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When generators or motors are started via variable frequency drive (VFD), initial frequency is very low, on the order of few hertz, and can be low for a considerable amount of time or even permanently. It is not well recognized in the industry about the consequences of low frequency on current transformers (CTs) performance and how this affects the protection performance as well. First, CTs are designed...
This paper presents transmission level voltage unbalance as measured by two different methods across the Tennessee Valley Authority (TVA) Transmission system. It also discusses the recent focus on distribution voltage control. Two national standards mentioning voltage unbalance are discussed as well as TVA's operations and limitations on voltage balancing. An example of equipment malfunction creating...
This paper presents an open, multilevel condition monitoring system for induction motors (IMs). The current, voltage, speed and temperature values of the IM are measured with commercial, industrial equipment (power analyzer, temperature relay), and transmitted to a programmable logic controller (PLC) through a MODBUS industrial network. The PLC program, developed under the IEC-61131–3 standard, performs...
This paper discusses the fundamentals of motor protection principles. Every motor is designed for a specific operating temperature depending upon its insulation. Once this limit is exceeded its life decreases drastically. Over heating condition may arise due to several factors like supply system disturbance, electrical unbalance conditions, faults, load variation and environment. It is essential to...
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