MECHANICALLY SWITCHED CAPACITOR DAMPING NETWORK
- INFLUENCE OF SWITCHING ON UNLOADED TRANSMISSION LINE
CALCULATION OF TRANSIENTS IN ELECTRIC POWER SYSTEMS
UNDER THE GUIDANCE OF PROF DR. JUTTA HANSON, MS. JULIA DRAGON AND MR.
ANDREAS WASSERRAB
PARTICIPANTS:
AKSHAY MAHAJAN
AVINASH MURALI
PARTHASARATHY S.
RAMAKRISHNAN V.
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
1
Theme
Impact of MSCDN Connection to Grid supplying an Unloaded Transmission Line
•
Over-voltages in Grid and across MSCDN Capacitor & Inductor
•
Over-currents in Grid and MSCDN Capacitor
•
Total Harmonic Distortion of the Grid Voltage
•
Losses in MSCDN Plant
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
2
MSCDN Configuration
Grid & MSCDN Specifications:
UN = 380 kV
L
Rd
C2
C1
Q = 300 Mvar
fT = 150 Hz
Transmission Line:
Four-conductor bundle 240/40
Al/St
Length – 50 km
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
3
Grid over-voltage
Variation in peak value of grid over-voltage with:
•
Fault Level: reduces (up to 30%) significantly with increase in fault level
•
Switching Instant: increases when switching at voltage maximum. This value
further increases with variation of damping resistance and initial voltage at the
capacitor. However, over-voltage reduces when fault level is increased
•
Initial voltage of C1: with an initial voltage at C1, marginal increase (about 4 to
15%) is observed; however, there is no variation when fault level is increased
•
Tolerance of C1: increases with variation in main capacitance; however, the
change is not significant (about 2%)
•
Damping Resistance: a change in damping resistance creates a minor change in
the grid over-voltage (nearly 5%)
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
(kV)
Grid over-voltage
t
Highest Grid Overvoltage Vmax = 605 kV
Switching Condition: Grid Fault Level = 5 kA, Rdamp=1000Ω, V=-Vmax , Vc1 = 0.8 Vcs
& C1 = C1nom +3 %
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
Capacitor over-voltage
Variation in peak value of over-voltage across main capacitor with:
•
Fault Level: reduces significantly (by 30%) with increase in fault level
•
Switching Instant: increases when switching at voltage maximum. Also increases
with variation of damping resistance (by 30%) and initial voltage at the capacitor
(by 60%). However, over-voltage reduces when fault level is increased
•
Initial voltage of C1: with an initial voltage at C1, significant increase (about 30%)
is observed; however, with variation in fault level, the increase is only up to 20%
•
Tolerance of C1: increases with variation in main capacitance; however, the
change is minimal (less than 2%)
•
Damping Resistance: a change in damping resistance creates about 10% variation
in the capacitor over-voltage
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
(kV)
Capacitor over-voltage
t
Highest Capacitor Overvoltage Vmax = 894.81 kV
Switching Condition: Grid Fault Level = 5 kA, Rdamp=1000Ω, V=-Vmax , Vc1 = 0.8 Vcs
& C1 = C1nom +3 %
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
Inductor over-voltage
Variation in peak value of over-voltage across inductor with:
•
Fault Level: increases (up to 30%) significantly with increase in fault level
•
Switching Instant: increases drastically when switching at voltage maximum. It
rises up to 200% with Rd = 1000 Ω and increases further with initial voltage at
the capacitor and fault level
•
Initial voltage of C1: with an initial voltage at C1, major increase (almost 80%) is
observed; shoots further to 200% with fault level at 50 kA
•
Tolerance of C1: increases with variation in main capacitance; however, the
change is not significant (almost 2%)
•
Damping Resistance: a change in damping resistance creates a notable
difference (almost 20%) in the over-voltage across the inductor
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
(kV)
Inductor over-voltage
t
Highest Inductor Overvoltage Vmax = -549 kV
Switching Condition: Grid Fault Level = 50 kA, Rdamp=1000Ω, V=-Vmax , Vc1 = 0.8 Vcs
& C1 = C1nom
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
Total Harmonic Distortion
Variation in peak value of Total Harmonic Distortion with:
•
Fault Level: Approximately 7-10 times higher value is observed at 5kA as
compared to 50kA fault level.
