Figure A.1 – Non-directional circular characteristic with directional supervision
Tải bản đầy đủ - 0trang
IEC 60255-121:2014 © IEC 2014
– 103 –
While in conventional electromechanical relays the MHO characteristic is a circle, in
microprocessor based relays in order to achieve better performance under different conditions
the MHO circle is used with additional blinders.
The characteristic used here should accommodate all characteristics in use as shown in
Figure A.2.
X
PsReactAng
PsReactRch
PsImpRch
PsImpAng
PsRisRch
OfsImpRch
DirChrAng1
PsRisAng
R
PsImpRch
PsImpAng
Positive Impedance Reach
Positive Impedance Angle
OfsImpRch
OfsImpAng
Offset Impedance Reach
Offset Impedance Angle
PsRisRch
PsRisAng
Positive Resistive Reach
Positive Resistive Angle
PsReactRch
PsReactAng
Positive Reactance Reach
Positive Reactance Angle
DirChrAng
Directional Characteristic Angle
OfsImpAng
IEC
0178/14
Figure A.2 – MHO characteristic
Polar reach
PsImpRch: The polar reach defines the reach of the MHO circle and corresponds to the
percentage of line impedance which is protected by the zone. For MHO circles without offset,
this represents the diameter of the circle. The reach is set with the two parameters:
–
PsImpRch and the PsImpAng are the two settings that define the polar reach.
–
PsImpAng is measured from the positive R-axis counter clockwise.
Offset
For setting an offset on the MHO circle the two parameters OfsImpRch and OfsImpAng are
used. OfsImpAng is measured from the positive R-axis counter clockwise.
Blinders
In some relays the MHO characteristic is combined with blinders which will limit the resistive
reach as well as the reactive reach of the MHO characteristic. The positive resistive blinder is
built by a line which crosses the R-axis at PsRisRch. The slope of the resistive blinder is set
with the setting via PsRisAng. PsRisAng is measured counter clockwise from the R-axis. The
area right from the blinder is excluded from the operating area.
Resistive reach scaling (loop based or phase based) needs to be identified .
The negative resistive blinder is built by a line which crosses the R-axis at NgRisRch. The
slope of the resistive blinder is set with the setting via NgRisAng. NgRisAng is measured
counter clockwise from the R-axis. The area left from the blinder is excluded from the
operating area.
The reactive reach blinder is built by a line which crosses the X-axis at PsReactRch.
– 104 –
IEC 60255-121:2014 © IEC 2014
The slope of the reactive blinder is set with the setting via PsReactAng. PsReactAng is
measured counter clockwise from the horizontal. The area above the blinder is excluded from
the operating area as shown in Figure A.2.
PsImpRch is the impedance reach of the bend point – the point on the horizontal line going
through the impedance reach tip where in some relays the reactive reach line can bend or tilt.
PsImpAng is the impedance angle with respect to the R-axis.
ImpRad is the radius of a circle with the centre at the impedance point – the midpoint of the
line between PsImpRch and OfsImpRch points on the circle.
ImpAdd indicates if this adds to or subtracts from the operating area of the characteristic
(True/False).
An active quadrant may be needed in some cases to limit the operating area of the distance
characteristic.
Polarization method
In many relays the polarization method is fixed. On other relays the polarization method is
dynamically selected based on certain conditions. The standard parameter set cannot
describe this internal selection logic. However, the settings needed to set the polarization
method(s) can be described here.
A.1.4
Quadrilateral/polygonal
Quadrilateral/polygonal is a characteristic that is used in many multifunctional transmission
line protection relays. It can have a different shape depending on the basic shape, number of
lines used and the settings of the relay.
The characteristic described in this annex as shown in Figure A.3 is an abstract characteristic
that can be used to represent most existing quadrilateral/polygonal characteristics using a
subset of the characteristic elements defined.
PsReactAng2
X
PsImpRchAng2
Z
PsReactRch
PsImpRchAng1
PsReactAng1
PsImpRch
PsImpAng
NgRisAng1
r
PsRisAng1
NgRisRch DirCharAng2
PsRisRch
NgRisAng2
DirChrAng1
NgImpAng
NgReactRch
NgImpRch
NgImpRchAng2
x
z
R
PsRisAng2
NgImpRchAng1
PsRisRch
PsRisAng1
PsRisAng2
Positive Resistive Reach
Positive Resistive Angle 1
Positive Resistive Angle 2
PsReactRch
PsReactAng1
PsReactAng2
Positive Reactance Reach
Positive Reactance Angle 1
Positive Reactance Angle 2
NgRisRch
NgRisAng1
NgRisAng2
Negative Resistive Reach
Negative Resistive Angle 1
Negative Resistive Angle 2
NgReactRch
NgReactAng1
NgReactAng2
Negative Reactance Reach
Negative Reactance Angle 1
Negative Reactance Angle 2
PsImpRch
PsImpAng
PsImpRchAng1
PsImpRchAng2
Positive Impedance Reach
Positive Impedance Angle
Positive Impedance Reach Angle 1
Positive Impedance Reach Angle 2
NgImpRch
NgImpAng
PsImpRchAng1
PsImpRchAng2
Negative Impedance Reach
Negative Impedance Angle
Negative Impedance Reach Angle 1
Negative Impedance Reach Angle 2
DirChrAng1
DirChrAng2
Directional Characteristic Angle 1
Directional Characteristic Angle 1
IEC
Figure A.3 – Quadrilateral/polygonal characteristics
0179/14
IEC 60255-121:2014 © IEC 2014
– 105 –
PsRisRch
Positive Resistive Reach – defines the positive resistive reach to limit the
coverage for fault resistance and at the same time to limit the
encroachment of the load impedance into the characteristic. The setting
determines the reach on the R-axis.
