Impact of Fault Resistance on Transmission Line

ICEEAC 2013 International Conference on Electrical Engineering and Automatic Control, Setif, 24-26 November 2013

Impact of Fault Resistance on Transmission Line Compensated by Series FACTS Devices Mohamed ZELLAGUI1, Abdelaziz CHAGHI1, Heba Ahmed HASSAN2, Azeddine GHODBANE3 and Amir GHORBANI4 1

2

LSP-IE Laboratory, Department of Electrical Engineering, Faculty of Technology, University of Batna, Algeria Department of Electrical and Computer Engineering, College of Engineering, University of Dhofar, Sultanate of Oman 3 Department of Electrical Engineering, École de Technologie Supérieure (ETS), Montréal, Canada 4 Department of Electrical Engineering, Science and Research Branch, University of Islamic Azad, Tehran, Iran [email protected], [email protected], [email protected], [email protected]

Abstract – This paper presents the impact of three series Flexible AC Transmission System (FACTS) devices, namely the Thyristor Controlled Series Capacitor (TCSC), GTO Controlled Series Capacitor (GCSC) and Thyristor Controlled Series Reactor (TCSR), on the short circuit calculations of a 400 kV electrical transmission line in case of a phase to earth fault in the presence of a fault resistance (RF). The case study is a 400 kV single transmission line in the northern Algerian transmission network which is compensated by each of the three mentioned FACTS devices, consequently. Each compensator is connected at the midpoint of the line to control the reactive power and reactance of the line. The obtained simulations results investigate the impact of the fault resistance, which varies between 0 to 50 Ω, on the parameters of short circuit calculations, without compensation and with each FACTS device. The obtained simulation results match the presented theoretical analysis.

I. INTRODUCTION Planning, construction and operation of power systems should provide safe, reliable and economic electrical power supply to various load types. Knowledge of equipment loading at the time of commissioning, prediction for the design, and determination of the individual equipment rating and of the power system as a whole are all necessary for proper system operation. Despite accurate planning, careful design, good maintenance and thorough operation of the system still shortcircuit faults in power systems cannot be completely avoided. External factors may cause faults such as faults following lightning strokes leading to voltage surges into phaseconductors of overhead lines, accumulation of moisture and contaminants specially in humid environment, damages of cables due to earth construction works, etc. Internal causes of faults are attributed to deterioration of insulation materials due to ageing, loose connections causing equipment overheating, voltage or mechanical stresses applied to the equipment, system-generated voltage surges due to switching as well as connection and disconnection of loads and equipment, [1-3]. Fault currents are known to have important influences on the design and operation of equipment in power systems. In the Algerian electrical transmission network, more than 83 % of the occurred faults on 220 and 400 kV power systems overhead transmission networks are single phase to ground type, 11 % of

faults are phase to phase fault while the remaining 6 % are three phase fault types, [4]. Recently, it is noticeable that the power demand has been increasing substantially worldwide. On the other hand, the expansion of power generation and transmission facilities and equipment has been severely limited due to limited resources and environmental restrictions. As a consequence, some transmission lines are heavily loaded and the system stability becomes a power transfer-limiting factor. FACTS controllers offer many benefits to the network and have been mainly used for solving various power system steady state control problems, [2], [5]. The impact of the Thyristor Controller Series Capacitor (TCSC) compensator on distance protection in the presence faults has been reported in [6-7].The measured impedance by distance relay for inter phase faults, as well as variation of the measured impedance in inter phase faults, when using TCSC on an adjacent transmission line, are reported in [8]. The effects of voltage transformers connection point for inter phase faults is also reported in [9]. The impact of using GTO Controlled Series Capacitor (GCSC) on the measured impedance by distance protection single phase to earth fault with a fault resistance varied when using GCSC compensator on 220 kV and 400 kV line, [10-11]. However, the impact of Static Synchronous Series Compensator (SSSC) on the measured impedance by distance relay on 400 kV transmission line without fault is reported in [12]. It was also addressed in the presence of single phase to ground fault on 220 kV transmission line in [13], and for inter phase faults on 400 kV transmission line in [14]. The effect of the Static Synchronous Compensator (STATCOM) on the performance of distance relay in electrical transmission systems is studied in [15-16]. The impact of using Static Var Compensator (SVC) on the transmission line distance protection schemes is studied for different fault types in [17]. The effects of hybrid FACTS devices like the Unified Power Flow Controller (UPFC) on the performance evaluation of a distance protection relay is applied to a transmission system, in case of inter phase fault for different fault conditions, [18].

