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  • Topic: Electricity distribution, Electric power transmission, Electrical substation
  • Pages : 30 (7776 words )
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  • Published : February 12, 2013
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2.

OVERVIEW OF CON EDISON SYSTEM AND LIC NETWORK 2.1. Electrical System Overview 2.1.1. Power Delivery System

Con Edison delivers electricity to 3.2 million customers in New York City and Westchester County – a service territory of 660 square miles with a population of approximately 9 million people. Electricity is delivered through approximately 94,000 miles of underground cable and almost 37,000 miles of overhead cable. As shown in Figure 2-1, the Con Edison electric power delivery system is comprised of three distinct sub-systems: generation, transmission, and distribution.

School

Connection to Other Systems/Utilities Generating Station

Apartment House

Transmission Substation

265 / 460 Volt Network Transformers
Commercial

120 / 208 Volt Network

Distribution Feeders

Hospital

Financial

Area Substation
Overhead Transformer

Network Customers

Residential and light commercial customers 4kV Unit Substation

Figure 2-1: The Power Delivery System

2-1

Central power plants1 generate electricity that is transmitted over high-voltage transmission lines (69,000, 138,000, and 345,000 volts) that have the capability of delivering electricity over long distances.2 These transmission lines supply the distribution substations – known as area substations – where the voltage is reduced to primary distribution levels of 27 kV for Brooklyn and Queens, 33 kV and 13 kV for Staten Island, and 13 kV for Manhattan, the Bronx, and Westchester County. From the area substations, high-voltage primary feeders distribute the power and feed a secondary system of low-voltage cables. In Figure 2-1, two different types of distribution systems (network and overhead) are shown. One type of secondary system is the underground network system in which each feeder supplies transformers located throughout local streets. These network transformers reduce the primary distribution voltage to a level used by customers. The network transformers supply a network grid of low-voltage (120-volt) cables located underground. There are 46 area substations in New York City. These area substations serve 57 networks in New York City with 1,070 primary feeders. A network may have from 8 to 28 primary high-voltage feeders connecting the area substation to the network. Both primary feeders and secondary cables run through underground electrical structures (such as manholes and service boxes) that are interconnected by an extensive conduit system. The Con Edison system has approximately 274,000 underground structures.

Since the restructuring of the industry in the late 1990s, Con Edison has sold most of its large electric generating plants. 2

1

The New York Independent System Operator (NYISO) administers the delivery of power through the bulk power transmission system from generating plants to the distribution systems of the state’s electric utility companies.

2-2

Approximately 86% of the electricity delivered by Con Edison is carried by the underground network distribution system. The remaining 14% consists of non-network distribution systems, which include radial and primary auto-loop systems, underground residential distribution (URD) systems, and 4 kV supply. The network system (which includes approximately 80,000 miles of underground cable in New York City) provides superior reliability when compared to the overhead non-network system because there are multiple and alternative paths for the electricity to flow through and reach customers and it is largely located underground where it is shielded from the effects of wind, trees, ice, lightning, and damage from vehicles. In addition, each network is designed to operate independently of every other network. As a result of this design, a problem in one network cannot affect customers in another network. 2.1.2. Primary Feeders Figure 2-2 is a simplified diagram of the primary feeders in a network.

Figure 2-2: Illustration of Con Edison’s Primary Feeder System...
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