Pos Description
1 Scheme earthing point
Note that it is of outmost importance to insure that only one earthing point
exist in such scheme.
2 One-phase plate with setting resistor and metrosil.
3 Necessary connection for the metrosil. Shown connections are applicable for both types of one-
phase plate.
4 Position of optional test switch for secondary injection into the high impedance differential IED.
5 Necessary connection for setting resistor. Shown connections are applicable for both types of
one-phase plate.
6 How to connect REFPDIF high impedance scheme to one CT input in IED.
7 Transformer input module where this current input is 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:
CTprim
=
1A
and
CTsec
=
1A
• For main CTs with 5A secondary rating the following setting values shall be entered:
CTprim
=
5A
and
CTsec
=
5A
• The parameter
CTStarPoint
shall always be left to the default value
ToObject
8 Connection made in the Signal Matrix, which connects this current input to first input channel
of the preprocessing function block (10). For high impedance differential protection
preprocessing function block in 3ms task shall be used.
9 Preprocessing block, which has a task to digitally filter the connected analogue inputs.
Preprocessing block output AI1 shall be connected to one instances of 1Ph high impedance
differential protection function HZPDIF (for example, instance 1 of HZPDIF in the configuration
tool).
5.4.2 Connecting to protective earth
Connect the protective earthing screw (pos 1 in figure 33) on the rear of the IED to
the closest possible earthing point in the cubicle. Electrical codes and standards
require that protective earth cables are green/yellow conductors with a cross
section area of at least 2.5 mm
2
(AWG14). The Power supply module (PSM),
Transformer input modules (TRM) and the enclosure are all separately earthed, see
figure
33 below.
The cubicle must be properly connected to the station earthing system. Use a
conductor with a core cross section area of at least 4 mm
2
(AWG 12).
1MRK 502 029-UEN A Section 5
Installing the IED
59
Installation and commissioning manual
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