modem, signal converter and a non-interruptible power supply. It monitors the field .... VI. REFERENCES. [1] B. Radha, R. T. F. Ah King and H. C. S. Rughooputh,.
DISTRIBUTION AUTOMATION USING WIRELESS COMMUNICATIONS FOR IMPROVING RELIABILITY Ch. Murthy#
Susmita Kar* R. C. Jha,MIEEE* #
*Department of Electrical and Electronics Engineering Birla Institute of Technology, Mesra Ranchi, India Abstract—A distribution system is the part of an overall power system which links the bulk system to the individual customers. The primary goal of any distribution system is to supply reliable and quality power to the consumers economically. Therefore reliability indices like system average interruption duration index (SAIDI), customer average interruption duration index (CAIDI), average service availability index (ASAI) are the important performance indices of a distribution system which need to be satisfied from the customer point of view. The edifice of distribution system automation is fast and reliable communication control technologies leading to reliable power delivery to the customers. Further the ever expanding power demand is increasing the complexity of power system, necessitating highly reliable, secure and efficient distribution system. An attempt has been made in this paper to assess the impact on reliability due to automatic feeder reconfiguration for smart distribution purposes. Keywords- distribution automation system (DAS), reconfiguration, mobile communication, reliability;
I.
feeder
INTRODUCTION
Distribution systems are critical links between the utility and the consumer. Usually distribution systems are designed to be efficient at peak load demand. Obviously the network can be made more efficient by reconfiguring it according to the variation of load demand. Recent studies indicated that 30 – 45% of the total power generated is wasted in the form of line loss at distribution level. Hence, it is of great benefit to reconfigure the distribution system, which in turn reduce power loss and improve reliability and quality of power supply by changing the status of the switches [1].The reliability of the electrical distribution system can be assessed by calculating the reliability indices like SAIDI, CAIDI[2-3]. This paper focuses the specific aspects of the design and operation of smart distribution system incorporating some automatic reconfiguration in feeders design and considering impact on reliability. II.
DISTRIBUTION SYSTEM RELIABILTY INDICES
Distribution networks are the parts of power systems that deliver energy from the area supply stations to the customers. They operate at several voltage levels (mostly from
D. K. Mohanta,SMIEEE*
National Institute of Science and Technology Berhampur, India
11 kV to 33 kV in India), and often include the networks of local or municipal utilities [4-5]. A. Reliability Indices (1) Time Frequency Duration Indices Failure frequency index (fF ) = Σ Cmn↨ fFmn /Σ Cmn Where the load point frequencies are weighed by Cmn , the number of customers on branch mn. Mean system failure duration TF = Σ CmnfFmn TFmn /Σ CmnfFmn Average total interruption time /customer / year HF = Σ Cmn fFmn TFmn /Σ Cmn From the equation it is evident that HF = Tf ff It should be observed that the above indices are not based on any definition of what events constitute system failure, but are computed by arbitrarily chosen equations. The frequency fFmn for example is not the frequency of any given event but is an arbitrary measure of the system’s performance [3]. (2) Customer Load Point Indices System Average Interruption Duration Index (SAIDI) is the average total duration of interruptions of supply per annum that a customer experiences. SAIDI = Total customer interruption duration/ Total no of customers served = Σ UiNi/ ΣNi Ui represents failure rate and down time of load point i. Where Ni is the number of customers in section or load point i. Customer Average Interruption Duration Index (CAIDI) is the average duration of an interruption of supply in the year for customers who experience interruption of supply. CAIDI= Total customer interruption duration/ Total no of customers interrupted = ΣUi Ni/ΣλNi Ni Where Ui is the outage time of the ith load per year, Ni is the sum of customers at the ith load point, and λi is the failure rate.
