Setting Guidelines; Directional Negative Sequence Overcurrent Protection - ABB 650 series Applications Manual

1MRK 511 423-UEN A
6.1.3
6.1.3.1
Bay control REC650 2.2 IEC
Application manual
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
operate 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 minimum operate current. Set IMinx below
StartCurr_OCx for every step to achieve ANSI reset characteristic
according to standard. If IMinx is set above StartCurr_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
earth-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 minimum pickup of
such protection function shall be set above natural system unbalance level.
An example will be given, how sensitive-earth-fault protection for power lines can
be achieved by using negative-sequence directional overcurrent protection
elements within a CVGAPC function.
This functionality can be achieved by using one CVGAPC function. The following
shall be done to ensure proper operation of the function:
Section 6
Multipurpose protection
GUID-F7AA2194-4D1C-4475-8853-C7D064912614 v4
IP15009-1 v2
M13088-237 v3
M13088-3 v5
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