Optimal Relay Coordination for Enhanced Protection ...

International Journal of Power Devices and Components for Smart Device Vol. 2, (2015), pp.1-12 http://dx.doi.org/10.21742/ijpdcsd.2015.2.01

Optimal Relay Coordination for Enhanced Protection of an Interconnected Power System Debniloy De and Sheila Mahapatra EECE Department, NC University formerly (ITM University, Gurgaon), Haryana, INDIA [email protected], [email protected] Abstract This paper presents simulation of 220kV Masudpur substation to obtain optimal load flow and short circuit data which is instrumental in designing the protection scheme by adequate relay coordination and setting. The single line diagram of the real time power system is simulated using MiPower software which provided accurate load flow results indicating active and reactive power flow with respect to normal, light and heavy loading conditions. The load flow results are utilized to generate the short circuit current and short circuit MVA values under different contingencies like symmetrical and unsymmetrical faults. These results which are vital for designing the protection scheme are used to determine the plug multiplier settings (PMS) and time multiplier settings (TMS) for overcurrent protection. These values of current and MVA will help us to know the ratings of the components that are required to protect the complete system. Keywords: MiPower software, three phase to ground fault, Time multiplier settings, and Plug multiplier settings

1. Introduction Demand for electrical power is increasing at a very fast rate in the developing countries. Due to these electrical networks is getting complicated day by day requiring more systematic protection system. Protection system is a very important part of any electrical power system. Protection system helps us to isolate the faulty part of the system from the remaining system. There are various protective devices which are implemented in a power system so that all the costly equipment are protected and there is no interruption in the electricity reaching to the consumers. The protective devices should be reliable, accurate, selective, and fast operative. Protective devices include current transformers, circuit breakers, voltage transformers, batteries and protective relays. If the values provided by these devices are above the normal conditions then the relay sense it as a fault condition and provides a signal to the trip circuit of the circuit breaker. After receiving the trip signals from the relays, the circuit breakers isolate the faulty part of the system and keeps it out till it is repaired. In distribution system fuses are used as protective devices and they are capable of sensing the fault and clearing the fault to isolate the system. MiPower software is used to do the various studies which are required for the complete analysis of the 220kV Masudpur substation. This highly interactive software has user friendly windows based power system analysis package. Different strategies are used for protecting the equipment connected in switchyard. Linear programming is used to minimize the operating time [1] and the optimization of time multiplier settings [2].

ISSN: 2205-8397 IJPDCSD Copyright ⓒ 2015 GVSchoolPub

International Journal of Power Devices and Components for Smart Device Vol.2 (2015)

2. Case Study: 220kV Masudpur Substation Protective studies are done on actual substation considering their single line diagram. The substation considered is a 220kV Masudpur substation which is located in Hisar, Haryana. It is a 72 bus system. Figure 1 represents the single line diagram of a 220KV Masudpur substation. As we can see from the figure there are three voltage levels in this substation i.e. 220kV, 132kV and 66kV. Double circuit line of 220kV is an incomer to this substation and it gives supply to 400kV Kirori substation and samain substation as a double circuit line. 220kV bays supply voltage to 132kV bays and 33kV bays. Two transformers each having a rating of 220/132kV and 220/33kV are stepping down 220kV to 132kV and 33kV respectively. Main bus-1 is working for both 220kV and 33kV voltage levels. Presently the 132kV system is not Working. Both the outgoing feeders and the capacitors banks are connected to the 33kV bays. There are total of 6 outgoing feeders out of which only 4 are used. These 4 outgoing feeders have a total load of 12.41 MW. Two capacitor banks each having a rating of 21.72 MVAR are presently not used. Station transformers of 33/0.433kV are also present in the system.

