IEEE Std C57.153 pdf free download
IEEE Std C57.153 pdf free download.Paralleling Regulating Transformers.
3. Definitions, acronyms, and abbreviations
3.1 Definitions
For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary Online3 and IEEE Std C57. I 2.8OTM should be consulted for terms not defined in this clause.
apparent circulating current: An expression of the difference in currents between paralleled regulating transformers due to a transformer turns ratio discrepancy, transformer impedance, or other external factors. See also circulating current: system-induced circulating current: tap position—induced circulating current.
circulating current: An expression of the dit1i.rence in currents between paralleled regulating transformers. See also apparent circulating current; system-induced circulating current: tap position— induced circulating current.
general paralleling application (CPA): Two or more paralleled regulating transformers connected to a common source bus, with matching impedances, load tap changers with equal tap step sizes, and ranges.
hunting condition: A system condition in which no combination of paralleled regulating transformers with either load tap changer or step-voltage regulator tap positions can satisfy the control requirements resulting in erratic voltage regulation.
iiia(ched impedances: A system condition where the impedances of paralleled regulating transformers at each transformer’s highest MVA rating are equal.
off-tap operation: An operating condition in which a paralleled regulating transformer’s tap position is not in the position to yield the lowest difference in load currents between the paralleled regulating transformers relative to their MVA ratings.
operational transformer impedance variation: An operating condition of paralleled regulating transformers such that simultaneous increasing or decreasing tap positions creates non-similar impedance changes.
regulating transformer: For the purposes of this guide, a transformer equipped with a voltage-regulating device, which may be either a load tap changer or an external step-voltage regulator.
runback: An algorithm that overrides the primary voltage-control algorithm to restore the terminal voltage within a defined range. A runback level is a voltage level that triggers the runback algorithm. separate source buses: A system condition in which paralleled regulating transformers do not have a common source bus. system-induced circulating current: An expression of the difference in currents between paralleled regulating transformers caused by system or equipment variations. See also apparent circulating current. tap position-induced circulating current: An expression of the difference in currents between paralleled regulating transformers caused by the disparity of turns ratio of the transformers, most commonly due to different tap positions of the transformer load tap changers or step-voltage regulators. See also apparent circulating current.Figure 3 shows a typical distribution substation with generation. In this application, there may be only one or several regulating transformers in parallel with one or more generation systems. The generation acts as an alternate source of power to the load and/or to the system. As such, it can have a large effect on the voltage of the distribution bus. If there is no active voltage control on the bus from the generator, as is most common in an induction generator application, the generator appears as a varying load to the system. In this case, the LTC is not considered to be in a paralleling application. However, if a generator voltage bus control is present, the LTC must be considered in parallel for most advantageous operation of both the generation and the system power flows.IEEE Std C57.153 pdf download.
