Pos Description
1 Scheme grounding point
It is important to insure that only one grounding point exist in this scheme.
2 Three-phase plate with setting resistors and metrosils. Protective ground is a separate 4 mm screw
terminal on the plate.
3 Necessary connection for three-phase metrosil set.
4 Position of optional test switch for secondary injection into the high impedance differential IED.
5 Necessary connection for setting resistors.
6 Factory-made star point on a three-phase setting resistor set.
The star point connector must be removed for installations with 670 series
IEDs. This star point is required for RADHA schemes only.
7 Connections of three individual phase currents for high impedance scheme to three CT inputs in
the IED.
7.1.3.2 Connections for 1Ph High impedance differential protection HZPDIF (87)
GUID-D68A237F-610C-4AF0-870F-273117F64D92 v10
Restricted earth fault protection is a typical application for 1Ph High impedance
differential protection HZPDIF
(87). Typical CT connections for the high impedance
based protection scheme are shown in figure
51.
Section 7 1MRK 511 401-UUS A
Differential protection
136 Bay control REC670 2.2 ANSI
Application manual
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