circuit protection devices are not error free. In the cases when the circuit […] Read more