IEEE Power & Energy Magazine - March/April 2016 - 63

failure rates and availability of spare components for the air
cooled thyristor valves, primarily at Les Mandarins, and 2)
the obsolescence of the analogue electronic control systems.
The HVdc link has become a critical component in both
power networks, giving essential power support and energy

figure 7. Air-cooled thyristor valves at Sellindge. (Photo
courtesy of National Grid.)

trading to both countries. It was determined that the power
equipment, other than the thyristor valves, still had 20 years
of life and would not be replaced at that stage.
A detailed feasibility study was carried out in 2006 that
established the best plan for refurbishment of the four converters at both terminals, with an optimum cost and outage
duration. This plan entailed carrying out a replacement of the
complete set of valves, controls, and cooling plant at both
ends simultaneously on one bipole followed a year later by
the same scope on the second bipole.
The dismantling of the old valve structures, the air handling cooling plant, and control cabinets was carried out
with appropriate care to avoid damaging adjacent equipment, as shown in Figure 8. Some remedial work was necessary to correct the effects of normal aging on some parts of
the building before preparing the floor and walls to support
the new equipment structures. The latest H400 generation of
thyristor valves is normally ceiling suspended. But to avoid
modifying the building structure to handle the additional
weight, a new floor-standing version of the H400 was developed specifically for the project.
The new control equipment was mounted in existing
rooms that were previously used as offices, allowing for
installation while the link was still in operation prior to the
outage. The actual outage for the bipole 1 valve halls and
other plant removal and replacement took place in March/
April of 2011. The new arrangement of H400 thyristor
valves and the Series V control equipment are now the same
at both terminals of the United Kingdom-France HVdc link.
This allows the two owners to share training, maintenance
personnel and processes, and spare parts, which was not previously possible.

Haenam-Jeju HVdc Link Refurbishment

figure 8. Partially removed thyristor valves at Les Mandarins.
(Photo courtesy of GE.)
62

ieee power & energy magazine

In 1994, the Haenam-Jeju HVdc submarine cable link went
into operation for KEPCO, in South Korea. The link is a
bipole rated at 2 × 150 MW, 180 kVdc, 840 Adc, with fully
rated sea electrodes. The project was intended to supply
power from the mainland of South Korea to the island of
Jeju, which had to rely on costly and environment-unfriendly
fossil fuel generation. The Haenam-Jeju link is somewhat
unusual in that the inverter controls on the island use current
regulation for the main control loop, and the rectifier on the
mainland uses dc voltage control. This is the opposite of the
more common arrangement for thyristor-based dc systems
that use dc current control at the rectifier and dc voltage control at the inverter. Development of this unusual arrangement
for Haenam-Jeju supported its use as the sole power supply
for the island. The converter stations have generally performed well and have met their performance requirements,
but there has been some concern over the availability of spare
equipment and components to maintain the control system.
In 2007, KEPCO embarked on a plan to develop a second
HVdc link between the mainland and Jeju island, this time
between Jindo on the mainland and a new location close to
march/april 2016

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2016