ABB Relion 650 Series Technical Manual page 164
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Also See for Relion 650 Series:
- Technical manual (754 pages) ,
- Applications manual (382 pages) ,
- Commissioning manual (182 pages)
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Section 6
Current protection
If DFT option is selected then only the RMS value of the fundamental frequency components of
each phase current is derived. Influence of DC current component and higher harmonic current
components are almost completely suppressed. If RMS option is selected then the true RMS values
is used. The true RMS value in addition to the fundamental frequency component includes the
contribution from the current DC component as well as from higher current harmonic. The
selected current values are fed to OC4PTOC (51/67).
In a comparator, for each phase current, the DFT or RMS values are compared to the set operation
current value of the function
the set operation current, outputs PICKUP, PU_STx, PU_A, PU_B and PU_C are, without delay,
activated. Output signals PU_A, PU_B and PU_C are common for all steps. This means that the
lowest set step will initiate the activation. The PICKUP signal is common for all three phases and all
steps. It shall be noted that the selection of measured value (DFT or RMS) do not influence the
operation of directional part of OC4PTOC (51/67) .
Service value for individually measured phase currents are also available on the local HMI for
OC4PTOC (51/67) function, which simplifies testing, commissioning and in service operational
checking of the function.
The function can be directional. The direction of the fault current is given as current angle in
relation to the voltage angle. The fault current and fault voltage for the directional function is
dependent of the fault type. To enable directional measurement at close in faults, causing low
measured voltage, the polarization voltage is a combination of the apparent voltage (85%) and a
memory voltage (15%). The following combinations are used.
Phase-phase short circuit:
V
= V
ref_AB
V
= V
ref_BC
V
= V
ref_CA
Phase-ground short circuit:
V
= V
ref_A
V
= V
ref_B
V
= V
ref_C
158
(Pickup1, Pickup2, Pickup3, Pickup4) . If a phase current is larger than
-V
I
= I
-I
A
B
dir_AB
A
B
-V
I
= I
-I
B
C
dir_BC
B
C
–V
I
= I
-I
C
A
dir_CA
C
A
I
= I
A
dir_A
A
I
= I
B
dir_B
B
I
= I
C
dirC
C
© Copyright 2011 ABB Power Grids. All rights reserved
1MRK 506 326-UUS B
Line distance protection REL650
Technical manual
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