ABB 615 series Technical Manual page 452

Section 4
Protection functions
446
1 1 1
I G j B V
( )
= + ⋅ ⋅
o stab ostab ostab
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The stabilized fundamental frequency residual current estimate, which is obtained (after
1
I conversion) from the corresponding admittance value by multiplying it with the system nominal
o stab
phase-to-ground voltage value.
The real-part of stabilized fundamental frequency residual current estimate.
1
I
o Cosstab
The imaginary-part of stabilized fundamental frequency residual current estimate.
1
I
o Sinstab
The main advantage of the filtering method is that due to the admittance calculation, the
resulting current value does not depend on the value of fault resistance, that is, the
estimated current magnitude equals the value that would be measured during a solid
ground fault (R = 0 Ω). Another advantage of the method is that it is capable of estimating
f
correct current magnitude also during intermittent or restriking faults.
The setting Min trip current defines the minimum trip current.
Setting Operating quantity defines whether the current magnitude supervision is based on
either the "Adaptive" or "Amplitude" methods.
When "Adaptive" is selected, the method adapts the principle of magnitude supervision
automatically to the system grounding condition. In case the phase angle of accumulated
sum admittance phasor is greater than 45 degrees, the set minimum trip current threshold
is compared to the amplitude of
accumulated sum admittance phasor is below 45 degrees, the set minimum trip current
threshold is compared to the resistive component of
the magnitude supervision enables secure and dependable directional determination in
compensated networks, and it is also valid when the network is ungrounded
(compensation coil is switched off).
In case operation direction is set to reverse, the resistive and amplitude sectors are
mirrored in the operation characteristics.
When "Amplitude" is selected, the set minimum trip current threshold is compared to the
1
I
amplitude of . This selection can be used in ungrounded networks.
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In compensated networks, setting Operating quantity should be set to
"Adaptive". This enables secure and dependable directional
1 1
I j I
= + ⋅
baseres oCosstab oSinsta b b
1
I
(see Figure
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1MAC059074-MB A
214). In case the phase angle of
1
I
. This automatic adaptation of
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615 series ANSI
Technical Manual
(Equation 64)