Eastern Area Power System Reinforcement study

The purpose of this study is to investigate methods for reinforcing the Eastern area power system by overcoming the present and future problematic conditions. In preparation of this paper, every possible effort is given to concise the contents without loosing the key topics. The study comprises three consecutive phases. The first phase consists of a comprehensive study of the Eastern area power system, finding out key problematic conditions, studying the potential solutions obtainable from within the same area under four different system operation scenarios. The second phase consists of two analytical stages. In the first stage, more concern is devoted to different types of solutions to overcome the present day problems such as the voltage droop, line overloading problems etc. Ten different types of proposals based on dependable view points, thoroughly revised with the help of power flow studies are also given in this section. The second stage search out possible solutions not only for the present but also for ten years ahead from year 2005. For the selected study period of 20052014, a series of detailed analysis have been carried out in yearly basis with remedial actions wherever seemed necessary. The final study consists of six different types of alternative solutions capable of withstanding five types of criteria under system normal condition as well as under single contingency condition. Final phase is a technoneconomic analysis of each of the six solutions selected, for optimisation. Although not included, a series of studies on fuel transportation and an account on social & environmental impact assessment also have been carried out which are inherently essential parts of a similar project.


Introduction
Reduction of power quality problems especially the dropping of voltage levels, associated with the Eastern area power supply were identified many years ago through investigations carried out by the Ceylon Electricity Board (C.E.B.). From time to time, several remedial action plans and suggestions have been proposed and submitted in order to rectify the prevailing situation. Unfortunately, all such efforts whether practicable or otherwise, proved to be fruitless endeavours. But in a broader sense the C.E.B. cannot be blamed because the economic problems of allocating funds, technical and environmental impact problems of layout and finally the social attitudes along with political interests emerged as customary obstacles to hinder such efforts whenever tabled. Hence it has become one of the critical problems lying at the planning divisions of the C.E.B. Although the Eastern province consists of three districts, namely, Trincomalee, Batticaloa and Ampara on the basis of political and administrative demarcations, the study focused on finding a solution to maintain an adequate and uninterrupted flow of electricity to the inhabitants of Eastern province without restricting to the above demarcations. And also, the out come of the study should guarantee not only the present day requirements but also the future, too.

Existing Problems of the Eastern Area Transmission System
The Eastern area is fed by three main 132 kV radial lines as clearly visualise from figure 1.
After a thorough study of present as well as past data of the Eastern area grid substations and 132 kV radial transmission feeders which are given in table 1, the following are identified as severe problematic conditions pertaining to the Eastern power system:  But other load centres will not experience such a critical situation in the near future and will operate under normal operating limits.

Low reliability
Except New Anuradhapura-Trincomalee feeder lines, the remaining long single feeders will make the Eastern area power system totally unreliable under N-l contingency condition.
By analysing several years in the past (table 2), following 'unavailability' results are obtained. • Eastern area suffers a series of problems and requires the necessity of a long term solution with multidirectional views.
• When compared with other feeders, New Anuradhapura-Trincomalee feeders may well function for several years to come with no problematic condition in the vicinity. So that, the study will not investigate anything regarding further development of the New Anuradhapura-Trincomalee feeder lines.

Substation overloading
Most of the grid substaHons in the Eastern area seem to be violating their firm substation capacities under single contingency (n-1) condition. And also Valachchenai is experiencing the overloading of transformers even under system normal condition. But there is a possibility of preventing this by transferring some of its loads to a near by grid substation as a short-term remedial action.

Contribution of the Inginiyagala power station
It is well identified as one of the most effective and critically sensitive generating point for Badulla and Ampara load centres. Although the Inginiyagala power station is fed from one of the Sri Lanka's largest irrigation tank, Seiisnai/ake Snmudraya, due to the following reasons the expected level of contribution cannot be obtained satisfactorily.
• No significant capacity improvement proposals are being identified • Involvement in water management policy where by priority is given for irrigation the past several years. Therefore it is obvious that a dependable contribution cannot be expected from Inginiyagala power station. Even with full capacity, Inginiyagala power station is unable to overcome the problematic situation. So, it cannot be considered as a potential solution and its level of contribution is considered as negligible.