Figure 1. Single Line Diagram of 220kV Masudpur Substation

3. System Data Table 1. BUS DATA 

2

Bus Data

Bus Number

Bus Voltage (kV)

1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,27,38 25, 26, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 74 72,73

220 132 33 0.4

Copyright ⓒ 2015 GVSchoolPub


Table 1 shows the voltage ratings of the different buses connected in the system. The different voltages in the system are 220kV, 132kV, 33kV and 400V. Table 2. Transformer Data 

Transformer Data

From Bus Name

To Bus Name

POSITIVE R(P.U) TAP

X(P.U) PHASE

ZERO R(P.U) FB-MVA

X(P.U) TBMVA

27

28

0.00501 1.00000

0.10027 0.000

0.00501 10000

0.10027 5000

38

39

0.00501 1.00000

0.10027 0.000

0.00501 10000

0.10027 1500

53

72

0.00294 1.05000

0.05883 0.000

0.00294 1500

0.05883 0

52

73

0.00294 1.05000

0.05883 0.000

0.00294 1500

0.05883 0

Table 2 shows the ratings of all the four transformers connected in the system. LOAD DATA Table 3. Load Data Bus Number

Real Power (MW)

Reactive Power (MVAR)

55

1.61

1.04

65

4.59

0

66

1.81

1.22

67

4.4

3.07

Table 3 shows the ratings of the load connected to 33kV bays of the substations. It shows both the real power (MW) and the reactive power (MVAR).

4. Load Flow Studies Load flow studies, also known as power flow studies in power system are conducted to study the steady state performance of power system under various working conditions. It helps us to determine the optimal design of the power system network, its economic power dispatch and also helps in the controlling of the existing power system network. Load flow study helps us to determine the voltages, currents, voltage profile, real power (MW) and reactive power (MVar) flowing in a system under a given load conditions. These studies form the basis of other studies such as short circuit studies, transient and dynamic stability studies and also for relay coordination. Load flow studies helps us to get an idea for additional required generation, MVar support to maintain the voltage within limits. There are various methods to do load flow studies i.e. Gauss Seidel Method (GS Method), Newton Raphson Method (NR method) and Fast Decoupled Method. Fast decoupled method is used because it is simple when compared with other two. It is efficient and it requires less number of iterations to converge.


3

International Journal of Power Devices and Components for Smart Device Vol. 2 (2015)

Existing System Configuration Figure 3 depicts the configuration of the existing system. Out of the two 220 KV circuits coming to the Masudpur substation only one is working as the load on the substation is less than the total capacity of the substation. Total power generated by single 220 KV circuit is equal to 12.4340 MW. Along with this active power, reactive power equal to 5.5250 MVar is also generated. Table 4. Load Flow Result (Existing System Configuration) Load flow results ( Existing Configuration) MW Generation MVar Generation MW Load

12.4340 5.5279 12.41r

MVar Load

5.3275

MW Loss MVar Loss

0.0240 0.2004

5. Short Circuit Studies Short circuit studies are used to calculate the protection capabilities of the switchgears during both the normal condition and the abnormal condition. Short circuit studies provide Fault MVA, Fault current which are prerequisites for the proper relay coordination. There are two types of faults i.e. symmetrical and unsymmetrical faults. Symmetrical fault is also known as three phase to ground fault. Unsymmetrical fault comprises of single line to ground fault, double line fault and double line to ground fault. Three phase to ground fault is chosen for the short circuit studies because it is the most severe faults and it helps us to choose the ratings of the breakers for the most severe conditions. Three phase to ground fault is done on different buses in existing Masudpur substation circuit so that the ratings of switchgears connected in the substation can be verified. This would help in keeping the substation equipment safe and also it will help us to know whether new switchgears are required or not.

Figure 2. Load Flow Analysis Followed by Three Phase Fault Simulation Circuit

4



Three phase to ground fault analysis is done on Bus 55 and the following results of fault current, fault MVA, post fault voltages and shunt contribution from fault connection. Table 5. Fault MVA and Fault Current at Bus 55 

Fault MVA and Fault Current Fault MVA

Fault Current Phase (A,B,C) Magnitude 14310 14310 14310

Phase (A,B,C) Magnitude 818 818 818

Angle -84.77 155.23 35.23

Table 7. Post Fault Voltage after Creating Fault at Bus 55 

Post Fault Voltages

Bus

19

Sequence (1,2,0) V 0.91 0 0

1, 3, 5, 7, 8, 9 , 10, 11, 15, 16, 17, 18, 21, 22, 23, 24, 27, 28 2, 4, 14, 20, 25, 26, 29, 30, 31, 32, 33, 34, 35, 36, 37 40, 41, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 72, 73, 74


