ZIV 7IRD-A, Инструкция по эксплуатации

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Chapter 6. Description of Operation of Protection Subsystem
6-3
M7IRDA2003I
7IRD-A/J/M: Distribution Protection & Control Terminal
© ZIV APLICACIONES Y TECNOLOGÍA, S.L.U. 2020
6.1 Overcurrent Elements
7IRD-A/J/M IED’s provide four directional overcurrent protection elements: three-phase and
ground.

7IRD-A/M Model
Each of these elements consists of an Instantaneous and a Time Overcurrent measuring
element. The Instantaneous measuring element is also equipped with an adjustable timer which
can be enabled or disabled. Instantaneous and Time Overcurrent element settings are made
for: Phase and Ground Time, Phase and Ground Instantaneous. Figure 6.4 shows the block
diagram of one of these units for checking its basic operation.

7IRD-J Model
Each of these elements consists of an Instantaneous and two Time Overcurrent measuring
elements. The Instantaneous measuring element is also equipped with an adjustable timer
which can be enabled or disabled. Instantaneous and Time Overcurrent element settings are
made for: Phase and Ground Time, Phase 1 and Ground 1 Instantaneous and Phase 2 and
Ground 2 Instantaneous. Figure 6.5 shows the block diagram of one of these units.
6.1.1 Time Elements
The circuit continuously processes the RMS value of current analog input I based on averaging
a full cycle of samples. Pickup takes place when the measured value exceeds 1.05 times the
pickup setting and reset occurs at the pickup setting.
The Time element integrates a measured value above pickup by incrementing a counter in the
integrator module using an amount proportional to the input current RMS value. When the
counter reaches the operate threshold, the Time Overcurrent element initiates a trip.
When the measured value drops below the pickup setting, the incrementing value is removed,
causing a rapid reset of the integrator module to its initial condition with the counter at zero. Any
new measured value above pickup must then start the integration interval from zero.
Three inverse time curves (
Inverse , Very Inverse and Extremely Inverse ), one Definite Time
curve and one User Programmable time curve can be selected. The User Programmable
curve is loaded into the terminal unit front RS232 port through the ZiverCom
®
communications
program.
Time-current characteristic curves have two independent settings:
Curve Family , and Time
Dial .