•
Switching Instant: An increase of 2-3 times is observed when switching is done at
negative peak voltage rather than at zero-crossing.
•
Initial Voltage of C1 : Increases by approximately 60% with 80% pre-charged main
capacitor in comparison to 0% initial voltage.
•
Tolerance of C1 : It is independent of the variation of capacitance.
•
Damping Resistance: An increase of about 15% is observed when damping
resistance is increased from 500 Ω to 1000 Ω.
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
(p.u)
Total Harmonic Distortion
t
Maximum THD = 69.1 %
Switching Condition: Grid Fault Level = 5 kA, Rdamp=1000Ω, V=-Vmax , Vc1 = 0.8 Vcs
& C1 = C1nom +3 %
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
MSCDN Power Loss
Variation in Steady State Power Loss of MSCDN with:
•
Fault Level: Increases when the short circuit current is increased from 5kA to
50kA.
•
Switching Instant: It is independent of the instant of switching (i.e., maximum
voltage or zero crossing)
•
Initial Voltage of C1: It is independent of the initial charge of the main capacitor.
•
Tolerance of C1: It is lower at C1-3% and higher at C1+3%.
•
Damping Resistance:
i.
ii.
At 5kA short circuit current, the power loss is lower at 1000 Ω damping
resistance.
At 50kA short circuit current, the power loss is lower at 500 Ω damping
resistance.
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
(MW)
MSCDN Power Loss
t
Steady state maximum power loss = 0.258 MW
Switching Condition: Grid Fault Level = 50 kA, Rdamp=1000Ω, V=-Vmax , Vc1 = 0.8 Vcs
& C1 = C1nom - 3 %
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
Grid Overcurrent
Variation in peak value of Overcurrent in the Grid with:
•Fault Level: Typically Higher @ 5 kA by 10-40 % compared to 50 kA Fault Level
Highest at 50kA Fault Level if MSCDN switched at Vmax of Grid
on pre-charged Capacitor and R=1000 switching(higher by 10%)
• Switching : Highest at Vmax (typically Higher by upto 200 %)
• Initial Voltage Across C1: Highest at 80 % Vcs (typically Higher by upto 50 %)
•Tolerance of C1: Lowest at C- & Highest at C+
•Damping Resistance: Increases with Damping Resistance (increases by 5-20%)
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
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(kA)
Grid Overcurrent
t
Highest Grid Overcurrent I max = 3.5 kA
Switching Condition: Grid Fault Level = 50kA, Rdamp=1000Ω, V=-Vmax , Vc1 = 0.8 Vcs
& C1 = C1nom +3 %
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
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Capacitor(C1) Overcurrent
Variation in peak of Overcurrent in the MSCDN Capacitor with:
•Fault Level: Typically Higher @ 5 kA by 10-40 % compared to 50 kA Fault Level
Highest at 50kA Fault Level if MSCDN switched at Vmax of Grid
on pre-charged Capacitor and R=1000 switching(higher by 10%)
• Switching Instant : Highest at Vmax (typically Higher by upto 200 %)
• Initial Voltage Across C1: Highest at 80 % Vcs (typically Higher by upto 50 %)
•Tolerance of C1: Lowest at C- & Highest at C+
•Damping Resistance: Increases with Damping Resistance (increases by 5-40%)
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
16
(kA)
Capacitor(C1) Overcurrent
t
Highest Capacitor Overcurrent I max = 3.44 kA
Switching Condition: Grid Fault Level = 50kA, Rdamp=1000Ω, V=-Vmax , Vc1 = 0.8 Vcs
& C1 = C1nom +3 %
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
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Comparison
Variation of values when MSCDN is connected to the grid feeding an unloaded
transmission line compared to MSCDN connected to grid without transmission line
Parameters
Average
difference(%)
Vpeak in Grid Vpeak across C1
(kV)
(kV)
0.8
0.3
Power Loss in
MSCDN (MW)
THDpeak(%)
Ipeak in Grid
(kA)
Ipeak in C
(kA)
9.5
8.5
4.3
-0.3
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
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Summary
• MSCDN networks play an important role for reactive power compensation
• Proper dimensioning of the MSCDN components is a must for minimizing
transient phenomena
• Switching conditions shall be ideal
• Surge arrestors must be installed to limit over-voltages
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
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Thank You
Fachgebiet Elektrische Energieversorgung unter Einsatz erneuerbarer Energien
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