Line-Line Magnitude

V 0.91 0.91 0.91

Angle -0.23 -120.23 119.77

0

124.63

0

0 0 0.883 0 0 1

Angle -0.23 -90 -90 124.6 3 -90 -90 1.14 -90 -90 0

0 0 0.883 0.883 0.883 1

4.63 -115.37 1.14 -118.86 121.14 0

0 0 0.833 0.833 0.833 1

0

-90

1

-120

1

0

-90

1

120

1

0.035

-37.47

0.035

-37.47

0.035

0 0

-90 -90

0.035 0.035

-157.47 82.53

0.035 0.035

0 55

Phase (A,B,C)

0.91 0.91 0.91

5


Table 8. Fault Contribution from Shunt Connection

From Bus

19,20 55, 65, 67, 66

Current (AMPS/DEGREE) Sequence (1,2,0) Magnitude Angle 2146 97.53 0 -90 0 -90 0 -90 0 -90 0 -90

Phase (A,B,C) Magnitude 2146 2146 2146 0 0 0

Angle 97.53 -22.47 -142.47 -90 -90 -90

MVA Phase (A,B,C) Magnitude 818 818 818 0 0 0

Figure 3. Three Phase Fault at Bus 55 

Graph

Proposed Configuration The system configuration has been modified by using both the circuit of 220kV line. 132kV system has been switched on. The following are the values of fault MVA, Fault current, post fault voltages and fault contribution from shunt connection. Table 9. Fault Current and Fault MVA 

Fault Current and Fault MVA Fault MVA Phase (A,B,C) Magnitude 869 869 869

6

Fault Current Phase (A,B,C) Magnitude 15200 15200 15200

Angle -83.01 156.99 36.99



Table 10. Post Fault Voltages after Creating Fault at Bus 55 

Post Fault Voltages Sequence (1,2,0) Bus V 0.938 1, 3, 5, 7, 8, 9 , 10, 11, 0 15,16, 17, 18, 21, 22, 23, 24,27, 28 0

2, 4, 14, 20, 25, 26, 29, 30,31, 32, 33, 34, 0 0 35, 36, 37 40, 41, 44, 45, 46, 47, 48,49, 50, 51, 52, 53, 0.037 56, 57,58, 59, 60, 61, 62, 63, 64,65, 66, 67, 0 68, 69, 72, 73,74 0

Line-Line Magnitude

Angle 0.6 -90

V 0.938 0.938

Angle 0.6 -119.4

-90

0.938

120.6

0.938

-90 -90 0

0 0 0 1

-174.83 65.17 -54.83 0

0 0 0 1

-90 -90

1 1

-120 120

1 1

-38.01

0.037

-38.01

0.037

-90

0.037

-158.01

0.037

-90

0.037

81.99

0.037

-174.83

0 0 0 1

55

Phase (A,B,C)

0.938 0.938

Table 11. Fault Contribution from Shunt Connection at bus 55 

Fault Contribution from Shunt Connection

From Bus

19,20 55, 65, 67, 66

Current (AMPS/DEGREE) Sequence (1,2,0) Magnitude Angle 1140 96.99 0 -90 0 -90 0 -90 0 -90 0 -90


Phase (A,B,C) Magnitude Angle 1140 96.99 1140 -23.01 1140 -143.01 0 -90 0 -90 0 -90

MVA Phase (A,B,C) Magnitude 434 434 434 0 0 0

7


Figure 4. Three Phase Fault at Bus 55

6. Relay Coordination The coordination of the protective devices is done to determine the timing of current interruption whenever there is an abnormality in electrical conditions. The main objective is to minimize the risk to a large extent. The coordination can also be done by dividing the power system into protective zones. Diving into zones will help us to identify the location of the fault quickly and necessary action can be taken immediately. Zones have various following features like overlapping of zones. Zones overlapping gives us the detail of the circuit breakers. Thus the defective circuit breakers can be easily isolated from the system to repair the fault. The overlapped regions is kept small such that when a fault occurs in the overlapping regions and the two zones which comprises the fault are isolated the sector of the power system isolated from the service will still be small.

