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Taiwan was just hit by a widespread power outage on 13 May. Two
coal-fired power units and two gas-fired power units of the Hsinta
power plant in Kaohsiung City tripped unanticipatedly owing to a
bus bar failure at the nearby Lubei extra high-voltage substation
at 2:37 pm that day, leading to an instant supply loss of nearly 2
GW. The outage spread to the rest of Hsinta's operating units, and
the whole power plant was unloaded in a short time. Rolling
blackouts among different counties were implemented from 3:00 pm
owing to lack of backups.
Although officials insist that the accident was caused by a grid
failure, IHS Markit believes the accident was a result of
inadequate power supply and vulnerable grid structure.
First of all, there was insufficient reserve capacity to deal
with unexpected situations. On the demand side, Taipower
underestimated the daily peak load by 4.9%. According to Taipower's
website, the power load peaked at 36.7 GW about 40 minutes before
the "513" outage, demanding the system to hold at least 40.4 GW of
firm capacity to keep a 10% reserve margin.
On the supply side, however, the output of renewables was
curtailed substantially caused by extreme weather. Dispatchable
units (excluding conventional hydro) could provide 34.5 GW of firm
capacity based on that day's unit schedule, indicating conventional
hydro, solar, and wind power plants have to achieve 85.4% output on
average to meet the required 40.4 GW. Unfortunately, the actual
supply of renewables was only approximately half of the
expectation.
IHS Markit estimates the actual peak time reserve capacity on 13
May was less than 850 MW, leaving the system running with a
dangerously low reserve margin of only 2.3%. As the rush hour
passed, the reserve margin recovered to about 5.8% right before the
accident, with system reserve capacity slightly over 2 GW—not
enough to deal with large-scale outage emergencies, like in the
Hsinta power plant case.
In addition, heavy reliance on large-scale concentrated power
plants weakened grid reliability. From a planning perspective,
power supply in Taiwan is not as diversified as in other markets.
In other words, there are a few large power plants serving too big
of a portion of grid demand, which implies potential reliability
issues. The top eight largest thermal power plants serve more than
75% of the system peak (see Table 1). The loss of any of these
plants will cause a significant supply shortage; even if the
planned reserve margin may have seemed adequate at that time.
Allen Wang, Ph.D. is a director on the Climate and
Sustainability team at IHS Markit, leads Southeast Asia power and
renewables research, and is the research manager for Asia Power and
Renewables Analytics.
Shan Xue is a Principal Analyst on the Climate and
Sustainability team at IHS Markit and focuses on Asian power market
modeling.
Posted 10 May 2021
This article was published by S&P Global Commodity Insights and not by S&P Global Ratings, which is a separately managed division of S&P Global.
