In any system it is mandatory to work out schemes within the given framework of policies, guidelines and Acts, besides addressing the technical requirements and features that promise translation of the scheme into a bankable DPR for implementation.The mandatory pre-requisites are adherence to Electricity Act, 2003, CEA guidelines, Safety Rules, State Government Regulations, Environmental Laws and related policies and guidelines. These are quite exhaustive and the scheme developer is expected to have an overview of the same. Each project has to respond to some general requirements as well as site-specific needs. These requirements are listed below.
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| Distribution Reform Initiatives |
•Adequate power supply at normal voltage should be available from main grid substation (GSS) to meet the system demand. In case of outage of one transformer, the other transformer should be of sufficient capacity to meet the system requirement alone.
• Non-coincident peak demands at the individual 33/11 kV sub-station should be used in the load flow studies for assessing the adequacy and reinforcements required for sub-transmission lines. However, for systems below 33 kV, diversities should be taken into account.
• The voltage drop in 33 kV and 11 kV feeders should not exceed 5% at the farthest point under peak load conditions as well as normal operation regime.
• The power factor of the system should not be less than 0.95 at 11 kV level.
• Every 33/11 kV substation may preferably be provided at least two incoming feeders from two different sources for reliability.
• The loading of lines should be kept as per economic loading level of the particular conductor.
• The 11 kV feeders should not be long under normal condition. If possible, their length should not exceed 15 km.
• The preferred transformer capacity for primary substation (i.e., 66/11 kV or 33/11 kV) should be 5 MVA, 6.3 MVA, 8 MVA, 10 MVA, 16 MVA and 20 MVA for urban areas and 1, 1.6, 3.15, 5 MVA for rural areas.
• As a guideline, the conductors/cables indicated in Table 9.1 should be preferred.
• Non-coincident peak demands at the individual 33/11 kV sub-station should be used in the load flow studies for assessing the adequacy and reinforcements required for sub-transmission lines. However, for systems below 33 kV, diversities should be taken into account.
• The voltage drop in 33 kV and 11 kV feeders should not exceed 5% at the farthest point under peak load conditions as well as normal operation regime.
• The power factor of the system should not be less than 0.95 at 11 kV level.
• Every 33/11 kV substation may preferably be provided at least two incoming feeders from two different sources for reliability.
• The loading of lines should be kept as per economic loading level of the particular conductor.
• The 11 kV feeders should not be long under normal condition. If possible, their length should not exceed 15 km.
• The preferred transformer capacity for primary substation (i.e., 66/11 kV or 33/11 kV) should be 5 MVA, 6.3 MVA, 8 MVA, 10 MVA, 16 MVA and 20 MVA for urban areas and 1, 1.6, 3.15, 5 MVA for rural areas.
• As a guideline, the conductors/cables indicated in Table 9.1 should be preferred.
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| Types of Conductors for Different Voltage Ratings |
• Separate 33/11 kV feeders should be laid for major industrial consumers.
• Maximum Demand of up to 100 kVA should be supplied at low voltage.
• Maximum Demand between 100 kVA and 1500 kVA should be supplied at 11 kV.
• Maximum Demand of up to 100 kVA should be supplied at low voltage.
• Maximum Demand between 100 kVA and 1500 kVA should be supplied at 11 kV.
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| Maximum Fault Level |
• Maximum Demand between 1.5 MVA and 5 MVA should be supplied at 33 kV.
• Maximum Demand of more than 5 MVA should be supplied at 66 kV (or higher voltage).
• Maximum fault level is given Table .
•Economic loss levels should be kept low and the power loss levels required for this are given in Table .
• Maximum Demand of more than 5 MVA should be supplied at 66 kV (or higher voltage).
• Maximum fault level is given Table .
•Economic loss levels should be kept low and the power loss levels required for this are given in Table .
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| Power Loss Levels for Low Economic Loss Levels |
As far as the loss levels are concerned, you should assess
• the existing loss level situation, and
• the level of improvement that can be achieved on implementation of the scheme being developed.This is a major element that contributes to the bankability of DPR.
REMEMBER: To develop an electrical distribution system, it is equally important to take care of all components of the network such as the voltage, current, frequency, and the factors affecting the calculations to decide the rating and capacity of equipment kVA-km tool to calculate voltage regulation of transmission line, the power triangle to calculate the kVAR required to improve the power factor,the diversity factor to know the pattern of the connected load. Voltage regulation is taken as indicator of power supply quality as it is quantifiable, measurable and controllable by utility. (The Appendix to this unit contains the technical details.)
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