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Phase Shifter Transformer,from design to operation
IEEE Power Engineering Society,
Event of 21. February at BKW
David Orzan
BKW/Titel/Kurzzeichen/Seite 2
Agenda
1. Problematic: Large transit in the transmission network
2. Specification: Load flow calculation and network contraints/requirements
3. Engineering and technology: The features to care about andthe details that matter
4. Operation: Experience and perspectives
BKW/Titel/Kurzzeichen/Seite 3
Transmission network in the region of Bassecourt
400 kV220 kV
BKW/Titel/Kurzzeichen/Seite 4
Substation of Bassecourt
BKW/Titel/Kurzzeichen/Seite 5
Failure of a 220 kV bushing in Bassecourt, Winter 2001
2*400 MVA
BKW/Titel/Kurzzeichen/Seite 6
Failure in the tap winding of theparallel transformer
2*400 MVA
BKW/Titel/Kurzzeichen/Seite 7
Learnings of Winter 2001Additional transformer capacity is needed in Bassecourt (Repair
may last months)
Power flow must be controlled more effectively (Diagonal control is not sufficient)
Critical transformer components must be monitored
Bushings must be specified with additional reserve (voltage andcurrent ratings)
Overvoltage protection of old transformers must be improved(modern surge arresters needed)
BKW/Titel/Kurzzeichen/Seite 8
Basic modelIllustration of the advantage of the phase shifter with 2 scenarios:
• Increase in transmitted power on the transmission system
• Contingency in the regional system
BKW/Titel/Kurzzeichen/Seite 9
Advantages of the phase shifterAbility to control power flows and thus...
Increase operation flexibility
Increase network security
Increase in transmission capacity
Reduction of the losses in the regional network
Reduction of the network costs when the transformer infeedsare subject to different tarifs for the transmission network usage
BKW/Titel/Kurzzeichen/Seite 10
Network studies• Operation requirements
• Scenarios
• Results
• Objective: define the rated power, voltage ratio, voltage step
BKW/Titel/Kurzzeichen/Seite 11
Operation requirements• Active power control
– Summer : between -100 MW and 100 MW– Winter : between 100 MW and 365 MW
• Voltage control– 380 kV : between 395 kV and 420 kV– 220 kV : between 223 kV and 245 kV– 132 kV : between 136 kV and 145 kV– 50 kV : between 47 kV and 51 kV
• Independent voltage and active power control• Maximum active power step: 20 MW per tap change• Ability to operate the main transformer (shunt unit) without the
quadrature regulating transformer (series unit)• Parallel operation with the other transformers for a short duration• Overload capability, Linear voltage control
BKW/Titel/Kurzzeichen/Seite 12
Parameter 1: Design variantesAmong all proposed designs 4 variantes have been studied extensively:
Var. 1.1: HT 400/141.6 kV (+/- 12 Stufen ; 1.2 kV/Stufe)RT +/- 17 Stufen ; 2.17 kV/Stufe
Var. 1.2 HT 400/141.6 kV (+/- 12 Stufen ; 1.2 kV/Stufe)RT +/- 17 Stufen ; 1.75 kV/Stufe
Var. 2.1: HT 400/151.6 kV (+/- 12 Stufen ; 1.2 kV/Stufe)RT +/- 17 Stufen ; 2.17 kV/Stufe
Var. 2.2: HT 400/151.6 kV (+/- 12 Stufen ; 1.2 kV/Stufe)RT +/- 17 Stufen ; 1.75 kV/Stufe
BKW/Titel/Kurzzeichen/Seite 13
Parameter 2: Network loadingParameter 3: Network configuration• Network loading: Winter/Summer, Today/Future, Day/Night, ...
• Many network configurations have been simulated by disconnecting parallel path (Transmission lines or transformerson the North-South axis, close to the substation of Bassecourt)
BKW/Titel/Kurzzeichen/Seite 14
Extensive load flow calculations
Transformer design
Var 1.1
Var 1.2
Var 2.1
Var 2.2
Network load
Winter todayWinter futureSummer todaySummer future...