ASAI (Average Service Availability Index) = Customer hours of service demanded/ Customer hours of service available. III. DISTRIBUTION AUTOMATION SYSTEM (DAS)USING WIRELESS COMMUNICATION AND FEEDER RECONFIGURATION As per IEEE DAS is defined as the system that enables an electric utility to remotely monitor , coordinate and operate distribution components in a real time mode from remote locations[6]. Usually control decisions are being initiated at one location, known as distribution control center (DCC), as shown in figure.1. The major components associated with DAS are RTU for data acquisition, mobile communication for sending of such acquired data to DCC for further decision making. The control decision also conveyed to remote locations for alarm and protective devices using same mobile communication link [7]. Data is collected by remote equipment i.e. remote terminal unit (RTU) and is transfer to distribution control center through wired or wireless communication media, where analysis is carried out for control decision and then control action is executed either in automatic or semi automatic mode. To communicate data from distribution control center to RTU and vice-versa, mobile communication can be used. Figure2 shows the communication system for DAS using mobile communication (wireless communication). RTUs are usually located at field location, to collect data, convert analog values to discrete and counter signal into serial digital format. So that permits all signals to be transmitted on a single telephone pair or radio circuit. The RTU consists of a microprocessor based modem, signal converter and a non-interruptible power supply. It monitors the field digital and analog parameters and transmits all the data to the distribution control center [8] through the selected medium. RTU can interface with the central station i.e. distribution control center through different communication media and Generating Station
220kv substation
Distribution control center
33kv substation
modem
11kv substation
RTU
Figure.1Block diagram of DAS
can support standard protocols (Modbus, IEC60870-5101/103/104,DNP3, ICCP etc) to interface any third party software. In a DAS, the various quantities such as voltage, current, switch status etc are recorded at the feeder using a data acquisition device called remote terminal units (RTUs). These system quantities are transmitted online to the base station (11kv) through a variety of communication media. That may be wireless or wired. Since the power lines traverse different difficult terrains, therefore, wireless communications is the preferred way. The measured field data are processed at the base station for display of any operator selected system quantities through graphic user interface (GUI). The power utilities in developing counties like India are more interested for indigenous DAS, which could be retrofitted in the existing distribution network to achieve better system operation through remote monitoring and control due to economic viability for adopting imported technologies. Figure1 is the block diagram of DAS.
IV.
CASE STUDY AND RESULTS
The distribution system performance analysis is basically adjudged based on reliability of power supplied to the consumers. The reliability indices like SAIDI, SAIFI, CAIDI and ASAI can be considered as an attributes for the reliability of the power. The one-line diagram for the purpose of load flow analysis as well as loss analysis has been created using ETAP. The ETAP based one-line diagram for R&D transformer is given below as figure 3.This transformer is of 500 KVA capacity, supplied at 11KV from Jharkhand State Electricity Board (JSEB). In the figure 3, an 11 KV bus is shown that receives power at 11 KV from JSEB and serves as incomer to the transformer. The outgoing of transformer is fed to main bus at 440 V (line-to-line, 3 phase). From the main bus, 5 feeders are being routed. They are: (i) Mandir feeder, (ii) Rocketry feeder, (iii) Hostel 9 feeder, (iv) VC line feeder, (v) R&D feeder. For mandir feeder, the feeder originates from main bus and is connected to pole I/63 (I-inner campus). Then next span is from pole I/63 to pole I/68. For this span, the nomenclature is given ‘MLINE 1’. The load flow analysis is being done using ETAP. Based on load flow analysis loss report is generated as shown in table 1. The objective of load flow is to compute the real and reactive load flow between any two nodes of networks, nodal voltages and the corresponding angles. As seen from table 4, real and reactive power flow between poles I/93 – I/94 is 6.0 KW and 4.0 KVAR respectively with a load current of 10.5 amperes. The one-line diagram for BIT electrical distribution system as shown in figure.3.is created using ETAP software. The concept of "composite network" was integrated in ETAP to provide flexibility in simplifying and organizing the electrical one-line diagram. Thereafter a load flow analysis is performed on this system in ETAP environment. The loss has been computed and is given in table 1. Subsequently, the load flow analysis has been carried out for the modified system as shown in figure 4 and the losses are computed. The loss report for the modified system is given as table 2.The main
objective of the present study is to reduce the overall system losses. To achieve this objective, reconfiguration is done by introducing the switches at appropriate positions in the system, assuming that incorporating the switches is economically feasible. The position of the switches in the system is determined by placing them between two feeders particularly between those one having a higher amount of loss and the other having lower amount of loss. Therefore feeders prioritized according to the loss contributed by each one of them. Once the system was modeled, it was subjected to load flow. If the overall loss is less by reconfiguring, then that switch position is fixed there only. Otherwise it has to be tried for the other position where the overall loss can be reduced. In this way five switches SW1, SW2, SW3, SW4, and SW5 have been introduced into the electrical distribution system of BIT. The modified system after introducing the switches is shown in figure .4. It is observed that the overall system loss was reduced by an amount 40% compared to the loss without the switches. Utilizing the loss report obtained from the ETAP, the reliability indices are calculated. The reliability indices like SAIDI, CAIDI ,ASAI are calculated for both the original system and the modified system as shown in the table 3. It is observed that the reliability of the system is improved.
