gokeefe wrote: ↑Sat Apr 18, 2020 9:14 pm
I was thinking about that and wondering if perhaps rough track conditions create momentary surges in the electrical systems onboard.
What may create additional surges are momentary loss of contact between contact wires and pantographs. But it doesn't seem to be a serious issue, as:
1. Amtrak engines are using one of the best pantographs in the world. Derived from Brecknell Willis's high speed pantograph, they are equipped with "aerofoils" which counteract the negative aerodynamic effects in high-speed operations, very simple in aerodynamic shape and are able to make swift changes in height.
2. The catenary used on former PRR lines is a somewhat "compound" catenary, consisted of a "contact wire", a "messenger wire" and an "auxiliary messenger wire". The contact wire, instead of being suspended by the auxiliary messenger wire, is clipped directly to the latter, so it is not a true compound catenary. Nevertheless, the presence of the auxiliary messenger wire makes the system very "elastic" and tolerant to vibrations. The section upgraded in the NJHSRIP program has true compound catenary, as well as tensioners that keep them in constant tensions now.
The drawback is the increased mass per unit length. The speed of transverse wave on a string is given by v=sqrt(T/l), where T is the tension and l the mass density. The larger the mass density, the slower the wave speed, and easier for trains to break the "sound barrier" on the catenary, a very dangerous situation never allowed to occur.
For this reason, compound catenarys are not used elsewhere after 1997, as HSRs built after that are aimed for true high-speed operations. As true high-speed operations would never occur in the near future on NEC, compound catenary is undoubtly the best option.
3. When the pantograph is off the contact wire, an arc forms in the gap. Arcs are natural current stabilizers, and are much more harmful to the pantograph themselves than the electric traction system.