Rockwell Automation 865 Differential Protection Relay - Manual (Page 114)

5-4 Measurement
Functions
865-UM001A-EN-P – July 2009
Some maximum and minimum values of the last 31 days and the
last twelve months are stored in the non-volatile memory of the
relay. Corresponding time stamps are stored for the last 31 days.
The registered values are listed in the following table.
Table 5.8 – Registered Values
Measurement Max Min Description
IL1, IL2, IL3 X Phase current (fundamental frequency value)
Io1, Io2 X Residual current
The value can be a one cycle value or an average according parameter
"Timebase".
Table 5.9 – Parameters of the day and month registers
Parameter Value Description Set
Timebase
20 ms
200 ms
1 s
1 min
demand
Parameter to select the type of the registered values.
Collect min & max of one cycle values
Collect min & max of 200 ms average values
Collect min & max of 1 s average values
Collect min & max of 1 minute average values
Collect min & max of demand values S
ResetDays Reset the 31 day registers S
ResetMon Reset the 12 month registers S
This is the fundamental frequency rms value of one cycle updated every 20 ms.
Many measurement values are shown as primary values although
the relay is connected to secondary signals. Some measurement
values are shown as relative values - per unit or per cent. Almost
all pick-up setting values are using relative scaling. The scaling
is done using the given CT and transformer / generator name
plate values.
The following scaling equations are useful when doing secondary
testing.
Current Scaling
NOTE: The rated value of the relay's current input, 5A and 1A,
does not have any effect in the scaling equations, but it defines the
measurement range and the maximum allowed continuous current.
See Chapter 9 for details.
Table 5.10 – Primary and Secondary Scaling
Current scaling
secondary ⇒ primary
SEC
PRI
SEC PRI CT
CT
I I ⋅ =
primary
⇒ secondary
PRI
SEC
PRI SEC CT
CT
I I ⋅ =
Maximum Values of the last
31 days and twelve months
Primary, Secondary and
per unit Scaling