EE 466: Power Systems Planning & Optimization

Technical Considerations in Power System Planning

• Technical considerations in power system planning involve both normal (steady-state) and abnormal (faulty) operating conditions.
• The considerations include modeling of network components, load flow analysis, voltage drop, system earthing, fault analysis, overvoltages, and overcurrents.

Modeling of Network Components

• Modeling is the mathematical representation of the components of the system.
• Equivalent circuits are used to represent various components, which are then combined to represent the interconnection of components in the actual electrical network.
• Network/circuit theories are used to analyze the system performance.

Load Flow Analysis

• Load flow studies provide information about the system under normal or steady-state conditions.
• Simulation or analytical tools like load flow analysis and contingency analysis are used to evaluate the capability of each alternative expansion plan for providing the desired level of performance.

Voltage Drop

• Voltage drop in cables and overhead lines is influenced by load current, load power factor, and dimensions (R and X) of the linking conductor.
• Accurate route lengths for cables and lines and the maximum continuous current the conductors will have to carry are essential information.
• Voltage drop can affect the conductor size chosen and may have a bearing on the starting characteristics of motor loads and the correct operation of electronic equipment.

Overvoltages

• Overvoltage is a condition when the peak value of the voltage applied to a device exceeds the limits defined in a standard or specification.
• There are three types of overvoltages: power-frequency overvoltage, switching overvoltage, and lightning overvoltage.
• Consequences of overvoltages include dielectric breakdown, degradation of equipment through aging, long interruptions, disturbances, and electrodynamic and thermal stress.
• Protective measures for overvoltages include lightning arresters, surge diverters, shielding, and rod gaps.

Overcurrents

• An overcurrent is either an overload or a short-circuit/fault current.
• Overload current is an excessive current that flows under normal conditions, but is confined to the normal conductive paths.
• Short-circuit current is one that flows outside the normal conductive paths, usually due to a fault or abnormal condition.
• Overloads can be transient or continuous, and may result from defective motors, overloaded equipment, or too many loads on one circuit.
• Short-circuit current can be many hundred times larger than the normal operating current.

Exercises

• Planning objectives include ensuring a good planning of an electrical power system.
• Technical considerations in the planning of a power transmission system include modeling of network components, load flow analysis, voltage drop, system earthing, and fault analysis.
• The three main categories of overvoltages are power-frequency overvoltage, switching overvoltage, and lightning overvoltage.
• Consequences of overvoltages that a planning engineer will seek to avoid include dielectric breakdown, degradation of equipment, long interruptions, disturbances, and electrodynamic and thermal stress.
• Protective measures for addressing overvoltages include lightning arresters, surge diverters, shielding, and rod gaps.