Figure 5. Relay Coordination Simulation Circuit

8



The following table will show the difference in the operating time of the relays when the three phase fault is introduced on the same bus in two different configuration. Table 12. Settings Configuration 3-ph fault at load bus 55 (existing settings) Relay name

 

Phase A Fault Current(Amps)

3-ph fault at load bus 55 (proposed settings)

Operating time Phase A Fault (SECS) Current(Amps)

Operating time (SECS)

R1

14310

INST 0.00

15200

INST 0.05

R8 R9

14310 2100

0.6812 0.8515

15200 2280

1.3624 1.5956

Graphs

Figure 6. Phase Relay Coordination when Fault at Bus 55 (Existing Configuration)

Figure 7. Phase Relay Coordination when Fault at Bus 55 (Proposed Configuration)


9


7. Conclusions This paper thus presents simulation results obtained by using MiPower software domain and its implementation on a real time power system 220kV Masudpur substation. The method includes using the single line diagram and system data to obtain the best results by load flow and short circuit studies and using these results to design the protective scheme for the existing system as well as developing a proposed system by incorporating changes in the relay setting and coordination considering increase in load demand for future use. All devices do provide adequate equipment protection and selectivity. There are no deficiencies in either equipment protection or selectivity have been identified. The settings that were done were currently limited to overcurrent, REF and instantaneous .In future we are planning to develop a relay setting scheme for Unit protections, Different schemes and distance relay protection for the transmission line. Also the relay discussed above are all electromechnical relays which will be replaced by numerical relays in order to an in order faster tripping so as not to effect the system which are not faulted.

Acknowledgements The authors are grateful to their organization for its support.

References [1] B. Chattopadhyay, “An on-line Relay Coordination Algorithm for Adaptive Protection Using Linear Programming Technique”, IEEE Trans. on Power Delivery, vol. 11, no. 1, (1996), pp. 165-173. [2] Coordination of Overcurrent Relays in Interconnected Power System", IEJ, vol. 74, (1993), pp. 59-65. [3] S. Ralhan and S. Ray, “Optimal Coordination of Directional Overcurrent Relays using Interval Two Phase Simplex Linear Programming”, International Journal of Advanced Computer Research, vol. 3, no. 3, issue 11, (2013) September. [4] D. Vijayakumar and R. K. Nema, “Simplified Velocity MPSO for Directional Over Current Relay Coordination”, International Journal of Recent Trends in Engineering, vol. 1, no. 3, (2009) May. [5] D. K. Singh and S. Gupta, “Protection Of Power System By Optimal Co-ordination of Directional Overcurrent Relays Using Genetic Algorithm”, International Journal of Modern Engineering Research, vol. 2, no.1, (2012) January-February. [6] D. Birla, R. P. Maheshwari and H. O. Gupta, “A New Nonlinear Directional Overcurrent Relay Coordination Technique, and Banes and Boons of Near-End Faults Based Approach”, IEEE TRANSACTIONS ON POWER DELIVERY, vol. 21, no. 3, (2006) July. [7] V. N. Rajput, R. P. Mehta and B. A. Oza,” Coordination of Overcurrent Relays for Industrial Radial System”, National Conference on Recent Trends in Engineering & Technology. th

[8] J. Sadeh, “Optimal Coordination of Overcurrent Relays in an interconnected power system”, 15 PSCC Liege, section 19, (2005).

Authors Debniloy De, he persuaded Bachelor of Technology in Electrical and Electronics from ITM University, Gurgaon in 2014.

10



Sheila Mahapatra, she received her B.Tech degree in Electrical Engineering from Utkal University, Orissa in 2002. She received her Masters degree in Power System & Automation from GITAM, Andhra University, Vizag in 2008. Presently she is working towards PhD in the Department of Electrical & Electronics Engineering, ITM University, Gurgaon, Haryana. She is a lifetime member of ISTE and has teaching experience of over 9years.


11


12
