DC cables
HVDC Light cables have lower losses than AC cables. One reason for this is that there are no dielectric losses in a DC cable as there are in AC cables. Also the full current capacity can be used for the power transmission as there is no 50 or 60 Hz charging current that causes conductor losses without any contribution to the active power. Losses for HVDC Light cables of various dimensions are given in chapter 4.3 "HVDC Light Cables" in
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Converter station
The losses, calculated according to IEC 61803 amount to about 1.6 % of the rated HVDC transmission capacity (per station) at rated load. The no-load (standby) losses are about 0.2 %. The main contributors to these losses are the IGBT valves (
»1.1%), the converter transformers(
»0.21 %) and the converter reactors (
»0.12 %). The rest comes from the AC filters, the station service power and the DC capacitor.
Total transmission losses
To get an overview of the total losses for a HVDC Light transmission here are two examples:
- A ±150 kV 350 MW HVDC Light link of 100 km has total losses in the order of 4.6 % at full load.
- A ±300 kV 1,000 MW HVDC Light link of 200 km has total losses in the order of 4.9 % at full load.
Loss minimization in AC network
If the HVDC link is operated in parallel with AC lines, there is a possibility to adjust the power on the HVDC link to minimize the total grid losses.
The HVDC Light stations can also use its reactive power capacity to automatically (and rapidly) control the AC voltage. This makes it possible to operate the AC grid at a higher voltage and to reduce the grid losses.