• A section in 25 KV OHE line in which there is no electricity is called a 'neutral section'. 25KV is being fed and maintained in Overhead electric wire through a number of Electric Substations. This is sent over long distances.
There are transmission and distribution losses in OHE. So to have continuous 25KV, in every 30-40 km , there is a Traction Sub-Station (TSS). There is a point where TSS-A ends its limit and TSS-B begins its limit. In between this, the section is called Neutral Section.
• Whenever a loco enters a neutral section, the loco is made off so as to prevent flash-off. Pantograph is lowered.
• Since a neutral section is around 40-50 metres, the speed has to be maintained by loco pilot such that just before entering neutral section, as the loco is made off, the loco can cover the gap section of 40-50 metres by its momentum.
Neutral Section cant be near Home Signal.
• It cannot be also near Starter or Advance starter.
• Neutral Section cannot be on an Up Gradient, as momentum looses as the loco is switched off. It cannot cover the distance of neutral section.
There are mainly two kinds of Neutral sections that have been used on IR. 1) On pure AC electrified sections, Neutral zones are short sections separating the OHE powered by two different substations. Normally in the 3-phase electrification system, the OHE is powered by a single phase. Usually each substation powers a short section of the route. After this short distance, another substation will power the next section of OHE. Since both substations will be operating on separate phases, they cannot be connected electrically. So, at the... more...
end of the OHE section powered by one substation, there is a short section where the OHE is not electrically connected to any external power. After this short section, the next substation takes over. The region where the OHE is not powered is called a neutral section. 2) Another kind of neutral section, that was there around Bombay, but not present now is a AC-DC neutral section. The railway electrification in Bombay and around was DC based, while the rest of IR was on AC. So, at stations like Igatpuri, there was a short section of OHE, which could be powered by either AC or DC (through a control switch). Normally this OHE would be disconnected from the supply, but based on the requirement, it can be either DC or AC.
Normally, as long as OHE wire is present and is with the correct tension, the panto need not be lowered. However, to prevent sparks and voltage spikes, the panto is disconnected from the internal electrical components of the loco. Essentially the loco is 'switched off' while passing through this section. However, depending on OHE condition and caution orders, sometimes the panto may be lowered even if the OHE wire is present in the neutral section.
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