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Generation, Transmission, and Distribution
Published in Joseph E. Fleckenstein, Three-Phase Electrical Power, 2017
Transformers in a three-phase circuit can be interconnected in either a delta or a wye configuration. In that a transformer has both primary windings and secondary windings, there are four possible configurations. When reference is made to the arrangement of the primary windings and the secondary windings, the primary is always mentioned first. For example, a delta–wye transformer would have a delta-connected primary and a wye-connected secondary. The four possible configurations are (1) delta–wye, (2) delta–delta, (3) wye–wye, and (4) wye–delta. For a specific application, one of these configurations will generally be preferred over another possible configuration. Each configuration has specific characteristics and features.
D
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
DeMorgan's theorem indicates a rising slope of the input signal. A "0" indicates a falling slope of the input signal. The sampling rate is dependent on the derivative of the signal, since a rapidly changing signal would require a rapid sampling rate for acceptable performance. delta modulation control a pulse-time modulation method transplanted from the delta modulation in signal processing. The difference between the control reference and the switched signal is integrated and fed to a Schmitt trigger. When the integrated value reaches a predefined upper bound the switch is turned off. When the integrated value reaches a predefined lower bound the switch is turned on. delta rule a supervised learning algorithm, based upon gradient descent, that was developed for application to single-layer networks of linear threshold units. For each input pattern x, the weight wi j connecting input x j to unit i is adjusted according to Dwi j = h(ti - wi · x)x j, where wi is the vector of weights wi j, ti is the target output for unit i, and h is a positive constant. This rule is also known as the Widrow-Hoff rule and the LMS algorithm. delta-delta transformer a three-phase transformer connection formed by connecting three single-phase transformers in which the windings on both the primary and the secondary sides are connected in series to form a closed path. delta-wye transform a transformation between delta and wye connections. delta-wye transformer a three-phase transformer connection formed by connecting three single-phase transformers in which the primary windings are connected in series to form a closed path while one end of each of the secondary windings is connected to a common point (the neutral). demagnetization the act of removing a device from being in a magnetic state, i.e., rearranging the atomic magnetic domains in a disoriented fashion. demagnetizing field the magnetic field produced by divergences in the magnetization of a magnetic sample. demand assign multiple access protocol telephone signalling mechanism in which the access is established for the duration of a call. demand fetch in a cache memory, the name given to fetching a line from the memory into the cache on a cache miss when it is requested and not before. demand meter an electric meter which shows both the energy used and the peak power demand in a given period. demand paging condition where each page in virtual memory is loaded into main memory, after first being referenced by the processor (i.e., not in advanced). The first reference to each page will thus always cause a "page fault" (page not in main memory). After these initial page faults, most of the pages needed by the program are in main memory. demodulation the process by which a modulated signal is recovered back to its original form. It is the general process of extracting the information-bearing signal from another signal. Modulation is the general process of embedding an information-bearing signal into a second carrier signal. An important objective in modulation is to produce a signal whose frequency range is suitable for transmission over the communication channel to be used. See also modulation. DeMorgan's theorem a formula for finding the complement of a Boolean expression. It has two forms: (1) A B = A B (2) A B = A B
Fault Ride-Through Capability Improvement of Grid Connected PV System Using Dynamic Voltage Restorer
Published in Electric Power Components and Systems, 2020
Ahmed AbuHussein, Mohammad Ashraf Hossain Sadi
Figure 1 shows the single line diagram of the power system under study. The PV plant is connected through a DC/DC converter and a DC/AC inverter to the grid. The DC/DC converter is controlled by the incremental conductance MPPT technique and boosts the PV voltage to 500 V across the DC link. The DC/AC converter inverts the voltage from DC to AC and synchronizes it with the grid frequency (60 Hz). A 0.260 kV/25 kV delta-wye transformer is employed to step up the inverter’s voltage to the grid voltage. A double transmission line with two circuit breakers (CB) placed at the end of the lines. The fault is considered to occur at point F1.
An Upper Bound on Magnitude Error of Voltage Drop Phasors in Distribution Lines Due to Phase Transposition Assumption
Published in Electric Power Components and Systems, 2021
Henrique Pires Corrêa, Flávio Henrique Teles Vieira, Maria Leonor Silva de Almeida
To validate the obtained bound, a case study based on the IEEE 4-bus test feeder is considered. This three-phase distribution feeder was selected due to it being an adequate system for evaluating models of distribution system components [25]. The 4-bus system is available in several combinations of specified load and transformer wiring. Two of such configurations are considered in this work, namely those with balanced and unbalanced load being supplied by a step-down delta-wye transformer.