02b_SGF100_procent_ protection.pdf

7/23/2019 02b_SGF100_procent_ protection.pdf

1/22

The year of Profitable Growth

Global networkof innovation

100% - Stator - Ground-

Fault Protection


2/22

Power Automation 2

Power Transmission and Distribution

Power AutomationProgress. Itsthatsimple.

Presenter: Dr. Hans-Joachim Herrmann

PTD PA13

Phone +49 911 433 8266E-Mail: [email protected]

Generator Protection

100%-Stator-Ground-Fault

Protection


3/22

Power Automation 3



Basic ProblemFaults Close to the Star Point

V0Displacement voltage

At faults close to the star point V0 goes to zero. Protection criteriadisplacement voltage and ground current do not work.

Alternatives: Evaluation of 3rd harmonics in the zero sequence voltage Additional injection of low frequency voltage into the star

point (20 Hz =Siemens principle)

U0


4/22

Power Automation 4



Distribution of 3rd Harmonics in a Generator

V0 3.Harm(V03H>)

V0 3.Harm(V03H


5/22

Power Automation 5



Considered Notes at the Applicationof 3rd Harmonics

? The distribution of 3rd. harmonics can be different fromgenerator to generator - the application of this principle canbe sometimes determined only during a primary test

? The harmonics (e.g. measuring location at the star point)are detectable not before the nominal voltage is available

? The part of harmonics depends also from the operationcondition of the generators (Influence of active and reactivepower)

- Application is not always possible

- Application has a restricted operating range


6/22

Power Automation 6



Measurements on a Generator

V0

G

7UM 61ILU0

VLILV0

1. Test device 7UM 61

2. Test device 7UM 61

6 MVA; Yd55,25/58,3 kV

6 MVA5250 V

400 Rpm

45 VA5P20

800/5 A

606 Ohm5250 100 100

?3 ?3 3 V5250?3

100 V60 kV

5 %+-


7/22

Power Automation 7



Measurements on a GeneratorInfluence of the Active and Reactive Power

Influence of theactive power isvisible

Approx. 15 V measured

without load

Release of theprotection functionat a determinedactive power is

recommended

150-Hz-Voltage at the star point as a function of

active power; Parameter reactive power

0

20

40

60

80

100

120

140

0 1 2 3 4 5 6

Active Power in MW

150-Hz-voltagein

V

150 Hz at Q = - 2 MVar 150 Hz at Q = 0 MVar

150 Hz at Q = 2 MVar 150 Hz at Q = 4 MVar


8/22

Power Automation 8



Comparison ofMeasuring Resultsbetween Star Pointand Terminals

Reactive Power 2 MVar

-150

-100

-50

0

50

100

150

200

250

300

0 2 4 6 8 10 12

Stator (0= star point; 10= terminal)

150-Hz-

voltage

in

V

P 2 MW P 3 MW

P 4 MW P 5,6 MW

Earth fault at 2 MVar and 4 MW

During an ground fault onthe star point the dis-

placement voltage on theterminal side was lowerthan the 3rd harmonics atfull load.A higher voltage wasexpected.


9/22

Power Automation 9



Fault RecordSwitching OFF of a Generators during Full Load

Generator: 25 MVA, 6,3 kV

iL3

VL3

VE

3rd harmonicsdrops


10/22

Power Automation 10



0 50 100 150 200 250 300 3500

2

4

6

8

10

Zeit in ms

Spannung

inV

10

0

5.58

9.3

U03hi

knU

10 tan( )i

312.633.344

181

tai

Fault on a Transmission Line (Ph-E ?) -An increasing of3rd harmonics on a broken delta winding was observed.

Pickup generatorovercurrentprotection

Drop off overcurrentprotection

Time in ms

Calculated 3rd harmonicsfrom a fault record

Secondarydisplacementvoltage(3rdharmonics

)

3rd harmonicsunder load


11/22

Power Automation 11



Logic Diagram

PreferredConnection:Star point(V3.H


12/22

Power Automation 12



Injection of a 20-Hz-voltage into the Star Point

Basic idea ? With the injection of a voltage into thestar point a electromotive force isavailable in case of an ground fault

? Also during an ground fault in the starpoint a fault current flows through thefault resistance.

? This measuring principle is independentfrom the operation conditions of thegenerator. A measuring during stand stillis possible.

