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Phase-Shifting Transformers

ABB AGPower Technologies Division

Transformers

We reserve all rights in this document and in the information contained therein. Reproduction, use or disclosure to third parties without express authority is strictly forbidden.

© ABB AG - Transformers 2008

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Phase-Shifting Transformers

Power Flow ControlUse of Phase-Shifting TransformersPay-back-ConsiderationsHow does a Phase-Shifting Transformer work?Examples of Technically and Commercially Driven Applications Differences to power transformers

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Phase-Shifting Transformers

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Power Flow Control with PST

Phase Shifting Transformers are Power Flow Controllers

The phase angle between two systems determine the power exchange

)sin( LSLS

XVVP φφ −=

XS L

VLVS

VS-VL

I

φS - φL + α)sin( αφφ +−

+= LS

T

LS

XXVVP

X XTLS

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Power Flow Control with PST

Power-flow between two synchronous systems

L

GG

L

G

VS , φS

L

LG

L

VL , φL

P

P

P

To change the angle φS or φLmay affect third party power exchange

PThe “natural” phase angle difference φS - φL leads to uncontrolled power flow at the interfaces.

PThe use of Phase-Shifting Transformers allows the independent control of power flow!

PP

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Power Flow Control

Network SolutionsControl power flow between networks of different utilitiesNo influence on power flow to other networksControl load sharing between parallel linesIncrease total transfer of powerTransmit forced power flow down the contract pathBlocks parasitic power flow from other networks

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Energy EfficiencyPSTs are a means to control power flows in transmission system.With control on power flows existing assets can be used more efficiently by

Allowing higher total flow in a given corridor w/o violation of N-1 criterionOptimization of total lossesAllowing access of new generation (e.g. wind turbine parks)

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Pay-Back-ConsiderationImprovement and Control of the power flow,

independent of the phase angle of the system:

Increased supply of power to the customer

e.g.100 MW for 2000 h/a will result in

approximately 4 MEuro/a revenues (at ~ 20 Euro/MWh)

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Pay-Back- Consideration

Pay back is possible within a period of 2 - 3 years !

The control of power flow is a pre-requisite for marketing transmission capacity

100 MW may have a value of

2 MEuro/year (at ~ 20 Euro/kW-year)

Selling transmission capacity

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Pay-Back- Consideration - ExampleItaly‘s import capacity increasedby ~ 1000 MW

“N-1” Criterion fulfilled at increased imports

Rapid move from stand-by to max. phase shiftin case of other import lines trips

Torino MilanF

EdFCH AT

SLO

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Two core design

V1S

Series transformer

Exciter transformer

V1L

V2S

V3S

V2L

V3L

Principle of Phase Shifting Transformers

Tapped voltage of the neighboring phases, optimized intermediate Voltage

Excited by the source voltage

Transformation of the injected voltage

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Principle of Phase Shifting Transformers

U1reg

U1e

V1S V1L

u1in

j

∆V

α

Source voltage Ueexcites the Exciter transformerTapped voltage of the neighbouring phases, optimised intermediate voltage to utilize the tap changer best

The resulting quadraturevoltage uinjWill be transformed and will be injected between source and load (Voltage ∆V)

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Principle of Phase Shifting TransformersThe phase shifter rotates the phasor orientation between the source and load side.

In pure phase shifting transformers a voltage in quadrature to the source voltage is injected into the line

∆V

αadv

VSVL

V1S

V2S

V3S

V3L

V1L

V2L

φL

φS

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3 x 600 MVA232/232 kV± 35° in 59 stepsTwo core design

3 units delivered Aug, Sept, Oct 2006.Incl. sound enclosures+ PSGuard WAM

In operation since Dec 1, 2006

Increase of Transmission Capability

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Example: Two Core Design

Power: 600 MVAVoltage: 232 / 232 kVAngle: +/- 35°

PST without cooling equipment during dielectric tests

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Example: PST with Sound HousePower: 600 MVAVoltage: 232 / 232 kVAngle: +/- 35°

-17dBsound enclosure

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Example: 1630MVA, 400kV PST in Test Field

