Patent ID: 8675327
Filing Date: 2014-03-18
Classification: H02H

Abstract:
1. An article of manufacture that includes a non-transitory computer readable medium useable by a processor, the medium having stored thereon a sequence of instructions which, when executed by the processor, causes the processor to provide impedance protection in transmission lines, wherein the impedance protection is provided by: interfacing, inputting, and digitizing voltages and currents associated with the transmission lines for a first distance zone; digitally filtering the digitized currents and voltages, with a pair of orthogonal filters, into derived pairs of orthogonal components; digitally extracting instantaneous operating signals and instantaneous polarizing signals from the derived pairs of orthogonal components; digitally comparing a first stage angular and magnitude relationship between the instantaneous operating and polarizing signals during a first half-cycle of a first power cycle in a fault event to determine if a fault is within the first distance zone; digitally comparing a second stage angular and polarization relationship between the instantaneous operating and polarizing signals during a second half-cycle of the first power cycle in the fault event to determine if the fault is within the first distance zone; digitally comparing a third stage angular and polarization relationship between the instantaneous operating and polarizing signals during a second power cycle, immediately subsequent to the first power cycle, in the fault event to determine if the fault is within the first distance zone; and outputting an impedance protection signal indicative of the first, second, and third stage comparison determinations, wherein at least one of the second and third stage comparisons respond to signal polarities defined by exceeding a finite non-zero threshold rather than a mathematical zero (0).