? Following additional devices arenecessary:

20-Hz-Generator,20-Hz-Band passCurrent CT

20 Hz

RE

max.200 V

I


13/22

Power Automation 13



20-Hz-Measuring Principle is the Real100%-Stator Ground Fault Protection

U0

100 % protection range includes VTsand low side of unit transformer

? Measuring principle is independent from the operationconditions of the generator

? Measuring is possible during stand still of the generator

? High sensitivity (negative influence of capacitive currentwill be eliminated)

? Different and independent measuring principle againstthe displacement measuring method

90 % protection range with displacement voltage measurement

10 % -25 % Protection range of 3rd harmonic, with additional limits(see previous slides)


14/22

Power Automation 14



Basic Scheme - Unit ConnectionInjection via Grounding or Neutral Transformer

Load resistor should be> 0,5 ?


15/22

Power Automation 15



Scheme DesignGas Turbine with Neutral Transformer

Currenttransformer:Direct orderat RitzKS60-03 Size 315VA Cl.1 FS5

UER13

R14

RL

Neutral

transformer

J7

J8

TD3

K18

K17 +

UErrExcitation

TD1K14

K13 +

IEE1

7XT33

7XT34

20-Hz-

Generator20-Hz-

Band pass

4A3

4A11B4

1A1

1A2

1A3

3A2

3A1

3A3

1B1

Wiring shielded

400A

5A

max 200 V

kl

7KG6+ 31

- 32

+ 12

- 11 (Amplifier)

max. 10 cm Wiring twisted and shielded

Shunt:10 A/ 150 mV

2A1

2A3BE

+UH-UH

UL1UL2

UL3

Deviceready

Auxi liary

voltage

DC AC

external

block

KL


16/22

Power Automation 16



100%-Stator Ground-Fault ProtectionNumerical Design

Replica:

ises

ises Vses

20HzRE RBCE

RE = Fault resistance

CE = Ground capacitance instator circuit

Vses

ises

1) Filtering

3) Impedance replica of fault 4) Calculation of fault resistor from 2) and 3)

2) Calculation of the real part

Yers CE RE Yers =1

RE

+ j ? CE RE =V2r+ V

2i

Vr. Ir + Vi

. Ii

Re

Vr. Ir+ Vi

. Ii

V2r+ V2

i

Fourierfilter

(20Hz)

V20 = Vr+ jVi

I20 = Ir+ jIi=

???

???

20

20

V

I


17/22

Power Automation 17



Filter Coefficients of the 20-Hz-FIR Filter

0 10 20 30 40 50 60 702

0

21.989

1.733

af1

bf1

630 f1

af1

cos 2 ?

32

f1 0.5( )? 1 cos 2 ? f1 0.5

64

??

bf1

sin 2 ?

32f1 0.5( )? 1 cos 2 ?

f1 0.5

64??

Filter window: 4 cycles (64 filter coefficients)


18/22

Power Automation 18



Compensation of Sources of an Error

? Angle error of CT 400A/5A

(measuring currents in mA - 20 Hz current can be max. 3A )

? Primary to secondary impedance of the grounding/ neutraltransformer

? Angle errors of relay transformers

Compensation of the angle error via parameter(5309 PHI I SES Correction angle for I SGF)

Primary to secondary resistance from grounding orneutral transformer can be set (that is New)(5311 SGF Rps Resistance Rps)

Calibration is only for one point possible, e.g. Trip stage

Final settings during the primary test


19/22

Power Automation 19



Fault Record during a Primary Test

At the device

inputs aresmallsecondaryvalues

The capacitivecurrent is visible.This disturbance

current will beeliminated by thealgorithm.

Phase to groundvoltage

Displacementvoltage

Ground current


20/22

Power Automation 20



100 % Stator Ground Fault Protectionwith Primary Load Resistor

UER13

R14

RL

J7

J8 IEE1

7XT337XT34

20-Hz-Generator20-Hz-

Bandpass

4A3

4A11B4

1A1

1A2

1A3

3A2

3A1

3A3

1B1

2A1

2A3BI

+UH-UH

UL1UL2UL3

Device

ready

Aux.

voltage

DC AC

external

Block

1A4 1A3

UN

?3500 V

CT Ratio 1: 1

Voltagetransformer

7UM62

1A1

Voltage transformer:two pole isolated,until VN saturation freefor 20 Hz should be Rps< 1000?20s approx. 3 kVA

Current transformer:5P10 or 5P15 (or 5FS10)1A secondaryCT Ratio: 1A/1A(max. Ampere windings)


21/22

Power Automation 21



Setting Sheet of the100% Stator Ground Fault Protection

Two Stages

Back-upovercurrent

Supervision

Calibration


22/22

Power Automation 22



Logic Diagram

02b_SGF100_procent_ protection.pdf

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