List of Tables
2. Zone 1, 2 and 3 of phase-to-phase distance element
R jX
ZK
ZZD
-ZS/2 Φ
Figure 3.6-19 Phase-to-phase operation characteristic for forward fault
Phase-to-phase positive sequence voltage is used as polarized signal for phase-to-phase distance protection.
For zone 1 and zone 2:
Operation voltage:
Polarized voltage:
Phase shift θ2 could be applied to polarized voltage of zones 1 and 2 just like θ1 in phase-to-ground distance element. It is also used for improving performance against high resistance fault in short line. The device provides an angle-shift setting, [21M.ZP.phi_Shift], to set value of θ2 among 0°, 15° and 30°. Their impedance shift characteristics towards quadrant 1 are respectively shown as the impedance circle A, B and C in Figure 3.6-23.
For zone 3:
Operation voltage:
Polarized voltage:
Phase-to-phase positive-sequence voltage is applied as the polarized voltage of this element.
Phase comparison equation is:
The operation characteristic of phase-to-phase distance element is shown in Figure 3.6-19.
Operation characteristic of ZK on R-X plane is a circle with line connecting ends of ZZD and -ZS/2 as the diameter. The origin is enclosed in the circle.
Figure 3.6-20 shows operation characteristic of measured impedance -ZK on R-X plane when an asymmetric reverse fault occurs. This characteristic is a circle with line connecting ends of ZZD and Z'S as the diameter. It will operate only when -ZK is in the circle. Therefore, directionality of the distanced protection is achieved.
N M
EM
Z
EN
F
Z′S
ZK
ZZD
IΦ
R jX
-ZK
ZZD
Z'S
Φ
Figure 3.6-20 Operation characteristic for reverse fault Z'S: total impedance between remote system and protective device location
R jX
ZZD
ZK
Φ
Figure 3.6-21 Steady-state characteristic of three-phase short-circuit fault
Phase-to-phase distance protection is also used for three-phase short-circuit fault. The operation characteristic is shown in Figure 3.6-21. Operation characteristic of ZK on R-X plane is a circle with setting impedance ZZD as the diameter.
R jX
ZZD
Circle A Circle B
Circle C ZK
-ZS
Φ
Figure 3.6-22 Operation characteristic of three-phase close up short-circuit fault
Where:
ZZD: the setting of distance protection (zone x)
ZS: total impedance between local system and protective device location ZK: measured impedance
Φ: positive-sequence characteristic angle, i.e. [phi1_Reach]
Circle A: transient characteristic
Circle B: steady-state characteristic shifting towards quadrant Ⅲ Circle C: steady-state characteristic shifting towards quadrant Ⅰ
As shown in Figure 3.6-22, the characteristic of the distance protection for a three-phase fault on a system is an impedance circle cross the origin, and there is a voltage dead zone around the origin.
In order to eliminate the dead zone of the distance protection for a close up three-phase fault memorized positive-sequence voltage is adopted as polarized voltage when the positive-sequence voltage drops down to 15%Un or below.
The transient (during process of memory) operation characteristic is shown as the impedance circle A in the above figure. The circle takes ZZD and -ZZS as diameter and thus the origin is within the impedance circle. When three-phase fault happens in reverse direction, its transient characteristic is shown in Figure 3.6-20, i.e. the distance protection has a clearly defined directionality and no dead zone during the process of memory.
For zone 1, zone 2 and zone 3 of the phase-to-phase distance protection, if distance protection operates with memorized polarizing voltage, this means a close up forward fault. When the memory fades out, the operation characteristic will be reverse offset a little to enclose the origin as impedance circle B shown in Figure 3.6-22 to ensure keeping operating of distance protection until the fault being cleared. If distance protection does not operate with memorized polarizing voltage,
it will be a close up reverse fault. When the memory fades out, the operation characteristic will be forward offset not to enclose the origin as impedance circle C shown in Figure 3.6-22, and the distance protection will not mal-operate even if voltage is zero.
