IEEE Power & Energy Magazine - March/April 2016 - 53

Keswick
345 kV
Chester SVC
Keene Road

G
115 kV
345 kV

345 kV
Orrington

115 kV

G
115 kV

Point Lepreau

Maine

345 kV
Maxcy's

115 kV
MY
115 kV

New Brunswick

manufacturer of the sVC was accepted. the review of valve options resulted in a determination to
replace the tCR valve and related
components. since there are three
sets of tsC valves, replacing one
set (with related components) created adequate spare parts for the
remaining two tsC valve stacks
for the foreseeable future. at such
time that additional spare parts for
the original tsC valve stacks are
needed, a second tsC can be replaced, freeing up additional spare
parts. Doing this in segments, instead of all at once, did not have
a significant cost penalty and deferred capital expenditures.

Final Benefits
figure 6. A transmission system in 2010.

changed so much that the sVC filters would no longer be
able to perform as intended.
in addition to the system changes, the sVC was now almost
20 years old (with technology that was even older), and the control system computer was experiencing age-related issues. one
issue was that the electronic components used in the system were
no longer available. another is that technical support from the
manufacturer was at risk as staff aged, retired, or became no longer available.
a third issue was that the solid-state valves used in the
tCRs and tsCs were becoming scarce. new valve designs
were not compatible with the older design, and the older components were no longer being manufactured. While the valves
were not experiencing significant failure, replacement segments were becoming hard to source.

Solutions
Harmonics

in 2010, the original manufacturer performed a study to
determine the harmonic performance of the system and the
sVC filters, which used a thevenin equivalent of the system. Both the individual harmonic distortion and telephone
interference factor were studied using the original design
thresholds as the goal and limits. in both cases, the harmonics present exceeded the original design and design limits.
this showed the need to redesign and replace the sVC filter,
which was now also subject to thermal overloading.
Valves and Control System

a quick review determined the need to replace the control
computer. few options existed, and the offer from the original
52

ieee power & energy magazine

Replacing the Chester sVC filter
with one that met the present thermal and harmonic need resolved
issues and concerns associated with the changes to the transmission system. this effort showed that future major changes
to the transmission system would require additional review of
the sVC and related systems.
Replacing the control computer with a new generation
computer and replacing the tCR and one tsC resolved spare
parts issues with these components. these upgrades were
performed at the same time a cooling system upgrade and
digital fault recorder upgrade were installed. While these did
not have the supply obsolescence issue that the valves and
computer had, they had reached the end of their functional
lives and were in need of replacement. With these changes,
the Chester sVC is capable of many more years of service.

New York Power Authority-
Performance Upgrade
Upgrades to relatively recent technologies can enhance system performance. the new York power authority (nYpa) has
installed a faCts controller known as a convertible statCoM (CsC) at its Marcy 345/756-kV substation in central
new York. it has been fully operational since June 2004.
the Marcy substation is located at a major convergence
of transmission lines in central new York state. the CsC, in
conjunction with two fixed capacitor banks (135 Mvar each)
installed at edic and oakdale substations, helps to improve
the voltage stability of the new York state grid, thus increasing its power transfer capability limit by 200 MW.
the CsC, represented in figure 7, is a custom-made
device intended for voltage control and for power flow
control on two 345-kV lines. it consists of two 100-MVa
converters using VsC technology operating in several configurations such as
march/april 2016

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