ABB Relion 615 series Technical Manual Download

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If the “Adaptive” option is selected and an OSB condition is not detected, but the
impedance enters the mho circle after remaining between the inner and outer blinders for
greater than 1.5 cycles, the function assumes a severe swing and assert the

TRIP

output.

The drop out delay for

TRIP

output can be set by

Trip dropout time

setting.

If the polarity of the voltage signal is opposite to the normal polarity, the correction can be
done by setting

Voltage reversal

to “Yes”, which rotates the impedance vector by 180

degrees.

The

DISABLE

input can be used to coordinate the correct operation during the start-up

situation. The function is blocked by activating the DISABLE signal. Once the DISABLE
signal is deactivated, the function remains blocked (outputs disabled) for additional time
duration as set through the setting

Disable time

Blocking logic

There are three operation modes in the blocking function. The operation modes are
controlled by the

BLOCK

input and the global setting in

Configuration/System/Blocking

mode

which selects the blocking mode. The

BLOCK

input can be controlled by a binary

input, a horizontal communication input or an internal signal of the protection relay's
program. The influence of the

BLOCK

signal activation is preselected with the global

setting

Blocking mode

The

Blocking mode

setting has three blocking methods. In the “Freeze timers” mode, the

operation timer is frozen to the prevailing value, but the

TRIP

output is not deactivated

when blocking is activated. In the “Block all” mode, the whole function is blocked and the
timers are reset. In the “Block TRIP output” mode, the function operates normally but the

TRIP

output is not activated.

4.7.1.5

Application

Out of step protection functions detect stable power swings and out of step conditions
based on the fact that the voltage/current variation during a power swing is slow compared
to the step change during a fault. Both faults and power swings may cause the measured
impedance to enter into the operating characteristic of a distance relay element. The
apparent impedance moves from the pre-fault value to a fault value in a very short time,
a few milliseconds, during a fault condition. However, the rate of change of the impedance
is much slower during a power swing or out of step condition than during a fault depending
on the slip frequency of the out of step. The impedance measurement should not be used
by itself to distinguish between a fault condition and an out of step condition from a phase
fault. The fundamental method for discriminating between faults and power swings is to
track the rate of change of the measured impedance.

The function measures the rate of change of the impedance using two impedance
measurement elements known as blinders together with a timing device. If the measured

ABB Relion 615 series, Technical Manual

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