Inside energized 380 kV AC / 450 kV DC converter station of Baltic Cable in Luebeck-Herrenwyk

[rsp196607]

380 ≈ √3 × 220

[soundseeker63]

I'm guessing the reason it is DC and not AC is so the power can be transferred between the two grid systems without them both having to be synchronized on the AC side?

What are those strange tower things at 2:32 for?

[kiendl]

@soundseeker63 No, the reason is that transmission of AC through a cable is much more lossy than transmission of AC. See the Wikipedia article on HVDC - a cable is basically a long capacitor, and with AC, you always need high currents to charge that capacitor.

[kiendl]

@kiendl Aaah, and forgot: those strange towers are capacitors in filter circuits that trap RF noise.

[pulliATwork]

Der Sterbeplatz der Möven an der Trave ;-)

[DJGahann]

I'm no high voltage/energy tech, but why would these lines be DC with its inherrent losses over distance? Costs?

[kiendl]

@DJGahann Of course you couldn't stretch your 12 V halogen lighting ropes over such a distance. But at high voltage, you can go from North Africa to Central Europe and lose just 10 %. At the time when electrification first came up, there just wasn't an economical way to transform DC voltages - semiconductor technology had not yet been invented at that time.

[CampKohler]

@DJGahann My guess is: DC is 100% duty cycle, whereas AC has peaks and valleys, the peaks requiring higher-voltage ratings of the equipment (as compared to the equivalent heating value, i.e. RMS) and the valleys not fully utilizing the equipment current ratings. Also I would think that AC would radiate some energy (a loss that increases with frequency), whereas DC would not radiate. So if you want better TV/radio reception (less interference), you would want the nearby lines to be DC.

[kiendl]

@CampKohler DC can be more of a TVI problem than AC. The converter stations, if improperly designed, emit RF noise on a lot of frequencies. That's what the filter circuits with the capacitor towers are for.

[RODALCO2007]

Nice high voltage footage

Thanks for posting.

How long is the Baltic Cable ?

[kiendl]

@RODALCO2007 It's 250 km long. AC cables are only economical for distances below some 70 km.

[RODALCO2007]

@kiendl That is correct, thanks for your reply.

In NZ we have a DC link between the North and South Island.

About 40 km under sea cable and 440 km overhead lines to Benmore.

Voltage 620 kV DC between phases.