Some of the criteria used for the technical analysis
During the study period, the system has been put through or subjected to modifications with new addition of generators, transmission lines, load growth of each load centre etc. Hence the study included the system configuration of commissioning and decommissioning of generators, 220/132 kV transmission lines, load growth of load centres, addition of new load centres and scheduled load transfer schemes.
Most of the data concerned in this study including existing generator data, grid substation data, transmission line data, transformer data, active & reactive load forecast and future generation, transmission, proposed grid substations and augmentations are all based on the CEB long-term transmission expansion plan for 2004-2014 period. Planning criteria used for this study include the voltage criteria, thermal overloading criteria, security or single contingency criteria and firm substation capacity criteria.

analytical stage 1
At this stage, concern is directed under ten different types of proposals to overcome the prevailing voltage droop problem. These ten proposals make way to uncover a number of solving methods which will be of immense use in finding a final solution. All the proposals considered at this stage have been checked under four worst case scenarios to find out the potentiality of superseding the voltage drop problem without allowing other problems to rise up at the same time. The four scenarios which have been taken into consideration are given below. By analysing the performance over future load growth for several years ahead, every aspect related to it has been noted down and further analysed. ENGINEER 1) Hydro maximum day peak Hydro power plants are given priority and put into service first. The rest of the requirements needed are to be fed by thermal power plants. Normally the loading is recorded around 11:00 hours.
2) Hydro maximum night peak Hydro power plants are given priority and put into service first. The rest of the requirements needed are to be fed by thermal power plants. Normally the loading is recorded around 19:30 hours.
3) Thermal maximum day peak Thermal power plants are given priority and put in to service first. The rest of the requirements needed are to be fed by hydro power plants.
Normally the loading is recorded around 11:00 hours. 4) Thermal maximum night peak Thermal power plants are given priority and put into service first. The rest of the requirements needed are to be fed by hydro power plants.
Normally the loading is recorded around 19:30 hours.
Ten types of proposals which are based on three types of correction methods, namely injection of reactive power by using suitable capacitor banks, injection of active power with the help of a power station and the construction of additional transmission lines, given in appendix table 4.

Transmission line from Valachchenai to Ampara
As stated in several proposals, concern has been given to check the feasibility of making the Eastern area power system loop by interconnecting the two radial feeders from Valachchenai to Ampara. Regarding this, little effort has been given previously by making it difficult to find out a transmission route for the study to proceed. As such 1:50,000 maps of Vakarai, Kalkudah, Aralaganwila, Batticaloa, Mahaoya, Padirippu and Ampara n Kalmunai have been used for the purpose of transmission routing. Every possible effort has been taken to minimise the interferences such as cultivated private lands, densely populated areas including towns and urban localities while at the same time keeping off the coastal belt. In compliance with the above demarcations, the route selected passes over paddy fields and alongside the boundaries of reservations and sanctuaries for a distance of about 84.1 km. Therefore an approximate length of 90 km is used to pave the way for planning and load flow studies to proceed. Apart from brief comments attached to each proposal given above and by considering individual performance of each project over several criteria, proposals 3,6,7 & 9 were further preceded with required remedial actions.

Analytical stage 2
Based on individual performances, filtering and modifying the selected proposals of analytical stage 1 are considered at this stage.    Required reactive power is obtained by both generators and a capacitor bank. Remedial action schedule is given in appendix, table 7.

Solution 3
Proposal 6 is to proceed with double circuit from Habarana to Valachchenai as shown in figure 7.
Remedial action schedule is given in appendix, table 8.

Solution 4
The system configuration for solution 3 is being initially launched and an active power injection carried out to operate Ampara as a "PV bus". Remedial action schedule is given in appendix, table 9.

