Читать книгу Practical Power Plant Engineering - Zark Bedalov - Страница 40

Mechanical engineers have their “flow diagrams.” Electrical engineers have their single‐line diagrams showing the electrical power flows and plant overall integration. As the name implies, it is the principal electrical diagram or our big picture of the plant or specific part of the plant, whereby the three phases are represented in a simplified single‐line form. The diagrams show all the major transformers, loads, circuit breakers, and cables or line connections, including the ratings: kW (HP), MVA, V, A, AWG (mm²), leading to the major plant equipment. The key diagram includes references to the partial more detailed one‐line diagrams for the specific process areas. One medium size industrial plant may have 20 individual one‐line diagrams starting from the key one‐line diagram down to the individual MCC 480 V (400 V) diagrams.

Figure 2.1 Part of a plant one line diagram.

Decisions must be made on the main switchyard, the number of incoming transformers, and the selection of the plant busbar voltages for distribution of power to the major load centers for large and small loads and primary and secondary power lines to remote plant facilities.

 Note: The voltages and frequency applied in this book will be those of the North American standards. The principles of calculations and application used here are equally applicable to the IEC system voltages used in the other parts of the world.