Connections For 1Ph High Impedance Differential Protection Hzpdif (87) - ABB RELION RET670 Applications Manual

1MRK 504 163-UUS A
7.2.3.2
Transformer protection RET670 2.2 ANSI
Application manual
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.

Connections for 1Ph High impedance differential protection HZPDIF (87)

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 57.
Section 7
Differential protection
GUID-D68A237F-610C-4AF0-870F-273117F64D92 v10
165