The function can be operating on instant or time delayed mode. If the stage is used in the instant mode
(e.g. set operating time delay is 0 s) for blocking purposes of other protection stages either Start or Trip
signal can be used. In time delayed mode the operation can be switched to de nite time or IDMT
mode. Start signal can be used for blocking other stages while in cases when the situation prolongs
can Trip signal be used for other actions as time delayed. 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, saturation
check, threshold comparator, block signal check, time delay characteristics and output processing.
The basic design of the protection function is 3-pole operation.
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 three output signal. 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.
In the following gure is presented the simpli ed function block diagram of the HOC function.
Figure. 5.4.6. - 28. Simpli ed function block diagram of the HOC function.
Measured input values
Function block uses analog current measurement values from the phase currents or residual currents.
For each measurement input the HOC function block utilizes the fundamental frequency and harmonic
components of the selected current input and by user selection the monitored magnitude can be either
per unit RMS values of the harmonic component or harmonic component percentage content
compared to fundamental frequency RMS. -20ms averaged value of the selected magnitude is used for
pre-fault data registering.
Table. 5.4.6. - 81. Analogic magnitudes used by the HOC function.
Signal
Description
Time
base
AQ-T257
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
72