electromagnetic transients in power systemscusp.umn.edu/napa_2014/friday/part 2/dharshana...
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Electromagnetic Transients in Power Systems
Dharshana Muthumuni
Manitoba HVDC Research Centre
Electromagnetic transients Due to interaction between L-C elements in the network
- Oscillations - Travelling waves
Triggered by - Switching of lines, cables, transformers - Faults - Lightning
Course Outline and Progress
Introduction and Basic concepts of electromagnetic transients
Selected applications in power systems
Preparation of notes and study cases(simulation examples) complete
Introduction and Basic concepts of electromagnetic transients
Response of LRC circuits
Representation of power system elements for a specific analysis
Model Data
Need for ‘sensitivity’ studies
Selected Applications in Power Systems
1. Transformer energizing
2. Transmission line and equipment switching
3. Capacitor bank switching
4. Circuit breaker Transient Recovery Voltage (TRV)
5. Overvoltages caused by lightning strikes
Transformer Energizing
240 Hz
380 Hz
0
1000
2000
3000
4000
5000
6000
7000
0 100 200 300 400 500 600 700 800 900
|Z+|
(oh
ms)
Frequency [Hz]
Core saturation Inrush current and harmonics
- Voltage dips
Network characteristics - frequency scans
- Over voltages due to harmonic resonance conditions
Ia
1.0
0.0
Ia (kA) [6] 0.00628253
Transmission line and Equipment Switching
Overvoltage magnitudes and equipment insulation levels - Surge arresters
Statistical distribution of overvoltage magnitude
Transmission line ‘flash-over’ rates
Investigation of overvoltage mitigation methods
E1 E2 E3 E4
Minimum: 364.6304 280.1849 332.9529 353.4259
Maximum: 395.8886 352.6374 413.6732 383.773
Mean: 379.7837 320.0234 375.2662 369.2719
Std Dev: 7.564519 17.03806 18.64495 7.544283
2% Level: 364.248 285.0315 336.9741 353.7778
98% Level: 395.3193 355.0153 413.5582 384.7659
Capacitor Bank Switching
s
Ak
dt
di
allow
326.21
10
602402
6
Inru
sh
Re
acto
r
Ca
pa
cito
r
25
MV
ars
pe
r ph
ase
/ste
p
3.7
6 [u
F]
Inru
sh
Re
acto
r
Ca
pa
cito
r
25
MV
ars
pe
r ph
ase
/ste
p
3.7
6 [u
F]
Ca
pa
cito
r
25
MV
ars
pe
r ph
ase
/ste
p
3.7
6 [u
F]
B1
B2
B3
Inru
sh
Re
acto
r
Ca
pa
cito
r
25
MV
ars
pe
r ph
ase
/ste
p
3.7
6 [u
F]
B4
0.0
00
27
7 [H
]
0.0
00
27
7 [H
]
0.0
00
27
7 [H
]
Inru
sh
Re
acto
r
0.0
00
27
7 [H
]
Back to back switching - Inrush reactors
Faults - Outrush reactors
Cable energizing
Resonance concerns
Circuit breaker Transient Recovery Voltage (TRV)
TRV is the voltage developed across the breaker poles immediately after current interruption
- Fast event - Simulation circuit should consider details of station equipment - Breaker TRV withstand capability limits
TRV
time(s) 0.2450 0.2500 0.2550 0.2600 0.2650 0.2700 0.2750 0.2800 0.2850
-150
-100
-50
0
50
100
150
200
250
300
kV
sysTRV
CC
VT
75
00
pF
75
00
pF
CC
VT
Station W
Station X1
Station X2
Station Z1Station Y1
Station Z2
Station Y2
b1
50MVAr Cap.Bank
b1
50MVAr Cap.Bank
b1
50MVAr Cap.Bank
a1
b1
a
b
LEGEND:
DSDS1BRKBRK1
a1
b1
b
a1
b1
a
b
a1
b1
a
b
a1
b1
a
b
a1
b1
a
b
b1
50MVAr Reactor
b1
50MVAr Reactor
b1
50MVAr Reactor
BAY A BAY B BAY C BAY D BAY E BAY F REACTOR 1
CAP BANK 1
CAP BANK 2
REACTOR 2 REACTOR 3
CAP BANK 3
Lightning Overvoltages
Lightning overvoltage studies are required to: Determine the required insulation levels of equipment (BIL). Surge arresters size and location Determine transmission line ‘flashover’ rates
- Very Fast event - Simulation circuit should consider details of station equipment
How do we represent system equipment - Line segments - Towers - Insulators - Tower footing resistance - Flashover mechanism
Motor Starting
Voltage dips and flicker caused by frequent starting of large motors at industrial plants is a power quality concern for utilities
- Model data to match manufactures T-S and I-S curves - Impact of rotating inertia - Power System impedance characteristics near the
interconnection point - Representation of load characteristics and the overall impact.
Thank you