IEEE Power & Energy Magazine - March/April 2016 - 26

Identifying and replacing only those systems
that have aged significantly compared to the rest of the facility
allows a utility to get the most from its existing equipment.
the construction of a new facility requires a significant amount of additional infrastructure to be built up for
new hVdc and Facts installations. this could include
repermitting existing property, additional ac substation
equipment, rerouting transmission lines, and adding communication facilities. refurbishment takes advantage of the
existing infrastructure without requiring costly add-ons. In
addition, outage constraints generally require a new facility
to be constructed and commissioned prior to removal of the
existing facility. doing so requires a nearby area be acquired
and permitted and the infrastructure built up to accommodate the different location.
hVdc and Facts technology is evolving very quickly, and
obtaining replacement parts can be challenging. refurbishment allows for the facility to take advantage of the new technology at a lesser cost than a complete replacement. In addition
to taking advantage of the latest in technology, refurbishment
can also be a way to upgrade a facility rating to increase shortand long-term ratings or improve the dynamic response time.
these items can improve the power system performance.

Where to Start
detailed, advance planning is vital to the success of a lifeextension program. the first step is to gather all of the available documentation from the owner/operator, such as final
system drawings, as-built construction drawings, software
manuals, instruction manuals, design and acceptance test
reports, and study models. the documentation found in
the owner's possession is probably the only existing documentation surviving the passage of time. It is doubtful the
manufacturer will have archived any of the facility's documentation. Unfortunately, this is one lesson owners are
shocked to learn, and it can impact every decision needed
for the refurbishment of the facility.
the next crucial task is to perform a complete life-assessment study to identify the condition of each piece of equipment or system within the hVdc or Facts installation. this
study will serve as a baseline of the facility at a point in time
and can then be used to develop a strategy for life extension
that includes replacement of components and systems over a
period of time. although hVdc and Facts installations are
purchased as one system, they can be broken down into components and systems and studied individually. see table 1,
which was compiled from industry sources, for an estimated
component life expectancy.
the life-extension strategy should contain a replacement
plan over a period of years. as noted in table 1, different
march/april 2016

components have different expected lifetimes. a solid lifeassessment study will help to determine the condition of
a piece of equipment or system and if it will last longer or
shorter than its expected lifetime. It is important to note that
this life-extension strategy will likely include replacing several systems multiple times.
because a life-extension strategy should represent a longterm approach to a facility, it is important that the complete
program is approved and funded. Ideally, this strategy would
allow the facility to remain in service indefinitely, much like
the service plan for ac facilities. part of a life-extension strategy may be to procure spare equipment, if possible. spare
parts allow for quick replacements, which minimize outages. they can also delay the need for an actual replacement
of that assembly.
equipment and systems don't always perform as expected,
so it is critical that equipment and systems are monitored
periodically and that the life extension plan be regularly
reviewed and adjusted as needed. this is especially important for long lead-time items or for items for which spare
parts are not readily available.
the life-extension strategy will likely result in both shortand long-term replacement options. rather than going to a

table 1. Major components
and their typical lifetimes.

Component

Expected
Lifetime
(Years)

Converter and SVC transformers

Thyristor valves

HVdc controls and protection (analog)

HVdc controls and protection (digital)

Valve hall cooling

Thyristor valve cooling systems (wet surface
cooling tower)

Thyristor valve cooling systems (dry surface
cooling tower)

dc smoothing reactors (air core)

dc smoothing reactors (oil filled)

dc filters

Ground electrode

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