A New Adaptive Technique in Development of IT Based Island Scheme For The Power System Utility Needs

A New Adaptive Technique in Development of IT Based Island Scheme For The Power System Utility Needs

M. Balasubramanyam R.V.S.Satyanarayana

Divisional Engineer Professor

Power System Protection, APTRANSCO Dept of Electronics and Communication Eng.

Vidyut souda, Hyderabad-INDIA SV University College of Engineering

Tirupathi, Andhra Pradesh-INDIA

Abstract:

This paper provides a new strategy in design and development of simple power system controlled separation scheme, aimed at maintaining of supply to certain important sector of loads and making fast restoration of the grid in the events of cascade outages leading to blackouts. This is found to be the need of an hour, particularly with respect to the emerging structural changes in power system and in the operation paradigms of utility grid. Special emphasis is given for modeling of the state grid with the base case, from which the reduced system is derived by making unique approach of load groping based on island participation index, for making the island scheme to extend supply to metros, in case of severe disturbances leading to blackout. The motivation behind is, that the recent blackout of new grid, occurred on 30th & 31st July 2012, in India, wherein the complete nations capital activity got paralyzed.

Keywords : Islanding, Island participation index, blackout, metros, slow cohesive generators, SCADA.

INTRODUCTION:

The power system network in this new scenario of deregulation and restructuring, is experiencing higher degree of stress, whatever so be the reasons like rapid load growth, penetration of large generators, without associated transmission system in place, maximum utilization of transmission system oscillating around maximum permissible limits etc. The ability of power system to be stable depends on the operation states. The various probable states that may occur during any disturbance are normal, alert, emergency, extreme emergency and restorative. In the extreme emergency the effective control strategy is to resort for control system islanding. The blackouts and disturbances which were experienced in US and Italy in 2003 and in central Europe in 2006 have demonstrated the vulnerability of new grids. In this trade the ultimate challenge for the system operators and transmission system planners is to ensure the system reliability and security by aiming to prevent the total system blackout by implementing proper control action to limit the extent of disturbance. The bases of formation of island is to reduce in to a small grid, making load- generation balance, thereby facilitating the easy restoration process in making final integration of the whole system

In this article the various aspects are described under different sections. In section II, the research aspects in island formation discussed. In section III, the analytical basis to form island by making use of new proposed approach in modeling of the system is presented. In section IV, the study results along with the simulation results are provided. section V, presents the conclusion and Section VI, includes References.

SECTION II – Research Aspects in Vogue

1. : Preamble

   In the power system major blackouts were initiated by local disturbances that cascaded across the transmission network. Based on various studies and inferences, it is to understand that the power system contingencies comprises three stages, depending on the duration of fault persistence. Initial stage wherein the temporary system fault occur and cleared rapidly in mille seconds. Intermediate stage, where in the system separates in seconds and final stage where the load and generation imbalance in minutes causes a blackout. In power systems which are now operated critically resulting in growing risk for a local failure, to cascade into catastrophic blackout. At this inception of disturbance, relays located on faulty transmission lines, operate to clear the fault. Because of these outages, depending on the severity, it induces variations in electrical power outputs, with the generator mechanical inputs remaining almost constant. The resultant effect of this power imbalance is formation of groups of coherent generators operating at different speeds swinging one against the other, which leads to the loss of synchronism and the splitting of the network.

2. Various adopted Methodologies

   However the islands so formed unintentional, may not have a balance of generation and load, which makes the failure to propagate further until a complete collapse of the system occurs. In order to prevent this, intentional controlled island schemes came in to the existence, based on many research contributions. The studies depicts that in the intentional islands, the power system is designed to deal with the situation and can survive, as this scenario has been planned. In unintentional island mode, there was no design and islanding occurs in unplanned fashion and hence the survival is doubtful. Controlled islands would occur, when the

   whole power system is divided into several islands, wherein the load generation should be in balance. The problem and the aim of research in this field is, where to form? When to form ? and how to form? The various approaches for island formations are

