# Glossary of Terms - R Radial Feed - One primary bushing per phase. Radio-Influence Voltage (RIV) - A high frequency voltage, generated by all sources of ionization current, that appears at the terminals of electric power apparatus or on power circuits. Rating - The rating of an arrester - either duty cycle or MCOV rating. Ratio - A reference to either the turns ratio or the voltage ratio of a transformer. Reactance - A component of impedance produced by either inductance or capacitance in an ac circuit. Reactor - A device for introducing inductive reactance into a circuit for motor starting, operating transformers in parallel, and controlling current. Recovery Voltage - The voltage potential established across the open electrodes of an overcurrent protection device after clearing the circuit at a current zero; a term used to designate the voltage impressed by the circuit upon the interrupting device after interruption of the current at or about the time of a natural current zero. Reduced Capacity Tap - Tap that is not designed to deliver the rated capacity of the transformer. Reference Current (Iref) - The reference current is the peak value of the resistive component of a power frequency current high enough to make the effects of stray capacitance of the arrester negligible. This current level shall be specified by the manufacturer. Reference Voltage (Vref) - The lowest peak value independent of polarity of power frequency voltage, divided by the square root of 2, required to produce a resistive component of current equal to the reference current of the arrester or arrester element. The reference voltage of a multi-unit arrester is the sum of the reference voltages of the series units. The voltage level shall be specified by the manufacturer. Resistor - Any device of material that limits the flow of current when voltage is applied. Resonance - A state in which the capacitance and the inductance values in a circuit are equal (net reactance is equal to zero) and the only quantity left is resistance. Resonant Frequency - Frequency at which the voltage and the current at the input terminals are in phase. Reactance is equal to zero. RMS Line Current - The square root of the average of the squares of all the instantaneous current amplitudes occurring during one cycle. Routine Tests - Test made by the manufacturer on every device or representative samples, or on parts or materials, as required, to verify that the product meets the design specifications.

Glossary Index