Service factor is the factor that, when applied to rated output, represents the allowable load that can be applied to motor continuously, under specified operating conditions. Note that this refers to continuous overload conditions, i.e., a power reserve that gives the motor a better capacity to withstand adverse operating conditions. Service factor should not be confused with momentary overload capacity during few minutes. A service factor = 1.0 means that the motor has not been designed for continuous operation above its rated output. However, this does not change its capacity to withstand instantaneous overloads. NBR 17094 specifies the most common Service Factors per motor output.
Breaker Schemes in Substations — Types, Design, Advantages, Disadvantages, and Comparison Author: Engr. Aneel Kumar Figure 1: Infographic overview of breaker schemes commonly used in substations. Introduction The breaker scheme or busbar arrangement in a substation defines how incoming feeders, outgoing feeders, and power transformers are connected to the bus. The choice of scheme has a direct impact on system reliability, maintainability, safety, and cost . A simple bus scheme is economical but vulnerable to outages, while advanced schemes such as breaker-and-a-half or double-bus/double-breaker provide very high reliability but at much higher cost and design complexity. Engineers select breaker schemes considering fault tolerance, maintenance needs, space requirements, expansion possibilities, protection coordination, and capital investment . Below, we explain eac...
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