06_01_TransformerProt

8/4/2019 06_01_TransformerProt

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ABB Power Automation LtdT2314 / trafoprot_a.ppt / F1 of 44

Transformer Protection in Transmission Networks

ABB

Transformer Protection

in

Transmission Networks


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Power transformers in a power system

400 kV AC Transmission

Generation

130 kV Subtransmission

Distribution

M

MV

LV


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Different vector group and neutral connections

Y d + zYN d11 + zn

Y y

YN yn0 (d1)

Y d

YN d1

D y

D yn11


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Different winding arrangements

2 windings+ unloaded

tertiary

3 windings Autotransformer+ tertiarye.g. Yy 6 d1e.g. YN Auto d1

2-winding transf.

+ Auxiliary

transformer

0


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Possible FaultsInsulation breakdown

Short circuits phase-to-phase

Inter-turns

Ground faults

Overvoltage U> (overexcitation U/f>)

Overtemperature

Oil leakage or contamination

Oil level monitor

Reduced cooling


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Possible Transformer Failures

Winding failures

Tap changer failures

Bushing failures

Core failures

Miscellaneous failures


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Selective Protection of:- two or

- three winding transformer

- autotransformer- generator-transformer unit

Detection of:

- all-phase faults

- earth-faults at solidly orlow-impedance earthed systems

- interturn faults


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ABB

Recommended Transformer Protection

Functions Rating

up to 2 MVA 2 - 5 MVA less 60 MVA over 60 MVA

Gas Detector

Relay (Buchholz)Overload Protection

(Thermal or

temperature

monitoring relay)

Overcurrent

ProtectionDifferential

Protection

Ground Fault

Protection

Voltage Regulating

Relay

Overexcitation for exposed overvoltage

situations

Oil level monitor


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Transformer Protection Basic VersionsTransformer Protection Basic Versions

Type of Transformer Unit High-Voltage Side Medium-Voltage Side Low-Voltage Si

Prot. Prot. 1 Prot. 2 Prot. 1 Prot. 2

(Main) (Back-up) (Main) (Back-up)

2-Winding (Star/Delta) Id I> + IN + TH + SBEF I>

Id REF I> + IN + TH + SBEF I>

2-Winding (Star/Stern) Id I> + IN + TH I> + IN + SBEF

Id REF I> + IN + TH REF I> + IN + SBEF

2-Winding (Star/Delta) + Earth.transf. Id I> + IN + TH I> + IN + SBEF

Id REF I> + IN + TH I> + IN + SBEF

3-Winding (Star/Star/Delta) Id I> + IN + TH I> + IN + SBEF I>

Id REF I> + IN + TH REF I> + IN + SBEF I>

3-Winding (Star/Star/Delta) + Earth.transf. Id I> + IN + TH I> + IN I> + IN + SBE

Id REF I> + IN + TH REF I> + IN I> + IN + SBE

2-Winding (Auto) Id + REF I> + IN + TH I> + IN

3-Winding (Auto) Id + REF I> + IN + TH I> + IN I>

Remark: The SBEF-Function (Stand-by EF Prot.) is only needed if earthing resistor is installed

Transformer Rating

S < 60 MVA S > 60 MVA


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ABB

Bu / LOL

OT / WT

I >

IN

TH

I

IN

I >REF

I >>

Transformer protection example (1)

IN


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ABB


I> 51T u 49

REF 87N I0 51N

87TU> 59B

87T

- Differential prot. (87T)

- REF (87N)

- Overcurrent (51T)- E/F protection (51N)

- Thermal overload prot. (49)

- Overvoltage prot. (59)


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I

Bu / LOL

OT / WT

I>IN

TH

Id

I>

I>

I N


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ABB


I

Bu / LOL

OT / WT

I >

IN

TH

Id

I >

IN

I >REF

I >>

REF


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Differential protection (87T)

Causes

phase faults in theprotection zone

effects

high currents potential damage to

transformer winding

expensive outage andrepair due to damage

Features / requirements

low impedance principle for two and three-winding

transformers

non-linear current-dependant

tripping characteristic high stability during through-

fault and CT-saturation

compensation for vector group

compensation for currentamplitude (CT-ratio)

inrush restraint


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Differential Protectionincludes:

C.T. Ratio adaption

Connection group adaption

Back-up functions

Large setting ranges

Features


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Id= I1+I2

by external faults can due to-ratio errors

-saturation

-losses in the transfomer

-tapchanger

a differential current can occur,therefore a stabilized tripping

characteristic is needed

Inrush can also provoke differential

current

87T Protectionzone


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Differential protection (87T)Features

