GE P24DM Technical Manual

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6.4.11 POWER AND ENERGY MEASUREMENT DATA FORMATSThe power and energy measurements are available in two data formats:Data Type G29: an integer format using 3 registersData Type G125: a 32 bit floating point format using 2 registersThe G29 registers are listed in the first part of the MEASUREMENTS 2 column of the Courier database. The G125equivalents appear at the end of the MEASUREMENTS 2 column.Data type G29Data type G29 consists of three registers:The first register is the per unit (or normalised) power or energy measurement. It is a signed 16 bit quantity. Thisregister is of Data Type G28.The second and third registers contain a multiplier to convert the per unit value to a real value. These are unsigned32-bit quantities. These two registers together are of Data Type G27.Thee overall power or energy value conveyed by the G29 data type is therefore G29 = G28 x G27.The IED calculates the G28 per unit power or energy value as:G28 = (measured secondary quantity/CT secondary)(110V/(VT secondary).Since data type G28 is a signed 16-bit integer, its dynamic range is constrained to +/- 32768. You should take thislimitation into consideration for the energy measurements, as the G29 value will saturate a long time before theequivalent G125 does.The associated G27 multiplier is calculated as:G27 = (CT primary)(VT primary/110V) when primary value measurements are selectedandG27 = (CT secondary)(VT secondary/110V) when secondary value measurements are selected.Due to the required truncations from floating point values to integer values in the calculations of the G29component parts and its limited dynamic range, we only recommend using G29 values when the MODBUS mastercannot deal with the G125 IEEE754 floating point equivalents.Note:The G29 values must be read in whole multiples of three registers. It is not possible to read the G28 and G27 parts withseparate read commands.Example of Data Type G29Assuming the CT/VT configurations are as follows:● Main VT Primary 6.6 kV● Main VT Secondary 110 V● Phase CT Primary 3150 A● Phase CT Secondary 1 AThe Three-phase Active Power displayed on the measurement panel on the front display of the IED would be 21.94MWThe registers related to the Three-phase Active Power are: 3x00327, 3x00328, 3x00329Register Address Data read from these registers Format of the data3x00327 116 G283x00328 2 G27P24xM Chapter 16 - CommunicationsP24xM-TM-EN-2.1 349