And, when you think about it, the golden cables had a maximum EU-packet size of 128 EUs. What's the point of having some High voltage cables (1024 I think) that lose tons of EUs, when you can just downgrade the amount of EUs with a transformer?
I never used High voltage cables: they had a poor efficiency, and I needed iron for other things.
You are looking at the EU loss rather than percentage lost.
If you need to send 10240 EU 100 blocks the best way to do it is with High Voltage (this holds true for ANY amount of EU over ANY distance).
10240EU / 2048/packet = 5 2048EU packets
Each packet will travel 100 blocks losing 1 EU per block. Total EU loss will be 500.
If sending the same amount of EU over copper cable:
10240EU / 32/packet = 320 32EU packets
Each packet will travel 100 blocks losing 1 EU every 5 blocks. Total EU loss will be 6400. Basically, in IC2 1.111, unless you are going distances short enough to be lossless (IE less than 5 blocks with Copper), it is better to up the voltage and move it back down at the end.