IEEE Power & Energy Magazine - March/April 2016 - 27

table 2. A typical life extension matrix.
Number
of Years in
Service*

Normal
Service Life
(Years)

Category

Item

Analog control system

Digital control system

Thyristor valves

Station HVAC

Filter resistors

Filter switching device

Cooling system (dry)

Cooling system (wet)

Converter transformers

Smoothing reactor (oil
filled)

Valve hall equipment

Ancillary equipment

Estimated
Remaining
Service Life
(Years)*

Estimated
Outage Time
(Days)*

Estimated
Replacement
Cost (US$M)*

*To be filled in by the user.

manufacturer (as the original one may no longer be in business), it is desirable to prepare a "specification" for components and systems identified as for immediate replacement
and or as those that can be delayed. the specification should
include provisions that allow for future replacements of the
equipment or system under consideration as well as other
systems. an example would be when preparing a specification for the control system, it is important to clearly define
interface points to allow for future replacement of the thyristor valves. It is highly desirable to require as much plug-andplay points as possible to allow for simpler replacements.

What Affects the Decision
decisions regarding facility refurbishment are not always
straightforward. costs, outages, condition of equipment, system reliability, and the experience level of personnel are all
factors. this becomes a true decision-matrix analysis where
there are a number of good alternatives to choose from and
many different factors to take into account before selecting
the best course of action.
the equipment items have been grouped into four suggested categories for the matrix shown in table 2, and it is
recommended that users of the matrix establish their own
criteria for categorization of their equipment. the columns
left blank should be filled in by users based on their utility's experience with these components over the life of the
facility. each category represents a set of items identified
as follows:
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ieee power & energy magazine

✔ Category 1: equipment in this category should be

refurbished or replaced within one to three years based
on risk of failure and to maintain reliable operation.
✔ Category 2: equipment in this category should be
refurbished or replaced within one to three years
based on end of life due to an excessive number of
operations and to maintain reliable operation.
✔ Category 3: equipment in this category should be refurbished or replaced within five to ten years based upon
equipment reliability and availability of spare parts.
✔ Category 4: equipment in this category should be
refurbished or replaced as necessary based on performance and maintenance requirements.
cost, both short and long term, is consistently important
for utilities. however, refurbishment costs for hVdc and
Facts facilities are more difficult to determine than for
traditional ac facilities. there are not established equipment
costs, and these costs are often dependent on how busy the
vendors are. some costs, such as for power transformers, can
be obtained for budgetary purposes from vendors. In addition to asking facility owners, who have undergone similar
refurbishments, for their costs; another way is to consider
costs for a new facility and use a percentage of that cost (for
example, control systems are approximately 7% of a new
facility cost).
It is important that a life-extension strategy be funded
throughout the life of a hVdc or Facts facility. otherwise,
the operator has to resort to reactive replacement rather than
march/april 2016

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