10
X - Raw input data in the range of RAW_LO to RAW_HI
ENG_LO,
ENG_HI
- Data low and high scales in engineering units (see Section 4 for device data
scales)
RAW_LO - Low conversion scale for raw device data:
RAW_LO = -32768 for a point with a negative LO scale,
RAW_LO = 0 for a point with a zero or positive LO scale
RAW_Hi - High conversion scale for raw device data: RAW_HI = 32767
Refer to Section 4 “Data Scales and Units” for applicable data scales and measurement units.
The default voltage scale in the device is 144V (120V+20%). It can be changed via the
supplemental PAS software. The recommended voltage scale is 120V+20% = 144V for using
with external PT’s, and 690V+20% = 828V for a direct connection to power line.
NOTE: If a source data value exceeds the device engineering scale, it is truncated to a
maximum allowable negative or positive number and the “over-range error” exception code
is returned in the response control word.
CONVERSION EXAMPLES
1. Voltage readings
a) Assume device settings (direct wiring): PT ratio = 1; Voltage scale = 828V (690V + 20%).
Voltage engineering scales (see Section 4):
ENG_HI = Vmax = 828.0 × PT ratio = 828.0 × 1 = 828.0V
ENG_LO = 0V
If the raw data reading is 4748 then the voltage reading in engineering units will be as follows:
Volts reading = (4748 – 0) × (828.0 - 0)/(32767 - 0) + 0 = 120.0V
b) Assume device settings (wiring via PT): PT ratio = 14,400V : 120V = 120; Voltage scale = 144V.
Voltage engineering scales (see Section 4):
ENG_HI = Vmax = 144.0 × PT ratio = 144 × 120 = 17,280V
ENG_LO = 0V
If the raw data reading is 27245 then the voltage reading in engineering units will be as follows:
Volts reading = (27245 – 0) × (17,280 - 0)/(32767 – 0) + 0 = 14,368V
2. Current readings
Assume device settings: CT primary current = 200A.
Current engineering scales (see Section 4):
ENG_HI = Imax = CT primary current × 2 = 200.00 × 2 = 400.00A
ENG_LO = 0A
If the raw data reading is 819 then the current reading in engineering units will be as follows:
Amps reading = (819 – 0) × (400.00 - 0)/(32767 - 0) + 0 = 10.00A
3. Power readings
a) Assume device settings (direct wiring): Wiring 4LL3; PT = 1; CT primary current = 200A; Voltage
scale = 828V.
Active Power engineering scales (see Section 4):
ENG_HI = Pmax = Vmax × Imax × 2 = (828.0 × 1) × (200.00 × 2) × 2 = 662,400W = 662.400kW
ENG_LO = -Pmax = -662.400kW
If the raw data reading is 18024 then the power reading in engineering units will be as follows:
Watts reading = (18024 - (-32768)) × (662.400 - (-662.400))/(32767 –(-32768)) +
(-662.400) = 364.368kW
If the raw data reading is -500 then the power reading in engineering units will be as follows:
Watts reading = (-500 - (-32768)) × (662.400 - (-662.400))/(32767 – (-32768)) + (-662.400) =
-10.097kW
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