Algeria, which is one of the largest North Africa countries, has an extensive AC network that spreads throughout the country. In 2012, the total length of the transmission network was 23,802 km with an increase of 6.29% when compared to 2011. While the electrification rate was 57% in 1977, more than 96% of the country has now access to electricity. Currently, Algeria is connected with its neighboring Tunisian and Moroccan grids by a 440 kV line each. This paper deals with the impact of fault resistance in the presence of phase (A) to earth fault at the end of a transmission line compensated by a three phase series FACTS device installed on 400kV Algerian transmission line network. This devices is located in the midline between two 400/200 kV substations, namely Salah Bey (Sétif) and Bir Ghbalou (Bouira) in Algeria. Sétif is the capital of Sétif province which is located in the north east of Algeria and to the east of the capital. Bouira is the capital of Bouira province which is in the central north of Algeria. This research study investigates the impact of fault resistance RF that varies between 0 to 50 Ω, on the short circuit parameters, namely the symmetrical current components (I1, I2 and I0), transmission line currents (IA, IB and IC), voltage symmetrical components (V1, V2 and V0), and transmission line voltages (VA, VB and VC). Section II presents the structure of the three series FACTS devices used in the paper, namely TCSC, GCSC and TCSR. The calculations of symmetrical parameters, in case of a phase to earth fault while using a series FACTS device in the presence of RF, are derived in Section III. The case study for the 400 kV line in the northern Algerian transmission network and simulation results are illustrated and analysed in Section IV. Section V provides the main contribution and conclusions of the paper.

A. TCSC This compensator can be modeled as a variable apparent reactance (XTCSC) as shows in Figure 2.

Fig. 2. Apparent reactance controlled by TCSC.

This compensator injects in the transmission line a variable apparent reactance (XTCSC) controlled by conduction angle () as indicated by Figure 2. Its value is a function of the line reactance XL where the device is located. The apparent reactance XTCSC is defined by [5], [19]:

XTCSC ( )  X L ( ) / / X C 

X L ( ).X C X L ( )  X C

   X C .X L      2  sin(2 )   X TCSC ( )     XC  X L      2  sin(2 ) 

(1)

(2)

B. GCSC This compensator can be modeled as a variable apparent reactance (XGCSC) as shows in Figure 3.

Fig. 3. Apparent reactance controlled by GCSC.

II. APPARENT REACTANCE CONTROLLED BY SERIES FACTS DEVICES Figure 1 represents different structures for series FACTS devices which are implemented in this paper and installed in the midline. In series compensation, the FACTS devices are connected in series with the transmission line AB between bus A (source) and B (load).

This compensator is installed in midline and modeled as a variable apparent capacitive reactance (XGCSC). From Figure 3, this reactance is defined as follows as in [10-11], [20]:

1  2  X GCSC ( )  X C .Max 1    sin(2 )     

(3)

C. TCSR This compensator can be modeled as a variable apparent inductive reactance (XTCSR) as shows in Figure 4.

Fig. 4. Apparent reactance controlled by TCSR. Fig. 1. Series FACTS devices on transmission line.

From Figure 4, the apparent reactance of the TCSR (XTCSR) injected on transmission line is defined as follows as in [2122]:

X TCSR ( )  X L1 ( ) / / X L 2

X ( ).X L 2  L1 X L ( )  X L 2

   L2 L1 2      2  sin(2 )   X TCSR ( )        L2  L1      2  sin(2 )   

From equation (7) and matrix (9), the symmetrical components of the currents take the following form:

I1  I2  I0 

(4)

IA 3

(10)

The symmetrical components of the voltages are:

V0  1 1 1  VA  V   1 1 a a2  V   1 3  B V2  1 a2 a  VC 

(5)

III. PHASE TO EARTH FAULT CALCULATION IN THE PRESENCE SERIES FACTS DEVICES Figure 5 shows the equivalent circuit of a transmission line in case of a phase to earth fault at line AB with a fault resistance, when a series FACTS devices is inserted in the midline.

