ABB REB670 Series, Applications Manual

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11.4.2 Application
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In power system networks, fault detection and operation of other protection functions is
reliably done by delta supervision functionality. Single phase networks are an important
application of delta supervision. In this type of network, a delta based release criteria is used
to release the protection funciton. The measurement of delta differs from country to country
between magnitude, vector or sample based detection.
In this function, a current based delta supervision is implemented in a phase segregated
design. The delta function has the following features:
• Instantaneous sample based delta detection (vectorial delta)
• True RMS value based delta detection
• DFT magnitude based delta detection
•
2
nd
harmonic blocking of delta function
•
3
rd
harmonic based adaption of starting value
Instantaneous sample based delta supervision is very fast; the delta is detected in less than a
cycle typically. This mode can be used for high impedance earth fault detection. All the other
supervision modes like RMS/DFT Mag requires minimum one cycle for delta detection.
Therefore, the choice of delta detection mode should be based on the application
requirement. Instantaneous sample based delta supervision can be used for functions that are
used as protection enabler or fault detector. For time delayed functions, other modes can be
used. Current based function can be used for load supervision also in DFT Mag based delta
mode.
11.4.3 Setting guidelines
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Operation: This setting is used to enable/disable the delta supervision function.
Imin: The minimum start level setting should be set as % of IBase. This setting enables the
function to start detecting delta. Typical setting is 10% of
IBase.
MeasMode: This setting is used to detect the mode of measurement; phase to phase or phase
to ground.
OpMode: This setting is used to select the mode of operation. For protection applications, this
should be set to
Instantaneous 1 cycle old. Load supervision can be done using DFT mag mode.
DelI>: This setting is used to detect the start value for instantaneous sample, RMS, DFT mag
based delta detection. Set a typical value of 200% of IBase to use this function as fault
detection.
DeltaT: This setting defines the number of old cycles data to be used for delta calculation in
RMS/DFT Mag mode. Typical value is 2 cycles.
tHold: This setting defines the pulse length for supervision start signal. Typical value is 100 ms.
EnaHarm2Blk: This setting should be set to ON, to enable blocking for heavy inrush currents or
other sources of 2
nd
harmonic injections.
Harm2BlkLev: This is the blocking level of 2
nd
harmonic with respect to the fundamental signal.
Typical setting is 15% of fundamental signal.
EnStValAdap: This setting should be set to ENABLE in special networks where settings in the
network are adapted with respect to 3
rd
harmonic level.
1MRK 505 370-UEN D Section 11
Secondary system supervision
Busbar protection REB670 247
Application manual