GE B90 UR Series, Инструкция по эксплуатации

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GE Multilin B90 Low Impedance Bus Differential System 10-9
10 APPLICATION OF SETTINGS 10.5 BUS DIFFERENTIAL SETTINGS
10
10.5BUS DIFFERENTIAL SETTINGS 10.5.1 DESCRIPTION
Taking the previous analysis from this chapter into account, the settings have been calculated as shown in below.
Table 10–9: NORTH BUS DIFFERENTIAL PROTECTION SETTINGS
SETTING VALUE COMMENTS
PICKUP 0.1 pu Default value. Lower or higher values may be entered upon security/dependability
requirements. The pu value is for the base of 1200A. This means the actual pickup is
120 A primary.
LOW SLOPE 25% Default value. Lower or higher values may be entered upon security/dependability
requirements.
LOW BPNT 1.79 pu None of the CTs will saturate for ac currents below 1.79 pu even with 80% remanence.
The dc component, however, combined with the remanence may saturate some CTs
even for currents below 1.79 pu. The B90 copes with saturation using the current
directional principle.
HIGH SLOPE 60% Default value. Lower or higher values may be entered upon security/dependability
requirements. The value of 60% ensures that the differential characteristic alone
(without the directional principle) will work correctly under ac saturation of the CTs
(26% of spurious differential during the fault on C-1 saturating CT-1).
HIGH BPNT 8.96 None of the CTs will saturate for ac currents below 8.96 pu. The dc component,
however, may saturate some CTs even for currents below 8.96 pu. The B90 copes with
saturation using the current directional principle.
HIGH SET 5.94 The maximum spurious differential current is 2.97 pu. Due to limited accuracy of
analysis and the effect of dc saturation a security factor of 2 has been adopted. The
highest internal fault current is 14kA, or 11.67 pu giving a good chance to clear a
number of faults by the unbiased differential operation.
Table 10–10: SOUTH BUS DIFFERENTIAL PROTECTION SETTINGS
SETTING VALUE COMMENTS
PICKUP 0.1 pu Default value. Lower or higher values may be entered upon security/dependability
requirements. The pu value is for the base of 1200A. This means the actual pickup is
120 A primary.
LOW SLOPE 25% Default value. Lower or higher values may be entered upon security/dependability
requirements.
LOW BPNT 1.83 pu None of the CTs will saturate for ac currents below 1.83 pu even with 80% remanence.
The dc component, however, combined with the remanence may saturate some CTs
even for currents below 1.83 pu. The B90 copes with saturation using the current
directional principle.
HIGH SLOPE 60% Default value. Lower or higher values may be entered upon security/dependability
requirements. The value of 60% ensures that the differential characteristic alone
(without the directional principle) will work correctly under ac saturation of the CTs
(24% of spurious differential during the fault on C-2 saturating CT-2).
HIGH BPNT 9.13 pu None of the CTs will saturate for ac currents below 9.13 pu. The dc component,
however, may saturate some CTs even for currents below 9.13 pu. The B90 copes with
saturation using the current directional principle.
HIGH SET 5.54 The maximum spurious differential current is 2.77 pu. Due to limited accuracy of
analysis and the effect of dc saturation a security factor of 2 has been adopted. The
highest internal fault current is 14kA, or 11.67 pu giving a good chance to clear a
number of faults by the unbiased differential operation.