V.
CONCLUSION
The automatic feeder reconfiguration leads to improved reliability due to enhanced capability in decision-making using an existing data base in conjunction with fast communication regarding fault detection and classification. Such an endeavor reduces the overall system down time, power loss and thus improves the reliability. The main challenges of real-time implementation are economic consideration as well as availability skilled personnel for operation and maintenance. But with ongoing revolution in information and technology sector avail the inexpensive communication and control technologies which welcome this barrier in near future case of in developing country. VI. [1]
[2]
[3] [4]
[5]
REFERENCES
B. Radha, R. T. F. Ah King and H. C. S. Rughooputh, "Optimal Network Reconfiguration of Electrical Distribution Systems", IEEE International Conference on Industrial Technology, Vol. 1, pp. 66-71, 2003. G. Sidana, "Management of Sub-Transmission and Distribution System in Power Utilities", The Geospatial Resource Portal, http://www.gisdevelopment.net/application/utility/power/ utilityp0016.htm J. Endrenyi, Reliability Modeling in Electric Power Systems, Toronto, John Wiley & Sons, 1980. D.K.Mohanta, M.Jaya Bharata Reddy, Abhishek Singh, Jayant Kumar Papneja, Shalabh Agarwal, “TitleDistribution System Reliability Evaluation Incorporating the Effect of Voltage Stability Index”, Proceedings of the 7th Int. Conference EEEIC 2008, Cottbus, 5-11.05.2008, pp. 31-34. R. Billinton, R. N. Allan, Reliability Evaluation of Engineering Systems, London, Plenum Press, 1992.
[6]
[7]
[8]
[9]
[10]
[11]
[12]
D. Bassett, K. Clinard, J. Grainger, S. Purucker, and D. Ward, “Tutorial Course: Distribution Automation”, IEEE Tutorial Publication 88EH0280-8-PWR, 1988. K. Ghoshal, “Distribution Automation: SCADA Integration is Key”, IEEE Computer Applications in Power, pp. 31-35, January 1997. D. J. Marihart, “Communications Technology Guidelines for EMS/SCADA Systems”, IEEE Transactions on Power Delivery, Vol. 16, No. 2, pp. 181-188, April 2001. C. S. Switches Chen and M. Y. Cho, "Energy Loss Reduction by Critical ", IEEE Transactions on Power Delivery, Vol. 8, Issue 3, pp. 1246 – 1253, July 1993. L. V. Trussell, “GIS Based Distribution Simulation and Analysis”, IEE International Conference and Exhibition on Electricity Distribution, Vol. 5, pp. 5, 2001. R.Billinton , S.Jonnavithalu “A test system for Teaching Overal Power System Reliability Assesment”. IEEE Transaction on Power delivery, Vol.11, Nov. 1996, pp.1670-1676. V.S.Murthy, S.Gupta, D.K. Mohanta, “Distribution System Insulator Monitoring using Video Surveillance and Support Vector Machines for Complex Background Images.”, Int. J. Power and Energy Conversion, Vol.1,No.1, 2009, pp.49-72. Table 1 Loss Report before Reconfiguration
