From an engineering trainee’s diary _Transmission line planning

The following article is based on my experience as a trainee electrical engineering undergraduate in “Lighting Sri Lanka-Hambanthota Project (LSHP)” under Ceylon Electricity Board (CEB).

Transmission and distribution lines are the live veins of a country’s power system. They simply interconnect generating stations, grid substations and distribution substations. In Sri Lankan context, we have generation voltages around 13.5 kV, transmission voltages of 132 kV and 220 kV and distribution voltages of 33 kV (CEB) and 11 kV (LECO and small portion of CEB). The ultimate objective of a power system utility such as CEB is to keep the above mentioned “live veins” as healthy as possible while keeping the generation cost and other operating costs at a minimum while maximizing customer satisfaction. In order to achieve those objectives designing, planning and construction of transmission lines along with timely and proper maintenance, must be carried out with extreme care.

Planning is the initial stage of any transmission or distribution line development project. Planning process can be divided into three stages namely, long term planning, medium term planning and operation planning.

Long term planning

Long term planning emphasizes on topics such as need of construction of new transmission lines, development and introduction of new technologies for transmission (e.g. introducing HVDC system to Sri Lanka) and distribution (e.g. introduction of equipment such as “Fuse saver” to improve reliability of distribution system). Basically Transmission and generation planning branch of CEB carries out the above mentioned planning functions. Long term transmission planning is carried out as a rolling plan with a time horizon of ten years. This plan will cater the growing demand for electricity while incorporating new technologies to enhance the performance of the existing system.

Medium term planning

Medium term planning consists of defining characteristics of system voltages, transmission and distribution lines and substations etc. The time horizon is much shorter than that of long term planning.

Short term planning

Operational or short term planning involves in maintaining the quality and availability of the power system. Regular maintenance and unintended interruption handling falls under operation planning. Generally, this segment of planning is done by area engineers.

During my time in LSHP, I got the opportunity to study the planning process of 33 kV medium voltage lines. During the planning, answers to the following questions need to be obtained.

• When the new distribution line or upgrading of the existing line is required?
• What will be the capacity of the line? 
• How many circuits are needed?
• What is the quality of the supply and the reliability level?

In order to find successful and acceptable answers for the above questions, a large amount of data is required. The data requirement can be fulfilled by using the already available data and through surveys.

Concerns on planning

Accurate technique(s) of forecasting is a must for a successful transmission planning because the time period required to complete a transmission project, from planning to commissioning, may sometimes extend up to a decade. But within that time, the society, or in other words the beneficiaries of the transmission project, will change drastically. The living standards of the people will rise, new industries may be established and rapid development of infrastructures may attract more and more people to the area (in Hambanthota district, the electrification level was 66% at 2006 and now it is almost 100%). When forecasting, all such dynamic facts should be taken into account. One must not forget that such transmission line, plan and design at present, constructing in another two years and commissioning in another five years must  at least last for another three or four decade in operation.

Preparation for Planning

Generally an electrical study is carried out in planning stages for a proposed transmission line. The areas such as power flow study,system stability and dynamic performance,selection of voltage levels (generally, the standard voltage levels are used in Sri Lanka as a practice),voltage and reactive power flow control (mostly for transmission lines),insulation and over voltage design,conductor selection,loss calculation,and protection scheme design should be carefully analysed for reliable planning.

Financial viability

Even a sound electrical design might be rejected by final decision makers, if the project cost is not financially feasible. Financial and economic aspects play a vital role in any engineering development. and the designers should be able to justify the expenditure for the project against the expected benefits. Thus, a proposed design should be checked for both economical and financial feasibility using analytical tools such as Net Present Value (NPV), Internal Rate of Return (IRR) and Cost to Benefit Ratio (CBR) etc.
Finally, the optimum design is selected based on the economic and technical analysis. But the factors such as capacity and the prior experiences of the electricity utility and local constraints also govern the decision.

Transmission line design and construction 

My training diary is further filled with notes on transmission line designing and construction as well. I’m more than happy to share some insight from those areas in the upcoming articles.

Expressing my gratitude

I would be obliged to Mr. S. Bogahawatta, the project director of lighting Sri Lanka Hambantota project for his immeasurable support extended to my team during our internship in the project.

Terminology

HVDC -  High voltage direct current (HVDC) is a electric power transmission system uses direct current for the bulk transmission of electrical power.

Fuse saver - Fuse saver is a new class of intelligent, compact and low cost single phase circuit breaker that minimizes interruptions by protecting spur line fuses from blowing on transient faults

Article By: Ayantha Sampath

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Posted in: Power System

Adapting to the Sri Lankan load profile _ Importance in understanding load profile

Battle between drought and electricity demand

“Switch off a light and save for future”. This is not a strange slogan for Sri Lankans as it was regularly being broadcasted through various media channels within the last few months. In recent times, ceylon Electricity Board has been experiencing in a crucial crisis due to the inability to satisfy electricity demand in the country, which adversely impacted on the generation plan and financial estimations. Main reason for this was unexpected drought prevailed. Water levels of all the reservoirs were low and hydro generation was strictly scheduled for a limited time period.