The distance protection with such design thoroughly eliminates the dead zone when three-phase close up fault occurs. It also has favorable directivity and will not operate for a reverse three-phase fault at busbar.
When receiving manual closing signal or 3-pole reclosing signal, the operation characteristic of phase to phase distance protection will always enclose the origin of impedance, with no dead zone, i.e. the reverse offset impedance circle B shown in Figure 3.6-22.
D A: 0°
B: 15° C: 30°
R jX
ZZD
-ZS
Figure 3.6-23 Shift impedance characteristic of zone 1 and zone 2
The impedance characteristic of phase-to-ground distance protection is the circle with line connecting ends of ZZD and -2ZS/3 as the diameter and that of phase-to-phase distance is the circle with line connecting ends of ZZD and -ZS/2 as the diameter.
In order to prevent the transient overreach caused by the infeed power supply from the remote end, the zero-sequence reactance line D is added. These measures have enhanced the capacity against fault resistance when using distance protection in short lines.
3. Zone 4
N M
EM
Z
EN
F I
ZK
ZZDR ZZDF
jX
R
ZZDR
ZK
ZZDF
Φ
Figure 3.6-24 Operation characteristic of reverse Z4 distance protection
Where:
ZZDF: impedance setting of zone 4 in forward direction, i.e. [21M.Z4.Z_Fwd]
ZZDR: impedance setting of zone 4 in reverse direction, i.e. [21M.Z4.Z_Rev]
Φ: positive-sequence characteristic angle, i.e. [phi1_Reach]
ZK: measurement impedance
When a fault occurs on the rear busbar, reverse distance element is provided to clear it with definite time delay and is taken as backup protection for reverse busbar fault. Its operation characteristic is shown in Figure 3.6-24.
3.6.5.2 Function Block Diagram
21M
21M.Z1.On 21M.En
21M.Blk 21M.Z2.On
21M.Z3.On
21M.Z4.On 21M.ZGx.En
21M.ZPx.En
21M.ZGx.Blk
21M.ZPx.Blk
21M.Zx.En_ShortDly
21M.Zx.Blk_ShortDly
21M.Z1.Op
21M.Z2.Op
21M.Z3.Op
21M.Z4.Op
21M.Z1.En_Instant
3.6.5.3 I/O Signals
Table 3.6-5 I/O signals of distance protection (Mho)
No. Input Signal Description
1 21M.En Distance protection enabling input, it is triggered from binary input or programmable logic etc.
2 21M.Blk Distance protection blocking input, it is triggered from binary input or programmable logic etc.
3 21M.ZGx.En Zone x of phase-to-ground distance protection enabling input, default value is
“1” (x=1, 2, 3, 4)
4 21M.ZGx.Blk Zone x of phase-to-ground distance protection blocking input, default value is
“0” (x=1, 2, 3, 4)
5 21M.ZPx.En Zone x of phase-to-phase distance protection enabling input, default value is
“1” (x=1, 2, 3, 4)
6 21M.ZPx.Blk Zone x of phase-to-phase distance protection blocking input, default value is
“0” (x=1, 2, 3, 4)
7 21M.Zx.En_ShortDly Enable accelerating zone x of distance protection (x=2, 3) 8 21M.Zx.Blk_ShortDly Accelerating zone x of distance protection is disabled (x=2, 3) 9 21M.Z1.En_Instant Enable zone 1 of distance protection operates without time delay
No. Output Signal Description
1 21M.Z1.On Zone 1 of distance protection is enabled 2 21M.Z2.On Zone 2 of distance protection is enabled 3 21M.Z3.On Zone 3 of distance protection is enabled 4 21M.Z4.On zone 4 of distance protection is enabled 5 21M.Z1.Op Zone 1 of distance protection operates 6 21M.Z2.Op Zone 2 of distance protection operates
7 21M.Z3.Op Zone 3 of distance protection operates 8 21M.Z4.Op zone 4 of distance protection operates 3.6.5.4 Logic
Figure 3.6-25 Logic diagram of enabling distance protection (Mho)
SIG Flag.21M.ZG1
Figure 3.6-26 Logic diagram of distance protection (Mho zone 1)
Where:
21M.Z1.Rls_PSBR: Please refer to Figure 3.6-38.