Branch Cable12 Cable2 Cable3 Cable7 VC CABLE VCLINE1 VC LINE2 H9 LINE1 H9 LINE2 H9 LINE3 M L1 ML 2 RCABLE RL1 H9 CABLE ROCKETRY LINE2 ROCKETRY LINE3 ROCKETRY LINE4 ROCKETRY LINE9 ROCKETRY LINE5 Cable4 Cable6 NCC CABLE Cable5 R&D CABLE BACK R & D BACK R&D CABLE FRONT R & D CABLE FRONT TFNEAR H5B
From – To Bus Flow MVA MW R -0.021 -0.021 -0.042 -0.022 0.000 -0.040 -0.007 -0.004 -0.039 -0.025 0.039 0.025 0.024 0.015 -0.033 -0.021 0.020 0.012 0.000 0.000 -0.018 -0.011 0.018 0.011 -0.045 -0.028 0.045 0.028 -0.045 -0.029 0.040 0.027
To - From Bus Flow MW
MVAR
0.022 0.044 0.001 0.008 0.041 -0.039 -0.024 0.033 -0.020 0.000 0.018 -0.018 0.046 -0.045 0.047 -0.040
0.021 0.022 0.040 0.004 0.025 -0.024 -0.015 0.021 -0.012 0.000 0.012 -0.011 0.028 -0.027 0.029 -0.026
LOSSES KVA KW R 0.6 0.0 1.4 0.1 0.9 0.0 0.0 0.0 1.4 0.1 0.1 0.8 0.1 0.3 0.1 0.6 0.0 0.2 0.0 0.0 0.0 0.2 0.1 0.5 1.8 0.1 0.2 1.1 1.8 0.1 0.2 0.9
0.035
0.023
-0.035
-0.022
0.1
0.7
0.025
0.016
-0.025
-0.016
0.1
0.4
-0.015
-0.009
0.015
0.009
0.0
0.1
-0.021
-0.013
0.021
0.013
0.0
0.3
-0.010 -0.007 -0.005 -0.008 -0.057
-0.005 -0.004 -0.003 -0.005 -0.036
0.010 0.008 0.005 0.009 0.061
0.005 0.004 0.003 0.005 0.036
0.1 0.0 0.0 0.1 3.5
0.0 0.0 0.0 0.0 0.1
-0.061 -0.075
-0.036 -0.046
0.067 0.082
0.036 0.047
6.4 7.0
0.4 0.3
-0.082
-0.047
0.097
0.047
0.6
0.287
0.318
-0.280
-0.294
15. 4 7.5
TOTAL LOSS
94. 7
23.3
59.0
Table 2 Loss Report after Reconfiguration
Distribution control center
Cable2 Cable3 Cable7 VC CABLE VCLINE1 VC LINE2
-0.042 0.000 -0.060 -0.039 0.039 0.024
-0.022 -0.040 -0.066 -0.025 0.025 0.015
TO FROM (T-F) BUS BUS FLOW FLOW KW (MW) ( MVAR) 0.061 0.054 4.3 0.044 0.022 1.4 0.001 0.040 0.9 0.065 0.066 5.1 0.041 0.025 1.4 -0.039 -0.025 0.1 -0.024 -0.015 0.1
H9 LINE1
-0.033
-0.021
0.033
0.021
0.1
0.6
H9 LINE2 H9 LINE3 ML1 ML 2 RCABLE
0.020 0.000 -0.019 0.019 -0.045
0.013 0.000 -0.011 0.011 -0.028
-0.020 0.000 0.019 -0.018 0.047
-0.012 0.000 0.012 -0.011 0.028
0.0 0.0 0.0 0.1 1.8
0.2 0.0 0.2 0.5 0.1
RL1 H9CABLE RL2 RL3 RL4 RL9
0.045 -0.045 0.040 0.035 0.025 -0.015
0.028 -0.029 0.027 0.023 0.016 -0.009
-0.045 0.047 -0.040 -0.035 -0.025 0.015
-0.027 0.029 -0.026 -0.022 -0.016 0.009
0.2 1.8 0.1 0.1 0.1 0.0
1.1 0.1 0.9 0.7 0.4 0.1
RL5 Cable4 Cable6 NCC CABLE Cable5 R&D CABLE BACK R & D BACK
-0.021 -0.010 -0.007 -0.044 -0.036 -0.057
-0.013 -0.005 -0.004 -0.048 -0.022 -0.036
0.021 0.010 0.007 0.047 0.037 0.061
0.013 0.005 0.004 0.048 0.022 0.036
0.0 0.1 0.0 2.7 1.1 3.4
0.3 0.0 0.0 0.1 0.0 0.1
