IEEE Power & Energy Magazine - July/August 2016 - 74

with a !200 MVa static synchronous compensator.
The main causes of the delayed
clearance of ac faults are breaker
failure and protection-missing
operation. For protection-missing
operation, CSG has taken full
dual fiber differential protection to
guarantee the reliability of protection relays; for breaker failure, special maintenance of breakers has
been carried out in key areas, however such work is time consuming
and does not yet completely avoid
breaker failure.

8 ac + 8 dc from West to East
Three Gorges

Guizhou
Yunnan
Guangxi
Guangdong

18.9 GW
Long Distance
Ultra-High Voltage

35 GW

Bulk Capacity
Hybrid Operation of ac/dc

DC Current Flowing
Through the Earth

3 GW

8.6 GW

34% of
GD Load

Hainan

The hVdc may be operated in
ground-return mode when the figure 3. An overview of the CSG transmission system.
system is in system test or after
monopole failure. in such cases,
there will be great amount of dc flowing through the earth- 30 min. if the same polarity poles of the niucong hVdc
ing electrode, which will affect the potential distribution, (2*3,200 Mw) block, the emergency current limitation
cause transformer magnetic bias phenomenon, accelerate will be initiated to prevent a gas pipeline explosion, resultcorrosion of buried pipelines, and harm pipeline workers. ing in a high risk of transmission element overload.
To reduce this, it is necessary to rationally arrange the
operating mode of the hVdc, build reliable current chan- Natural Disasters
nels, reduce the grounding resistance of ground electrode, Frequent natural disasters will increase the risks to the
and rationally configure the grounding points and ground- power grid. Guangdong and Guangxi are located in a
ing modes of ac transformers in ac power network.
typhoon zone while Yunnan and Guizhou are located in
in CSG, all hVdc equipment is located close together an earthquake zone. inclement weather will cause multiwithin the receiving grid, of which average distance is line cascading tripping and even regional blackouts. For
under 100 km, and it is difficult to select the sitting of elec- example, because of an ice storm on 25 January 2008, part
trode. The electrode of niucong hVdc is only 10 km away of the overhead lines was covered by 50-mm-thick ice,
from a gas pipeline. Thus, when the niucong hVdc oper- causing serious damage to power facilities. This disaster
ates in ground-return mode, dc power needs to be decreased caused outages of over 7,541 overhead lines (10 kV and
fast to ensure that the earth current is below 1,200 a within above), collapse and damage to 126,247 towers and poles,

95.9

2009

104.4

2010

113.2

2011

119.7

2012

128.9
15.0

2013

Peak Load of Unified
Power Generation Management (GW)

2009

13.7

2010

11.4

11.0

10.5

2011

2012

2013

Investment in
Power Grid Construction (US$ Billion)

figure 4. Peak load and investment in CSG.
july/august 2016

ieee power & energy magazine

75
Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - July/August 2016
