5.3
Date Code 20100129 Instruction Manual SEL-751A Relay
Metering and Monitoring
Metering
Fundamental
Metering
Table 5.1 details each of the fundamental meter data types in the SEL-751A.
Section 8: Front-Panel Operations and Section 7: Communications describe
how to access the various types of meter data using the relay front panel and
communications ports.
All angles are displayed between –180 and +180 degrees. The angles are
referenced to VAB or VAN (for delta- or wye-connected PT, respectively) or
IA. If the voltage channels are not supported, or if VAB < 13 V (for delta-
connected PT) or VAN < 13 V (for wye-connected PT), the angles are
referenced to IA current. Figure 5.2 shows an example of the METER
command report.
The SEL-751A calculates percent imbalance current in one of two ways,
depending on the magnitude of the average current. When the average current
(Iav) is greater than the CT rated current (I
NOM
) the relay calculates the
percent imbalance as shown in Equation 5.1.
Equation 5.1
Table 5.1 Measured Fundamental Meter Values
Relay Option Meter Values
All Models Line Currents IA, IB, IC and IN (Core-Balance Ground Fault Current) magnitudes
(A) and phase angles (deg)
IG (Residual Ground Fault Current) magnitude (A) and phase angle (deg)
IAV (Average Current Magnitude)
Negative-Sequence Current (3I2)
Current Imbalance %
System Frequency (Hz)
With Voltage Option (3AVI Card)
(MOT …x71x…)
OR
With Voltage and Arc-Flash Detection Inputs
Option
(3 AVI/4 AFDI Card)
MOT…x74x…)
VAB, VBC, VCA or VAN, VBN, VCN, VG magnitudes (V) and phase angles
(deg)
Average Voltage (L-L or L-N)
Negative-Sequence (3V2)
Voltage Imbalance %
Real Power (kW)
a
Reactive Power (kVAR)
a
Apparent Power (kVA)
a
Power Factor
a
With Enhanced Voltage Option With Monitor-
ing Package (5 AVI Card)
(MOT …x72x…)
OR
With Enhanced Voltage Option With Monitor-
ing, Advanced Metering and Protection Pack-
ages
(5AVI-A Card)
(MOT …x73x…)
VAB, VBC, VCA or VAN, VBN, VCN, VG magnitudes (V) and phase angles
(deg)
Average Voltage (L-L or L-N)
Negative-Sequence (3V2)
Voltage Imbalance %
Real Power (kW)
a
Reactive Power (kVAR)
a
Apparent Power (kVA)
a
Power Factor
a
VS (sync check voltage) magnitude (V) and phase angle (deg)
VDC (station battery voltage) (V dc)
a
Three phase measurements for DELTA connected PTs and three phase and single phase measurements for WYE connected PTs.
To Next Page
Loading...