Network configuration
Elt. 1 outElt. 2 out...Elt. n Out
BKW/Titel/Kurzzeichen/Seite 15
OutputFunction(Transformer design ; Network load ; Network configuration)
Output:• Loading of the network elements• Voltage in the region of Bassecourt• Controlability of the PST: The ability of the transformer to control
the 132 kV voltage and the active power transmitted independantly
BKW/Titel/Kurzzeichen/Seite 16
Control of voltage and active powerVariante 1.2 (400/141.6 , 1.75 kV) ; Summer today ; All elt. connected
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
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Possible working pointVoltage limit in the 132-kV-network
U1 > 145 kV
Voltage vector
BKW/Titel/Kurzzeichen/Seite 17
Active power control depends on the network loading
Power flow in the transformer 400/132 kV (Variante 1.2)
-300
-200
-100
0
100
200
300
400
500
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Step of the series unit
P (M
W)
Summer todayWinter todayWinter future
Positive means flow from the transmission to the regional network
Last slide
BKW/Titel/Kurzzeichen/Seite 18
Comparision with different transformer designsSummer today, comparision of different transformer design
Big influence on the controlability1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
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Var. 1.2400/141.6 kV1.75 kV
Var. 2.1400/151.6 kV2.17 kV
Var. 2.2400/151.6 kV1.75 kV
BKW/Titel/Kurzzeichen/Seite 19
Control of voltage and active powerVariante 1.2 (400/141.6 , 1.75 kV) ; Winter today
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
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Possible working point
Limit of the voltage in the 132 kV network
Limit of the transformer (MVA)
U1 < 136 kV
U1 > 145 kV
BKW/Titel/Kurzzeichen/Seite 20
Active power control depends on the network loading
Power flow in the transformer 400/132 kV (Variante 1.2)
-300
-200
-100
0
100
200
300
400
500
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Step of the series unit
P (M
W)
Summer todayWinter todayWinter future
Positive means flow from the transmission to the regional network
Last slide
BKW/Titel/Kurzzeichen/Seite 21
Comparision with different transformer designsWinter today, comparision of different transformer design
Big influence on the controlability
Var. 1.2400/141.6 kV1.75 kV
Var. 2.1400/151.6 kV2.17 kV
Var. 2.2400/151.6 kV1.75 kV
BKW/Titel/Kurzzeichen/Seite 22
Active power control with different PST designs
Active power through the transformer (Summer today)
-400
-300
-200
-100
0
100
200
300
400
500
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Tap position of the series unit
P (M
W)
Var. 1.1Var. 1.2Var. 2.1Var. 2.2
BKW/Titel/Kurzzeichen/Seite 23
Active power steps in differentnetwork loading conditions
Active power step per tap change (Variante 1.2)
0
5
10
15
20
25
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Tap position of the series unit
ΔP
(MW
)
Summer todayWinter todayWinter future
BKW/Titel/Kurzzeichen/Seite 24
Active power steps with different PSTdesigns
0
5
10
15
20
25
30
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Δ P (M
W)
Var. 1.2Var. 2.1Var. 2.2Var. 1.1
Active power step per tap change (Summer today)
Tap position of the series unit
BKW/Titel/Kurzzeichen/Seite 25
Diagonal controling PST
Summer today Winter today Winter future
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• Working point on a line (Voltage and active power closely linked)• Results in unwanted reactive power flows• A diagonal regulation would have been too restrictive and
could not have fullfiled the operation requirements
BKW/Titel/Kurzzeichen/Seite 26
Engineering and project ManagementexperienceSpecifications and construction
Quality control and test
Transport
Project in an existing substation
BKW/Titel/Kurzzeichen/Seite 27
Shunt and series units
400 kV
132 kV
Compensation Transformer(Utertiary=cst)
Tertiary windings
Aut
otra
nsfo
rmer
BKW/Titel/Kurzzeichen/Seite 28
Data sheetShunt unit400 MVA, auto transformerYNa0d11400/140 kV ± 9x1,68 kV / 49 kV425 tonnes (240 t without oil)L x B x H: 14,17 x 8,34 x 10,21 m
