Abstract： BS IEC 60076-21:2011 pdf free download.Power transformers Part 21: Standard requirements, terminology,and test code for step-voltage regulators. current transformer: An instrument transfonner intended to have its primary winding connected i...

BS IEC 60076-21:2011 pdf free download.Power transformers Part 21: Standard requirements, terminology,and test code for

step-voltage regulators.

current transformer: An instrument transfonner intended to have its primary winding connected in series with the conductor carrying the current to be measured or controlled.

dielectric withstand oItagc tests: Tests made to determine the ability of insulating materials and spacings to withstand specified overvohages for a specified time without Ilashover or puncture.

NOTE —The purpose of the tests is to determine the adequacy against breakdown of insulating materials and spacings under normal or transient conditions.

excitation current: The current that flows in any winding used to excite the voltage regulator when all other windings are

open-circuitet It is usually expressed in percent of the rated current of the voltage regulator.

impedance drop: The phasor sum of the resistance voltage drop and the reactance voltage drop.

NOTE—For voltage regulators, the resistance drop. the reactance drop. and the impedance drop are, respectively, the sum of the

primary and secondary drops reduced to the same terrns They are determined from the load-loss measurements and are usually

expressed in per unit or percent of the rated voltage of the voltage regulator. Since they ditler at different operating positions of the voltage regulator, two values of impedance shall be considered, in practice. to be the tap positions that result in the

minimum and the maximum impedance. Neutral position has the minimum amount of impcdance.

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