October 2013

A DC uninterruptible power supply is basically a battery bank and a charger. However, it differs from a simple battery and charger system that may be associated with starting diesel engines, or similar rugged functions, because the output voltage must be maintained within a close tolerance of the nominal DC voltage. DC uninterruptible power supplies […]

Static inverters are used to convert DC voltage into AC voltage. The simplest forms of inverters produce an output waveform that is rectangular, as a result of the simple switching, rectangular waveform can be used to feed some types of AC equipment e.g. incandescent lamps, domestic equipment such as kitchen mixers and kettles. Equipment that

DC motors consist of one set of coils, called armature winding, inside another set of coils or a set of permanent magnets, called the stator. Applying a voltage to the coils produces a torque in the armature, resulting in motion. Stator The stator is the stationary outside part of a motor. The stator of a

A number of auxiliary systems and related controls are provided throughout the hydroelectric plant to support the operation of the generating units. These include the following: 1. Switchyard systems. 2. Alternating current (AC) station service. Depending on the size and criticality of the plant, multiple sources are often supplied, with emergency backup provided by a

The turbine-generator unit and related equipment are protected against mechanical, electrical, hydraulic, and thermal damage that may occur as a result of abnormal conditions within the plant or on the power system to which the plant is connected. Abnormal conditions are detected automatically by means of protective relays and other devices and measures are taken

A general hierarchy of control is illustrated in Table 5.1. Manual controls, normally installed adjacent to the device being controlled, are used during testing and maintenance, and as a backup to the automatic control systems. Figure 5.5 illustrates the relationship of control locations and typical functions available at each location. Automatic sequences implemented for starting,

The excitation system fulfills two main functions: 1. It produces DC voltage (and power) to force current to flow in the field windings of the generator. There is a direct relationship between the generator terminal voltage and the quantity of current flowing in the field windings. 2. It provides a means for regulating the terminal

The governor system is the key element of the unit speed and power control system. It consists of control and actuating equipment for regulating the flow of water through the turbine, for starting and stopping the unit, and for regulating the speed and power output of the turbine generator. The governor system includes set point

The generator circuit breaker and associated isolating disconnect switches are used to connect and disconnect the generator to and from the power system. The generator circuit breaker may be located on either the low-voltage or high-voltage side of the generator step-up transformer. In some cases, the generator is connected to the system by means of

The generator output is connected to terminal equipment via cable, bus bar, or isolated phase bus. The terminal equipment comprises current transformers (CTs), voltage transformers (VTs), and surge suppression devices. The CTs and VTs are used for unit protection, metering and synchronizing, and for governor and excitation system functions. The surge protection devices, consisting of