Principle Of Operation - ABB Relion 650 Series Technical Manual

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Inverse time characteristics

If there is a risk of intermittent faults. If the current IED, close to the faults,

starts and resets there is a risk of unselective trip from other protections in the

Delayed resetting could give accelerated fault clearance in case of automatic

reclosing to a permanent fault.

Overcurrent protection functions are sometimes used as release criterion for

other protection functions. It can often be valuable to have a reset delay to

assure the release function.

Principle of operation

Mode of operation

The function can operate in a definite time-lag mode or in a current definite inverse

time mode. For the inverse time characteristic both ANSI and IEC based standard

curves are available. Also programmable curve types are supported via the

component inputs: p, A, B, C pr, tr, and cr.

Different characteristics for reset delay can also be chosen.

If current in any phase exceeds the set start current value (here internal signal

startValue), a timer, according to the selected operating mode, is started. The

component always uses the maximum of the three phase current values as the

current level used in timing calculations.

In case of definite time-lag mode the timer will run constantly until the time is

reached or until the current drops below the reset value (start value minus the

hysteresis) and the reset time has elapsed.

For definite time delay curve ANSI/IEEE Definite time or IEC Definite time are

The general expression for inverse time curves is according to equation 39.

EQUATION1189 V1 EN-US

are constants defined for each curve type,

is the set start current for step n,

is set time multiplier for step n and

is the measured current.

1MRK 511 424-UEN B

IP15777-1 v2

(Equation 39)

Bay control REC650 2.2 IEC

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