Setting Guidelines - ABB RELION 670 SERIES Applications Manual

1MRK 506 369-UUS -
12.1.3
12.1.3.1
Line distance protection REL670 2.2 ANSI
Application manual
There is a risk that the current into the generator at inadvertent energization will be limited
so that the "normal" overcurrent or underimpedance protection will not detect the
dangerous situation. The delay of these protection functions might be too long. The
reverse power protection might detect the situation but the operation time of this
protection is normally too long.
For big and important machines, fast protection against inadvertent energizing should,
therefore, be included in the protective scheme.
The protection against inadvertent energization can be made by a combination of
undervoltage, overvoltage and overcurrent protection functions. The undervoltage
function will, with a delay for example 10 s, detect the situation when the generator is not
connected to the grid (standstill) and activate the overcurrent function. The overvoltage
function will detect the situation when the generator is taken into operation and will
disable the overcurrent function. The overcurrent function will have a pick-up value about
50% of the rated current of the generator. The trip delay will be about 50 ms.

Setting guidelines

When inverse time overcurrent characteristic is selected, the trip time of
the stage will be the sum of the inverse time delay and the set definite time
delay. Thus, if only the inverse time delay is required, it is important to set
the definite time delay for that stage to zero.
The parameters for the general current and voltage protection function (CVGAPC) are set
via the local HMI or Protection and Control Manager (PCM600).
The overcurrent steps has a IMinx (x=1 or 2 depending on step) setting to
set the minimumpickup current. Set IMinx below PickupCurr_OCx for
every step to achieve ANSI reset characteristic according to standard. If
IMinx is set above PickupCurr_OCx for any step the ANSI reset works as
if current is zero when current drops below IMinx.
Directional negative sequence overcurrent protection
Directional negative sequence overcurrent protection is typically used as sensitive
ground-fault protection of power lines where incorrect zero sequence polarization may
result from mutual induction between two or more parallel lines. Additionally, it can be
used in applications on underground cables where zero-sequence impedance depends on
the fault current return paths, but the cable negative-sequence impedance is practically
constant. It shall be noted that directional negative sequence OC element offers protection
against all unbalance faults (phase-to-phase faults as well). Care shall be taken that the
Section 12
Multipurpose protection
605