   1. Controlled islanding approach based on the graph spectral method [1]

   2. Slow coherency grouping of generators and determination of minimal cut sets [2],

      [3] by using DYNRED (Dynamic Reduction Program Software)

   3. Graph theoretical approach called OBDD i.e., ordinary binary decision diagram [4], [5]

SECTION-III proposed new approach and modeling

1. Why is it needed?

   With the increased size of the grid, the various approaches earlier presented based on main principle of grouping of various generators on slow coherency and determining the minimal cut sets taking into account the least generation load imbalance, doesnt ensure the choice of specific essential loads grouping. This is required to be addressed on top priority for ensuring supply atleast to metros in the event of black out. Earlier the power plant capacities were of lower capacity and are distributed apart. Now with the increased available size of the unit, to the extent of around 800MW per each unit, the power plant capacity is increased. A light is thrown on the search of new methodology, were in the large power plant as source, the major computational burden involving grouping of generators with slow coherency could be avoided. In this paper, the issue is addressed in new dimension by grouping all the required essential loads like metros, maintaining the generation load balance.

2. Modeling

AP power system is modeled with the 89 generators and 575 load buses. The transmission system is also modeled consisting of 400kv, 220kv and 130kv EHT lines making 1215 branches in the study. The basic power flow study is conducted for the maximum demand condition of 11946 MW. CYME international software is used for carrying over the power flow studies. The next steps involves the identification of specified loads and designing of the island with single large power plant. Here RTPS (Ramagundam thermal power

station) is considered as the large single source with installed capacity of 2600MW. The power flows are obtained for all the loads grouped based on the Ipx, which determines the inclusion of the loads in the proposed island schemes. The cut sets obtained for fixing the island boundaries are made use in bifurcation of the whole system. The resulting island consists of RTPS, metros and other essential loads observing the generation load balance. The methodology adopted for island detection is, by providing of under frequency relays

SECTION-IV Simulation Results

1. Scenario (1)

   The table (1) and the power flow diagram(1) shows power flows of whole system intact. The total generation found required is 11946MW for meeting the demand of 11527MW. In this the RTPS was injecting 2074MW.With the automatic islanding initiation by the under frequency relays, the predetermined inter connecting lines are disconnected in facilitating for the formation of the required islanding.

   Figure 1. Power Flow Diagram of an Integrated System

   Table 1. Modeled Integrated System Power Flow Results.

   —VOLTAGE— —-LOAD- NAME ZN KVOLT DEGREE MW MVAR

   -> 225RST 21 1M	FX	205.12	-7.79
   -> 225RST 21 2M	FX	205.12	-7.79
   -> 299RST 21 1M	FX	198.37	105.25
   -> 402GHP 15 3M		274.79	-42.86
   -> 402GHP 15 4M		274.79	-42.86
   -> 404TPL 23 1		209.18	-86.88
   -> 404TPL 23 2		209.8	-86.88
   -> 413DICH 18 1		255.92	-17.88

   403RST 21 404.012 1.2 0.00 0.00

   -> 245GBL 15 2 0.00 0.00

   -> 245GBL	15 4		0.00	0.00
   -> 272MLK	15 1		-168.57	-15.33
   -> 272MLK	15 2		-168.57	-15.33
   ->1138SHN	15 1M	FX	93.62	8.07
   ->1138SHN	15 2M	FX	93.62	8.07
   ->1138SHN	15 3M	FX	60.54	5.22