Countries such as Sri Lanka have to inevitably face numerous problems under such weather condition, since generation from hydro sources contributes to a significant portion of total generation in the country. Hydro and other sources weigh 40% and 60% from total generation respectively in a period with average hydrological conditions. Hydro generation came down below 20% during this season and the deficit of electricity demand had to be purchased from independent power producers (IPPs) who generate power using diesel, incurring substantial amount of rupees during the peak time.

DSM as a solution

As an immediate solution to mitigate the problems arises, supply side had to be equipped with demand side management (DSM) tools. As a basic step, supply side tried to control the electricity demand by managing consumer behavior towards energy saving. This was the point where above mentioned slogan came into play through public media like Television, Radio, Newspapers, Social network…etc. All these urged to save electricity by avoiding unnecessary usage.  As night peak hours from 6.30 p.m. to 9.30 p.m. are more critical in this case, their attention was mainly focused on night peak hours. Though morning peak hours from 5.30 am to 6.30 am deliver less impact, as electricity consumers, our attention should be given to that period as well. This campaign was successful to a certain extent with the theme of “Janawiduli balagara”.

But the real situation is, consumers don’t have a proper understanding about these peak hours and the advantages of saving electricity during peak hours.  It might be an easy task to stimulate consumers towards positive attitudes in energy saving, if they have a clear view and understanding regarding the load profile of Sri Lanka.

Behavior of load profile

Load Profile is a chart in which electricity demand is plotted against the time, 24 hours of a day. The shape of this chart is almost same on all five weekdays. But it gets deviated slightly on weekends and holidays. Following graph represents the load profile of a normal weekday.

The above load profile extracted from the energy balance 2010, illustrates the variation of electricity demand for a day within year 2010 with an average hydrological condition. It is apparent that the Sri Lankan load profile is fluctuating significantly between numerous peaks and valleys. Two specific time slot of this graph could easily catch the eyes and those are well-known as the peak hours.

Peak hours are the time periods in which the electricity demand is significantly higher than the average demand level. As per the diagram illustrates, 5.30 a.m. to 6.30 a.m. period is identified as “Morning peak” and period from 6.30 p.m. to 9.30 p.m. is identified as “Night peak”. It is evident that demand is very low during the midnight and early in the morning. The time slot from 2.00 a.m. to 4.00 a.m. reports the lowest demand within a day which could be identified as the “Base load” of the system.

Next article of this series will bring you a comprehensive analysis of load profile, a discussion on the criticality of peak hours and the importance of providing a general understanding about them to the public in the way of effective utilization of electricity.

Terminology

IPP- Independent power producer is an entity which is granted with permission to generate electricity for sale to utilities and end users

Supply side- This includes all the bodies that are responsible for power generation, transmission and distribution

DSM-Demand side management is a method of encouraging the consumers to use energy efficiently and effectively.

Article By: Janaka Lakmewan

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Posted in: Utility and Social

Zero Energy Building Concept

Action towards energy saving

In this fast moving competitive world, “energy” plays a major role due to the limitation of availability and the cost of utilization. As people try to grab the maximum portion of energy available, no doubt that the globe will further suffer from this energy crisis. Before the problem goes worse, it’s better to take necessary and prompt actions to at least mitigate the energy crisis.

In most of the countries throughout the world, buildings are responsible for more than 40% of energy use. As it is very much important to reduce the energy usage and conserve energy, it’s better to pay attention towards the concept of zero energy building. Although zero energy building concept is not a novel idea, implementation of the concept in a practical environment is new to a country like Sri Lanka.

Zero energy building concepts

Zero energy building has been defined in many ways. But the gist is that the net energy consumption and carbon emission should be zero . In a simpler explanation, building produces sufficient energy to feed its energy need. Zero energy buildings can meet all their energy requirements from low cost, locally available, non polluting renewable energy sources. The two major sectors of energy consuming buildings are domestic and industrial. Thus,it’s essential to consider both types of buildings with respect to the zero energy building concept. 

Zero energy concept for industrial buildings 

As the phenomenon of global warming strikes alarms gradually, putting the blue planet in danger, measures are mandatory to dampen the negative effects of it.Commercial buildings have been identified as a major contributor in increasing global warming. Increasing energy efficiency and on site power generation in buildings can reduce the negative impact on the environment. It is worthwhile spending a fraction out of huge profits generated to make the building less energy intensive. 

Domestic approach

This concept is not a far fetched dream to houses. Though it is difficult to convert existing houses into this form, newly constructed houses can be planned well in advance to ameliorate energy efficiency. Necessary guidance may be needed by the architects to make their designs energy efficient, having zero energy houses as the ultimate goal.

A deeper look 

Realization of “Zero energy building” concept is a multi folded exercise and  main components comprise of  on-site energy generation, indoor lighting, sun control and shading devices,natural ventilation  and water conservation. Further, “ Zero energy building” concept presents numerous advantages to its users like reducing the cost of living, isolating the building from future energy price increases, improvements in reliability and the increment in the value of the building parallelly to the increase in energy costs.

Though the story sound fairy, implementation encounters many complexities. All of the above mentioned components and inherited benefits will be discussed extensively in the next couple of episodes of this article. 

Article By:

Tharangi Gunarathna

Muditha Karunathilake

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Posted in: Sustainable Energy and Policy