IEEE Std 1250 pdf free download

IEEE Std 1250 pdf free download.Identifying and Improving Voltage Quality in Power Systems.
Interconnection of the generation, transmission, and distribution systems takes place in an electrical substation. Substations may include transformers that raise or lower the voltage depending on the need. A substation that has a step-up transformer increases the voltage while decreasing the current, whereas a step- down transformer decreases the voltage while increasing the current for distribution. Electric power may flow through several substations between generating plants and consumers, and it may be changed in voltage several times. The generation and transmission components are typically connected in an interconnected grid fashion. Within the_ “grid,” the transmission lines transport bulk power for long distances that typically cross multiple service territories and multiple utilities. Figure 2 shows a simple transmission system. referred to as a transmission network, illustrating how most of the substation buses have more than one source. In most circumstances, the loss of a single line or generator should not cause overloads within the remaining network. This offers a high degree of reliability because power can be maintained to most buses even with the loss of a line or source.
Distribution lines (commonly called primaries) are usually not interconnected but are designed in a radial fashion except in some cities that use a mesh distribution scheme. Radial distribution systems consist of a source originating at a substation in which the system voltage is stepped down (Figure 3). The distribution bus has breakers that feed lines (feeders) that carry the power to many customers in an area. There are usually line protective components (reclosers and fuses) downstream of the substation breaker on distribution lines. These components create situations in which only a portion of the distribution line may need to be de-energized to clear a fault (short circuit). thereby saving many customers on the line from experiencing interruptions unnecessarily.
Power system voltages are typically expressed in line-to-line kV. The line-to-line voltage is 1.732 times the line-to-neutral voltage on wye systems. Practically all generation and transmission is three phase. Distribution lines typically leave the substation as three phase and may proceed that way for several miles. But they may also have_ lateral tap_ lines that are only providing two phases or even a single phase, depending on the loads being served. Electrical services to customers may be from the transmission or the distribution system. Table 1 describes the various components and typical voltage ranges of the utility system.
A significant goal related to the operation of the utility power system is to provide reliable power with a minimum number of intrruptions. The utility systems are designed to isolate problem areas quickly and to interrupt as few customers as possible. The system protection schemes must quickly identify a faulted line section and then trip or open the proper isolating component to cause the fewest number of customers to experience the loss of power.
Each of these two basic categories has indices associated with it. Indices provide the foundation for characterizing the supply system voltage quality levels in a consistent manner. Indices can be used to establish baselines of performance as a_ function of system characteristics. The_ following subclauses describe indices that can be used to describe voltage quality levels in both of these major categories along with example benchmarking results that can provide the basis for establishing targets and limits.IEEE Std 1250  pdf download.