GE L90 Instruction Manual page 414

5.9 TRANSDUCER INPUTS AND OUTPUTS
examples). The setting is entered in per-unit values. The base units are defined in the same manner as the FlexEle-
ment™ base units.
The
DCMA OUTPUT H1 MIN VAL
the
DCMA OUTPUT H1 SOURCE
NOTE
Three application examples are described below.
EXAMPLE 1:
A three phase active power on a 13.8 kV system measured via UR-series relay source 1 is to be monitored by the dcmA H1
output of the range of –1 to 1 mA. The following settings are applied on the relay: CT ratio = 1200:5, VT secondary 115, VT
connection is delta, and VT ratio = 120. The nominal current is 800 A primary and the nominal power factor is 0.90. The
power is to be monitored in both importing and exporting directions and allow for 20% overload compared to the nominal.
The nominal three-phase power is:
The three-phase power with 20% overload margin is:
The base unit for power (refer to the FlexElements section in this chapter for additional details) is:
The minimum and maximum power values to be monitored (in pu) are:
5
minimum power
The following settings should be entered:
DCMA OUTPUT H1 SOURCE
DCMA OUTPUT H1 RANGE
DCMA OUTPUT H1 MIN VAL
DCMA OUTPUT H1 MAX VAL
With the above settings, the output will represent the power with the scale of 1 mA per 20.65 MW. The worst-case error for
this application can be calculated by superimposing the following two sources of error:
• ±0.5% of the full scale for the analog output module, or
• ±1% of reading error for the active power at power factor of 0.9
For example at the reading of 20 MW, the worst-case error is 0.01 × 20 MW + 0.207 MW = 0.407 MW.
EXAMPLE 2:
The phase A current (true RMS value) is to be monitored via the H2 current output working with the range from 4 to 20 mA.
The CT ratio is 5000:5 and the maximum load current is 4200 A. The current should be monitored from 0 A upwards, allow-
ing for 50% overload.
The phase current with the 50% overload margin is:
The base unit for current (refer to the FlexElements section in this chapter for additional details) is:
The minimum and maximum power values to be monitored (in pu) are:
minimum current
The following settings should be entered:
5-278
and
DCMA OUTPUT H1 MAX VAL
is set to FlexAnalog value based on power factor measurement).
× ×
P 3 13.8 kV 0.8 kA
=
×
P 1.2 17.21 MW
=
max
× ×
P 115 V 120
=
BASE
– 20.65 MW
= ------------------------------ = – 1.247 pu,
16.56 MW
: "SRC 1 P"
: "–1 to 1 mA"
: "–1.247 pu"
: "1.247 pu"
×
I 1.5 4.2 kA
=
max
I
=
BASE
0 kA
= ----------- - = 0 pu, maximum current
5 kA
L90 Line Current Differential System
settings are ignored for power factor base units (i.e. if
×
0.9 17.21 MW
=
20.65 MW
=
1.2 kA 16.56 MW
=
20.65 MW
maximum power = -------------------------- -
16.56 MW
± × ( – ( ) ) ×
0.005 1 – 1 20.65 MW
6.3 kA
=
5 kA
6.3 kA
= ---------------- - = 1.26 pu
5 kA
5 SETTINGS
(EQ 5.29)
(EQ 5.30)
(EQ 5.31)
= 1.247 pu
(EQ 5.32)
±
= 0.207 MW
(EQ 5.33)
(EQ 5.34)
(EQ 5.35)
GE Multilin