Transcript
8/17/2019 1_Basic Protection Principles
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The year of Profitable Growth
Basic ProtectionPrinciples
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
Overcurrent-time protection
Definite-time
overcurrent-
protection
Inverse-timeovercurrent-protection
t
I I
N I
> I
>>
t2
t1
t
I I N
t
I I N
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
Differential protection
Load condition
Fault condition
Load condition
Fault condition
I A I B
I C
I A I B
I C
Line
Busbar
Istart - Iend = 0 ∆I = 0
Istart - Iend≠ 0 ∆I ≠ 0
IA + IB + IC ≠ 0 ΣI ≠ 0
IA + IB + IC = 0 ΣI = 0
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
Overvoltage - Undervoltage
U >
UN
U <
Overvoltage
Undervoltage
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
Time grading
t = 700 ms
t = 400 ms
t = 100 ms
I>
I>
I>
I > I > I >
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
t
t
t
t
I>>
I>
OFF
IE>>
IE>
IL1
IL2
IL3
IE
Valid for all devices with 4 input transformers
OFF
Function definite-time-protection
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
IL1
IL2
IL3
(IE)
OFF
I>> t
I> t
suitable for all types of neutral-point connection
I>>
I>
I>>
I>
IL1
IL2
IL3
IE
IE is calcuated,
(min. 0.1 x IN)and equipped with
timer
Function definite-time-protection (three current inputs)
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
Function definite-time protection (three current inputs)
I>> t
I> t OFF
OFF
t
t
L2 is calculated
I>>
I>
I>>
I>
IL1
IL2
IL3
IE
IL2
IL1
IL3
(IE)
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
t [sec]
0.5
1.0
1.5
2.0
x IN0.5 1.0 1.5 2.0 2.5
I> I>>
Tripping area
Tripping characteristic curve of a two-step definite-time protection
Definite-time protection, Characteristic curves
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
x IN0.5 1.0 1.5 2.0 2.5
t [sec]
0.5
1.0
1.5
2.0
Tripping characteristic curve of an inverse-time protection
Characteristic curves:
IECANSI British Standard
Inverse-time protection, Characteristic curves
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
IL1
UL1
OFF&
I>> t
Direction
I> t
Instantaneous zone (I>>) directional
Back-up zone (I>) non-directional
Directional definite-time-protection
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
I1
I2
I3
I4
I5
Measuring principle of differential protection devices
Kirchhoff law: I1 + I2 + I3 + I4 + I5 = 0
Current direction definition , .
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple. 1 (1) 2 (2)
Setting of the differential protection at a line / cable
1 + 2 - - 0
0, 1 + 2 - /
2.5.. 4 ≥ 0.15..0.2 , ( )
1 500 , 2 -300 , , 500 , 50
2,5 / , 0.25
/, 500 / 500 + (-300 / 500) 1.0 - 0.6 0.4
/ , -
I2
CT2
IDiff
Voltage
source U1
CT1 Voltage
source U2IC
I1
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
IS = |I
1| + |I
2|
Restraint current
IDiff = | I1+I2|
Differential current
Tripping area ->
trip
Restraint area -> No tripIDiff
>
Differential current due to line
capacity / cable capacity
Differential current due to linear
errors of the primary current transformers
Differential current due to non-linear
errors of the primary current transformers
k1=0.25
I1 I2
IDiff
k2=0.5
Possible differential
currentdue to errors
Tripping characteristic
Line differential protection: Resulting tripping characteristic
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Power Transmission and Distribution
Power AutomationProgress. It‘s that simple.
Summed up currents: I M1 = 5•I 1 + 3•I 2 + 4•I 3 I M2 = 5•I 1 + 3•I 2 + 4•I 3
U1 = Rb • Ib1 U2 = Rb•Ib2
Measuring principle of the two pilot-wire differential protection
⇒ Voltage comparision:
Side 1 Side 2
7SD600 7SD600
Device 1 Device 2Twisted pair pilot wire
I 1
I 2 I 3 I 3 I 2 I 1
L1
L2
L3
I M1
I a
I a
I M2
I b2 I b1
Rb Rb
Ra
Ra
R/2
R/2
U1
U2
transformer
Summation Summation
transformer
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