RELAY CO-ORDINATION IN A 11KV SUBSTATION USING ETAP

Transcription

1 International Journal of Recent Innovation in Engineering and Research Scientific Journal Impact Factor by SJIF e- ISSN: RELAY CO-ORDINATION IN A 11KV SUBSTATION USING ETAP Ms. Serene C Kurian 1 and Mr. K Navin Kumar 2 1 Department of Electrical Engineering, KCG College of Technology, Chennai, India 2 Protection and Communication, TANTRANSCO, TNEB, Chennai, India Abstract- The paper deals with study of a 11kV utility sub-station. It includes load flow analysis, shortcircuit analysis and the Protective relay coordination of the system under consideration. The single line diagram of the system is constructed and ETAP software is used for simulation of the system. Power flow studies is required to plan ahead and account for various hypothetical situations. For instance, what if a high-tension line with in the power system properly supplying loads must be taken offline for maintenance, then remaining line in the system must handle the required loads without exceeding the rated parameter. Load flow studies determine if system voltage remains within specified limits under normal or emergency operating condition. Short-circuit study determines the magnitude of the currents that flow during an electrical fault. Short Circuit Analysis is performed by faulting all the buses in order to find the fault current through all the buses. Protection Coordination is the sequence in which the devices operate to trip the circuit during faulty condition A three phase fault is considered and the reports for load flow and short circuit analysis of the system are generated. The time current characteristic curve is also generated. Keywords- ETAP, Load flow, Relay coordination, Short circuit I. INTRODUCTION ETAP is the most comprehensive analysis platform for the design, simulation, operation, and automation of generation, distribution, and industrial power systems. ETAP is developed under an established quality assurance program and is used worldwide as a high impact software. Load flow studies determines if system voltage remains within the specified limits under normal or emergency operating condition and it is conducted using Newton Raphson method. Short circuit analysis of an electric system determines the magnitude of the currents that flow during an electrical fault. Electrical fault is an abnormal condition that has two or more phases unintentionally coming into contact. Result of such an analysis helps to determine losses and reactive power allocation transmission capacity of underground cables and helps to plan economical operation of the system. Contingency can be defined as the nonfunctionality in the power system of a device such as generator, transformer, transmission line. Power blackout is a short term or long-term loss of electric power to a particular area. Cascading failure is a failure in a system of interconnected in which the failure of the part can trigger the failure of the successive parts. Different techniques for relay coordination using software techniques has been presented in the paper Literature review on relay co-ordination using software techniques [1]. Now days, the demand of electricity is increasing. So, the network of electricity from generation to distribution is very large. The network of state electricity boards typically has 10 to 15 or more buses, 40 to 50 transmission lines and 80 to 100 overcurrent relays. The exercise of load flow analysis, fault level calculations and listing the primary backup pairs will be very tedious [2]. The exercise is very difficult because one has to consider line contingencies and relay setting are to be decide based on the worst case. Also, several iterations would be required to calculate TMS of relays so that minimum discrimination margin as required is found between relay and its backup relays. This is only by using some computer programming. In this paper, shows some algorithm techniques and also discuss the advantages of latest software ETAP.In rights Reserved Page 18

2 power system network, protection should be designed such that protective relays isolate the faulted portion of the network at the earliest, to prevent equipment damage, injury to operators and to ensure minimum system disruption enabling continuity of service to healthy portion of the feeder. specific equipment, transmission/distribution lines/feeders or primary zone protective relays, do not operate and clear the fault in their primary protection zone, backup relays located in the backup zone, must operate to isolate the fault, after providing sufficient time discrimination for the operation of the primary zone relays [4]. The protective relays must also be able to discriminate between faulted conditions, normal operating conditions and abnormal operating conditions and function only for the specific protection for which they are designed, without operating for any normal and short term acceptable abnormal events for which they are not intended to act and provide protection. To study power systems, load flow analysis is very important. Moreover, it is forms the basis of power system. Load flow analysis facilitates in the planning of accompaniments/extensions to generation and transmission facilities [3]. Further, load flow analysis forms the basis of execution of monitoring systems. ETAP Load Flow analysis facilitates power engineers to compute bus voltages, currents, branch power factors and power flows throughout the system [5]. It permits for voltage regulated, swing and nonregulated power sources with several generator connections and grids. Additionally, load Flow allows the user to choose from three different approaches which are Gauss Seidel, Newton Raphson and Fast Decoupled, in order to attain the optimum calculation efficiency. ETAP load flow benefits the power engineer by fast pursuing the long calculations and providing better simulation results. Figure 1 Single Line Diagram of 11kV substation The power system infrastructure, grid to on- premise wiring and from generation resources to the electric electrical equipment, is a complex system that requires extensive analysis to operate efficiently and effectively. Every new load, upgrade, extension, and reconfiguration of the network can create unexpected stresses and interactions to the original power system which was not designed for. Power sys- Available Online at : Page 19

