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OPERATING CHARACTERISTICS OF SHUNT REACTOR

1) LINEARITY:

For normal operating voltages there is a linear relationship between applied voltage and reactor current (i.e. a small increase in voltage will result in a proportional increase in current). Magnetic fluxes and flux densities are also proportional to the time integral of the applied voltage. With a voltage of sinusoidal shape the fluxes and flux densities are also proportional to the voltage. The deviation from a true sinusoidal shape in line voltage is in general negligible for normal operating voltages.

As the magnetic flux to a great extent has its path in magnetic core steel the core steel will get saturated for flux densities above a certain level, the saturation point. Below and up to the saturation point only a small current is needed to magnetize the core steel and the extra current needed to reach a marginal increase flux density is small. Once above the saturation point the extra current needed to further increase the flux density will be large.

2) HARMONIC CONTENT:

Steady state harmonics in reactor current arise from partial saturation in the magnetic circuit. These effects are in fact very small, and without practical importance for relaying and communication interference. Of all harmonics the third harmonic will be dominant. In the reactor neutral the third harmonics in the three phases add together and act like a zero sequence current.

3) ASYMMETRY BETWEEN PHASES:

The tolerances on asymmetry between phases of a three-phase reactor or between single-phase units forming a three-phase bank can be judged by the amount of residual harmonics. The result is a zero sequence current in the neutral connection. Standards are realistic, but better tolerances are possible to achieve. A usual figure is 0.5 %.

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