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CHAPTER 10: PROGRAMMING GROUP 1 – VOLTAGE, AMP AND WATT SCALE SETTINGS GROUP 1, FUNCTION 2
EPM 5300 SERIES ADVANCED POWER METERS – INSTRUCTION MANUAL 10–79
10.3 Group 1, Function 2
- SCALE SELECTION AND DECIMAL PLACEMENT FOR WATTS -
Programming GROUP 1 also provides decimal positioning for maximum resolution. The
following examples assist in selecting the best decimal position for FUNCTION 2.
Note
Shift the decimal left to increase resolution. Wattage should not exceed a numeral value
of 2500. Shift the decimal one position right to decrease resolution.
Full Scale Wattage (FSW) is the product of FSV and FSA. For FSW for three phases multiply
the FSW per phase by 3.
Example 1: Full Scale Voltage (FSV)=120 V
Full Scale Amperage (FSA)=5.00 A
FSW (one phase) =120 Vx5.00 A
FSW (one phase)=600 W
FSW (three phase)=600 Wx3 = 1,800 W
Here the FSW is too small a value for a Megawatt meter. FSW in the Kilowatt meter equals
1.800 KW. In FUNCTION 2, four 9s appear. Place the decimal point after the first digit. The
user cannot change the four digits. The user can only move the decimal point placement.
Example 2: 480/120 PT, 1000/5 CT
FSV=480 V
FSA=1000 A
FSW (one phase)=480 V ⋅ 1000 A
FSW (one phase)=480,000 W
FSW (three phase)=480,000 W
⋅
3 = 1,440,000 W
FSW for a Kilowatt meter equals 1440. KW. FSW for a Megawatt meter equals 1.440 MW. In
FUNCTION 2 place the decimal point after the last digit for a Kilowatt meter and after the
first digit for a Megawatt meter. It is important to note which type of bezel labeling you
have when making this decision.
Example 3: 14.4 KV/120, 1000/5 CT
FSV=14.40 KV
FSA=1000 A
FSW (one phase)=14,400 Vx1000 A
FSW (one phase)=14,400,000 W
FSW (three phase)=14,440, 000 Wx3 = 43,200,000 W
FSW for a Kilowatt meter equals 43,200 KW. Here the FSW is too large a value for a
Kilowatt meter (the range is 000–2500). FSW for a Megawatt meter equals 043.2 MW. In
FUNCTION 2, place the decimal after the third digit.
Note
In some applications where the load is normally very low, the watts resolution can be
increased by moving the decimal point one position left.