CAPACITOR INRUSH/ OUTRUSH REACTORS BASIC AND TUTORIALS


CAPACITOR INRUSH/ OUTRUSH REACTORS BASIC INFORMATION
What Are Capacitor Inrush/ Outrush Reactors?

Capacitor switching can cause significant transients at both the switched capacitor and remote locations.

The most common transients are:
• Overvoltage on the switched capacitor during energization

• Voltage magnification at lower-voltage capacitors

• Transformer phase-to-phase overvoltages at line termination

• Inrush current from another capacitor during back-to-back switching

• Current outrush from a capacitor into a nearby fault

• Dynamic overvoltage when switching a capacitor and transformer simultaneously

Capacitor inrush/outrush reactors (Figure 2.9.15) are used to reduce the severity of some of the transients listed above in order to minimize dielectric stresses on breakers, capacitors, transformers, surge arresters, and associated station electrical equipment.

High-frequency-transient interference in nearby control and communication equipment is also reduced. Reactors are effective in reducing all transients associated with capacitor switching, since they limit the magnitude of the transient current (Equation 2.9.5), in kA, and significantly reduce the transient frequency (Equation 2.9.6), in Hz.


where
Ceq = equivalent capacitance of the circuit, F
Leq = equivalent inductance of the circuit, H
VLL = system line-to-line voltage, kV

Therefore, reflecting the information presented in the preceding discussion, IEEE Std. 1036-1992, Guide for Application of Shunt Power Capacitors, calls for the installation of reactors in series with each capacitor bank, especially when switching back-to-back capacitor banks.

Figure 2.9.16 shows a typical EHV shunt-capacitor installation utilizing reactors rated at 550 kV/1550 kV BIL, 600 A, and 3.0 mH


550-kV capacitor inrush/outrush reactors.

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