BRANCH Cable12
Figure 2. Communication System for DAS
Figure.3 One-line diagram of BIT campus (Original System)
FROM TO (F-T) BUS FLOW ( MVAR ) -0.056 -0.054
BUS FLOW(MW)
R&DFRONT R & D CABL FRONT ML5 TFNEARH5B
0.2 0.1 0.0 0.2 0.1 0.8 0.3
-0.065
0.005
0.070
-0.005
5.3
0.4
-0.015 -0.015
0.043 0.046
0.015 0.015
1.4 3.1
0.1 0.1
0.000 0.324
0.000 0.402
0.000 -0.313
0.000 -0.368
0.0 10.9 63.1
0.0 33.8 62.1
Table 3 Reliability Indices
Figure 4 One-line diagram of BIT campus (Modified System )
KVAR
-0.042 -0.043
TOTAL LOSS
SAIDI
Ff
Tf
Hf
/yr/ct
hr/yr
hr/ct/yr
ORIGINAL
0.174
222.7
38
48.8
279.8
.9944
MODIFIED
0.185
48.3
8.9355
48.4
261.62
.9944
SYSTEM
LOSSES
hr/ct/y r
CAIDI hr/ct
ASAI
Table 4 Load Flow Report after Reconfiguration
KV
%KV Operati ng
ANG -LE
Bus3 Bus5 Bus9
0.44 0.44 0.44
93.475 93.904 94.609
-0.7 -1.8 -1.5
BUS H1
0.44
96.571
BUS H7
0.44
I/145
G E N M W 0
GE N MV AR
LF LOA D MW
LOAD MVAR
0.021 0.021 0.005
0.021 0.021 0.005
0.5
0.042
0.022
92.543
0.2
0.073
0.038
0.44
99.011
1.1
0
0.04
BUSPHAR MACY
0.44
98.707
-0.1
0.007
0.004
I/25
0.44
95.369
-0.3
FROM POLE ID
I/45
0.44
92.406
-2
I/46 I/60
0.44 0.44
92.406 93.992
-2 -0.9
I/61
0.44
96.139
-1.1
I/63a
0.44
95.018
-0.2
I/63b
0.44
94.999
0
0.02
-0.2
0.012
0.012
0.007
I/64
0.44
93.716
-1.1
0.004
0
I/70
0.44
94.568
-2.2
0.007
0.004
I/83 I/86 I/87
0.44 0.44 0.44
94.032 89.187 89.489
-2.6 -4.3 -4.1
0.007 0.01 0.005
0.004 0.006 0.003
I/93
0.44
89.945
-3.7
0.004
0.003
I/94
0.44
89.757
-3.9
XmerinH5B
11
100
0
Xmerin H7
11
100
0
XmerinR&D
11
100
0
XmerinWAT ER SUPPLY
11
100
0
0. 29 0. 32 0. 32
0.3 18 0.2 67 0.1 88
0. 08
0.0 84
MW
LF MVAR
AMP
Xmer out near H5B Xmer out near H5B Xmer out near H5B Xmer out nearWATER SUPPLY Xmer out near H7 Xmer out nearWATER SUPPLY Xmer out nearWATER SUPPLY Xmer out near R&D I/ 33 I/44 I/46 I/45 I/63b I/44 I/116 I/70 Xmer out near R&D I/64 Line7-DB2 Xmer out near R&D I/60 I/63a I/65 I/61 I/72 I/83 I/72 I/87 I/93 I/86 I/DP I/94 I/87 I/93
-0.021 -0.021 -0.005
-0.021 -0.021 -0.005
41.6 41.4 9.6
-0.042
-0.022
65.1
-0.073
-0.038
117.1
0
-0.04
52.8
-0.007
-0.004
11.3
-0.039
-0.025
64.2
0.039 -0.02 0 0 -0.033 0.033 -0.018 0.018
0.025 -0.012 0 0 -0.021 0.021 -0.011 0.011
64.2 33.1 0 0 55 55 29.7 29.6
-0.045
-0.028
73
0.045 0
0.028 0
73 0
-0.045
-0.029
74
0.033 -0.045 0.04 -0.018 0.012 0.007 -0.007 -0.01 -0.015 0.01 -0.021 0.006 0.015 -0.006
0.022 -0.027 0.027 -0.011 0.007 0.004 -0.004 -0.006 -0.009 0.006 -0.013 0.004 0.009 -0.004
55 73 67.8 29.6 19.1 10.9 10.9 16.9 25.4 16.9 35.9 10.5 25.4 10.5
Xmer out near H5B
0.287
0.318
22.5
Xmer out near H7
0.323
0.267
22
0.32
0.188
19.5
0.084
0.084
6.3
TO POLE ID
Xmer out near R&D Xmer out nearWATER SUPPLY
