ABB Relion 670 Series Applications Manual page 252

Section 11
Multipurpose protection
If required, this CVGAPC function can be used in directional comparison protection scheme for the
power line protection if communication channels to the remote end of this power line are
available. In that case typically two
one for reverse direction. As explained before the OC1 stage can be used to detect faults in
forward direction. The built-in OC2 stage can be used to detect faults in reverse direction.
However the following shall be noted for such application:
• the set values for
• setting
• setting parameter
OC1 element (that is, typically 60% of OC1 set pickup level) in order to insure proper operation
of the directional comparison scheme during current reversal situations
• pickup signals from OC1 and OC2 elements shall be used to send forward and reverse signals
to the remote end of the power line
• the available scheme communications function block within IED shall be used between
multipurpose protection function and the communication equipment in order to insure
proper conditioning of the above two pickup signals
Furthermore the other built-in UC, OV and UV protection elements can be used for other
protection and alarming purposes.
11.1.3.2 Negative sequence overcurrent protection
Example will be given how to use one CVGAPC function to provide negative sequence inverse time
overcurrent protection for a generator with capability constant of 20s, and maximum continuous
negative sequence rating of 7% of the generator rated current.
The capability curve for a generator negative sequence overcurrent protection, often used world-
wide, is defined by the ANSI standard in accordance with the following formula:
=
t
op
æ
I
ç
è
EQUATION1740-ANSI V1 EN-US
where:
t
op
TD
I
NS
I
r
By defining parameter x equal to maximum continuous negative sequence rating of the generator
in accordance with the following formula
=
x 7%
EQUATION1756-ANSI V1 EN-US
246
RCADir and ROADir settings will be as well applicable for OC2 stage
DirMode_OC2 shall be set to Reverse
PickupCurr_OC2 shall be made more sensitive than pickup value of forward
TD
2
ö
NS
÷
I ø
r
is the operating time in seconds of the negative sequence overcurrent IED
is the generator capability constant in seconds
is the measured negative sequence current
is the generator rated current
=
0.07 pu
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NegSeq overcurrent steps are required. One for forward and
1MRK 511 401-UUS F
M13088-5 v4
(Equation 101)
(Equation 102)
Bay control REC670
Application manual