Journal of Power and Energy Engineering, 2015, 3, 200-205
Published Online April 2015 in SciRes. http://www.scirp.org/journal/jpee
http://dx.doi.org/10.4236/jpee.2015.34028
How to cite this paper: Li, Z.H., Gao, F., Wang, Q., Zhang, S., Luo, H.M. and Liang, J. (2015) Study on Effect of UHV Power
Grid Construction Schemes on Short Circuit Current. Journal of Power and Energy Engineering, 3, 200-205.
http://dx.doi.org/10.4236/jpee.2015.34028
Study on Effect of UHV Power Grid
Construction Schemes on
Short Circuit Current
Zaihua Li1, Feng Gao2, Qing Wang1, Shuang Zhang2, Hongmei Luo1, Jian Liang2
1China Electric Power Research Institute, Beijing, China
2Ningxia Electric Power Research Institute, Yinchuan, China
Received January 2015
Abstract
The commissioning of Southern Hami-Zhengzhou ±800 kV UHVDC transmission project has im-
portant significance to heighten operation reliability, transfer capability and supply electric abili-
ty of Henan power grid. However, short circuit currents of 500 kV buses in the Center of Henan are
almost close to the operation upper limitation. In order to decrease the short circuit currents ef-
fectively, it’s necessary to strengthen the network structure of Center of Henan power grid and
calculate short circuit currents. Two schemes of strengthening the network structure of Center of
Henan power grid are studied. The calculated values of short circuit currents of some important
500 kV buses in the two schemes are still bigger than excepted. According to the late s t Plan of
State G rid, Yubei UHV substation and Zhumadian UHV substation loc ated in Henan power grid. The
calculated values of short circuit currents of some important 500 kV buses with the commission-
ing of Yubei UHV and Zhumadian UHV are qualified. So, reasonable network structure with UHV is
suitable to heighten transfer capability and supply electric ability of Henan power grid.
Keywords
UHV, UH VDC , Construction Scheme, Short Circuit Current
1. Introduction
By the year of 2014, the main network structure of Henan power grid is a 500 kV trap ezoid structure with two
vertical and four ho r iz ont al lines. In 2013, peak load of Henan power grid is about 48,010 MW, while the gener-
ate ability of Henan power grid is only 46,260 MW. Therefore, there’s a power shortage more than 3000 MW
when considering reserved capacity. The installed capacity of coal-fired thermal power units accounted for 90
percent of the total installed capacity of Henan p ro vince . Considered from environment protection and susta i na-
ble development point of view, the commissioning of Southe r n Hami -Zhengzhou ±800 kV UHVDC tran s mi s-
sion proj ect (i.e. Hami-Zhengzhou UHVDC) has important sig nificanc e to heighten operation reliability, transfer
capability and supply electric ability of Henan power grid.
The load center of Henan locates in the Center of Henan power grid, and the power comes from North of Henan,

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West of Henan and South of Henan, so the suitab le location of Henan power grid integrating Hami- Zhen gzho u
UHVDC is the Center of Henan power grid. However, short circuit curr ents of 500 kV buses in Center of Henan
power grid are almost close to the operation upper limitatio n. In order to decrease the short circuit cur r e nt s ef-
fectively, it’s necessary to improve and strengthen the network structure of the Center of Henan power grid and
calculate short circuit cur r ents in the new network str uct ur e [1].
2. Effect of Short Circuit Current
Short circuit current calculation and control is one of the most important functi ons in power system analysis.
Effect of short circuit current can be summarized as below [2]:
1) Short circuit is a kind of seri ous fault, it may break the stable operation of power system, break the power
supply and even bring blackout.
2) It will decrease the voltage of power system greatly, damage industry equipment and product, and debase
the quality of power energy.
3) The flaring electric arc may burn out the equipment, and if the short circuit current exceeds the interrupting
ability of breaker, it may cause more serious fault.
4) It brings thermo effect and electromotive force effect, they may damage the equipment.
