Bus Zone; Currents - GE B90 Instruction Manual

METERING

6.4.2 Bus zone

ACTUAL VALUES  METERING  BUS  BUS ZONE 1(6)
 BUS ZONE 1

These values display the differential and restraint currents phasors for each bus zone. The magnitudes are displayed in
6
primary amperes.
There is no cutoff level applied to the differential and restraint currents computed by the B90. Therefore, a small
differential current reflecting CT inaccuracies and bus leakage current can be present during balanced conditions.
This is done to achieve a more accurate differential balance and to provide a direct indication of the real differential
current, as excluding small currents or not accounting for CT errors can impose significant unaccounted
differential current. It is advisable to set the minimum pickup for 87B protection greater than the maximum
differential current during normal load conditions.

6.4.3 Currents

ACTUAL VALUES  METERING  CURRENTS
 CURRENTS

The metered current values for each terminal are displayed in this menu.
6-10
Figure 6-2: UR phase angle measurement convention
BUS ZONE 1 DIFF:

0.000 A 0.0°
BUS ZONE 1 REST:

0.000 A 0.0°
F1 CURRENT:

0.000 A 0.0°
F2 CURRENT:

0.000 A 0.0°

S8 CURRENT:

0.000 A 0.0°
B90 LOW IMPEDANCE BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: ACTUAL VALUES