Flag.21M.ZG1 means that measured impedance by zone 1 of phase-to-ground distance protection is within the range determined by the setting [21M.ZG1.Z_Set].
Flag.21M.ZP1 means that measured impedance by zone 1 of phase-to-phase distance protection is within the range determined by the setting [21M.ZP1.Z_Set].
LoadEnch.St (PG) means that load trapezoid characteristic for distance element is enabled and measured phase-to-ground impedance into the load area.
LoadEnch.St (PP) means that load trapezoid characteristic for distance element is enabled and measured phase-to-phase impedance into the load area.
SIG Flag.21M.ZG2
Figure 3.6-27 Logic diagram of distance protection (Mho zone 2)
Where:
21M.Z2.Rls_PSBR: Please refer to Figure 3.6-38.
Flag.21M.ZG2 means that measured impedance by zone 2 of phase-to-ground distance protection is within the range determined by the setting [21M.ZG2.Z_Set].
Flag.21M.ZP2 means that measured impedance by zone 2 of phase-to-phase distance protection is within the range determined by the setting [21M.ZP2.Z_Set].
SIG Flag.21M.ZG3
[21M.ZP3.t_ShortDly] 0
&
Figure 3.6-28 Logic diagram of distance protection (Mho zone 3) Where:
21M.Z3.Rls_PSBR: Please refer to Figure 3.6-38.
Flag.21M.ZG3 means that measured impedance by zone 3 of phase-to-ground distance protection is within the range determined by the setting [21M.ZG3.Z_Set].
Flag.21M.ZP3 means that measured impedance by zone 3 of phase-to-phase distance protection is within the range determined by the setting [21M.ZP3.Z_Set].
SIG 21M.ZG4.Enable
Figure 3.6-29 Logic diagram of distance protection (Mho zone 4)
Where:
Flag.21M.ZG4 means that measured impedance by zone 4 of phase-to-ground distance protection is within the range determined by the settings [21M.Z4.Z_Fwd] and [21M.Z4.Z_Rev].
Flag.21M.ZP4 means that measured impedance by zone 4 of phase-to-phase distance protection is within the range determined by the settings [21M.Z4.Z_Fwd] and [21M.Z4.Z_Rev].
3.6.5.5 Settings
Table 3.6-6 Settings of distance protection (Mho)
No. Name Range Step Unit Remark
1 21M.ZG.phi_Shift 0, 15 or 30 Deg Phase shift of zone 1, 2 of phase-to-ground distance protection 2 21M.ZP.phi_Shift 0, 15 or 30 Deg Phase shift of zone 1, 2 of
phase-to-phase distance protection 3 21M.ZG1.Z_Set (0.000~4Unn)/In 0.001 ohm Impedance setting of zone 1 of
phase-to-ground distance protection
4 21M.ZG1.t_Op 0.000~10.000 0.001 s Time delay of zone 1 of
phase-to-ground distance protection
5 21M.ZG1.En 0 or 1
Enabling/disabling zone 1 of phase-to-ground distance protection 0: disable
1: enable
6 21M.ZG1.En_BlkAR 0 or 1
Enabling/disabling phase-to-ground zone 1 of distance protection operation to block AR
0: disable 1: enable
7 21M.ZP1.Z_Set (0.000~4Unn)/In 0.001 ohm Impedance setting of zone 1 of phase-to-phase distance protection
8 21M.ZP1.t_Op 0.000~10.000 0.001 s Time delay of zone 1 of
phase-to-phase distance protection
9 21M.ZP1.En 0 or 1
Enabling/disabling zone 1 of phase-to-phase distance protection 0: disable
1: enable
10 21M.ZP1.En_BlkAR 0 or 1
Enabling/disabling phase-to-phase zone 1 of distance protection operation to block AR
0: disable 1: enable
11 21M.ZG2.Z_Set (0.000~4Unn)/In 0.001 ohm Impedance setting of zone 2 of phase-to-ground distance protection
