16 - Prevost IT- Technology & Design

Instrument Instr ument Transfor ransf ormer mer - Technolo echno logy gy & Desi Design gn Conference on Electrical Power Equipment Diagnostics Bali, Indonesia Thomas Prevost

31 October 2013

Inst nstrum rume ent Transfor Transformers: mers: Link Lin k between between prima prim ary and se s econd conda ary equipment

Func unction tion of an Instrum ent Transfor Transformer mer

• Measurement  – Transform the primary signal into a secondary signal which can be transmitted and measured to secondary equipment.

• Isolation  – Isolation of the secondary circuit and equipment from the high voltage of the primary circuit.

Measurement Function

• Transf ransfor orm m the the prim primar ary y sign signal al int into oa secondary signal which can be transmitted and measured to secondary equipment  – Transform primary current into secondary current Ip = 1000 1000 A

Is = 1 A

 – Transform primary voltage into secondary voltage Up = 400/√3 kV

Us = 110/ √3 V

CT for Mea easu suri ring ng and Pro Protecti tection on

CT for Measuring: • High accuracy in the range of rated current • Saturation with over current (FS) CT for Protection : • 1% accuracy at rated current • defined accuracy in high high current range (e.g. 5P20  error < 5% for 20 times rated current)

 Ac  A c c u r ac acy y f o r Meas Measu u r i n g CT  Accuracy classes according according to to IEC 60044 – 1 class 0.2 - 0.2S and 0.5 - 0.5S 1.6

100

cl. 0.2 cl. 0.2S

   %1.4

cl. 0.5 cl. 0.5S

1.2

  n    i   m

cl. 0.2 cl. 0.2S

90

cl. 0.5 80

cl. 0.5S

70

1

60 50

0.8

40

0.6

30

0.4 20

0.2

10

0

0

0

20

40

60

80

100

120

Current in % I N

Limits of amplitude error

140

0

20

40

60

80

100

120

140

Current in % I N

Limits of phase displacement

 Ac  A c c u r ac acy y f o r Pr Pro o t ec ectt i o n CT •

Standard acc acc uracy c lasses for p rotectio rot ectio n 5P and 10P 10P

•

Defini tion ti on acc ordi or ding ng to IEC60 IEC6004 044 4 -1 § 12: 12:

•

Burden Bur den in VA VA (cos (cos φ = 0.8), Accuracy limit factor (ALF) and accuracy limits

•

Exampl e: 30 VA 5P20 5P20 (max. 5% Error at 20 times ti mes rated cur rent) rent )

 Ac  A c c u r ac acy y f o r Pr Pro o t ec ectt i o n CT Other accuracy classes for protection cores acc. IEC 60044-1:

PR:

PX:

- 5PR and 10PR Accuracy defined as 5P and 10P - low remanence factor Kr ≤ 10

- defined with knee point voltage EK and max. excitation current Ie at EK (with increase of voltage E K to EK + 10% max. increase of excitation excitati on current 50 %) - max. secondary resistance RCT at 75°C

 Ac  A c c u r ac acy y f o r Pr Pro o t ec ectt i o n CT

Transient requirements according to IEC 60044 – 6: TPS:

defined with knee point voltage and max. excitation current

TPX:

max. error during defined breaker cycle no requirements for remanence

TPY: TPY:

max. error during defined breaker cycle max. remanence 10 %

TPZ:

max. Error (only a.c. component) Specified secondary time constant Very Very low remanence remanenc e

Hystere ysteresis sis for dif differe ferent nt CT De Defin finitio itions ns B P, TPS TPX

TPY

TPZ

Remanence points

H

ref Trench

Induc nductance tance during durin g transient t ransient curr c urre ent (TPY cores)

B

without air gap

Saturation threshold

with air gap

t t’ 1st fault duration

tfr  dead time

tal permissible time to accuracy limit

ref Trench

t’’ 2nd fault duration

 Acc  Ac c u r ac acy y Def Defii n i t i o n f o r Vo l t ag age e Tr Tr an ans s f o r m er ers s IEC 60044-2

Measuring Voltage Transformers (0.8 …1.2 UN,)

Protection Voltage Voltage Transformers (0.05 … fu UN)

 Acc  Ac c u r ac acy y o f Vo l t ag age e Tr Tr an ans s f o r m er ers s

Func unction tion of an Instrum ent Transfor Transformer mer

• Measurement  – Transform the primary signal into a secondary signal which can be transmitted and measured to secondary equipment.

• Isolation  – Isolation of the secondary secondary ci rcuit rcui t and and equipment qui pment from fro m the high hig h voltage vol tage of the th e prima pri mary ry circui t.