   -> 245GBL 15 3 84.26 7.08

   259MLI 15 214.671 -10.5 0.00 0.00

   -> 272MLK 15 1 -110.62 1.45

   -> 272MLK 15 2 -110.62 1.45

   ->1089MLI 15 1M FX 51.98 -0.68

   ->1089MLI 15 2M FX 84.62 -1.11

   ->1089MLI 15 3M FX 84.62 -1.11

   245GBL 15 212.095 -12.7 0.00 0.00

   -> 226SHN 15 1M -122.87 -10.77

   -> 226SHN 15 2M 0.00 0.00

   -> 226SHN 15 3M -83.99 -8.54

   -> 226SHN 15 4M 0.00 0.00

   -> 237YML 17 1M 69.74 19.68

   -> 294TND 15 1 125.74 43.02

   -> 311SVR 15 1 -78.37 -25.81

   -> 311SVR 15 2 -125.87 -37.07

   ->1189GBL 15 1M FX 46.59 4.21

   ->1189GBL 15 2M FX 46.59 4.21

   ->1189GBL 15 3M FX 46.59 4.21

   ->1189GBL 15 4M FX 75.85 6.86

   272MLK 15 215.035 -10.0 0.00 0.00

   ->1474MLK 15 1M FX	60.77	29.79
   291HYD 15 216.451 -10.5	0.00	0.00

   -> 205CHG 15 1M 0.00 0.00

   -> 309HIAL 15 1M 124.77 49.75

   -> 309HIAL 15 2M 109.89 44.04

   -> 311SVR 15 1 185.33 59.07

   -> 363SHAM 14 1 189.12 57.27

   -> 364SHAD 16 1 168.56 47.87

   -> 411HYD 15 1 FX -259.22 -86.00

   -> 411HYD 15 2 FX -259.22 -86.00

   -> 411HYD 15 3 FX -259.22 -86.00

   311SVR 15 214.183 -11.6 0.00 0.00

   -> 245GBL 15 1M 78.69 23.83

   -> 245GBL 15 2M 126.45 35.11

   -> 291HYD 15 1M -184.52 -56.57

   -> 309HIAL 15 1 -214.62 -57.42

   ->1147SVRP 15 1M FX 64.67 18.35

   ->1147SVRP 15 2M FX 64.67 18.35

   ->1147SVRP 15 3M FX 64.67 18.35

   241DIC1 18 212.019 -5.8 0.00 0.00

   -> 240DIC 18 1M 127.10 23.99

   -> 240DIC 18 2M 127.10 23.99

   -> 413DICH 18 1 FX -127.10 -23.99

   -> 413DICH 18 2 FX -127.10 -23.99

   225RST 21 216.486 -3.4 0.00 0.00

   -> 224RDM 21 1M 205.12 -24.31

   -> 224RDM	21 2M	205.12	-24.31
   -> 403RST	21 1 FX	-205.12	24.31
   -> 403RST	21 2 FX	-205.12	24.31

   309HIAL 15 216.098 -10.6 8.24 4.00

   -> 205CHG 15 1M 10.74 30.80

   -> 291HYD 15 1 -124.69 -49.70

   -> 291HYD 15 2 -109.82 -44.08

   -> 311SVR 15 1M 215.54 58.98

   316GJWL 17 212.434 -8.4 0.00 0.00

   -> 288MDC 15 1M 0.00 0.00

   -> 289MIN 17 1 105.75 45.23

   -> 353KMRD 18 1M 82.45 2.26

   -> 420GAJWL 17 1 FX -162.14 -43.20

   -> 420GAJWL 17 2 FX -162.14 -43.20

   ->1243GAJWLN17 1M FX 68.04 19.46

   ->1243GAJWLN17 2M FX 68.04 19.46

   224RDM 21 216.451 -3.5 0.00 0.00

   ->	225RST	21	2	-205.03	24.57
   ->	265DRS	21	1	109.46	23.96
   ->	265DRS	21	2	109.46	23.96
   ->	280NML	19	1	156.03	12.79
   ->	302RSTD	21	1	-116.62	-79.90
   ->	308JGT	21	1	101.04	27.77
   ->	312NAGA	20	1	-30.90	-42.31
   ->	312NAGA	20	2	-30.90	-42.31
   ->	356BLPL	19	1	44.15	-26.70

