ABB Relion RES670, Applications Manual

Page: 203 / 382

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 RCADir and ROADir settings will be as well applicable for
OC2 stage
• setting DirMode_OC2 shall be set to Reverse
• setting parameter StartCurr_OC2 shall be made more sensitive than pickup
value of forward 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
• start 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 start 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
M13088-5 v4
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:
2
op
NS
r
k
t
I
I
=
æ ö
ç ÷
è ø
EQUATION1372 V1 EN-US
(Equation 84)
where:
t
op
is the operating time in seconds of the negative sequence overcurrent IED
k is the generator capability constant in seconds
I
NS
is the measured negative sequence current
I
r
is the generator rated current
By defining parameter x equal to maximum continuous negative sequence rating of
the generator in accordance with the following formula
1MRK 511 407-UEN C
Section 11
Multipurpose protection
Phasor measurement unit RES670 2.2 IEC 197
Application manual