ABB RELION RET670, Applications Manual

Page: 294 / 1016

Calculate the step-up transformer impedance, in primary ohms, from the 13kV side as
follows:
2
2
10 13
0, 26
100 100 65
t r
T
x U
X
S
= × = × = W
IEC-EQUATION2318 V1 EN-US
Then the reach in primary ohms shall be set to 100% of transformer impedance. Thus
the reach shall be set to 0,26Ω primary.
Set the first zone of Full-scheme distance measuring, Mho characteristic ZMHPDIS
(21) to disable phase-to-ground loops and enable phase-to-phase loops:
• The parameter GlobalBaseSel shall be set in order to select the global base value
group GBASVAL where the base voltage UBaseVBase and the base current IBase
are defined; UBaseVBase is the generator rated phase-phase voltage
( VBase =13,2kV) and IBase is the generator rated phase current ( IBase =3062A).
• Parameter DirMode shall be set to Offset.
• Parameter OffsetMhoDir shall be set to Non-directional.
• The phase-to-ground measuring loops shall be disabled by setting
OpModePG = Disabled
• The phase-to-phase measuring loops shall be enabled and corresponding settings
in primary ohms for forward and reserve reach and time delay shall be entered
accordingly:
•
Parameter ZPP shall be set to 0,260Ω.
• Parameter ZrevPP shall be set to 0,260Ω.
• Parameter tPP shall be set to 1,0000s.
• Parameter ZAngPP shall be set to default value 85 Deg .
Set the following for the directional element ZDMRDIR:
• The parameter GlobalBaseSel shall be set in order to select the global base value
group GBASVAL where the base voltage UBaseVBase and the base current IBase
are defined; UBaseVBase is the generator rated phase-phase voltage
( VBase =13,2kV) and IBase is the generator rated phase current ( IBase =3062A).
• Parameter DirEvalType shall be set to Imp/Comp .
• Other settings can be left on the default values.
By doing this offset mho characteristic for zone one will be achieved as shown in
figure
136 . Note that for this particular example ZPP = ZRevPP = 0,26Ω . Thus the
operating characteristic for this particular application will be a circle with a centre in
the impedance plane origo.
By following the same procedure other mho zones can be set.
Section 8
1MRK 504 163-UUS A
Impedance protection
288 Transformer protection RET670 2.2 ANSI
Application manual