Externa xternall Insu nsulation lation Requirements: • Withstand voltages: A.C. lightning and switching impulse  arcing distance • Withstand voltage during rain  arcing distance, shed profile • Pollution requirements  Shed form, creepage distance • Mechanical requirements  Material, sizes Porcelain Porcelain Insulator

Composit e Insulator

Interna nternall Insu nsulation lation • Insulation between cores and housing • Bushing insulation • Voltage grading inside the bushing Oil-Paper Insulation:

SF6 Insulation:

• Paper impregnated with mineral oil • Compact design • Low aging when hermetically sealed against outside air • Maintenance free

• Gas insulation with overpressure of some bar • Some bigger design • No aging • Pressure monitoring

Conventional Instr ument Transfor ransformers mers Inductive principle

Cur urrent rent Transfo ransform rme er

Oil-Paper Insulation 72.5 kV … 550 kV

SF6 Insulation 72.5 kV … 800 kV

Prin rinci cipl ple e of Current Transf Transform orme ers

i1

n1

Inductive transformer secondary side short circuited i1 : primary current n1 :primary turns

n2

i 2

Magnetic core

i2 =

i2 : secondary current n2 : secondary turns

n1 x i1 n2

Equi quiva valent lent circui cir cuitt and and pha ph asor diagra d iagram m of Current Transformers

IXh I‘1

I2 R‘1

U1

 ΔI

X‘1

R2

I0 RFe

XH

UH

IFE

X2

RB U2

I1

RB

I2

δ

I2 ·X 2 I2 ·R 2

UH

I2 ·X B

U2 I  ·R 2 B

Prin rincip ciple le of Curr Curre ent Transfor ransformers mers insulation •

•

Magne agneti tic c cor core e with ith sec secon onda darry winding to fulfill the measuring task

core metallic shield

Inte Interrnal nal and and exte extern rnal al ins insul ulat atio ion n to fulfill the isolation task primary bar

secondary wires

Cur urrent rent Transf ransform ormer er

(Oil-paper insulated) metallic bellow



Cores



primary rod



high voltage insulation



bushing



filling oil



terminal box





aluminium cap



terminals



head casing



lifting lug



external insulator

Cur urrent rent Transf ransform ormer er Metallic expansion bellows (hermetically (hermetically sealed)

Oil / paper high voltage insulation design for AIS 72.5 – 550kV active part CT

High voltage terminal Insulator (Porcelain or composite) Fine grade bushing

Ground electrode CT measuring cores

Current Transformer

Cur urrent rent Transf ransform ormer er SF6 gas insulation design for AIS 245 – 550kV High voltage terminal

grading cylinder Composite insulator

Secondary connection

SF6 gas device incl. monitor

Vol oltage tage Transf Transfor ormers mers

Oil-Paper Insulation 72.5 kV … 550 kV

SF6 Insulation 72.5 kV … 800 kV

Prin rinci ciple ple Vol oltage tage Transf Transform ormers ers

u1, n1

high voltage bushing insulation

u2, n2

Secondary windings iron core

u2 = n2 x u1 n1

Primary winding

Conventional Conven tional measuring devices – voltage transformer transformer High voltage terminal Metallic expansion bellows (hermetically (hermetically sealed) Insulator (Porcelain or composite) Fine graded bushing HV electrode Primary winding Secondary winding Iron core

Oil / paper high voltage insulation design for AIS 36 – 245kV

Equivalent Circ Circuit uit and pha ph asor diagram of Voltage Transformers

I‘1·X’ 1 I‘1 R‘1 U1

U1

I2 I0

X‘1 RFe

XH

R2 UH

X2

 ΔU

I‘1·R’ 1 I2·X 2

RB

UH

U2

I2·R 2

XB

I2·XB

δ

U2

I2·R B IXh IFe I2

I‘1

Vol oltage tage Trans Transfo form rmer er

Vol oltag tage e Trans Transff or ormer mer Typ ype e

(Oil-paper insulated) metallic bellow filling oil bushing







aluminium cap



external insulator



lifting lug



terminal box



high voltage insulation



Windings



iron core



Gas Ga s ins ulated Vol Voltage tage Transf Transfor ormers mers GIS-voltage transformer  rupture disk LV - winding

HV-electrode

pressure vessel

HV-spacer 

GIF-outdoor voltage transformer

Conventional Conven tional measuring devices – voltage transformer transformer SF6 gas insulation design for AIS Type EGF 245 – 550kV

High voltage terminal

HV electrode

HV connection

Ground electrode

Composite insulator

Grading cylinder Primary winding Secondary winding Iron core SF6 gas device incl. monitor

Conventional Conven tional measuring devices – CVT’ CVT’ss High voltage terminal

Oil / paper high h igh voltage insulation design for AIS

Metallic expansion bellows (hermetically sealed)

72.5 – 550kV

Insulator (Porcelain or composite) High voltage capacitor (C-divider) Bushing (tap voltage approx. 8 – 12 kV) MV – VT (EMU) Primary winding Secondary winding Compensating coil

Capacitive Voltage Transformer

metallic bellow



capacitor



intermediate transformer + compensating coil

 Active part



primary terminal



lifting lug



head



porcelain insulator



housing



terminal box



Housing

Prin rinci ciple ple of CVT Acti Active ve Part Part

High voltage Compensating coil

Damping impedance and varistor

Capacitive divider Secondary windings Intermediate transformer

Secondary windings N NHF

Spark gap

Combined CT/VT Type EJGF 245 – 550kV

Type EJOF 72.5 – 170kV

Current transformer Voltage transformer

Combined Transformer Type IVOKT

(Oil-paper insulated) high voltage

Voltage transformer active part

Current transformer active part

Questions