Analysis on the Operation of 750kV Controllable Shunt Reactor
in Gansu Power Grid of China
Rong Xiaoyun
, Shao Chong
, Wang Weizhou
, Hou Yanpeng
, Liu Fuchao
Jia Cunxi
and Li Zhengyuan
North China Electric Power University, Zhuxinzhuang, Dewai, Beijing, China
The University of Edinburgh, School of Engineering, The King's Buildings,Edinburgh, U.K.
Gansu Electric Power Research Institute, Qilihe District, Lanzhou, P.R. China
Gansu Electric Power Maintenance Company, Anning District, Lanzhou, P.R. China
Keywords: Controllable Shunt Reactor, 750kV Super-high Voltage Grid, Operation, Wind Power.
Abstract: Super High Voltage is the efficient way to achieve low power losses in long distance power transmission,
but power frequency overvoltage and secondary current still exist. In order to improve the stability of the
system, high voltage controllable shunt reactor (CSR) is added to the system. This thesis was based on the
large amount of data about the 750kV controllable shunt reactor operated in the 750kV substation of
Dunhuang, which is the first CSR applied in 750kV super-high voltage grid in China. The relationship
between the variation of the voltage and the switching on/off of CSR was analized, the actual impacts of the
CSR on the reactive power distribution and the active power loss were studied. Furthermore, a certain
theory basis for the CSR maintenance was provided.
Northwest of China is rich in wind power, a 10GW
wind farm has being developed. In order to transmit
and transform the large scale wind power, two
750kV super high voltage transmission lines have
been constructed. Because of the long distance
transmission of large scale power and the dramatic
intermittency and unpredictability of wind power,
the reactive power balance and voltage control
problem of the grid became prominent (Wang,
As the controllable shunt reactor (CSR) can
adjust reactive power of the system flexibly, inhibit
overvoltage and secondary arc current, reduce
network loss (IEEE Standard Requirements, 2008),
improve the stability and the delivery capacity of the
system (Belyaev and Smolovik, 2005), it becomes
the first choice to solve the problems relating to the
large scale wind power integration from long
distance in Northwest China, especially in Jiuquan,
Gansu (Pan et al., 2007). In November, 2011, the
750kV CSR, which has the highest operating voltage
in the world, self-developed by China, was
successfully put into comercial operation in
Dunhuang substation of Jiuquan (Liu et al., 2012).
The map of the position of Dunhuang and Jiuquan is
as shown in Figure 1, marked with read circle.
Figure 1: Map of Dunhuang and Jiuquan.
It has solved the reactive power and voltage
fluctuation of the 750kV Dunhuang substation
effectively, and improved the utilization rate of the
750kV wind power delivery system, as the 750kV
Dunhuang substation is one of the main substations
with large scale wind power integrated into power
Xiaoyun R., Chong S., Weizhou W., Yanpeng H., Fuchao L., Cunxi J. and Zhengyuan L..
Analysis on the Operation of 750kV Controllable Shunt Reactor in Gansu Power Grid of China.
DOI: 10.5220/0004358801050109
In Proceedings of the 2nd International Conference on Smart Grids and Green IT Systems (SMARTGREENS-2013), pages 105-109
ISBN: 978-989-8565-55-6
2013 SCITEPRESS (Science and Technology Publications, Lda.)
grid concentratedly (Li et al., 2010).
This thesis was based on 340 sets of data,
measured from the related power system when the
operation state of CSR in Dunhuang is changed .
Later, combined with the actual operation state, the
voltage of the 750kV Bus and the reactive power of
the system, the operation states and the effectiveness
of CSR were analysed, and the advises for operation
and maintenance were given.
2.1 CSR Introduction
According to the different constitutions and basic
principles, the CSR in the world can be classified
into magnetic control CSR and high-impedance
transformer CSR (Bryanteev et al., 2006). And
according to the different applications, it can be
sorted into the bus shunt reactor and the line shunt
reactor (Xie and Chen, 2008).
Magnetically controllable shunt reactor has
advantages like continuously adjustable reactive
power, small and low harmonic component, and
economical control system. It is mainly used as bus
shunt reactor. But because of low response speed, it
is not suitable for line shunt reactor, and can not be
used in 750kV wind power delivery system
characterised by frequent fluctuation of power (Zhou
et al., 2003) .
