An alternate means of transmitting electricity is to use high-voltage direct current (HVDC) technology. As the name implies, HVDC uses direct current to transmit power. Direct current facilities are connected to HVAC systems by means of rectifiers, which convert alternating current to direct current, and inverters, which convert direct current to alternating current. Early applications […]
There are a number of designs used for substations. However, there are elements common to all: >> A BUS: is the physical structure to which all lines and transformers are connected. Buses are of two generic types: open air and enclosed. Enclosed buses are used when substations are located in buildings or outdoors where space
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Substations are locations where transmission lines, transformers, and generators are connected. They fulfill a number of functions: Allow power from different generating stations to be fed into the main transmission corridors. Provide a terminus for interconnections with other systems. Provide a location where transformers can be connected to feed power into the sub transmission or
The primary components of an overhead transmission line are: Conductors Ground or shield wires Insulators Support structures Land or right-of-way (R-O-W) 1) CONDUCTORS: are the wires through which the electricity passes. Transmission wires are usually of the aluminum conductor steel reinforced (ACSR) type, made of stranded aluminum woven around a core of stranded steel that
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Disturbances may also change the voltage at the generator’s terminals. In response, the generator’s automatic voltage regulating system will sense the change and adjust the generator’s field excitation, either up or down, to compensate. Transient stability or instability considers that period immediately after a disturbance, usually before the generator’s governor and other control systems have
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YAW CONTROL The yaw control continuously orients the rotor in the direction of the wind. It can be as simple as the tail vane, or more complex on modern towers. Theoretical considerations dictate free yaw as much as possible. However, rotating blades with large moments of inertia produce high gyroscopic torque during yaw, often resulting
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Transformers are susceptible to damage by secondary short-circuit currents having magnitudes that can be many times rated load current. The damage results from the following effects: >> The I2R losses in the winding conductors are increased by the square of the current. This increases the temperature rise of the windings. >> Because protective devices limit the duration of
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The design of new substations has the advantage of starting with a blank sheet of paper. The new substation will typically have many IEDs for different functions, and the majority of operational data for the SCADA system will come from these IEDs. The IEDs will be integrated with digital two-way communications. The small amount of
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The following additional design trade-offs are available to the system engineer: NUMBER OF BLADES This is the first determination the design engineer must make. Wind machines have been built with the number of blades ranging from 2 to 40 or more. The high number of blades was used in old low, tip-speed ratio rotors for
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The wind power system is comprised of one or more units, operating electrically in parallel, having the following components: The tower. The wind turbine with two or three blades. The yaw mechanism such as the tail vane. The mechanical gear. The electrical generator. The speed sensors and control. The modern system often has the following
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