5) Short circuit current may disturb communication system and ele ctronic system nearby.
However, short circuit current is far from having no benefit. Bigger short circuit current means stronger abili-
ty to tole rate serious short circuit fault for a certain power system. In order to ensure the security and stab ility of
power system, it’s necessary to keep a certain short circuit current level and control the short circuit current
within an appropriate range.
3. Analysis of Short Circuit CURRENT
3.1. Calculation Conditions of Short Circuit Current
The calculation conditions of short circuit current in the paper are as below [3] [4]:
1) Calculating result is the effective value of industrial frequency current co mpo nent injected into the short
circuit point at the moment at which the shor t circuit a rise s.
2) The thr ee -phase AC system is a symmetrical system, the structures of three phases of stator windings are
symmetrical, and the spatial position differs by 120˚ electrical angle.
3) The short circuit is a b olted fault, and the short circuit impedance in the fault point has a value of zero.
4) To suppose the quadrature axis subtransient reactance is equal to the direct axis subtransient reactance. The
model of sync hr o nous generator with the direct axis subtransient reactance a nd constant subtransient electromo-
tive force is used. The magnetic saturation effect of generator and the skin effect of co nduc t o r ar en’t considered.
5) Magnetic saturation effect of static components is n’t considered, parameters of electric equipment won’t
change with the value of current.
6) The tap of transformer is used with the actual setting.
7) The operation mode of Henan power grid is with all generators and all lines operated, the load model of
constant impedance load and induction motor is used.
3.2. Short Circuit Current of 500 kV System in Henan in 2013
The calculation results of three-phase short circuit current of some important 500 kV buses in Henan power grid
in 2013 are shown in Table 1.
From the above table, if the induction motor model was considered, then three-phase short circuit current of
some important 500 kV buses in Center of Henan power grid will exceed 63 kA. In fact the calculation cond i-
tions of short circuit current are somewhat conservative. In order to keep pace with the actual status in field, in-
duction motor may be not taken into account in the succeeding study. Even if the induction motor isn’t taken in-
to account, the maxi mu m value of thr ee -phase short circuit current in Henan power grid is close to the limit
breaking capacity of breaker. It’s necessary to decrease short circuit current by some measures.
3.3. Short Circuit Current of 500 kV System in Henan in 2014
The calculation results of three-phase short circuit current of some important 500 kV buses in Henan power grid

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in 2014 are shown in Table 2.
From the above table, short circuit current level of the Henan power grid is i ncreasing accord ingly year by
year because of the growth of economy, and short circuit current problem is more obvious. Even if the induction
motor isn’t taken into account, the three-phase short circuit current in Henan power grid is enlarged and closer to
the limit breaking capacity of breaker. So it’s urgent necessary to decrease short circuit current by some
measure s.
4. Two Schemes of Strengthening the Network Structure
To heighten the breaking ability of breaker is a directional way, but now the breaker with breaking ability above
63 kA is too much expensive. In general, it’s not economical to use breaker with breaking ability above 63 kA
widely. In order to ensure the security of power system, to strengthen and improve the network struc t ur e is a
better choice by far now.
According to the characteristic of Henan power grid and source of short circuit current in some important
500kV buses, the network struc tur e can be improved and optimized. The strengthening measures can’t do much
harm to the security and stabi lity of power system. When considering all-round, two schemes of improving and
strengthening the network stru cture of Center of Henan power grid are studied as below [5].
4.1. Scheme No. 1.
The network str uc t ur e of Center of Henan power grid of strengthening scheme 1 is shown in Figure 1 as below.
The 1st scheme is to connect one of Songshan-Zhengzhou d ouble circuit 500 kV transmission lines and one of
Zhen gz ho u -G ua nd u double circuit 500 kV transmission li ne s in series outside the 500 kV Zhengzhou Substation.
Calculation verified that the strengthening measures won’t do much harm to the security and stabilit y of power
system. The network structure meets the requirement of Guide on Security and Stability for Power System (DL
755 - 2001). The calculation result of three-phase short circuit current of strengthening scheme 1 is shown in ta-
ble 3 as below.