True measurement for three-wind.

transformer

compares the greatest current the with

sum of the two others

I-instantaneous independ. of inrush

Inrush

eval.ratio 2nd.harm to fundamental

detection of largest phase current

detection of energised transformer using

load current Adaptive characteristic (b-line)

g

v

g-high

b

Id/ IN

Ih/ IN

Trip for

I1 / IN < b or

I2 / IN < bTrip

No Trip


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AI 1,2,3 AI 7,8,9

AD DIFF

AD



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AI 1,2,3

AI 7,8,9

AD

DIFF

A

D

AD

AI 4,5,6

Differential protection for 3 windings


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Differential protection 87T

CT's at the Aux. transformer

must have the same ratio as

the other two. Correction of the ratio with

Ref.-Value or a-Factor in the

protection function

G

87GT

10'000/ 5

10'000/ 5

800/ 5

300MVA

220/ 18 KV

300MVA18 KV

30MVA

18/ 6 KV


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Fault inside protected zone

1

2

3

4

1 2 3 4 5 IH

DII1 I2

IH = 0

g

cos a < 0


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Fault outside protected zoneLow short circuit current

Load

1

2

3

4

1 2 3 4 5 IH

DI

v=50%

I1 I2

IH = I1 = I2 =

ILoad < (1.5...3)*Irated g

I < (1.5...3) * Irated

cos a = 1

IH I1 I2 cos= a


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Isc

1

2

3

4

1 2 3 4 5 IH

DI

v=50%

I1 I2

IH = I1 = I2g

I > (1.5....3) * Irated

cos a = 1

v= infinite

IH I1 I2 cos= a

b

Fault outside protected zoneHigh short circuit current


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vg

1 2 3b

Restraint

I

IN

OperationOperation for

I1

IN< b

orI2

IN< b

IH

IN

I 1 I 2Protected unit

2)-1;

12

211

H

21H

H

321

I(II-II

I;IofgreatestI:where

0cosfor0I0cosforcosIII

current.Restraint....................I

currentOperating....IIII

=

D=

=


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Vector group adoption for Yd5 transformer


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Restricted earth-fault protection (REF)

AI

Trip

REF

Id

REF

Id Trip

Used at direct and low

impedance earthing

Clears internal EFsinstantaneously

Unaffected by inrush currentand external fault


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Thermal overload protection

Time

0,63

Rise of temperature

t


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Definite

V/Hz inverse

t

V/Hz

Overexcitation protection


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Requirements for overcurrent protection

Fast operation for primary short circuit

Non operation for inrush

Discrimination with other overcurrent

protectionNon operation at short or long term overload

Back up protection for network faults,

outside the transformer


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Transformer protection

Control unit

Busbar protection

R

E

C

OFF 1

ON

OFF 2

Application, typical HV bay


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Protection function structure

Ir12 = 0,80 A

Ir22 = 0,98 A

110 V3

Ur22 = 110/3 V

30 MVA

145 kV

11 kV

Ir1 = 120 A

Ir2 = 1575 A1600 / 1 A

150 / 1 A

11 kV3

150 / 1 A IrN12 = 0,80 A

A/D

conv.

BI

DIFF

TOC

REF

etc.

NOV

Trip

logic

Trip

F

il

t

e

r

in

g

>1

f


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Main functions

Compact design including: Basic SW functions and transformer protection functions:

- Differential protection

- Overcurrent protection(Definite time or inverse functions)

- Thermal overload

- Overvoltage protection

- Metering U I f P Q

- Distance protection

- Overexcitation U/f

- FUPLA

- Logic functions,delay & counter

- Disturbance Recording

- Check functions (I, U)

T f P t ti i T i i N t k


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Main Features- No interposing CT's

- Standard wiring diagram

- Inputs for external functions (Buchholz, temperature sensors) available

- Programmable indication of tripping and signalling

- Indication of measuring values

- Continuous self-monitoring- Modular SW protection functions

- 4 serial interfaces:* one front for local commmunication (PC)

* one rear for remote communication SPA or VDEW6* two others (spare)

- Member of the 316*4-family and part of PYRAMID

- Fits into ABB solution

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Transformer Protection Options

I> back up

Sensitive earth fault I0>for not grounded windings

Restricted earth fault

(High impedance principle) Thermal overload

U>, U

Documents

06_01_TransformerProt