Transmission and Distribution
Globally, the power plants classically produce 50 cycle/second (Hertz), alternating-current (AC) along with voltages among 11 kV and 33 kV. Electric power is brought from the power plant to the consumer by an extensive transmission and distribution (T&D) system comprising distribution networks, regional grids state and grids. The several stages of the process are given below:
1.) At the power plant site, the 3-phase voltage is produced and stepped up to a higher voltage for transmission on cables strung on cross- country towers.
2.) High voltage (HV) and extra high voltage (EHV) transmission is a next stage to transport A.C. power from the power plant over long distances at voltages such as 220 kV, 400 kV and 760 kV. To longer distances and higher powers, higher voltages are economical. In special cases HVDC (high voltage direct current transmission) is preferred.
3.) Sub-transmission network at 132 kV, 110 kV, 66 kV or 33 kV constitutes the further link towards the end user.
4.) Distribution at 11 kV/ 6.6 kV / 3.3 kV constitutes the last connect to the consumer, who is linked directly or through step-down transformers. These transformers bring a voltage levels down to 400V for 3-phase, 4 wire secondary distribution. The single phase residential lighting load is connected among any phase and neutral (230 V) and 3-phase load is connected across 3-phase lines directly.
The transmission and distribution network involves sub-stations, lines and distribution transformers. Sub-stations, holding step-down transformers, decrease the voltage for distribution to industrial, commercial and residential customers. These substations and distribution lines are referred to as the distribution system.
Transmission lines are commonly capable of transmitting large quantities of electrical energy over long distances. They operate at high voltages. Distribution lines hold limited quantities of power over shorter distances.
The State Electricity Boards (SEBs) or governments (by the state electricity departments) primarily own and operate the distribution networks and state grids. The Power Grid Corporation of all countries owns and operates most of the inter-regional transmission lines (creating a part of the national grid) in order to facilitate transfer of surplus power to a deficit region. The interconnected transmission system inside each region is also known as the Regional Grid. Each region or zone has its load control centre.
The establishment of a National Power Grid by the year 2012 is being planned along with an inter-regional power transfer capacity of about 37,150 MW. A perspective transmission plan has been evolved for strengthening the regional grids along with the objective of establishing a strong and vibrant National Grid to support the envisaged generating capacity addition of 1,00,000 MW . This move is expected to help in optimal development and utilization of coal and hydro resources. It is also aimed at improving the economy, reliability and quality of power supply. For example, the energy resources in global are unevenly distributed. That is, some regions do not have adequate natural resources for setting power plants to meet their future needs while others have abundant natural resources. The National Power Grid as an integrated entity could serve as an effective tool to accommodate energy requirement of various regions and transfer electricity from power surplus regions to power deficit regions.
A major portion of the distribution network is controlled through SEBs or their restructured entities and a extremely small section through private power utilities. As a part of this system, you are responsible for its efficient working. You will agree that a well-managed power distribution network holds the key to consumer satisfaction, a healthy economy and national prosperity.
We have so far presented a broad picture of the electricity sector. It is unfortunate that in spite of having abundant energy resources and a large pool of highly skilled human capital we are faced with many problems in all three components of the power supply system: transmission, generation and distribution. We list some of these in Table 1. You might like to add to the list.
Table 1: Problems in the Generation, Transmission and Distribution Segments of the Power Sector
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Generation
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Transmission
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Distribution
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Inadequate power generation capacity
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Inadequate inter-regional transmission
links
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Inadequate and ageing sub-transmission & distribution network leading to frequent power cuts and local failures/faults, erratic
voltage and low or high supply frequency.
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Lack of optimum utilization of the existing producing capacity
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Lack of grid discipline and poor grid management
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Large scale theft, skewed tariff structure, inefficient use of electricity by the end consumer.
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Distribution losses up to 50%.
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Transmission losses up to
17%
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Day to day problems of the consumers like hurdles in getting new connections or enhancement of loads, stiff procedures, unfriendly commercial policies, tardy metering, inflated billing and insufficient collection avenues, hostile staff, massive churning of the consumers, poor dispute resolution mechanisms.
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The end users of electricity such as farmers, households, commercial establishments and industries confront several problems like as often power cuts (both scheduled and unscheduled), faulty metering and inflated billing. Erratic voltage and low or high supply frequency have additionally added to the 'power woes' of the consumer. Instead, people in a large number of villages and small towns have limited or no access to electricity.
Have you asked yourself: Where does the problem lie? What areas need to be improved? How can we bring about a change for the better? We shall address these and other such questions in Sector.