High-impedance transformer CSR (stepped
controllable shunt reactor) always has great losses,
high-level harmonics and noises when applied into
super high voltage system. Compared with
magnetical CSR, high-impedance CSR has simple
principle, faster dynamic response speed, easier
operation and maintenance. When its control system
is in failure, it can operates as fixed reactor (Zhou et
al., 2007). The structure principle of the 750kV CSR
is as shown in Figure 2. This kind of CSR is
appropriate for large scale wind power concentrated
integration in Hexi area in Gansu province of China
(Li et al., 2010).
Figure 2: Structure Principle of the 750kV CSR.
2.2 750kV Dunhuang Substation
At present, about 5.5GW wind power as the first-
stage construction of JiuQuan super wind power
base in Gansu have been integrated into 330kV
power system and connected with the 750kV system
through seven 330kV booster stations and two
330kV transformer stations. Expected total wind
power in 2015 will reach to 1270 million watts
At that time, 750kV Dunhuang substation would be
rated as the biggest capacity and highest voltage
level single substation in the world for the wind
power integration, as almost all the wind power of
Jiuquan would integrate into its 330kV bus (Zhou et
al., 2006).
As wind power fluctuate frequently, the highest
voltage of the 750kV bus of the Dunhuang
substation had reached 802kV and the lowest 755kV.
The voltage and reactive power adjustment of the
power grid is very difficult.
In order to enhance the voltage stability, balance
reactive power, reduce grid losses, improve the
reliability and security of the systems operation, the
300Mvar stepped CSR was developped as the
750kV bus CSR of 750kv Dunhuang substation.
The adjustable range is 25, 50, 75, 100 of
the nominal capacity (Pan et al., 2007).
2.3 Operational Data of the CSR
This thesis is based on the CSR operational data,
collected from 14 January, 2012 to 6 August, 2012,
340 valid sets altogether. Contents mainly included
are actuation time, adjustment level, voltage change
and the reactive and active power in high and
medium voltage side of the primary transformer. For
example, at 04:24, 6 August, 2012, the capacity of
the CSR was adjusted from 75% to 50%
automatically, bus voltage was adjusted from 755kV
to 758kV, the active and reactive power in high
voltage side of the primary transformer 2 were -
735MW and 156Mvar, in medium voltage side were
736MW and 56Mvar. As for primary transformer 3,
the active and reactive power in high voltage side
were -734MW and 156Mvar, in medium voltage
side were 736MW and 57Mvar.
The voltage level and power capacity of 750kV
Dunhuang substation CSR are both the highest in the
world. Its operating environment is really harsh
(plateau section, gobi desert). A plentiful operational
data has been accumulated, after one-year running.
Operational data mining has great practical
significance for the improvement of the operation
and maintenance performance of this CSR and for
the optimal structure designing of other CSR.
3.1 CSR Capacity State Analysis
The adjustment level of CSR illustrates its capacity,
operation states and corresponding action of
thyristor. The analysis of this sets of data is
conducive to the maintenance of CSR.
Figure 3: Percentage of Capacity States.
Figure 3 is the percentage of the four different
capacity states which is obtained from 340 sets of
statistical data. It is obvious that 50% and 75%
accounts for the largest percentage, nearly reach to
the twice of 25% and 100%. The state that the whole
capacity is out of service never shows up.
Figure 3 indicates that the capacity of this CSR
was reasonably designed, as more than half of the
capacity is utilized. The rated capacity put into
operation also happened but in a small proportion.
Figure 3 also shows that the valve bodies which
control the 75% and 50% capacity act relatively
frequent, so they should be treated as key elements
during maintenance. And because 25% capacity is
always put into operation, so it also needs more care.
3.2 Analysis of CSR Action Conditions
Figure 4 is derived from the action time statistics of
CSR, and it is useful to design maintenance and
inspection time.
Figure 4 is the distribution density of the total
action times for these four different levels at
different period. The action (put or cut) of the CSR
mainly occurred between March and July, especially
between early May and the end of June.
Taking the weather during this period in
Dunhuang as reference, it is clear that the main
reason which causes this variation is the wind speed
in Dunhuang was really unstable from May to July,,
causing grid connection capacity of wind power
fluctuated frequently and the varying of voltage and
reactive power of system, finally leading to the CSR
switching frequently.
02/01 03/22 05/11 06/30
Figure 4: Numbers of Action and it’s Time Distribution.
This indicates that the best maintenance time of CSR
in Dunhuang is between January and March or May
and July. Strengthened inspection of equipment must
be done to prevent potential accident which may
caused by the frequent switching.
