ZIV 7IRD-A - Open Phase Element

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Chapter 6. Description of Operation of Protection Subsystem

M7IRDA2003I

7IRD-A/J/M: Distribution Protection & Control Terminal

6-10

6.3 Open Phase Element

 Without Minimum Load in the Line Setting

The Open Phase element is designed to detect an open phase in the monitored three-phase

circuit by measuring the ratio of the negative to positive sequence current. Figure 6-11 shows

the block diagram of this function.

Figure 6.7 Open Phase Element Block Diagram (without Minimum Load in the Line Setting).

Open Phase Pickup is initiated when this ratio exceeds the user adjustable setting. Once the

Open Phase element has picked up, output T_FASE_A is initiated. If the T_FASE_A signal is

present for a period of time equal to or greater than the T_FASE_A Time Delay setting, an

Open Phase Trip Output occurs.

The operation of this function is controlled by the element enable setting, the position of the

breaker and the positive sequence current level. If the breaker is open or the positive sequence

current level is less than 100 mA, the element is disabled. This function is also disabled when

any of the Phase or Ground, Time or Instantaneous Overcurrent elements are picked up.

If this function is disabled, positive and negative sequence current measurement is still provided

for metering display purposes.