ABB RELION REX640 Technical Manual page 541

1MRS759142 C
REX640
Technical Manual
If the phase angle of accumulated sum admittance phasor is greater than 45 degrees,
current magnitude supervision is based on the amplitude of
the set minimum operate current threshold. If the phase angle of accumulated sum
admittance phasor is below 45 degrees, current magnitude supervision is based on the
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resistive part of , which must exceed the set minimum operate current threshold.
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This automatic adaptation of the magnitude supervision condition enables secure and
dependable directional determination in compensated networks, and it is also valid
when the network is unearthed (compensation coil is switched off).
If operation direction is set to reverse, the resistive and amplitude sectors are mirrored
in the operation characteristics.
Setting Operating quantity should be set to "Adaptive" in resonant
earthed systems, except when protected feeders are overcompensated
by distributed coils. In such a case, Operating quantity should be set to
"Resistive".
Setting Operating quantity to "Adaptive" enables secure and
dependable directional determination in compensated networks,
which is also valid when the compensation coil is switched off and the
network becomes unearthed. In case of an unearthed network, Min
operate current is automatically compared to the amplitude of
In case of restriking earth-faults, harmonics created by the fault type
make the accumulated sum admittance phasor behave as in case of an
unearthed network. Therefore, operation can be achieved without the
need for resistive part of
networks during earth faults with rich harmonic content in residual
quantities, operation can be achieved without the parallel resistor of
the centralized compensation coil.
When Operating quantity is set to "Resistive", the set minimum operate current
threshold (setting Min operate current) is compared to the resistive component of
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in the whole defined operate sector (see
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Protection functions
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. This also means that in compensated
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Figure 291).
Section 4
, which must exceed
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.
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