The switching of CSR will cause the change of bus
100 to 75
75 to 50
50 to 25
25 to 50
50 to 75
75 to 100
adjust level
Figure 5: The Influence of CSR Switching on Voltage.
Distribution density
Date day/mouth
In theory, when CSR level is adjusted from low
to high, the reactive capacity increases and the
voltage decreases, vice verse. Three dimensional
scattering projection diagram 5 is derived from 340
sets of statistic data. This figure reflects the
occurrence number of some certain voltage
difference caused by the change of capacity.
4.1 Main Impact on Voltage
When the operating capacity of CSR decreases, most
of the voltage increases although the amplitude are
generally small. Nearly 90% of the voltage
differences are concentrated between 1kV and 6kV.
Voltage differences reach to 10kV or 20kV also
occurred, but most are 2kV. When the operating
capacity increasesmost of the voltage decreases.
Nearly 90% of the voltage drops are concentrated
between 1kV and 6kV. Voltage drops reach to 10kV
also occurred, but most are 2kV as well. From above,
CSR with total capacity of 300Mvar, switching at
75Mvar of each level, do not significantly affects the
voltage of 750kV bus, as amplitude of variation
always within 1%, tending to nominal value.
Through the analysis of the data, putting the CSR
into operation and its frequent switching won’t
influence the operation of 750kV equipment.
4.2 Analysis of Special Circumstances
As stated, after the switching of CSR, some voltage
differences are not within 6kV. Two main classes,
one is the amplitude of variation bigger than 6kV.
For example, within the 340 sets of data, voltage
differences (increase) reach to 20kV appeared twice,
12kV appeared twice. Voltage differences (decrease)
reach to 9kV appeared once, 8kV appeared once.
Although they conform to the theory but are
different from normal situation. Another is when the
operating capacity increases, bus voltage also
increases and when the operating capacity decreases,
bus voltage also decreases, opposite to the theory, as
shown in Figure 5 within red circles.
In the first situation, increasing 20kV for
example, referring to the nearby switching actions
and corresponding weather information, wind speed
changed rapidly at that time so the grid connection
capacity of wind power is bigger. At 14:29,
31/03/2012, the operation capacity of CSR dropped
from 100% to75%, causing voltage increase from
756kV to 758kV, 2kV increment. Then at 14:38
31/03/2012, the operation capacity dropped from
75% to 50%, causing voltage increase from 758kV
to 778kV, 20kV increment. This phenomenon
appears many times within small period furing 340
sets of data, and always accompanied with large
amplitude of voltage variation. This phenomenon
indicates that the primary causes of large amplitude
of voltage variation after CSR put into operation are
the big variation of grid connection capacity of wind
power and lacking of CSR switching capacity within
one operation time. Introducing short term wind
power predicting outcomes into control logic of CSR
is a promising method to solve this problem.
In the second situation, the variation of voltage
goes against the theory. Firstly, because all the data
were recorded manually, so man-made faults won’t
be eliminated. What’s more, another possibility is if
wind power changes quite fast, bus voltage
fluctuated frequently, so during a small period the
voltage increments or decrements caused by the
wind power grid connection is bigger than the
voltage decrements or increments caused by the
switching of the CSR, so the variation of voltage
goes against the theory.
CSR is the effective means in solving voltage and
reactive power problems of the power grid caused
by the large scale wind power integration. This
thesis combines with the actual operation states of
300Mvar stepped CSR in Dunhuang 750kV
substation of China, analyzed its operating
characteristics, summarized the impact of switching
actions on bus, the conclusion is as follows:
(1) 300Mvar CSR is sufficient in solving the voltage
and reactive power fluctuation problems of the
power grid of Dunhuang.
(2) The switching times of CSR is relatively high
during the period when wind power fluctuates
frequently. It is suggest that maintenance
between January and March and strengthened
inspection of equipment between May and July
be arranged.
(3) The thyristor switching of 50% and 75%
capacity act relative frequently and 25% capacity
is always put into operation, so they all should be
treated as emphasis during the maintenance.
(4) After putting the CSR into operation, the
variation of bus voltage is limited nearly within
the acceptable range. That means CSR don’t
have large impact on bus voltage.
(5) As wind power changes with large amplitude and
frequently, large amplitude of voltage variation
after the variation of CSR capacity may
occurred. Introducing short term wind power
predicting outcomes into control logic of CSR is
a promising method to solve this problem.
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