Series unit66.4 MVAIII y n49 kV and 12 x 1,75 kV165 tonnes (55 t without oil)L x B x H: 12,4 x 6,15 x 8,24 m
BKW/Titel/Kurzzeichen/Seite 29
Schedule plan
1. Q 2. Q 3.Q 4.Q 1.Q 2.Q 3.Q 4.Q 1.Q 2.Q 3.Q 4.Q
KonzeptSpezifikationEvaluationAnlagenerweiterungTrafobestellung, Dez.03Konstruktion1. Design-ReviewFabrikation / PrüfungRedesignFabrikation / PrüfungAbschluss WerkprüfungTransport/MontageInbetriebsetzungKommerzieller Betrieb
2003 2004 2005
BKW/Titel/Kurzzeichen/Seite 30
Acceptance tests in the factory
BKW/Titel/Kurzzeichen/Seite 31
Challenging transport (240 t for the shunt unit)
BKW/Titel/Kurzzeichen/Seite 32
Challenging transport
BKW/Titel/Kurzzeichen/Seite 33
Extensive acceptance tests on site
BKW/Titel/Kurzzeichen/Seite 34
Extensive acceptance tests on site
BKW/Titel/Kurzzeichen/Seite 35
Technical features and specialitiesCompensation transformer
Protection systems
Monitoring systems
BKW/Titel/Kurzzeichen/Seite 36
Why a compensation transformer?U(TapShunt; TapSeries)
1 3 5 7 9
11 13 15 17 19 211
6
11
16
21
100
110
120
130
140
150
160
170
Voltage [kV]
Series unit
Shunt unit
160-170150-160140-150130-140120-130110-120100-110
BKW/Titel/Kurzzeichen/Seite 37
Why a compensation transformer?φ(TapShunt; TapSeries)
1 3 5 7 9 11 13 15 17 19 211
5
913
1721
25
-5
0
5
10
15
20Phase (°)
15-20
10-15
5-10
0-5
-5-0
Series unit
Shunt unit
BKW/Titel/Kurzzeichen/Seite 38
ProtectionThe protection system of normal transformers are well known
A phase shifter transfomer needs additional protection schemes– Strategic unit– Presence of a series winding– Ability to operate the main transformer (shunt unit) without
the quadrature regulating transformer (series unit)– Presence of a bus bars connecting the tertiary of the main to
the series winding
BKW/Titel/Kurzzeichen/Seite 39
Overview of the protection schemes
Distanz-schutz
Differential-schutz
Hochimpedanz-schutz
BKW/Titel/Kurzzeichen/Seite 40
Point on the wave switching
[pu]
0 4 8 12 16 20
0.0
0.3
0.6
0.9
1.2
1.5
[ms]
dT
Voltage between the circuit breaker contacts
Dielectric strength of the inter contact spac
BKW/Titel/Kurzzeichen/Seite 41
Why point on the wave swichtingTo reduce the electromechanical forces when energizing the
transformer (Inrush current)
0 4 8 12 16 200
200
400
600
800
1000[A]
[s]
0.00 0.02 0.04 0.06 0.08 0.100
200
400
600
800
1000
10.00 10.02 10.04 10.06 10.08 10.100
3
6
9
12
15
19.90 19.92 19.94 19.96 19.98 20.00-3
-2
-1
0
1
2
3
BKW/Titel/Kurzzeichen/Seite 42
On Line MonitoringDissolved gas in oil monitoring
Bushing monitoring
Tap changer monitoring
Not for protection function: Alarm, i.e on tripRecording and archiving of the data for trend analysis and decision
making (condition based maintenance)Communication also possible via mobile phone (Expert)On line monitoring and off line periodic measurement (DGA, Frau,
SDS) complet each other
BKW/Titel/Kurzzeichen/Seite 43
Disolved Gaz in oil on line monitoring
(H2, CO)
BKW/Titel/Kurzzeichen/Seite 44
Bushing on line monitoring
GelernteVektor
Fault identificationHomopolar current
Fehler-Fall
BKW/Titel/Kurzzeichen/Seite 45
Tap changer on line monitoringMonitored parameters: Torque, Temperature, Contact erosion, Number
of switching operation
BKW/Titel/Kurzzeichen/Seite 46
Operation experienceThe transformer can be operated as expected by the simulations
(Voltage and active power control)
Parallel operation is possible under specific conditions and for ashort duration (some minutes)
Stable protection: Some short circuit on transmission lines close tothe substation have not resulted in a false trip of the transformer
Control and monitoring systems work as expected
BKW/Titel/Kurzzeichen/Seite 47
Example of the control capability
Typischer Lastverlauf
7
9
11
13
15
17
19
0 25 50 75 100
Stuf
enst
ellu
ngen
-100-50050100150200250300350
Q [M
Var]
P
[MW
]
Quer LängsP [MW] Q [MVar]P ohne Regelung [MW]
Nacht Tag Nacht Tag
BKW/Titel/Kurzzeichen/Seite 48
Perspective and improvementsControl the active power more actively for example to reduce
losses in the regional network.
Dynamic transformer loadability
BKW/Titel/Kurzzeichen/Seite 49
On line transformer loadability monitoring