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How are DC locos swapped for AC locos at the point where traction power changes from DC to AC?

June 22, 2019, 1:23 PM
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Today [3/05] while the the Mumbai area is still mostly at 1.5kV DC, there are a couple of important AC-DC transition points such as Igatpuri — [2/06] now Kasara — and Virar. In time, when 25kV AC becomes the norm and DC traction is decommissioned, these transitions will be history and there will be no more traction changeovers! Sad for railfans, but perhaps more efficient for IR. Already, CR has recently [2/06] switched the Kasara – Igatpuri section to 25kV AC.

This is what used to happen at Igatpuri for a DC-AC change. The catenary connected to the DC power supply does not reach all the way to the catenary connected to the AC power supply; there is a neutral section between them.

ये भी पढ़े – हमेशा के लिए बदल गया ‘एक किलो’, जानिए इससे क्या फर्क पड़ेगा

The catenary spanning the neutral section overlaps with both the DC and AC catenary sections as indicated above. This cable can be connected to either the DC or the AC power supply. Before the arrival of the DC loco, this section is connected to the DC supply. Once the loco gets detached and goes off the main line (a DC branch loop is provided for this purpose from the last DC section), the cable spanning the neutral section is switched over to the AC power supply and energized, so that the AC loco can now come in. Before entering neutral sections, electric locos often switch off power temporarily to the traction motors so as to prevent any transient disturbances and sparking.

Because the neutral section is switched between AC and DC supply, it is also known as the dynamic neutral section or the switched neutral section.

Source – IFRCA.org

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