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A schematic representation of long distance electric power transmission. From left to right: G=generator, U=step-up transformer, V=voltage at beginning of transmission line, Pt=power entering transmission line, I=current in wires, R=total resistance in wires, Pw=power lost in transmission line, Pe=power reaching the end of the transmission line, D=step-down transformer, C=consumers.
A right-hand railroad switch with point indicator pointing to right Animated diagram of a right-hand railroad switch. Rail track A divides into two: track B (the straight track) and track C (the diverging track); note that the green line represents direction of travel only, the black lines represent fixed portions of track, and the red lines depict the moving components.
Diagram showing the use of trap points to protect the main line at the exit of a siding An insulated track circuit interrupter fitted to trap points. Trap points are found at the exit from a siding or where a secondary track joins a main line. A facing turnout is used to prevent any unauthorised movement that may otherwise obstruct the main ...
One voltage cycle of a three-phase system. A polyphase system (the term coined by Silvanus Thompson) is a means of distributing alternating-current (AC) electrical power that utilizes more than one AC phase, which refers to the phase offset value (in degrees) between AC in multiple conducting wires; phases may also refer to the corresponding terminals and conductors, as in color codes.
The solution principles outlined here also apply to phasor analysis of AC circuits. Two circuits are said to be equivalent with respect to a pair of terminals if the voltage across the terminals and current through the terminals for one network have the same relationship as the voltage and current at the terminals of the other network.
is the phase angle difference between the sending-end and receiving end voltages From the above equations, it can be seen that there are three variables that affect real and reactive power flow on a Transmission Line: [ 12 ] the voltage magnitudes at either bus, the line reactance between the buses, and the voltage phase-angle difference ...
For example, power semiconductors connected to the line voltage may be switched by opto-isolators driven from low-voltage circuits, which then need not be insulated from the higher line voltage. Transformers allow the output of a device to float relative to ground to avoid potential ground loops. Power isolation transformers increase the safety ...
In an alternating current (AC) electric power system, synchronization is the process of matching the frequency, phase and voltage of a generator or other source to an electrical grid in order to transfer power. If two unconnected segments of a grid are to be connected to each other, they cannot safely exchange AC power until they are synchronized.