3 tem studies provide information that allows to understand the root of present or future power system. problems and to make correct decisions in planning upgrades or extensions in the power system, which lead to reduced operating cost, increased availability and minimized equipment or system failure Figure 2: Flow chart for the process II. METHODOLOGY 2.1 Load Flow Analysis ETAP provides four load flow calculation methods: Adaptive Newton-Raphson, Newton- Raphson, Fast Decoupled, and Accelerated Gauss-Seidel. They possess different convergent characteristics, and sometimes one is more favourable in terms of achieving the best performance [4]. We can select any one of them depending on your system configuration, generation, loading condition, and the initial bus voltages. Adaptive Newton-Raphson Method This improved Newton-Raphson Method introduces a set of smaller steps for iterations where a potential divergence condition is encountered. The smaller increments may help to reach a load flow solution for some systems where the regular Newton- Raphson method might fail to reach one. 2.2 Short Circuit Analysis Short-Circuit Analysis program analyses the effect of 3-phase, line-to-ground, line-to-line, and double line-to ground faults on electrical distribution systems. The program calculates the total short circuit currents as well as the contributions of individual motors, generators, and utility ties in the system. The ANSI/IEEE Calculation Methods section lists standard compliance information and both general and detailed descriptions of calculation methods used by ETAP. 2.3 Protection Coordination Analysis The Protection Coordination is represented by a star view in ETAP. A Star View is a presentation containing one-line diagram elements and their associated characteristic curves and diagrams. Star View provides a graphical user interface for viewing, coordinating, and customizing element curves and Available Online at : Page 20

4 diagrams. First in line of defense is main protection which ensures quick action and selective clearing of faults within the boundary of the circuit section or the element it protects [6]. Main protection is essentially provided as a rule. Back up protection gives back up to the main protection, when the main protection fails to operate or is cut out for repairs. III. SIMULATION REPORTS AND DISCUSSIONS In this paper, the systematic analysis of substation is analysed using ETAP The various tests performed on the system are i) Load Flow Analysis ii) Short Circuit Analysis iii) Protection Coordination. The Single Line Diagrams and results of the above tests are discussed below: 3.1 Load flow Analysis Report Figure Load flow report summary Available Online at : Page 21

5 Figure Branch Loss Summary in Load flow analysis Available Online at : Page 22

6 Figure Summary of Load flow analysis 3.2 Short Circuit Analysis Report The report generated summarizes the fault current values at different buses and equipment. The report is generated for all the buses in the considered test system. The report for a three-phase fault at Bus, Paint shop 1 is given as a sample. The fault current for a three-phase fault and line to ground fault is simulated and results are obtained. Short circuit report of power system tends to be more complex due to mixture of load which contributes to fault current [7]. In a typical modern industrial system, the basic sources of fault currents are the utility, the in-plant generation and synchronous and induction motors. These sources contribute additional exponentially decaying currents which make fault current magnitudes at various locations time dependent. ETAP is capable to generate the report for 3 phases, Line to Line, Line to ground, Double Line to ground faults. Available Online at : Page 23

7 Figure Short Circuit Analysis Report Figure Short Circuit analysis of fault at bus PAINT SHOP 1 Available Online at : Page 24

8 Figure Short Circuit summary for fault at Paint shop Figure Summary of Sequence of operation of Events after fault 3.3 Coordination of Protective Relays Circuit breakers are the protective devices used in this system and they are coordinated with respect to time and represented in the Time Current Characteristic Curve (TCC Curve). The Circuit Breakers are coordinated from downstream in order to avoid the black out in the system. The coordination of breaker is shown for a particular section of the entire system under consideration. circuit breakers are operating from the low voltage side in order to avoid blackout condition. In the curve current is plotted along X-axis and time is plotted along Y-axis. Thus, from curve the time at which device operates for fault current is found. A separate identified setting sheet for the circuit breaker is also generated. Available Online at : Page 25

9 From this curve, the coordination of devices can be found with respect to time. The circuit breakers CB 5, CB 57 are coordinated with CB 70, CB 71, CB 72 from the single line diagram. Figure TCC Curve for protective relaying IV. CONCLUSION The single line diagram of 11kV substation is drawn in One-line view and a section of the substation is simulated in ETAP software. Load flow analysis is performed and report is generated. A threephase fault was introduced in the sample bus considered and short circuit report is generated. The relay coordination procedure is performed and the sequence of operation of circuit breakers for the fault is generated. From the obtained sequence, a Time current characteristic curve is obtained to show the device coordination. REFERENCES [1] Vipul Rajput, Ankit Rabari, Amit Patel (2015). Literature review on relay co-ordination using software techniques, International journal of advanced engineering and research development, ISSN , [2] Daljeet Kaur, Dr. S.K. Bath, Darshan Singh Sidhu (2014). Short Circuit Fault Analysis of Electrical Power System using MATLAB IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE) e-issn: , p-issn: , Volume 9, Issue 2 Ver. III (Mar Apr. 2014). [3] Keith Brown, Herminio Abcede, Ferrokh Shokooh, Interactive simulation of power system and ETAP application and techniques, IEEE operation technology, California. [4] Vijeta, K., Sarma, D.V.S.S.S. (2012). "Protection of distributed generation connected distribution system," Advances in Power Conversion and Energy Technologies (APCET), 2012 International Conference, vol.no.1, pp.1,6, 2-4 Aug [5] Jadeepsinh.C. Baria, Viral.S. Chaudhari, Paresh S. Chaudhari and Y.R. Prajapati (2011). Short Circuit Analysis of Realistic Application for Modeling of Power System using MiPower Software, National Conference on Recent Trends in Engineering and Technology, [6] Albert0 J. Urdaneta Member, IEEE Ram & Nadira, Member, IEEE, Luis G. Luis G. Pdrez Jimdnez (2010). Optimal Coordination of Directional Overcurrent Relays Interconnected Power Systems, IEEE Transactions on Power Delivery, Volume 3, No. 3., Power System Technology, vol. 24, no. 4, [7] Dharamjit and D.K. Tanti (2012). Load Flow study on IEEE 30 Bus system, International Journal of Scientific and Research Publications, Volume 2, Issue 11, ISSN , April Available Online at : Page 26