Sel 751A - Thermal Metering; Table 5.2 Thermal Meter Values; Figure 5.2 METER Command Report with Enhanced Voltage Option with Monitoring Package

5.4
SEL-751A Relay Instruction Manual Date Code 20100129
Metering and Monitoring
Metering
When the average current is less than the I
NOM
current, the relay calculates
the percent imbalance as shown Equation 5.2.
Equation 5.2
In either case, the UB% is not calculated if the average phase current
magnitude is less than 25% of the I
NOM
current. Voltage Imbalance % is
calculated similar to the Current Imbalance described above except that the
effective nominal voltage (Vnm, see Note on page 4.30) is used instead of
I
NOM
.
=>MET <Enter>
SEL-751A Date: 06/04/2008 Time: 09:29:35
FEEDER RELAY Time Source: Internal
IA IB IC IN IG
Current Magnitude (A pri.) 2395.3 2390.9 2395.8 0.0 25.7
Current Angle (deg) -32.5 -152.2 88.3 129.7 -164.3
Ave Curr Mag (A pri.) 2394.0
Neg-Seq Curr 3I2 (A pri.) 34.5
Current Imb (%) 0.1
VA VB VC VG VS
Volt Mag (V pri.) 22222.6 22229.8 22237.5 322.9 22002.8
Volt Angle (deg) 0.0 -119.4 121.0 -112.9 1.3
Avg Phase (V pri.) 22230
Neg-Seq Volt 3V2 (V pri.) 326.1
Voltage Imb (%) 0.0
A B C 3P
Real Pwr (kW) 44886 44660 44858 134404
Reactive Pwr (kVAR) 28611 28815 28741 86168
Apparent Pwr (kVA) 53229 53149 53276 159654
Pwr Factor 0.84 0.84 0.84 0.84
LAG LAG LAG LAG
Frequency (Hz) 60.0
VDC (V) 125.0
=>>
Figure 5.2 METER Command Report With Enhanced Voltage Option With
Monitoring Package
Thermal Metering
The thermal metering function reports the RTD meter values (see Table 5.2 for
details) and also reports the state of connected RTDs if any have failed (see
Table 5.3 for details).
where:
UB% = Current imbalance percentage
Im = Maximum deviation of Iav from highest and lowest
magnitudes of the phase currents
Iav = Magnitude of the average phase current
I
NOM
= CT rated current
UB% 100
Im
I
NOM
--------------
•=
Table 5.2 Thermal Meter Values
Relay Option Thermal Values
With External SEL-2600 RTD Module or
Internal RTD Option
All RTD Temperatures