(11)

From equation (8) and the matrix in equation (11), the direct components of voltage become:

V1   V0  V2   RF .I A

(12)

And,

Vs  VFACTS  I1  n F .Z AB.1  X FACTS .1   A  B  C (13) Where, the coefficients A, B and C are defined as:

1 A      nF .Z AB.0  X FACTS .0  .I 0  3 1 B     nF .Z AB.2  X FACTS .2  .I 2  3 C  RF .I A

(14) (15) (16)

The coefficients ZAB-T and ZFACTS-T are defined for simplicity as:

Z ABT  Z AB.1  Z AB.2  Z AB.0

X FACTS T  X FACTS .1  X FACTS .2  X FACTS .0 Vs  VFACTS 

With series FACTS inserted in the midline, the new impedance of transmission line (ZAB-FACTS) is defined by:

IA 

(6)

The basic equations for this type of fault [1], [23] are:

Ib  Ic  0

(7)

Va  V1  V2  V0  RF .I a  0

(8)

The symmetrical components of currents are [24-25]:

 I0  1 1 1   I A   I   1 1 a a2   I   1 3  B  I 2  1 a2 a   IC 

(18) (19)

From equations (17), (18) and (19), the current at phase (A) in the presence of a series FACTS device is given by:

Fig. 5. Earth fault equivalent circuit with series FACTS.

Z AB FACTS  RAB  j  X AB  X FACTS 

IA  nF .Z AB T  X FACTS T   RF .I A 3

(17)

3.VS  VFACTS  nF .Z ABT  X FACTS T  3.RF

(20)

From equations (10) and (20), the symmetrical components of the currents in the presence of a series FACTS in the midline are:

I1  I 2  I0 

VS  VFACTS nF .Z ABT  X FACTS T  3.RF

(21)

The direct component of the voltage is defined by:

V1  VS  VFACTS   nF .Z AB.1  X FACTS .1  .I1 (9)

 V1 

VS  VFACTS  . Z AB ' X FACTS ' 3.RF  nF .Z ABT  X FACTS T  3.RF

(22) (23)

Where, the coefficients ZAB' and XFACTS' are defined as:

Z AB '  Z AB.2  Z AB.0  2.Z AB.1

(24)

X FACTS '  X FACTS .2  X FACTS .0  2. X FACTS .1

(25)

The inverse component of voltage is defined by:

V2    nF .Z AB.2  X FACTS .2  .I 2  V2  

VS  VFACTS  . Z AB.2  X FACTS.2  nF .Z ABT  X FACTS T  3.RF

(26) (27)

The zero component of the voltage in is:

V0    nF .Z AB.0  X FACTS.0  .I0  RF .I0  V0  

(VS  VFACTS ). Z AB.0  X FACTS .0  RF 

(28) (29)

Fig. 6. Algerian electrical transmission network [26].

Z2 '  Z AB.2  X FACTS .2

(30)

Z0 '  Z AB.0  X FACTS .0

(31)

Sa  3.a 2  1

(32)

Figure 7.a, b, c represents the variation of the current symmetrical component I1, I2 and I0 respectively and Figure 8.a, b, c represents the variation of the line currents IA, IB and IC respectively as a function of the fault resistance with/without using the three series FACTS devices (TCSC, GCSC and TCSR).

Sb  3.a 1

(33)

nF .Z ABT  X FACTS T  3.RF

The coefficients ZAB' and XFACTS' are defined as:

From equations (23), (27) and (29), the three phase voltages of the transmission line in presence of FACTS are:

VA 

VB 

3.RF .VS  VFACTS  nF .Z ABT  X FACTS T  3.RF

VS  VFACTS  .  a2  a  Z2 '  a2 1 Z0 ' Sa RF )

VC 

nF .Z ABT  X FACTS T  3.RF

VS  VFACTS  .  a  a2  Z2 '  a 1 Z0 ' Sb RF ) nF .Z ABT  X FACTS T  3.RF

(34)

(35)

(36)

(a)

Hence, the short circuit calculations are only related to the following: - FACTS parameters: VFACTS, XFACTS and operation mode, - Fault conditions: location (nF) and resistance (RF), - Sequence circuit parameters: positive, negative and zero. IV. CASE STUDY AND ANALYSIS OF SIMULATION RESULTS The case study of this research work is the 400 kV electrical transmission networks, 50 Hz, in the north part of the Algerian power system as shown in Figure 6, [26]. The series FACTS devices is installed in the midline between the busbar A at Salah Bey (Sétif) substation and busbar B at Bir Ghbalou (Bouira) substation. The series FACTS and parameters of transmission line are given in the Appendix.

(b)

From Figure 7, the three symmetrical currents are equal with or without using the series FACTS systems which matches equations (10) and (21). The increase of RF value decreases the value of the three studies current components. From Figure 8, it is noticeable that the line currents of phases B and C are always zero which is confirmed by equation (7), however the increase of RF value reduces the line current of the faulty phase (A) with or without using FACTS.

