5.4.5. Directional earth fault I0Dir> (67N)
Directional earth fault function (DEF) is used for instant- and time delayed earth fault protection for
various applications including feeder and machine applications of utilities and industry. IED with both
voltage and current protection module may have four available instances of the function (I0Dir>,
I0Dir>>, I0Dir>>>, I0Dir>>>>). Function constantly measures selected neutral current –or voltage
magnitudes on which the operating decisions are based. Available residual current magnitudes are
fundamental component RMS, TRMS values (including harmonics up to 31
st
) or peak-to-peak values of
residual current measurement inputs I01 and I02 or from phase current measurements calculated
residual current I0Calc. Current angle is compared to the angle of measured or calculated zero
sequence voltage. Certain amount of zero sequence voltage has to be present to activate the trip.
Blocking signal and setting group selection controls the operating characteristics of the function during
normal operation.
Outputs of the function are Start 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. Directional earth fault
function utilizes total of eight separate setting groups which can be selected from one common source.
The function can be operating on instant or time delayed mode. In time delayed mode the operation
can be switched to de nite time or IDMT mode. For IDMT operation IEC and ANSI standard time
delays are supported as well as custom parameters.
The operational logic consists of input magnitude processing, input magnitude selection, threshold
comparator, angle check, block signal check, time delay characteristics and output processing.
Inputs for the function are the operating mode selections, setting parameters and measured and pre-
processed current magnitudes and binary input signals. Function outputs START, TRIP and BLOCKED
signals which 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 output signals. In instant operating mode
the function outputs START and TRIP events simultaneously with equivalent time stamp. Time stamp
resolution is 1ms. Function provides also cumulative counters for START, TRIP and BLOCKED events.
Simpli ed function block diagram of the DEF function is presented in the gure below.
AQ-F255
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
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