ABB Relion REC615, Техническое руководство

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G
o stab
1
The real-part of stabilized fundamental frequency conductance estimate.
B
o stab
1
The imaginary part of stabilized fundamental frequency susceptance estimate.
I G j B U I j I
o stab ostab ostab baseres oCosstab oSinsta
1 1 1 1
= + ⋅ ⋅ = + ⋅
( )
b b
1
(Equation 41)
I
o stab
1
The stabilized fundamental frequency residual current estimate, which is ob-
tained (after conversion) from the corresponding admittance value by multiply-
ing it with the system nominal phase-to-earth voltage value.
I
o Cosstab
1
The real-part of stabilized fundamental frequency residual current estimate.
I
o Sinstab
1
The imaginary-part of stabilized fundamental frequency residual current esti-
mate.
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 earth fault (R
f
= 0 Ω). Another advantage of the method is
that it is capable of estimating correct current magnitude also during intermittent
or restriking faults.
The setting
Min operate current defines the minimum operate 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 earthing condition. In case the phase
angle of accumulated sum admittance phasor is greater than 45 degrees, the
set minimum operate current threshold is compared to the amplitude of
I
o stab
1
(see
Figure 198
). In case the phase angle of accumulated sum admittance
phasor is below 45 degrees, the set minimum operate current threshold is
compared to the resistive component of
I
o stab
1
. This automatic adaptation of the
magnitude supervision enables secure and dependable directional determination
in compensated networks, and it is also valid when the network is unearthed
(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 operate current threshold is
compared to the amplitude of
I
o stab
1
. This selection can be used in unearthed
networks.
In compensated networks, setting
Operating quantity should be
set to “Adaptive”. This enables secure and dependable directional
determination on compensated networks and it is also valid when
compensation coil is switched off and network becomes unearthed.
Protection functions 1MRS758755 C
396 REC615 & RER615
Technical Manual