Practical Examples - نورپردازی

Copyright © Siemens AG 2008. All rights reserved.

Sector Energy PTI NCTheodor Connor

Practical Examples

01.2008For internal use only. / Copyright © Siemens AG 2008. All rights reserved.

PTD SE PTITh. Connor

Content

Industrial network

Coal mine supply network

Rural supply network



110 kV

6 kV switchgear(with circuit breakers)

0.4 kV busbar

6 kV unit substation (with load interrupter switches and HV fuses)

Performance of Industrial Network improved by Low Resistance Neutral Treatment



IC=100A

transient earth fault relay

Initial state (isolated neutral)

unreliable operation of transient earth fault relayshigh overvoltages (transient and power frequent)high fault current over a long time

virtually every earth fault results in multi-pole faulthigh voltage dips in 0.4 kV system in case of multi-pole 6 kV faultman power needed for fault location and switch off



Steps of Investigation

Measurements for data acquisitionZero sequence impedance; Reduction factor of cable shieldEarthing and touch Voltages

Calculation of earth fault currents

Comparison of variants of neutral treatmentEffects on operation; Risk of fault propagationDevices for fault detection and protectionNeutral devicesCompliance with touch voltage criteria

Installation of proposed variant of neutral treatmentCommissioning and earth fault test



Measurements for data acquisition

ItestCurrent source

A VItest U

6 kV cableNYFG(b)Y

V

remote stationfeeding station

V

measurement of earthingand touch voltages

A Isheath

A Iearth

measurement of earthingand touch voltages

Results:• Z0 1,5 /km + j 1,5 /km

• rE = 0,60 ... 0,80

• UE 20 V/kA

• UB 10 V/kA

Results:• Z0 1,5 /km + j 1,5 /km

• rE = 0,60 ... 0,80

• UE 20 V/kA

• UB 10 V/kA



Improved operation with isolated neutral

no interruption of supply no cost for neutral devices

high fault current over a long time risk of multi-pole fault high overvoltages (transient and power frequent) risk of double faultnew capacitive directional earth fault relays necessaryman power needed for fault location and switch off

IC=100A

capacitive earth fault relayIE> = 50 A



Operation with earth fault compensation

no interruption of supplysmall earth fault current low risk of multi-pole fault

high overvoltages (transient and power frequent) risk of double faultnew wattmetric earth fault relays and window-type transformers necessaryhigh costs for neutral earthing transformer and arc suppression coil man power needed for fault location and switch off

IRest<10A

wattmetric earth fault relaywindow-type current transformer

ICoil = 140 A



Low impedance earthing 2000 A

fast fault clearing low risk of multi-pole faultno transient overvoltages low risk of double faultexisting overcurrent-time relays with phase fault detection can be used

setting of phase fault detection must changed to - smaller starting currents (to detect earth faults) and -higher delay times (to prevent tripping by inrush currents)

voltage dips of up to 10 % in 0.4 kV system in case of 6 kV earth faultsunselective or no tripping of HV fuses

Ik1,max=2kA Ik1,min=0,77kA

overcurrent-time relay(phase fault detection)t» = 0,3 s



Low impedance earthing 500 A

fast fault clearing and low fault current low risk of multi-pole faultno transient overvoltages low risk of double faultlow voltage dips in 0.4 kV system in case of 6 kV earth faults

new overcurrent-time relays with earth fault detection necessary

unselective or no tripping of HV fuses

Ik1,max=500AIk1,min=310A

overcurrent-time relay(earth fault detection)IE> = 200A; tE> = 0,3 s



Comparison of Investment Costs

Isolatedneutral

Earth fault compensation

Low impedance earthingIk1 = 2000 A

Low impedance earthingIk1 = 500 A

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%cost for protection devices

costs for neutral device



Equipment used for low impedance earthing

Neutral earthing transformer

Neutral resistor



Results of the short-circuit test

R

6 kV

0,4 kV

voltages 6 kV system

voltages 400 V system

earth fault current



Operational experience

low impedance earthing (Ik1 = 500 A) is in operation for more than 2 years

2 earth fault were selectively cleared by protection relays

no unselective tripping in response to earth fault starting

no sensible voltage dips in 0.4 kV system during 6 kV earth faults



Adequate neutral treatment for 25kV power supply systems of a new huge open cast lignite mine



Open cast mine typical equipment



Charakteristics of power supply of open castlignite mine

Movement of equipment like stations, transformers, conveyer belts and excavators´ following the work progressHeavy duty conditions due to large mechanical stress, dust, rock, rain, heavy vehiclesMovement of ground due to soil instability in excavation or fill up areasNot all areas are accessible at all time due to work progressReliability requirements regarding permanent output of coal mines due to nearby power stations and maintaining ground water levelFault detection selectivity and speed of fault clearing due to reliability requirements



