ABB RELION REX640 Technical Manual page 916

Protection functions
T
refresh
The function Roundup rounds up the result to the next higher time multiple of 0.2 s
because the result of the division is not a multiple of 0.2 s in case of an odd
interval setting (1, 3, 5...120 mins).
U
Refresh
N
=
N
Calculation of RMS average voltage
The RMS average voltage is calculated by aggregating the RMS U
time period equal to the
U
Average
M
M = Round
At the initialization of the function, the average voltage is calculated considering
initial values as zero. On the IEC 61850 mapped data, the quality of the calculated
average voltage value is indicated as "Questionable" until the first complete
time interval passes. The calculated average voltage measurement for the set
Time interval for all three phase-to-earth and phase-to-phase voltages U_MEAN_A,
U_MEAN_B, U_MEAN_C, U_MEAN_AB, U_MEAN_BC and U_MEAN_CA is available in
the Monitored data view.
The calculated average voltage can be reset by the RESET binary input. The
calculated average voltage can also be reset using PHVPTOV1 Reset mean on the
Clear menu.
When the INITIALIZE input is activated, the average voltage measurement value is
initialized with the 10/12-cycle RMS voltage. The average voltage measurement value
can also be initialized using PHVPTOV1 Ini mean on the Clear menu.
916

Time interval in seconds
= Roundup


2
N
1
( )
∑
=
U i
10 12 / cycles
N
i = 1
Number of values to be aggregated as defined by
 
T
refresh
 
 
0 2 .
Time interval .
2
M
1
( )
∑
= U i
Refresh
M
=
i 1
Number of values to be aggregated as defined by

Time interval in seconds


T
Refresh



200



1MRS759142 F
(Equation 255)
Time
(Equation 256)
Equation 257
(Equation 257)
voltage over a
refresh
(Equation 258)
Equation 259
(Equation 259)
REX640
Technical Manual