GE N60 Instruction Manual page 425

CHAPTER 5: SETTINGS
Application example 1
A three phase active power on a 13.8 kV system measured via UR source 1 is to be sent via Direct Outputs, bits 20 through
27, to a remote location. The following settings are applied on the relay: CT ratio = 1200:5, VT ratio = 120, and VT secondary
= 66.4 V. 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 as compared with the nominal.
• Nominal three-phase power:
• Three-phase power with the 20% overload margin: P
• UR base unit for power: P
(see the FlexElements section for details)
• Maximum power to be monitored (pu): 20.65 MW/9.56 MW = 2.160 pu
The following settings are applied:
Using these settings, the output represents power with the scale of 127 per 20.65 MW; for example, 1 count of a digitizer
output represents 20.65 MW / 127 = 162.6 kW.
The direct outputs are configured as follows:
: "DIGITIZER 1 BIT 0"
DIRECT OUT 20 OPERAND
: "DIGITIZER 1 BIT 4"
DIRECT OUT 24 OPERAND
: "DIGITIZER 1 BIT 1"
DIRECT OUT 21 OPERAND
: "DIGITIZER 1 BIT 5"
DIRECT OUT 25 OPERAND
: "DIGITIZER 1 BIT 2"
DIRECT OUT 22 OPERAND
: "DIGITIZER 1 BIT 6"
DIRECT OUT 26 OPERAND
: "DIGITIZER 1 BIT 3"
DIRECT OUT 23 OPERAND
: "DIGITIZER 1 BIT 7"
DIRECT OUT 27 OPERAND
On the receiving location, bits 20 through 27 are configured to drive eight direct inputs. The latter is configured accordingly
to use the incoming information (typically via the eight-bit comparator feature).
The following table illustrates this application for four sample power values.
Table 5-40: Sample power values
Power N
out
15.00 MW 92
20.00 MW 123
–5.00 MW –31
–12.00 MW –74
N60 NETWORK STABILITY AND SYNCHROPHASOR MEASUREMENT SYSTEM – INSTRUCTION MANUAL
Figure 5-145: Digitizer logic
max
= VT ratio x VT secondary x CT primary = 120 x 66.4 V x 1.2 kA = 9.56 MW
BASE
= "SRC 1 P" and
DIGITIZER 1 SOURCE
B7... B0
01011100
01111011
10011111
11001010
= 1.2 x 17.21 MW = 20.65 MW
= "2.160 pu".
DIGITIZER 1 LIMIT
CONTROL ELEMENTS
5
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