Power supply system of Garzweiler ll

Nine 110kV bays, single bus bar, located at 110/25kV main substation JackerathSix 110/25kV transformers with together 390 MVA, located at 110/25kV substation JackerathEighty 25kV bays, double bus bar, located in the main substation Jackerath165 km of 25kV lines and cables feeding 45 medium voltage transformers (25/6kV) with together 438MVA.The network is operated as radial system equipped with over current protection



Parameters for Comparison

Voltage dependent aspectsTransient over voltagesPower frequency over voltages

Current dependent aspectsDamages at fault locationTouch VoltageInductive interferenceThermal stress of equipment

OperationalFault detectionFault locationAmount of switching for re-supply requiredPossibility for automation of operation

InvestmentCost for neutral treatment equipmentCost for protection



Measurements for data collection



Results of Heavy Current Injection Tests

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10Station

UE a

nd U

T in

V

Ground potential riseTouch voltage

Tolerable touch voltage based on t <0,4s



Construction of a Stope Cable



Earth fault trails in the new25kV system



Preparation of Test Stope Cable

-1500

-1000

-500

0

500

1000

1500

-100 0 100 200 300 400 500 600Time in ms

Cur

rent

L1

in A

Current of faulted phase:



Readings of voltages during test

-40

-30

-20

-10

0

10

20

30

40

-100 0 100 200 300 400 500 600Time in ms

Volta

ge L

1 in

kV

-40

-30

-20

-10

0

10

20

30

40

-100 0 100 200 300 400 500 600Time in ms

Volta

ge L

2 in

kV

-40

-30

-20

-10

0

10

20

30

40

-100 0 100 200 300 400 500 600Time in ms

Volta

geL3

in k

V

Voltage of faulted phase Voltages of unfaulted phases



Advantages of proposedcurrent limiting neutral earthing

The risk of earth fault developing into cross-country faults is eliminated

Fast and selective tripping of faulty feeder by protection devices

Fast fault location

Possibility of automation of network operation is given

Lowest Costs



And it happens!

Uen

Ie

IL1



EARTH FAULT TRAILS AND MEASUREMENTS IN RURAL 20 kV NETWORKS

Investigated 20kV network



Results of earth fault trials

110 kVnetwork

Earth faultlocation

Feedingsubstation

Measurement ofUL1, UL2, UL3, U0, I0

Measurement ofUL1, UL2, UL3, U0, IL1

Petersen coil

Neutral earthingtransformer

20 kV network

...

Switchingstation

-30

-20

-10

0

10

20

30

-40 -20 0 20 40 60 80 100 120 140 160

t[ms]

UL2

[kV]

-30

-20

-10

0

10

20

30

-40 -20 0 20 40 60 80 100 120 140 160

t[ms]

UL3

[kV]

-30

-20

-10

0

10

20

30

-40 -20 0 20 40 60 80 100 120 140 160

t[ms]

Uen

[kV]

-1500

-1000

-500

0

500

1000

1500

-40 -20 0 20 40 60 80 100 120 140 160

t[ms]

IL1

[A]



Harmonic analysis of residual current

-200-150-100-50

050

100150200

200 220 240 260 280 300 320 340 360 380 400

t[ms]

IL1

[A]

0

10

20

30

40

50

60

70

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

I res

idua

l in

A



Results of heavy current injection test

IMessCurrent - source

VIMess U

V

Measurement of Earthelectrode voltage- and

touch voltages

Earthing system ofremote station

Earthing systemof tested station

A

High voltagecable

0

30

60

90

120

150

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Substation

UE

and

UT i

n V

Ground potential riseTouch voltage

Tolerable Touch voltage

0

0,5

1

1,5

2

2,5

NA2XSY

NAKLEY

NEKBA

OHL

Line type

Impe

danc

e in

Zero sequence resistanceZero sequence reactance



Comparison of variants of neutral treatment

Existing network

Operation with arc-supression coil:

ICE = 720 AIres > 66 A

Actual networkstructure

EKO

KNSE

NSE

Var.1.1

Var.1.3

Var.1.2

Restructurednetwork

ICE < 400 A EKO

KNSE

NSE

Var.2.1

Var.2.3

Var.2.2

EKO: Operation with arc supressioncoils

KNSE: Short time current limiting neutral earthing

NSE: Current limiting neutral earthing

Practical Examples - نورپردازی

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