(c) Fig. 7. Impact of RF on the current symmetrical components. a) I1 = f (RF), b) I2 = f (RF), c) I0 = f (RF)

(a)

Figure 9.a, b, c represents the variation of the voltage symmetrical components V1, V2 and V0 respectively and Figure 10.a, b, c represents the variation of the line voltages VA, VB and VC respectively as a function of the fault resistance with/without using the three series FACTS devices.

(a)

(b)

(b)

(c)

(c)

Fig. 8. Impact of RF on the transmission line currents. a) IA = f (RF), b) IB = f (RF), c) IC = f (RF)

Fig. 9. Impact of RF on the voltage symmetrical components. a) V1 = f (RF), b) V2 = f (RF), c) V0 = f (RF)

V. CONCLUSIONS This research work investigates the impacts of the fault resistance on the parameters of short circuit calculations in the presence of phase to earth fault on a 400 kV Algerian electrical transmission line compensated by three series FACTS devices (TCSC, GCSC and TCSR). The protected transmission line and short circuit parameters are influenced by the apparent reactance controlled by series FACTS devices studies.

(a)

(b)

The short circuit calculations are directly related to the parameters of pre-fault conditions, specially the fault resistance and the apparent reactance. For each case, the proposed method calculates new parameters for short-circuit and the varied fault current between minimum and maximum values. In order to increase the total system protection performance in the presence of series FACTS compensator on transmission line, more care must be taken, mainly concerning the variation of the fault current. Simulation results obtained in this paper highlight the importance of changing the new calculus of settings for different principal protection devices used for protecting high voltage transmission lines, such as distance and overcurrent relays. This will be highly necessary in order to avoid the unwanted tripping of circuit breakers, the poor selectivity of protection relays and to improve the overall performance of protection relays. More research work that addresses this point is currently under publication by the authors. REFERENCES J. Schlabbach, “Short-Circuit Currents”, second edition, Institution of Engineering and Technology (IET), London, United Kingdom, 2008. [2] H. Hassan, “The Deployment of FACTS in High Voltage Networks: A Case Study in Oman”, The 5th IET International Conference on Power Electronics, Machines and Drives (PEMD), Brighton, United Kingdom, April 19 - 21, 2010. [3] A. A. Yusuff, A. A. Jimoh, and J. L Munda, “Determinant-based Feature Extraction for Fault Detection and Classification for Power Transmission Lines”, IET Generation, Transmission & Distribution, vol. 5 , no. 12, pp. 1259-1267, 2011. [4] Group Sonelgaz/OS, “Rapport: Statistics of Faults on Electrical Networks 220 and 400 kV”, Algiers, Algeria, December 2012. [5] K.K. Sen, and M.L. Sen, “Introduction to FACTS Controllers: Theory, Modeling and Applications”, John Wiley & Sons and IEEE Press, New Jersey - USA, 2009. [6] M. Khederzadeh, T.S. Sidhu, “Impact of TCSC on the Protection of Transmission Lines”, IEEE Transactions on Power Delivery, vol. 21, no. 1, pp. 80-87, January 2006. [7] S. Jamali, A. Kazemi, and H. Shateri, “Measured Impedance by Distance Relay for Inter Phase Faults with TCSC on a Double Circuit Line”, The 18th Australasian Universities Power Engineering Conference (AUPEC), Sydney, Australia, 14-17 December 2008. [8] S. Jamali, A. Kazemi, and H. Shateri, “Measured Impedance by Distance Relay for Inter Phase Faults in Presence of TCSC on Next Line”, IEEE Region 10 Conference (TENCON), India, 19-21 November 2008. [9] S. Jamali, A. Kazemi, and H. Shateri, “Effects of Voltage Transformers Connection Point on Measured Impedance at Relaying Point for Inter Phase Faults in Presence of TCSC”, 2nd IEEE International Conference on Power and Energy (PECon), Johor Baharu, Malaysia, Dec.1-3, 2008. [10] M. Zellagui, and A. Chaghi, “Measured Impedance by MHO Distance Protection for Phase to Earth Fault in Presence GCSC”, ACTA Technica Corviniensis - Bulletin of Engineering, Tome 5, Fasc. 3, pp. 81-86, 2012. [1]

(c) Fig. 10. Impact of RF on the transmission line voltages. a) VA = f (RF), b) VB = f (RF), c) VC = f (RF)

From Figure 9, the increase of RF value increases the positive voltage component, while the inverse and zero voltage components are decreased with or without using FACTS as confirmed by equations (23), (27) and (29). From Figure 10, it is obvious that the increase of RF value increases the value of the line voltages of phases A and B, compared the voltage phase C which is decreased with the increase of RF for the studied cases.

