2821
44
CBF1
5
CBFP OFF
2822
44
CBF1
6
Block ON
2823
44
CBF1
7
Block OFF
2824
44
CBF1
8
DO monitor On
2825
44
CBF1
9
DO monitor Off
2826
44
CBF1
10
Signal On
2827
44
CBF1
11
Signal Off
2828
44
CBF1
12
Phase current On
2829
44
CBF1
13
Phase current Off
2830
44
CBF1
14
Res current On
2831
44
CBF1
15
Res current Off
In the register of the CBFP function recorded events are activated, blocked etc. “On” event process
data. Table below presents the structure of CBFP function register content. This information is available
in 12 last recorded events for all provided instances separately.
Table. 5.4.9. - 104. Register content
Date & Time
Event
code
Trigger current
Time to
RETRact
Time to
CBFPact
Ftype
Stype
Used
SG
dd.mm.yyyy
hh:mm:ss.mss
2816-
2831 Descr.
Phase and residual
currents on trigger
time
Time remaining
before RETR is
active
Time remaining
before CBFP is
active
Monitored
current
status code
Activate
start
triggers
1 - 8
5.4.10. Restricted earth fault / cable end differential (REF) I0D> (87N)
Restricted Earth Fault function (REF) is used for residual differential current measurement for
transformers. This function can also be used for Cable End Differential (CED) functionality. Operating
principle is low impedance differential protection with settable bias characteristics where differential
current is calculated in between of summed phase currents and selected residual current input. In CED
mode the function provides natural measurement unbalance compensation to have higher operating
sensitivity for monitoring cable end faults.
REF function constantly monitors phase currents and selected residual current instant values as well as
calculated bias current and differential current magnitudes.
Blocking signal and setting group selection controls the operating characteristics of the function during
normal operation.
Outputs of the function are REF Trip and Blocked signals. Setting parameters are static inputs for the
function which are changed only by user input in the setup phase of the function. REF function utilizes
total of eight separate setting groups which can be selected from one common source. Also, the
operating mode of the REF can be changed by setting group selection.
The operational logic consists of input magnitude processing, differential characteristic comparator,
block signal check and output processing.
Inputs for the function are setting parameters and measured and pre-processed current magnitudes.
Function output signals can be used for direct IO controlling and also for user logic programming. The
function registers its operation into 12 last time-stamped registers and also generates general time
stamped ON/OFF events to the common event buffer from each of the two output signals. Time stamp
resolution is 1ms. Function provides cumulative counters for REF Trip and BLOCKED events.
In the following gure is presented the simpli ed function block diagram of the REF function.
AQ-F255
Instruction manual
Version: 2.00
115
© Arcteq Relays Ltd