7.1.7 Operation principle
M12913-3 v8
The sampled analogue phase currents are pre-processed in a discrete Fourier filter
(DFT) block. The RMS value of each phase current is derived from the
fundamental frequency components, as well as sampled values of each phase
current. These phase current values are fed to the instantaneous phase overcurrent
protection 3-phase output function PHPIOC. In a comparator the RMS values are
compared to the set operation current value of the function (IP>>).
If a phase current is larger than the set operation current a signal from the
comparator for this phase is set to true. This signal will, without delay, activate the
output signal TRLn (n=1,2,3) for this phase and the TRIP signal that is common
for all three phases.
There is an operation mode (OpMode) setting: 1 out of 3 or 2 out of 3. If the
parameter is set to 1 out of 3, any phase trip signal will be activated. If the
parameter is set to 2 out of 3, at least two phase signals must be activated for trip.
There is also a possibility to activate a preset change of the set operation current
(StValMult) via a binary input (ENMULT). In some applications the operation
value needs to be changed, for example, due to transformer inrush currents.
The operation current value IP>>, is limited to be between IP>>Max and
IP>>Min. The default values of the limits are the same as the setting limits for
IP>>, and the limits can only be used for reducing the allowed range of IP>>.
This feature is used when remote setting of the operation current value is allowed,
making it possible to ensure that the operation value used is reasonable. If IP>> is
set outside IP>>Max and IP>>Min, the closest of the limits to IP>> is used by the
function. If IP>>Max is smaller then IP>>Min, the limits are swapped. The
principle of the limitation is shown in Figure
80.
hi
u
lo
y
MIN
MAX
IP>>_used
IP>>Max
IP>>
IP>>Min
IEC17000016-1-en.vsdx
IEC17000016 V1 EN-US
Figure 80: Logic for limitation of used operation current value
PHPIOC can be blocked using the binary input BLOCK.
1MRK 506 382-UEN A Section 7
Current protection
Line distance protection REL650 2.2 IEC 161
Technical manual
To Next Page
Loading...
