GE 745 TRANSFORMER MANAGEMENT RELAY User Manual

GE Power Management 745 Transformer Management Relay 6-7
6 ACTUAL VALUES 6.3 A2 METERING
6
6.3.3 HARMONIC CONTENT
The 745 can determine the harmonic components of every current that it measures. This allows it to calculate
total harmonic distortion (THD) as well as a harmonic derating factor that can be used to adjust phase time
overcurrent protection to account for additional internal energy dissipation that arises from the presence of har-
monic currents.
a) HARMONIC SUB-COMPONENTS
The 745 is capable of measuring harmonic components up to a frequency of 21 times the nominal system fre-
quency. An actual value is calculated for each phase of each monitored winding.
The example below shows what is displayed in a typical case for harmonic components (in this case the sec-
ond harmonic). Similar displays exist for all harmonics up to the 21
st
.
b) TOTAL HARMONIC DISTORTION (THD)
THD is calculated and displayed. Every THD value is calculated as the ratio of the RMS value of the sum of the
squared individual harmonic amplitudes to the rms value of the fundamental frequency. The calculations are
based on IEEE standard 519-1986
The following Actual Value messages are repeated for Windings 1, 2, and 3.
y HARMONIC CONTENT
y [ENTER] for more
This message indicates the start of the Harmonic Content actual values. To
view these actual values press or press for the next section.
y 2nd HARMONIC
y [ENTER] for more
This message indicates the start of the Second Harmonic actual values. To
view these actual values press or press for the next
sequential harmonic section.
W1 (% ƒo) H2a: 0.0
H2b: 0.0 H2c: 0.0
The second harmonic magnitude for each phase current of Winding 1 is
displayed. Values are expressed as a percentage of the magnitude of the
corresponding fundamental frequency component.
W2 (% ƒo) H2a: 0.0
H2b: 0.0 H2c: 0.0
The second harmonic magnitude for each phase current of Winding 2 is
displayed. Values are expressed as a percentage of the magnitude of the
corresponding fundamental frequency component.
W3 (% ƒo) H2a: 0.0
H2b: 0.0 H2c: 0.0
The second harmonic magnitude for each phase current of Winding 3 is
displayed. Values are expressed as a percentage of the magnitude of the
corresponding fundamental frequency component.
y THD
y [ENTER] for more
This message indicates the start of the THD actual values. To view these
actual values press or press for the next section.
W1 THDa (2nd-21st):
0.0% fo
This message displays the THD for Winding 1 phase A current, expressed
as a percentage of the fundamental frequency component. The numbers in
parentheses indicate the programmed frequency band (in terms of harmonic
number) over which THD is being calculated.
W1 THDb (2nd-21st):
0.0% fo
This message displays the THD for Winding 1 phase B current, expressed
as a percentage of the fundamental frequency component.
W1 THDc (2nd-21st):
0.0% fo
This message displays the THD for Winding 1 phase C current, expressed
as a percentage of the fundamental frequency component.
ENTER
MESSAGE
ENTER
MESSAGE
ENTER
MESSAGE

GE 745 TRANSFORMER MANAGEMENT RELAY Specifications

General

Brand	GE
Model	745 TRANSFORMER MANAGEMENT RELAY
Category	Relays
Language	English