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# Note for ELECTRICAL DISTRIBUTION SYSTEM - EDS by Nikhil K

• ELECTRICAL DISTRIBUTION SYSTEM - EDS
• Note
• Jntu anantapur - Jntua
• Electrical and Electronics Engineering
• B.Tech
• 325 Views
Nikhil K
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#### Text from page-2

fault N.O. As indicated previously, the standard primary distribution voltage levels include 4.16kV, 7.2kV, 12.47kV, 13.2kV, 14.4kV, 23.9kV, and 34.5kV. However, equipment is specified in terms of voltage class. Equipment of one voltage class may be utilized in at any operating voltage assigned to that class. For example, an insulator of voltage class 15 kV may utilized in a 12.47kV, 13.2kV, and 13.8kV system. There are four major distribution-level voltage classes: 5kV, 15kV, 25kV, and 35kV. The 15kV voltage class is the most prevalent. 1.2.2Secondary Distribution:Branching from the main feeder are laterals, also referred to in the industry as taps or branches. The laterals may be three-phase, two-phase (two phases of the three-phase feeder with a neutral), or single-phase (one phase from the single phase feeder and a neutral). The laterals are usually protected with fuses so that faulted laterals do not cause interruption at the feeder level. • • • Standard secondary voltage levels are 120/240 single phase 120/208 3 phase 277/480 3 phase The 120/240 configuration is obtained from the low-side of a HV/240 volt transformer, where HV is the rated voltage on the high voltage side, and the 240 is the rated voltage on the low voltage side. Then a center tap is connected to the low voltage winding and grounded along with the low side of the primary winding. This provides three wires on the low voltage side. One is +120V, one is -120V, and one (the center tap) is 0. Thus, two are “hot,” one is ground (neutral). The 240V connection is obtained by connecting across the two hot wires. The 120V connection is obtained by connecting from either hot wire to the neutral wire. 1.3.ELEMENTS OF A DISTRIBUTION SYSTEM:In general, the distribution system is the electrical system between the sub-station fed by the distrubution system and the consumers meters. It generally consists of feeders, distributors and theservice mains. (i) Feeders. A feeder is a conductor which connects the sub-station (orlocalised generating station) to the area where power is to be distributed. Generally, no tappings are taken from the feeder so that current in it remains the same throughout. The main consideration in the design of a feeder is the current carrying capacity.