Functions
2.5 Distance Protection
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
170
In total, the following zones are available:
Independent zones:
• 1st zone (fast tripping zone) Z1 with
ZR(Z1)
; may be delayed with
T1-1phase
or
T1-multi-phase
,
• 2nd zone (backup zone) Z2 with
ZR(Z2)
; may be delayed with
T2-1phase
or
T2-multi-phase
,
• 3rd zone (backup zone) Z3 with
ZR(Z3)
; may be delayed with
T3 DELAY
,
• 4th zone (backup zone) Z4 with
ZR(Z4)
; may be delayed with
T4 DELAY
,
• 5th Zone (backup zone) Z5 with
ZR(Z5)
; may be delayed with
T5 DELAY
• 6th Zone (backup zone) Z6 with
ZR(Z6)
; may be delayed with
T6 DELAY
Dependent (controlled) zone:
• Overreaching zone Z1B with
ZR(Z1B)
; may be delayed with
T1B-1phase
or
T1B-multi-phase
.
2.5.3.2
Setting Notes
General
The function parameters for the MHO characteristic only apply if during the configuration of the scope of func-
tions the MHO characteristic was selected for phase-to-phase measurement (address
115
) and/or phase-to-
earth measurement (address
116
).
Grading coordination chart
It is recommended to initially create a grading coordination chart for the entire galvanically interconnected
system. This diagram should reflect the line lengths with their primary impedances Z in
Ω
/km. For the reach of
the distance zones, the impedances Z are the deciding quantities.
The first zone Z1 is usually set to cover 85% of the protected line without any trip time delay (i.e. T1 = 0.00 s).
The protection clears faults in this range without additional time delay, i.e. the tripping time is the relay basic
operating time.
The tripping time of the higher zones is sequentially increased by one time grading interval. The grading margin
must take into account the circuit breaker operating time including the spread of this time, the resetting time of
the protection equipment as well as the spread of the protection delay timers. Typical values are 0.2 s to 0.4 s.
The reach is selected to cover up to approximately 80 % of the zone with the same set time delay on the short-
est neighbouring feeder (Figure 2-59).
Figure 2-70
Setting the reach - example for device A
s1, s2 Protected line section
