ABB 615 series Technical Manual page 549

1MAC059074-MB A
615 series ANSI
Technical Manual
the star-connected winding of the transformer. 87LOZREF is normally applied when the
transformer is grounded solidly or through low-impedance resistor (NER). 87LOZREF
can be also applied on the delta side of the transformer if a grounding transformer (zig-zag
transformer) is used there. In 87LOZREF, the difference of the fundamental component
of all three phase currents and the neutral current is provided to the differential element to
detect the ground fault in the transformer winding based on the numerical stabilized
differential current principle.
Connection of current transformers
The connections of the primary current transformers are designated as "Type 1" and "Type
2".
• If the positive directions of the winding 1 and winding 2 protection relay currents are
opposite, the CT connection type setting parameter is "Type 1". The connection
examples of "Type 1" are as shown in figures and .
• If the positive directions of the winding 1 and winding 2 protection relay currents
equate, the CT connection type setting parameter is "Type 2". The connection
examples of "Type 2" are as shown in figures and .
• The default value of the CT connection type setting is "Type 1".
• If the positive directions of the winding 1 and winding 2 protection relay currents are
opposite, the CT connection type setting parameter is "Type 1". The connection
examples of "Type 1" are as shown in figures
• If the positive directions of the winding 1 and winding 2 protection relay currents
equate, the CT connection type setting parameter is "Type 2". The connection
examples of "Type 2" are as shown in figures
• The default value of the CT connection type setting is "Type 1".
In case the groundings of the current transformers on the phase side and the neutral side
are both either inside or outside the area to be protected, the setting parameter CT
connection type is "Type 1".
If the grounding of the current transformers on the phase side is inside the area to be
protected and the neutral side is outside the area to be protected or if the grounding on the
phase side is outside the area and on the neutral side inside the area, the setting parameter
CT connection type is "Type 2".
Section 4
Protection functions
270 and 271.
272 and 273.
543