12 21M.ZG2.t_Op 0.000~10.000 0.001 s Time delay of zone 2 of
phase-to-ground distance protection 13 21M.ZG2.t_ShortDly 0.000~10.000 0.001 s Short time delay of zone 2 of
phase-to-ground distance protection
14 21M.ZG2.En 0 or 1
Enabling/disabling zone 2 of phase-to-ground distance protection 0: disable
1: enable
15 21M.ZG2.En_BlkAR 0 or 1
Enabling/disabling phase-to-ground zone 2 of distance protection operation to block AR
0: disable 1: enable
16 21M.ZP2.Z_Set (0.000~4Unn)/In 0.001 ohm Impedance setting of zone 2 of phase-to-phase distance protection
17 21M.ZP2.t_Op 0.000~10.000 0.001 s Time delay of zone 2 of
phase-to-phase distance protection 18 21M.ZP2.t_ShortDly 0.000~10.000 0.001 s Short time delay of zone 2 of
phase-to-phase distance protection
19 21M.ZP2.En 0 or 1
Enabling/disabling zone 2 of phase-to-phase distance protection 0: disable
1: enable
20 21M.ZP2.En_BlkAR 0 or 1
Enabling/disabling phase-to-phase zone 2 of distance protection operation to block AR phase-to-ground distance protection
23 21M.ZG3.t_Op 0.000~10.000 0.001 s Time delay of zone 3 of
phase-to-ground distance protection 24 21M.ZG3.t_ShortDly 0.000~10.000 0.001 s Short time delay of zone 3 of
phase-to-ground distance protection
25 21M.ZG3.En 0 or 1
Enabling/disabling zone 3 of phase-to-ground distance protection 0: disable
1: enable
26 21M.ZG3.En_BlkAR 0 or 1
Enabling/disabling phase-to-ground zone 3 of distance protection operation to block AR
0: disable 1: enable
27 21M.ZP3.Z_Set (0.000~4Unn)/In 0.001 ohm Impedance setting of zone 3 of phase-to-phase distance protection
28 21M.ZP3.t_Op 0.000~10.000 0.001 s Time delay of zone 3 of
phase-to-phase distance protection 29 21M.ZP3.t_ShortDly 0.000~10.000 0.001 s Short time delay of zone 3 of
phase-to-phase distance protection
30 21M.ZP3.En 0 or 1
Enabling/disabling zone 3 of phase-to-phase distance protection 0: disable
1: enable
31 21M.ZP3.En_BlkAR 0 or 1
Enabling/disabling phase-to-phase zone 3 of distance protection operation to block AR distance protection in forward direction 34 21M.Z4.Z_Rev (0.000~4Unn)/In 0.001 ohm Impedance setting of zone 4 of distance protection in reverse direction 35 21M.Z4.t_Op 0.000~10.000 0.001 s Time delay of zone 4 of distance
protection
36 21M.ZG4.En 0 or 1
Enabling/disabling zone 4 of phase-to-ground distance protection 0: disable
1: enable
37 21M.ZG4.En_BlkAR 0 or 1
Enabling/disabling phase-to-ground zone 4 of distance protection operation to block AR (Internal setting, its default value is “1”)
0: disable 1: enable
38 21M.ZP4.En 0 or 1
Enabling/disabling zone 4 of phase-to-phase distance protection 0: disable
1: enable
39 21M.ZP4.En_BlkAR 0 or 1
Enabling/disabling phase-to-phase zone 4 of distance protection operation to block AR (Internal setting, its default value is “1”)
0: disable 1: enable
3.6.6 Quadrilateral Distance Protection
3.6.6.1 Impedance Characteristic
Features available with quadrilateral distance protection include 3 forward zones (zone 1~3) phase-to-ground or phase-to-phase distance elements and 1 reverse zone (zone 4) phase-to-ground or phase-to-phase distance element. Each zone can respectively enable or disable power swing blocking releasing. Quadrilateral distance protection will be disabled when VT circuit fails.