Table 1. Short circuit currents of some important 500 kV buses in 2013.
Bus short circuit current (kA)
With motor Without motor
YU_Songshan50 67.42 60.03
YU_Zhengzhou50 66.42 59.31
YU_Huojia50 62.51 55.14
YU_Zhengbei50 62.44 56.15
YU_Zhengnan50 50. 68 47.06
Table 2. Short circuit currents of some important 500 kV buses in 2014.
Bus short circuit current (kA)
With motor Without motor
YU_Songshan50 68.91 61.23
YU_Zhengzhou50 66.63 59.33
YU_Huojia50 62.70 55.31
YU_Zhengbei50 62.41 55.96
YU_Zhengnan50 50. 74 47.08
YU_Xiangshan50 59.21 54.04

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Figure 1. Scheme 1 of strengthening the network.
4.2. Scheme No. 2
The network str uc t ur e of Center of Henan power grid of strengthening scheme 2 is shown in Figure 2 as below.
The 2nd scheme is to open the Songshan-Zhengzhou 500 kV double-circuit transmission lines, so as to enlarge
the ring network in Center of Henan power grid. The new 500 kV ring network in Center of Henan is comprised
by lines of Son gs han-Mashi-G o ng yi -M ud a n-J ia he -Zhen gz ho u -G uandu-Zhengzhou UHVDC convertor substa-
tion-Zhe ngb ei-Songshan. Calculation verified that the measures won’t do much harm to the security and stabil i-
ty of power system. The network structure meets the requirement of Guide on Security and Stability for Power
System (DL 755 - 2001) [6 ] . The calculation results of thre e -phase short circuit current of some important 500
kV buses in strengthening scheme 1 and scheme 2 are shown in Table 3 as below.
From the above table, it’s obvious that the calculated values of short circuit currents are still bigger than ex-
cept. They are still close to the limit breaking capacity of br eaker. The two strengthening schemes only have ob-
vious effect on relative substations, and have lit tle effect on other substations.
4.3. Scheme No. 2 with Yubei UHV and Zhumadian UHV
According to the latest Plan of State Grid, Henan UHV power grid will be an important constituent part of the
national UHV power grid. There are 2 vertical transmission passagewa ys and 1 hori zo nt al transmission passa-
geway go across Henan UHV power grid. The 1000-kVYubei UHV substation locates in North of Henan, and it
has 4 outgo i n g line s of 500 kV. And, the 1000-kV Zhumadian UHV substation locates in South of Henan, and it
also has 4 out go i ng line s of 500 kV.
The calculated values of short circuit cur re nt s of some important 500 kV buses with the commissioning of
Yubei UHV substation and Zhumadian UHV substation based on the scheme 2 are shown in Table 4.
From the above table, it’s obvious that the calculated values of short circuit currents with the commissioning
of Yubei UHV substation and Zhumadian UHV substation are smaller than the fo r e go ing two strengthening
schemes. It can effect on more substations than the scheme without Yubei UHV substation and Zhumadian
UHV substation.
In order to integrate Hami-Zhengzhou UHVD C project, the network structure of Center of Hena n power grid
has to be strengthened. In the future, the commissioning of Yubei UHV substation and Zhumadian UHV substa-
tion also will strengthen the Henan power grid.
It’s all known that if a power network is strengthened, in general the short circuit curr ent will be enlarged ac-
cor d ingly. So it’s interesting that why the short circuit cur r ent be decreased in Henan power grid.
4.4. The Venin Equivalent Reactance of the Power System
In order to verify the above simulation and analysis, the T he venin equivalent reactance of the power system is
calculated [7]. In the Scheme No. 2 without Yubei UHV and Zhumadian UHV, the 1st 500 kV bus in Zhengzhou
substation is selected as the short circuit point. The ve nin equivalent reacta nce is about in the range of 0.015621

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Figure 2. Scheme 2 of strengthening the network.