   -> 225RST 21 1 -205.03 24.57

   ->1127RDM 21 1M FX 34.17 26.80

   ->1127RDM 21 2M FX 34.17 26.80

   265DRS 21 212.139 -6.2 0.00 0.00

   -> 224RDM	21	2M	-108.41	-25.17
   -> 268SDP	17	1	46.43	-16.51
   -> 268SDP	17	2	46.43	-16.51

   -> 224RDM 21 1M -108.41 -25.17

   ->1078DRS	21	2M	FX	41.32	27.79
   ->1078DRS	21	3M	FX	41.32	27.79

   ->1078DRS 21 1M FX 41.32 27.79

   268SDP 17 212.649 -7.8 0.00

   -> 265DRS	21	2M		-46.18	9.42
   ->1136SDP	17	1M	FX	46.18	-9.42
   ->1136SDP	17	2M	FX	46.18	-9.42

   -> 265DRS 21 1M -46.18 9.42

   From the study, the elements of cut sets, which determines the formation of the proposed island are shown in the table no (2)

   Sl. No	Form bus	To bus
   1	403	435
   2	403	404
   3	408	411
   4	409	411
   5	291	368
   6	291	363
   7	245	237
   8	245	294
   9	226	217
   10	272	284
   11	272	283

   Table 2. Elements of Cut set

2. Scenario (2)

The table (3) and the power flow diagram(2) shows power flows of the proposed new island. The total generation found required is 1976MW form RTPS power plant alone to meet the demand of 1934MW including 38 number of buses and 91 number of branches feeding the essential loads of metros.

Figure 2. Power Flow Diagram of Designed Island to Feed Metros

Table 3. Modeled Island System Power Flow Results

491MLK 15 376.453 -9.8 0.00 0.00

-> 272MLK 15 1M FX 228.39 65.41

-> 272MLK 15 2M FX 228.39 65.41

-> 402GHP 15 1 -47.25 -16.74

-> 403RST 21 1M -409.54 -114.09

316GJWL 17 208.083 -9.0 0.00 0.00

-> 288MDC 15 1M 152.88 23.83

p>-> 420GAJWL 17 1 FX -76.44 -11.91

-> 420GAJWL 17 2 FX -76.44 -11.91

288MDC 15 201.542 -14.5 0.00 0.00

-> 272MLK 15 1M 0.00 0.00

-> 272MLK 15 2M 0.00 0.00

-> 316GJWL 17 1 -150.00 -16.72

->1370MDC-1 15 1M FX 41.35 4.61

->1370MDC-1 15 2M FX 41.35 4.61

->1370MDC-1 15 3M FX 67.31 7.50

265DRS 21 215.822 -3.2 0.00 0.00

-> 224RDM 21 1M -70.04 2.18

-> 224RDM 21 2M -70.04 2.18

-> 268SDP 17 1 20.04 -7.17

-> 268SDP 17 2 20.04 -7.17

->1078DRS 21 1M FX 33.33 3.33

->1078DRS 21 2M FX 33.33 3.33

->1078DRS 21 3M FX 33.33 3.33

268SDP 17 215.717 -3.8 0.00 0.00

-> 265DRS 21 1M -20.00 -1.29

-> 265DRS 21 2M -20.00 -1.29

-> 210GHP 15 3M FX 198.90 27.08

403RST 21 400.000 0.0 0.00

1976.82 376.34 (SW.)

