Hitachi Relion 670 Series Product Manual page 38

Line differential protection RED670
Version 2.2
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Operation area Operation area
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Figure 13. Load encroachment influence on the offset mho
characteristic
The distance protection zones can operate, independent of
each other, in directional (forward or reverse) or non-
directional mode (offset). This makes them suitable,
together with different communication schemes, for the
protection of power lines and cables in complex network
configurations, such as parallel lines, multi-terminal lines
and so on.
The possibility to use the phase-to-earth quadrilateral
impedance characteristic together with the mho
characteristic increases the possibility to overcome eventual
lack of sensitivity of the mho element due to the shaping of
the curve at remote end faults.
The integrated control and monitoring functions offer
effective solutions for operating and monitoring all types of
transmission and sub-transmission lines.
Full-scheme distance protection, quadrilateral for
earth faults ZMMPDIS, ZMMAPDIS
The line distance protection is an up to five (depending on
product variant) zone full scheme protection function with
three fault loops for phase-to-earth fault for each of the
independent zones. Individual settings for each zone
resistive and reactive reach give flexibility for use on
overhead lines and cables of different types and lengths.
The Full-scheme distance protection, quadrilateral for earth
fault functions have functionality for load encroachment,
which increases the possibility to detect high resistive faults
on heavily loaded lines , see Figure 14.
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Figure 14. Typical quadrilateral distance protection zone with Phase
selection, quadrilateral characteristic with settable angle
function FRPSPDIS activated
The independent measurement of impedance for each fault
loop together with a sensitive and reliable built in phase
selection makes the function suitable in applications with
single phase auto-reclosing.
The distance protection zones can operate, independent of
each other, in directional (forward or reverse) or non-
directional mode. This makes them suitable, together with
different communication schemes, for the protection of
power lines and cables in complex network configurations,
such as parallel lines, multi-terminal lines.
Directional impedance element for Mho characteristic
ZDMRDIR
The phase-to-earth impedance elements can be optionally
supervised by a phase unselective directional function
(phase unselective, because it is based on symmetrical
components).
Mho impedance supervision logic ZSMGAPC
The Mho impedance supervision logic (ZSMGAPC) includes
features for fault inception detection and high SIR detection.
It also includes the functionality for loss of potential logic as
well as for the pilot channel blocking scheme.
ZSMGAPC can mainly be decomposed in two different
parts:
1. A fault inception detection logic
2. High SIR detection logic
Faulty phase identification with load encroachment
FMPSPDIS
The ability to accurately and reliably classify different types
of fault so that single phase tripping and autoreclosing can
be used plays an important roll in today's power systems.
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