Pack catenaires LGV en N

thingiverse

This is a formula used to minimize the number of substations for powering the line. The substation (1) converts the power from the HT-B network (2) and feeds the catenary (3) and an aerial feeder cable named feeder (5), which are in opposition of phase, each at a potential of 25 kV relative to the rail (4), resulting in a voltage difference of 50 kV between the catenary and the feeder. A regular interval, an autotransformer (9) connects the rail (10), the feeder (5), and the catenary (8) to power the train (7) at 25 kV. The result is that electrical power is then transported over a large part of the route — between the substation and the autotransformer — under a voltage of 50 kV (between the feeder and the catenary), while the autotransformer delivers power to the train at 25 kV (between the catenary and the rail). Furthermore, the current that powers the train comes from the two autotransformers that flank it (in front of and behind it), which divides the current in a section of the catenary. French LGVs and most newly electrified axes in France are electrified on this principle. On current tracks, at right angles to supports, values are, except for particular cases, 5.08 m on high-speed lines (LGV) and 5.50 m on other tracks. The friction of the arched contact on the contact wire generates a mechanical wave that propagates in both directions from the point of contact. For a normal voltage of the contact wire, this wave propagates at less than 500 km/h. If the TGV reaches this speed, the pantograph catches up with the wave — it is the Mach phenomenon, sometimes called the catenary wall. It can lead to the removal of catenaries and destruction of the pantograph. This is one of the causes of the speed limit of trains of type TGV. To avoid this phenomenon, it is necessary to increase the voltage of the wire, which increases the speed of propagation of the wave. This raises the problem of mechanical resistance of the catenary. A compromise must be found between good mechanical retention of the catenary and its good electrical conductivity — to limit energy losses by Joule effect. In addition to the mechanical tension exerted on the catenary, an increase in the speed of the wave has been obtained (in operation) by stiffening the catenary supports and blocking the pantograph at a constant height (5.08 m on French LGVs). The amplitude of this wave is also reduced by adjusting the vibration frequencies of the supports so that they absorb this wave. This system is simpler to implement, requires substations spaced only 50 to 70 km apart, or even more with the 2 x 25,000 V (energy losses being lower than those of catenaries fed under lower continuous currents) and these are simpler (no need to rectify or smooth the current). It follows a kilometric cost largely inferior to that of the 1,500 V catenary. On the other hand, near certain substations, a section of separation of power sources is implemented. This non-powered section has the purpose of preventing two consecutive catenaries from being bridged by one or more pantographs of an electric current circulation, whose phases differ between them (due to monophasic connection on a triphasic network of the electrical transmission network). In France, the 25 kV networks departing from Paris are located at Gare du Nord, Gare de l'Est, and Gare Saint-Lazare. All new lines in France are now powered under this voltage as well. The higher voltage increases the constraints on electrical safety, particularly during maintenance operations.