-> 225RST 21 1M FX 60.91 -41.42

-> 225RST 21 2M FX 60.91 -41.42

-> 299RST 21 1M FX 59.20 70.46

->1474MLK 15 1M FX 60.77 30.48

288MDC 15 201.542 -14.5 0.00 0.00

-> 272MLK 15 1M 0.00 0.00

-> 272MLK 15 2M 0.00 0.00

-> 403RST 21 1M -434.36 -106.15

309HIAL 15 202.930 -16.6 8.24 4.00

-> 205CHG 15 1M 33.33 29.44

-> 291HYD 15 1 -125.41 -30.81

-> 291HYD 15 2 -110.49 -27.42

-> 311SVR 15 1 194.33 24.79

311SVR 15 201.642 -17.6 0.00 0.00

241DIC1 18 214.884 -1.4 0.00 0.00

-> 413DICH 18 1 FX -25.00 -13.06

-> 413DICH 18 2 FX -25.00 -13.06

->1168DICH 21 1M FX 16.67 8.70

->1168DICH 21 2M FX 16.67 8.70

->1168DICH 21 3M FX 16.67 8.70

259MLI 15 201.356 -16.4 0.00 0.00

-> 272MLK 15 1 -110.00 -15.99

-> 272MLK 15 2 -110.00 -15.99

->1089MLI 15 1M FX 51.69 7.51

->1089MLI 15 2M FX 84.15 12.23

->1089MLI 15 3M FX 84.15 12.23

1089MLI 15 120.643 -20.0 220.00 110.00

-> 259MLI 15 1 FX -51.69 -4.26

-> 259MLI 15 2 FX -84.15 -6.93

-> 259MLI 15 3 FX -84.15 -6.93

1189GBL 15 119.746 -22.7 275.00 130.00

-> 245GBL 15 1 FX -59.42 7.47

-> 245GBL 15 2 FX -59.42 7.47

-> 245GBL 15 3 FX -59.42 7.47

-> 245GBL 15 4 FX -96.73 12.17

226SHN 15 200.364 -18.0 0.00 0.00

-> 245GBL 15 1 66.93 -21.05

The validity of the adopted process in formation of island is compared with the real time SCADA data by modeling the same. The figure (3) shows the real time simulation snapshot of the proposed, utility modeled and implemented island scheme.

Figure 3. Simulated Islanding Scheme

SECTION-V

Conclusion:

The methodology proposed for providing an island of the required capacity to feed the metros and other essential loads, which is the concern of the state grid is addressed by suitably modeling. The survival of this island, will help in extending the restorative support in integration of the whole state power system during the black out, as the extension

291HYD 15 203.211 -16.4 0.00 0.00

-> 205CHG 15 1M 42.27 27.56

-> 309HIAL 15 1M 125.49 30.92

-> 309HIAL 15 2M 110.56 27.45

-> 311SVR 15 1 170.25 29.23

-> 411HYD 15 1 FX -149.53 -38.39

-> 411HYD 15 2 FX -149.53 -38.39

-> 411HYD 15 3 FX -149.53 -38.39

316GJWL 17 208.083 -9.0 0.00 0.00

-> 288MDC 15 1M 152.88 23.83

SECTION-VI

References:

1. Li, H., Rosenwald, G., Jung, J., and Liu, C. (2005). Strategic power infrastructure defense. Proceedings of the IEEE, 93(5), 918-933.

2. Haibo You, Student Member, IEEE, Vijay Vittal, Fellow, IEEE, and Zhong Yang. Self-

   Healing in Power Systems: An Approach Using Islanding and Rate of Frequency Decline-Based Load Shedding.

3. Haibo You, Student Member, IEEE, Vijay Vittal, Fellow, IEEE, and Xiaoming Wang, Student Member, IEEE. Slow Coherency- Based Islanding.

4. Q. Zhao, K. Sun, D. Z. Zheng, J. Ma and Q. Liu, A study of System Splitting Strategies for Island Operation of Power System: A Two Phase Method Based on OBDD, IEEE Transactions on Power System, Vol. 18, No. 4, pp. 1556-1565, Nov. 2003.

5. K. Sun, D. Z. and Q. Liy, Splitting Strategies for Islanding Operation of Large-Scale Power System Using OBDD-Based Methods, IEEE Transactions on Power Systems, Vol. 18, No. 2, pp. 912-923, May 2003.

6. P. M. Anderson and M. Mirheydar, An Adaptive Method for Setting Underfrequency Load Shedding Relays IEEE Transaction on Power Systems, Vol. 7, No. 2, May 1992, pp. 720-729.