When using the release delay option where the operating time counter is calculating the operating time
during the release time, function will not trip if the input signal is not activated again during the release
time counting.
Stage forcing
It is possible to test the logic, event processing and the operation of the protection system of the relay
by controlling the state of the protection functions by hand without injecting any current into the relay
with stage forcing. To enable stage forcing set the Enable stage forcing to Enabled in General menu.
After this it is possible to control the status of a protection function (Normal, Start, Trip, Blocked etc.) in
the Info page of the function.
NOTE: When Stage forcing is enabled protection functions will change state also by user input, injected
currents/voltages also affect the behavior of the relay. Despite this it is still advised to disable Stage
Forcing after testing has ended.
5.4.2. Non-directional overcurrent I> (50/51)
Overcurrent function (NOC) is used for non-directional instant- and time delayed overcurrent/short
circuit protection for various applications including feeder, lter and machine applications of utilities and
industry. The number of available instances of the function depends of the IED model. Function
measures constantly phase current magnitudes which on the operating decisions are based. Available
phase current magnitudes are fundamental component RMS, TRMS values (including harmonics up to
32
nd
) or peak-to-peak values. 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. Non directional
overcurrent 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 switched to de nite time or IDMT mode. For IDMT operation IEC and ANSI standard time delays
are supported as well as custom parameters. Function includes CT saturation checking which allows
the function to start and operate accurately also in case of CT saturation condition.
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 NOC function.
AQ-F255
Instruction manual
Version: 2.00
59
© Arcteq Relays Ltd
