Transporting and Accessing Charge at EHV, Part IV

More on accessing charge already delivered at high voltage

Following from the calculations I made last time, if a 310 farad dissectible capacitor within an 800kV dome could be charged, dissected, discharged to the dome and reassembled, at a rate of 10 cycles of operation per second (10Hz), it would deliver about 3350 megawatts. This is comparable to the rated power per pole of one of the world's largest high voltage direct current (HVDC) transmission links, the 7200 MW Xiangjiaba - Shanghai link, also designed to operate at 800kV.

Fig. 4. Converter transformer produced at the Siemens manufacturing plant in Nuremberg for the ±800 kV 7200MW Xiangjiaba - Shanghai HVDC link. See http://www.siemens.com/press/en/presspicture/?press=/en/presspicture/2009/Power_Transmission/EPT200911020-01.htm

HVDC — a proven method

I have raised the topic of HVDC transmission because this technology provides a well-proven way of accessing electrical energy that is delivered as direct current at very high voltage. Converter transformers, such as shown in Figure 4, are used to step up voltage at the "sending" end of an HVDC link (the rectifier) and also to step down voltage at the "receiving" end (the inverter). 

Usually in HVDC links, groups of thyristors are used in three-phase Graetz bridge circuits, to perform either rectification or inversion as required; depending on the direction in which power is to be transmitted. At the inverter, such circuits convert the electrical energy from direct current back to alternating current, in conjunction with converter transformers which transform it to the voltage required to match that of the network into which the energy is to be fed.

We recall that, in principle, a transformer can take electrical energy at any voltage and current, and deliver it at any other voltage and current, as desired, such that overall losses are generally very small.

Technological advances awaited

Currently, it seems at first sight anyway, that we are still waiting for technological advances in one or two areas before any real breakthroughs could be achieved in transporting and accessing charge at very high voltage, which would then permit this technology to deliver free energy at (very) high power.

These advances are the development of good insulating fluids, as previously discussed in my post of 6 June 2015, and/or the development of fast-switching, dissectible supercapacitors, as discussed in my previous post and above.

Unfortunately, as things are in the current world, I won't be holding my breath waiting for either of these advances to occur.

Fig. 5. The Xiangjiaba dam under construction, at the rectifier end of the Xiangjiaba - Shanghai HVDC link. This facility incorporates eight Francis turbine hydroelectric generators, with a claimed total generation capacity of 6,448 MW.
Could very large, costly, structures such as these dams and their generators be replaced by fast-switching, dissectible supercapacitors, in much less expensive devices of far smaller total volume?

image from http://english.cwe.cn/show.aspx?id=1823&cid=43