Table 3. Short circuit currents of strengthening scheme in 2014.
Bus short circuit current (kA)
Original Scheme 1 Scheme 2
YU_Songshan50 61.23 58.94 58.91
YU_Zhengzhou50 59.33 50.24 48.93
YU_Huojia50 55.31 54.83 5 4.66
YU_Zhengbei50 55.96 54.73 55.20
YU_Zhengnan50 47. 08 46.62 4 6.09
YU_Xiangshan50 54.04 53.75 53.72
Table 4. Short circuit currents of some important 500 kV buses with UHV in 2014.
Bus short circuit current (kA)
Original Scheme 2 with UHV
YU_Songshan50 61.23 45.62
YU_Zhengzhou50 59.33 44.48
YU_Huojia50 55.31 50.25
YU_Zhengbei50 55.96 46.21
YU_Zhengnan50 47. 08 44.16
YU_Xiangshan50 5 4.04 52.36
- 0.015722. In the Scheme No. 2 with Yubei UHV and Zhumadian UHV, the venin equivalent reacta nc e is about
in the range of 0.015685 - 0.015791. With the commissioning of Yubei UHV substation and Zhumadian UHV
substation and other relational improvements in Henan power grid, the venin equivalent reactance of the power
system is enlarged in some degree, so the short circuit cur r ent is decreased.
The network structure of Hen an power grid has been opti mized so as to inte gr at e Hami -Zhengzhou UHVDC
project. Though the network structure is strengthened, the Center of Henan power grid is simplified and sparser,
so the venin equivalent reactance of the power system is enlarged. It’s the reason of t he short circuit cur r ent was
decreased obviously. The calculation results of the venin equivalent reactance and the short circuit cur r ent can

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verify the simulation and analysis from two aspects.
5. Conclusions
After the calculation and analysis, conclusions can be obtained as below.
1) Ther e ’s a big power shortage in Henan power grid and the power-receiving ratio will be higher in the fu-
ture. And the short circuit curr ent will grow continuously. So, it’s necessary to take appropriate measures to de-
crease short circuit cur re nt.
2) According to the operating characteristic of power grid and source of short circuit current, it’s feasible to
decrease short circuit current by improving and optimizing the network struc tur e while not to do harm to the se-
curity and stabilit y of power system.
3) If a network is strengthened, whe t her the short circuit cu rrent will be enlar ge d or not can be verified by the
venin equivalent reactance.
4) Reasonable network structure with UHV is suitable to heighten operation reliability, transfer capability and
supply electric ability of Henan power grid, and the short circuit cur r e nt problem can be solved in a certain de-
gree.
References
[1] National Power Dispatching and Communication Center (2009 ) The Report about Research Special Projects Such as
Short Circuit Current, Electromagnetic Loop Network and Transmission Capacity Is Lo w. State Grid Corporation of
China, 11. (In Chines e)
[2] Tan g, X. J., Li , Z.H., Wu, L.H., et al. (2011) Investigation and Analysis on Short Circuit Current. China Electric Power
Research Institute, 06. (In Chi nese)
[3] IEC 6 0909 -0: 2001 (20 01) Short Circuit Currents in Three-Phase Acsystems—Part 0: Calculation of Currents. 0 7.
[4] IEEE Standard 241 -1990 (1990) Electric Power Systems in Commercial Buildings.
[5] Lu o , H.M., Tang, X.J., Li, X.J., et al. (2012) Research on the Adaptability of Structural Strength before and after
Commissioning of the Large Capacity Hami -Zhengzhou UHVDC Project. China Electric Power Research Institute. 09.
(In Chin ese)
[6] State Economic and Trade Commission of the People’s Republic of China (2001) Guide on Security and Stability for
Power System (DL 755-2001).
[7] Li , Z.H. (2012) Research on Thevenin Equivalent Parameters Based on Time Domain Simulation. China Electric Pow-
er Research Institute, 12. (In Chinese)