In the phasor diagrams representing the operation of 67/51N, 67/50N, the polarity of the
polarizing quantity (VG or V2) is reversed, that is, the polarizing quantity in the phasor
diagrams is either -VG or -V2. Reversing is done by switching the polarity of the residual
current measuring channel (see the connection diagram in the application manual).
Similarly the polarity of the calculated IG and I
2
is also switched.
For defining the operation sector, there are five modes available through the Operation
mode setting.
Table 344: Operation modes
Operation mode Description
Phase angle The operating sectors for forward and reverse are
defined with the settings
Min forward angle
,
Max
forward angle
,
Min reverse angle
and
Max reverse
angle
.
IoSin
The operating sectors are defined as "forward" when
|IG| x sin (ANGLE) has a positive value and "reverse"
when the value is negative. ANGLE is the angle
difference between -VG and IG.
IoCos
As "IoSin" mode. Only cosine is used for calculating
the operation current.
Phase angle 80 The sector maximum values are frozen to 80
degrees respectively. Only
Min forward angle
and
Min reverse angle
are settable.
Phase angle 88
The sector maximum values are frozen to 88
degrees. Otherwise as "Phase angle 80" mode.
Polarizing quantity selection "Neg. seq. volt." is available only in the
"Phase angle" operation mode.
The directional operation can be selected with the Directional mode setting. The
alternatives are "Non-directional", "Forward" and "Reverse" operation. The operation
criterion is selected with the Operation mode setting. By setting Allow Non Dir to "True",
non-directional operation is allowed when the directional information is invalid, that is,
when the magnitude of the polarizing quantity is less than the value of the Min trip voltage
setting.
Typically, the network rotating direction is counter-clockwise and defined as "ABC". If
the network rotating direction is reversed, meaning clockwise, that is, "ACB", the
equation for calculating the negative sequence voltage component need to be changed.
The network rotating direction is defined with a system parameter Phase rotation. The
calculation of the component is affected but the angle difference calculation remains the
same. When the residual voltage is used as the polarizing method, the network rotating
direction change has no effect on the direction calculation.
1MAC059074-MB A Section 4
Protection functions
615 series ANSI 329
Technical Manual
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