[11] M. Zellagui, and A. Chaghi, “Impact of GCSC on Measured Impedance by Distance Relay in the Presence of Single Phase to Earth Fault”, 32th International Conference on Power Systems Engineering (ICPSE), Dubai, UAE, 8-9 October 2012. [12] S. Jamali, and H. Shateri, “Locus of Apparent Impedance of Distance Protection in the Presence of SSSC”, European Transactions on Electrical Power (ETEP), vol. 21, no.1, pp. 398-412, 2011. [13] M. Zellagui, and A. Chaghi, “Impact of SSSC on Measured Impedance in Single Phase to Ground Fault Condition on 220 kV Transmission Line”, Leonardo Journal of Sciences (LJS), vol. 11, issue 20, pp. 109-124, 2012. [14] S. Jamali, A. Kazemi, and H. Shateri, “Measured Impedance by Distance Relay for Inter Phase Faults in Presence of SSSC”, IEEE/PES Power Systems Conference and Exposition, (PSCE), USA, 15-18 March 2009. [15] A. Salemnia, M. Khederzadeh, and A. Ghorbani, “Impact of Static Synchronous Compensator (STATCOM) on Performance of Distance Relay”, IEEE Power Tech Conference (PowerTech), Bucharest, Romania, 28 June - 2 July, 2009. [16] M.V. Sham, and K. Panduranga Vittal, “Simulation Studies on the Distance Relay Performance in the Presence of STATCOM”, Journal of Electrical Engineering (JEE), vol. 11, no. 3, Sept. 2011. [17] F.A. Albasri, T.S. Sidhu, and R.K. Varma, “Performance Comparison of Distance Protection Schemes for Shunt-FACTS Compensated Transmission Lines”, IEEE Transactions on Power Delivery, vol. 22, no. 4, pp. 2116-2125, October 2007. [18] X. Zhou, H. Wang, R.K. Aggarwal, and P. Beaumont, “Performance Evaluation of a Distance Relay as Applied to a Transmission System With UPFC”, IEEE Transactions on Power Delivery, vol. 21, no. 3, pp. 1137-1147, June 2006. [19] X.P. Zhang, C. Rehtanz, and B. Pal, “Flexible AC Transmission Systems: Modelling and Control”, Springer Publishers, Germany, May 2006. [20] L.F.W. de Sow, E.H. Watanabe and M. Aredes, “GTO Controlled Series Capacitors: Multi-Module and Multi-pulse Arrangements”, IEEE Transactions on Power Delivery, vol. 15, no. 2. pp. 725-731, April 2000. [21] M. Zellagui, and A. Chaghi, “Impact of Apparent Reactance Injected by TCSR on Distance Relay in Presence Phase to Earth Fault”, Advances in Electrical and Electronic Engineering (AEEE), vol. 11, no. 3, pp. 156168, June 2013. [22] M. Zellagui, and A. Chaghi, “Distance Protection Settings Based Artificial Neural Network in Presence of TCSR on Electrical Transmission Line”, International Journal of Intelligent Systems and Applications (IJISA), vol. 4, no. 12, pp. 75-85, November 2012. [23] S. Jamali, and H. Shateri, “Impedance based Fault Location Method for Single Phase to Earth Faults in Transmission Systems”, 10th IET International Conference on Developments in Power System Protection (DPSP), Manchester -United Kingdom, 29 March - 1 April, 2010. [24] C.L. Fortescue, “Method of Symmetrical Coordinates Applied to the Solution of Polyphase Networks”, Transactions of AIEE, vol. 37, pp. 1027-1140, 1918. [25] J. Lewis Blackburn, and A.F. Sleva, “Symmetrical Components for Power Systems Engineering”, second edition, published by CRC press, London - United Kingdom, June 2011. [26] Sonelgaz Group, “Topology of Electrical Transmission Networks High Voltage”, Algerian Company of Electrical Transmission, GRTE, Algiers, Algeria, 30 December 2012.

APPENDIX A. Transmission line: UL = 400 kV, UMax = 440 kV, UMin = 380 kV, Length = 205 km, Z1 = 0.0291 + j 0.3081 Ω/km, Z0 = 0.0873 + j 0.9243 Ω/km. B. Series FACTS devices: TCSC : QMax = 31 / - 42 MVar, C = 8.30 μF, L = 0.19 mH. GCSC : QMax = - 60 MVar, C = 212.20 μF. TCSR : QMax-L1 = 70 MVar, QMax-L2 = 30 MVar, L1 = 10.610 mH, L2 = 18.189 mH. C. Fault conditions: nF = 100%, RF = 0 to 50 Ω.