ABB RET670 Applications Manual page 148

Section 3
IED application
142
Pos Description
1 Scheme grounding point
Note that it is of outmost importance to insure that only one grounding point
exist in such scheme.
2 Three-phase plate with setting resistors and metrosils.
3 Necessary connection for three-phase metrosil set. Shown connections are applicable for both
types of three-phase plate.
4 Position of optional test switch for secondary injection into the high impedance differential IED.
5 Necessary connection for setting resistors. Shown connections are applicable for both types of three-
phase plate.
6 The factory made star point on a three-phase setting resistor set.
Shall be removed for installations with 650 and 670 series IEDs. This star point
is required for RADHA schemes only.
7 How to connect three individual phase currents for high impedance scheme to three CT inputs in
the IED.
8 Transformer input module, where the current inputs are located.
Note that the CT ratio for high impedance differential protection application
must be set as one.
• For main CTs with 1A secondary rating the following setting values shall be entered:
= 1A and CTsec = 1A
• For main CTs with 5A secondary rating the following setting values shall be entered:
5A and CTsec = 5A
=
• The parameter
9 Three connections made in the Signal Matrix, which connect these three current inputs to the first
three input channels of the preprocessing function block (10). For high impedance differential
protection preprocessing function block in 3ms task shall be used.
10 Preprocessing block, to digitally filter the connected analogue inputs. Preprocessing block outputs
AI1, AI2 and AI3 shall be connected to three instances of 1Ph high impedance differential
protection HZPDIF (87) function blocks, for example instance 1, 2 and 3 of HZPDIF (87) in the
configuration tool.
Connections for 1Ph High impedance differential protection HZPDIF (87)
Restricted earth fault protection REFPDIF (87N) is a typical application for 1Ph High
impedance differential protection HZPDIF (87). Typical CT connections for high
impedance based REFPDIF (87N) protection scheme are shown in figure 39.
CTStarPoint shall be always left to the default value ToObject .
1MRK504116-UUS C
CTprim
CTprim
Application manual