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MiCOM Px2 relays FAQ. IEC 60870-5-103 ASDU9 measurement implementation.

As described in the standard and user guide the ASDU 9 measures are stored with a rate such as: 2,4 * nominal value = 4096

It means that value is sent as 16 bit were 13 bits (from 3 to 15) corresponds to the analogue value and 3 bits are reserved (from 0 to 3). The full scale for measurement is 240 percent of the nominal equal to 4096.

Example with the relay setting
        0104         Frequency                    50Hz   
        0120         Line CT Primary           1A       
        0121         Line CT Sec                 1A       
        0124         Line VT Primary           0.10kV
        0126         Line VT Sec                 100.0V

and injection of 0,5A and 98V.

MiCOM Px2 sends following ASDU 9 frame
68 1A 1A 68 08 01 09 09 02 01 A0 94 20 1A 00 00 00 00 30 34 00 00 30 34 50 15 00 00 50 35 3E 16

 
  Injection Nominal value Value max corresponding to 4096
(In/Un/Pn/Fn*2,4)
Value from device Value in 13bits Value of 13 bits (decimal) Recalculated value as a part of full scale
Ia 0,5A 1A 2,4 201Ah
0001101000100
836  (836*2,4)/4096 = 0,4898A
Ua 98V 100V 240 3034h
0011010000110
1670 (1670*240)/4096 = 97,85V
P  40W40W 1x100 = 100W  240240  5015h5015h 0001010101010 682 (682*240)/4096 = 39,96W
  F 50Hz 50Hz 120 5035h  0011010101010   0011010101010  1706 (1706*120)/4096 = 49,98Hz

Where:
Injection – secondary value injected to the relay
Value max – nominal value in the primary or secondary units
Value from device – hexadecimal value send by the IED
Value in 13 bits – conversion from hex to binary with last 3 bits stripped out
 
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