Metering Conventions - GE B90 Instruction Manual

6.3 METERING
6.3METERING
a) UR CONVENTION FOR MEASURING PHASE ANGLES
All phasors calculated by UR-series relays and used for protection, control and metering functions are rotating phasors that
maintain the correct phase angle relationships with each other at all times.
For display and oscillography purposes, all phasor angles in a given relay are referred to an AC input channel pre-selected
by the 
SETTINGS
defines a particular AC signal source to be used as the reference.
If the AC signal pre-selected by the relay upon configuration is not measurable, the phase angles are not referenced. The
phase angles are assigned as positive in the leading direction, and are presented as negative in the lagging direction, to
more closely align with power system metering conventions. This is illustrated below.
6
PATH: ACTUAL VALUES
 BUS ZONE 1

These values display the differential and restraint currents phasors for each bus zone. The magnitudes are displayed in pri-
mary amperes (see chapter 8: Theory of operation for additional details).
There is no cutoff level applied to the differential and restraint currents computed by the B90. Therefore, a small dif-
ferential current reflecting CT inaccuracies and bus leakage current could be present during balanced conditions.
This is done to achieve a more accurate differential balance and provide the user a direct indication of the real dif-
NOTE
ferential current, as excluding small currents or not accounting for CT errors may impose significant unaccounted
differential current. It is advisable to set the minimum pickup for 87B protection greater than the maximum differen-
tial current during normal load conditions.
6-8

SYSTEM SETUP POWER SYSTEM
o
-225
o
-180
o
-135
Figure 6–1: UR PHASE ANGLE MEASUREMENT CONVENTION
  
METERING BUS BUS ZONE 1(4)
BUS ZONE 1 DIFF:
0.000 A
BUS ZONE 1 REST:
MESSAGE
0.000 A
B90 Low Impedance Bus Differential System

FREQUENCY AND PHASE REFERENCE
o
-270
o
-315
positive
angle
direction
o
0
UR phase angle
reference
o
-45
o
-90
0.0°
0.0°
6 ACTUAL VALUES

6.3.1 METERING CONVENTIONS

setting. This setting
827845A1.CDR
6.3.2 BUS ZONE
GE Multilin