PsRisAng1
Positive Resistive Angle in the first quadrant. This angle is measured
counter clockwise from the R-axis. The area right from the blinder is
excluded from the operating area.
PsRisAng2
Positive Resistive Angle in the fourth quadrant. This angle is measured
clockwise from the R-axis.
PsReactRch
Positive Reactance Reach – defines the positive reactive reach to limit the
coverage for fault reactance. The setting determines the reach on the Xaxis.
PsReactAng1
Positive Reactance Angle 1 to the right of the line impedance. This angle is
measured clockwise from the horizontal line going through the reactive
reach on the X-axis. The area above the line is excluded from the
operating area.
PsReactAng2
Positive Reactance Angle 2 to the left of the line impedance. This angle is
measured counter clockwise from the horizontal line going through the
reactive reach on the X-axis. The area above the line is excluded from the
operating area.
NgRisRch
Negative Resistive Reach – defines the negative resistive reach. The
setting determines the reach on the R-axis.
NgRisAng1
Negative Resistive Angle 1 in the second quadrant. This angle is measured
counter clockwise from the R-axis. The area left from the blinder is
excluded from the operating area.
NgRisAng2
Negative Resistive Angle 2 in the third quadrant. This angle is measured
counter clockwise from the R-axis. The area left from the blinder is
excluded from the operating area.
NgReactRch
Negative Reactance Reach – defines the reactance reach in the reverse
direction.
NgReactAng1
Negative Reactance Angle 1. This angle is measured clockwise from the
horizontal line going through the negative reactance reach on the X-axis.
The area below the line is excluded from the operating area.
NgReactAng2
Negative Reactance Angle 2. This angle is measured clockwise from the
horizontal line going through the negative reactance reach on the X-axis.
The area below the line is excluded from the operating area.
PsImpRch
Is the impedance reach of the quadrilateral/polygonal characteristic. In
many cases the impedance or reactive reach line is a horizontal line. In
some relays it also can be the bend point – the point on the horizontal line
going through the impedance reach tip where the reactive reach line can
bend or tilt with an RsImpRchAng angle. In some relays there can be one
tilt angle on the right of the impedance line (PsImpRchAng1) and another
tilt angle on the left of the impedance line (PsImpRchAng2). The reactive
reach line can also tilt instead at the intersection of the reactance axis X
and the reactive reach line. The tilt in this case will be defined by
PsReactAng1 and in some cases PsReactAng2.
The same may apply on the negative reach of the quadrilateral/polygonal
characteristic.
PsImpAng
Positive Impedance Characteristic Angle – this is the line impedance angle
in the forward direction (first quadrant). This angle is measured counter
clockwise from the positive R-axis.
NgImpAng
Negative Impedance Characteristic Angle – this is the impedance angle in
the reverse direction (third quadrant). This angle is measured counter
clockwise from the negative R-axis.
– 106 –
IEC 60255-121:2014 © IEC 2014
DirChrAng1
Directional Characteristic Angle 1 – this is the directional characteristic
angle in the fourth quadrant. This angle is measured counter clockwise
from the positive R-axis.
DirChrAng2
Directional Characteristic Angle 2 – this is the directional characteristic
angle in the second quadrant. This angle is measured counter clockwise
from the positive R-axis.
A.2
A.2.1
Example characteristics
General
The following are examples based on the models described above.
A.2.2
Non-directional circular characteristic (ohm)
The non-directional circular characteristic is shown in Figure A.4.
jX
ImpRch
R
IEC
0180/14
Figure A.4 – Non-directional circular characteristic (ohm)
The following setting is applicable to this characteristic:
–
ImpRch is the setting of the distance element.
A.2.3
Reactive reach line characteristic
The reactive reach line characteristic is shown in Figure A.5.
IEC 60255-121:2014 © IEC 2014
– 107 –
X
Z
PsReactAng1
PsReactRch
R
IEC
0181/14
Figure A.5 – Reactive reach line characteristic
The following settings are applicable to this characteristic:
–
PsReactRch is the Positive Reactance Reach setting of the relay.
–
PsReactAng1 in the case of a horizontal line will be zero.
A.2.4
MHO characteristic
The MHO characteristic is show in Figure A.6.
X
PsImpRch
PsImpAng
R
IEC
0182/14
Figure A.6 – MHO characteristics
The following settings are applicable to this characteristic:
–
PsImpRch is the impedance reach setting of the distance element.
–
PsImpAng is the characteristic angle.
A.2.5
Resistive and reactive intersecting lines characteristic
Resistive and reactive lines intersecting lines characteristic is shown in Figure A.7.