Solution 5
The initial system configuration is same as in solution 2 (a). Rantembe-Ampara transmission line is being connected to the system at the appropriate time. Remedial action schedule is given in appendix table 10.

Solution 6 (additional study)
The initial system configuration is as in solution 2 (b) but always maintained the bus voltage at Ampara, more than 125.4 kV (0.95 p.u.) all the time. Required reactive power is obtained by both generators and capacitor banks. Remedial action schedule is given in appendix, table 11.

Financial Analysis of Options
Since the study has unearthed six possible solutions which are technically feasible, concern has been given to the technon economic study of each alternative solution for the sake of optimising one of those for the proposed period of 10 years. In the financial analysis, first step was to identify the required substation modifications, construction and upgrading of Analysis), concern has been given to the Cost Benefit analysis of each of the alternative solutions. As study period is restricted to only 10 years ahead (will be about 8 or 7 years after allowing two or three years for the initial constructions), a comparison with the total life time of a project (>20 years) will prove that most of the benefits are left uncovered even though almost all costs happen to be within the time frame.

Cost calculations
In order to minimise the complexity, all implementations are categorised into three sections such as generation, transmission and substation modifications.

Generation
Finding out the required active power injection for technical analysis, was not restricted to a particular mode of generation. But for economical analysis a specific type of plant had to be chosen. To fulfil the requirement, preference was given to several types of candidate plants designated for Sri Lanka power system by the C.E.B. During the preliminary screening it was found that we would have to use either diesel power plants or gas turbines. But in the course of final screening gas turbines has to be selected even though the large burden of annual running costs is inherent. In N-l contingency, loss of a generator unit is taken as 26.25 MW and also due to the following two reasons and lack of other options, made way to depend on gas turbines. Firstly, the W.A.S.P. optimisation gives two types of gas turbines as future generation additions consisting of 75 MW and 105 MW in capacity. Secondly, it is now becoming a national policy not to use any diesel generation plants as future candidate plants.
Costs calculation mainly consists of the following factors. • It is worthwhile to find out the possibility of changing the type of fuel from auto diesel to furnace oil which is cheaper.

Transmission
The costs of transmission line projects consist mainly of two components.

Loss benefits
Finding out of losses that occur in each of the transmission lines of the area for each solution for several years is not an easy task. But a genuine effort was taken to make an account under this topic in which it seems that generator option is more advantages when compared with the transmission option. All loss benefit analysis is being obtained in comparison to the present day losses. Area loss is estimated as 41.3 MWh per day and the loss factor is assumed to be around 0.3 -0.35.
Cost benefit analysis for each of the projects during the total study period are tabulated in table 3.

Conclusion
As clearly visualise from the gist of contents regarding this study the solutions 1,3 and 4 will only be able to cover up the expenses, incurred for each as found during the study period. All other options seem to be uneconomical because of their massive expenses. Hence, the final conclusion is to go ahead with solution 3, as it is the best economically viable solution in hand to strengthen the Eastern area power system. As clearly pointed out from the figures given above one could easily understand how much loss is incurred in delaying without a fitting solution.
As not in the case of social welfare projects like rural area electrification, this project could earn its expenses within a short period of time. As it is revealed during this study, the next major construction which is most appropriate would definitely be a power station located with in this area. But the exact place & year for commencing and its type/size may subjected to be changed in its detailed design stage. Also by the end of year 2014, Ampara and Padirippu grid substations are most likely to reach their firm substation capacity requesting the necessity of constructing a new grid substation at or near Batticaloa to meet that increasing demand. It will be necessary to interconnect Valachchenai and Ampara grid substations at that time.  Found it out as a potential solution to the voltage drop problem and for thermal overloading, not only for the present but also for few years ahead without remedial action and also it increases the reliability of continuous supply without failure to Ampara grid substation. The benefactors are those consumers covered up under Ampara Grid Substation. Although the voltage and thermal overloading problems could be averted, this proposal cannot be regarded as a fine solution since the failure of existing feeder, Badulla-Ampara will result in isolating Ampara (islanding) from the rest of the system