1630 MVA

400/ 400 kV

+18°

Losses ~ 2600 kW

Mass ~ 820000 kg

Dimensions

13.2 x 15.3 x 10.2 m

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Typical specification:1630 MVA through power400 kV + 18° in certain incrementsImpedancesInsulation levels BIL and AC

The resulting equivalent rating or physical size is a result of the shifting power of

1630 MVA x 2 sin Φ/2 = 528 MVA for the main unit and1630 MVA x 2 sin Φ/2 = 528 MVA for the series unit

Ratings of Phase Shifting Transformers

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1630 MVA400/ 400 kV+18°

Example: 1630MVA, 400kV in the substation

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Transportation

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Example: Loss Minimization

∆V1V1L

V2L

V3L

u

wr2-vr1

α

Optimum sharing of flow on parallel 400 kV and 132 kV systemsPower: 500 MVAVoltage: 400 / 132 kVRegulation: + 22°, ± 12 %1 active partSeparate windingsLosses: ~ 1200 kWWeight: 617,000 kgTank 13.2 x 4.4 x 5.2 m

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Principle of Phase Shifting Transformers

Asymmetrical extended Delta design

Excitation of the core by the phase voltage connected in Delta

V2S

V1S V1L

V3S

V3L

V2L

α

∆V

A part of the resulting voltage between phase 2 and 3 Will be transformed and will be injected between source and load (Voltage ∆V)

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Principle of Phase Shifting Transformers

Extended Delta DesignExcitation of the core by the phase voltage connected in Delta

V1S V1L

V2S V2L

A part of the resulting voltage between phase 2 and 3 will be transformed and will be injected between source and load (Voltage ∆V)

∆V

V3S V3L

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Principle of Phase Shifting Transformers

Single-core, symmetric designV1S V1L

V3S

V3L V2S

V2L

α

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Principle of Phase Shifting TransformersV1S

ue11

ue12V1L Single-core,

symmetric designV2S

V2L

V3S

V3L

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Example: Control of Loading of a Cable

450 MVA138 / 138 kV+/- 58°extended deltadesign, with separate reactor14.7 x 10.8 m553,000 kg

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Tanking of a450 MVA,138 / 138 kV, 58 °

Active Part of an Extended Delta PST

active part,247,000 kg

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Example 1 for economically driven PST project

EnBW

SWU

UW West

UW Süd

UW Ost

0 – 80 MW

~ 0 MW

~ 0 MW

Dellmensingen

Municipal utility of Ulm, DE

Supply from EnBW via three 110 kV substations

One line leased with very favorable conditions up to 80 MW

Incentive for PST:Savings in transmission fees

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Example 1 for economically driven PST project

100 MVA110/110 kV+7° in 32 stepsAsymmetrical two core design

ABB scope:Support of load flow studyTechnical proposalSupport in specification of power flow controllerDelivery and erection

In operation since 12/07

Payback within about 2 years

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Viertelstundenwerte vom 25.11.2005 - 1.12.2005

0

10

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50

60

70

80

90

25-11-200500:00:00

26-11-200500:00:00

27-11-200500:00:00

28-11-200500:00:00

29-11-200500:00:00

30-11-200500:00:00

01-12-200500:00:00

02-12-200500:00:00

Zeit

Wirk

leis

tung

Del

lmen

sing

en in

MW

Without PST

With PSTBenefit

¼ hour values of Nov 25, 2005 – Dec 1, 2005

Rea

l Pow

er D

ellm

ensi

ngen

in M

W

Time

Example 1 for Economically Driven PST Project

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Example 2 for economically driven PST project

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Example 2 for Economically Driven PST Project330 MVA230/230 + 5% kV± 79° in 32 stepsTwo core design

ABB scope:Load flow studiesEquipment rating studySpecification of PSTDelivery to site and erection of PSTSubstation designsProtection & Control?

Line construction starting fall 2007

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Differences to normal power transformers

Power for which phase shifter is dimensioned depends on maximum phase angle

Higher insulation demands

Larger, more complex tapped windings

Demanding specs on OLTCs: step voltages, switching power, reactance and capacitance of large tapped windings

Phase shift in load currents on a given core limb cause additional stray flux, forces, losses

Multitude of load cases to be checked for optimisation