Ampacity

Abstract: Photovoltaic generating units connected to distribution systems represent a type of distributed generation (DG) that has been experiencing increased growth in recent years. Higher DG penetration levels may be interesting from many different points of view, but raise important issues about distribution system operation. Therefore, new techniques are needed to determine the maximum amount of DG that may be installed without requiring major changes in the existing electric power system. According to the literature, voltage rises at load bus bars are a serious limiting factor when installing DG. This paper presents and discusses studies proving that conductor ampacity and voltage rises are limiting factors that manifest themselves under different conditions. The present study highlights situations in which line overloads are more restrictive than voltage rises. Variation in substation voltage, load, and its power factor were simulated in a simplified radial distribution system model, and the amount of distributed generation that may be installed was obtained. Mathematic formulae were developed to determine the amount of distributed generation for existing utility systems.

Abstract: Real-time power line rating may be provided. First, sensor data may be received corresponding to a conductor of a power line. The sensor data may provide real-time weather conditions for the conductor's environment. The sensor data may be received from a sensor device configured to collect the sensor data. The sensor data may correspond to the weather conditions at a location of the sensor device on the power line. Next, design limitations for the power line having the conductor may be received. The conductor of the power line may have a design ampacity based upon the design limitations and assumed weather conditions for the conductor's environment. Then a dynamic ampacity may be calculated for the power line based upon the received sensor data and the received design limitations for the power line. The power line may then be operated according to the calculated dynamic ampacity instead of the design ampacity.

Abstract: For the first time a Real Time Thermal Rating System has been developed for overhead transmission lines using actual meteorological data and real-time conductor temperatures and line loadings. This System provides, on a probability basis, much higher ampacity ratings than those derived from conventional methods. As a portion of this System, a steady state thermal rating procedure is presented in the companion paper, which includes forced convection heat transfer equations taking into account the effect of wind turbulence or gustiness, conductor yaw (wind direction), conductor height above ground, smooth versus rough (stranded) conductor surfaces, the proximity of conductors in a bundle, and conductor pitch. A natural convective heat equation is developed for stranded conductors. The conductor temperature is solved directly without resorting to an iterative solution.

Abstract: A new type of overhead conductor with a polymer composite core is evaluated in terms of the mechanical properties and operating characteristics. The conductor is composed of trapezoidal O'-tempered aluminum wires helically wound around a hybrid glass/carbon composite core produced by pultrusion. The conductor is intended for electrical power transmission, and is designated ACCC/TW, for aluminum conductor composite core/trapezoidal wire. Measurements of core properties and conductor sag at high temperatures were compared to conventional ACSR (aluminum conductor, steel-reinforced) of the same diameter. The tensile strength of the ACCC/TW was /spl sim/1.5 times greater than conventional ACSR of the same outer diameter. The CTE of the composite core was approximately 4 times lower than the steel core in ACSR. The ACCC/TW conductor exhibited a six-fold reduction in high-temperature sag compared with conventional ACSR (Drake) when operated at the same current. The ACCC/TW conductor also exhibited greater ampacity than ACSR conductor at all operating temperatures.