ABB Relion REG670, Техническое руководство

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there will be a slightly variable underreach, on average in the same order as the
magnitude ratio between the harmonic and the fundamental component.
7.4.7.2 Distance measuring zones
The execution of the different fault loops within the IED are of full scheme type, which
means that earth fault loop for phase-to-earth faults and phase-to-phase faults for
forward and reverse faults are executed in parallel.
Figure 81 presents an outline of the different measuring loops for the six distance
zones.
IEC05000458-2-en.vsd
L1-N L2-N L3-N
L1-N L2-N L3-N
L1-N L2-N L3-N
L1-N L2-N L3-N
L1-L2 L2-L3 L3-L1
L1-L2 L2-L3 L3-L1
L1-L2 L2-L3 L3-L1
L1-L2 L2-L3 L3-L1
L1-N L2-N L3-N L1-L2 L2-L3 L3-L1
Zone 1
Zone 2
Zone 3
Zone 4
Zone 5
L1-N L2-N L3-N L1-L2 L2-L3 L3-L1
Zone RV
IEC05000458 V2 EN
Figure 94: The different measuring loops at phase-to-earth fault and phase-to-
phase fault
The use of full scheme technique gives faster operation time compared to switched
schemes which mostly uses a start element to select correct voltages and current
depending on fault type. Each distance protection zone performs like one independent
distance protection function with six measuring elements.
It is well-known that transients from CVTs may have a significant impact on the
transient overreach of a distance protection. At the same time these transients can be
very diverse in nature from one type to the other; in fact, more diverse than can be
distinguished by the algorithm itself in the course of a few milliseconds. So, a setting
is introduced in order to inform the algorithm about the type of CVT applied and thus
providing the advantage of knowing how performance should be optimized, even
during the first turbulent milliseconds of the fault period.
There are basically two types of CVTs from the function point of view, the passive and
the active type, which refers to the type of ferro-resonance suppression device that is
employed. The active type requires more rigorous filtering which will have a negative
impact on operate times. However, this will be evident primarily at higher source
impedance ratios (SIRs), SIR 5 and above, or close to the reach limit.
It is worth mentioning here that the IEC 60044-5 transient classification is of little or
no use in this connection. It is not primarily the damping of transients that is important;
Section 7
1MRK502052-UEN B
Impedance protection
238
Technical manual