ETC GDPR 01a Power System Design

7/31/2019 ETC GDPR 01a Power System Design

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TOPIC OBJECTIVES

Better understanding of:

why and how the Power system design have influence on the securityof the system

possible causes of faults on lines, transformers, busbars or equipmentin switchyards

switchgear arrangements - maintainability and reliability

hardware and software of fault clearance and control system

specifics about Electric Power System of Nigeria


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Transmission lines design

Voltage level

Overhead line or cable Single or double circuit

Insulator chain design

Towers design

Shield wires

Tower footing earthing

Conductor thermal capability


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Faults on transmission line possible causes

Lightning

Switching

Pollution

Salt storms

Growing trees

Bush fires Damage or sabotage

The most often!


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Power transformers design

Voltage level Insulation level

kV kV0.4 0.42

0.415

1

6 7.2

10 12

11 12

15 15.75

20 24

33 36

35 38

66 72

110 123

132 145

220 245

330 362

400 420

750

1000

EHV

Group

LV

MV

HV

Purpose and capacity

Step up or step down, ratio

Insulation levels

Neutral point earthing

Tap changing (off/on load)

Dry or oil immersed

Cooling system

Single phase or three phase

Two/three windings or autotransformer

Efficiency (loses)

Impedance

Vector group


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Power transformers vector groups

N

A

B

C

a

b

c

YNd11

N

A

B

C

ma

mb

mc

b

c

a

YaNd11

ZNyn1NA

B

C

a

b

c

n

EARTHING TRANSFORMER

POWER TRANSFORMER 132/33 KV INTERCONECTION AUTOTRANSFORMER330/132 KV

TERTIARY WINDING


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Power transformer faults possible causes:

Deterioration and ageing of insulation

Mechanical damage of insulation Damage of conductor, poor contact in joints

Tap-changer, wear, mechanical failure

Tap-changer switching during overcurrent condition

Transient overvoltage , e.g. at lightning or switching

Contaminated oil Corona discharge

Mechanical forces on windings and bushings

Heavy current during external faults, switching-in, or at resonance

Overheating

High load current or circulation current between parallel transformers Reduced or lost cooling, sustained through-fault current

Overexcitation or voltage rise with transformer core saturation


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Power transformer faults

IEEE statistics about transformer faults

Earth fault

Short circuit Turn-to turn fault

Flash over from HV to LV winding

Core fault

Tank fault

External fault


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Switchyard design

In many cases there is a tendency to have richly equippedswitchyards.

The reason for this is often to have high dependability for the

fault clearance, have a high probability of fault disconnection.

We have to keep in mind that more equipment we have , thehigher probability for faults in the equipment we get!


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Switchyard design: HV equipment

Busbar conductors and drop off connections, fittings

Isolators/disconnectors

Circuit breakers

Current transformers

Voltage transformers

Surge arrestors Earthing switches

Line (wave) traps

The most important is typeof switchgear arrangement

and the placement of HVequipment


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Switchyard design:Single breaker - single busbar

Cheap, simple, in distribution sector


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For more feeders and incomers

Bus section

Switchyard design:Single busbar with bus section


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No feeder outage during maintenance of CB

Switching logic of tripping to Line CB or Transfer bay CB

Transfer bus

Transfer bay

Switchyard design:Single busbar with transfer bay


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Switchyard design: Double busbar

The most common arrangement

Bus coupler


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SWITCHGEAR ARRANGEMENTS: Breaker and a half

For two lines Three breakers =3/2 = 1 1/2


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Single busbar +

Reserve busbar

13%

Single busbar

27%

Double busbar

42%

Poligone (ring)

busbar

1%Double busbar with

2 breakers

2%

Double busbar with

1.5 breaker

4%

Triple busbar

4%

Double busbar +

Reserve busbar

7%

SWITCHGEAR ARRANGEMENTS

CIGRE statistics about applied switchgear arrangements


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SWITCHGEAR ARRANGEMENTS: Busbar faults

Fault causeType and number of faults

Total %PE PPE 3P Unknown

Flash over on busbar insulators 20 6 1 27 21%

Circuit Breaker failure 16 2 2 20 16%

Insulation on switching devices 19 2 1 22 17%

Other on insulation 4 1 4 9 7%

Current transformers 3 3 2%

Disconnector opening on load 8 1 6 15 12%

Not removed temporary earthing 6 1 8 15 12%

Contacts (birds and other) 9 1 2 1 13 10%

Misc. and unknown 2 1 1 1 5 4%Total 87 15 24 3 129

% 67% 12% 19% 2%100%

CIGRE statistics for 400 kV busbars 91-96.


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PROTECTION

EQUIPMENT

TRIP

COIL

TELE

COM

DC SYSTEM

FAULT

VOLTAGE

TRANSFORMER

CURRENT

TRANSFORMER

CIRCUIT BREAKER

FAULT CLEARANCE SYSTEM


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PROTECTION

EQUIPMENT

TRIP

COIL

TELE

COM

DC SYSTEM

FAULT

VOLTAGE

TRANSFORMER

CURRENTTRANSFORMER

CIRCUIT BREAKER

FAULT CLEARANCE SYSTEM

HARDWARE DC supply system Current transformers Voltage transformers Protective relays Switching devices Telecommunication equipment Wiring

SOFTWARE

Design Construction (installation) Configuration of the protection relays Setting of the protection relays Maintenance


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CONTROL SYSTEM

Control commands(open, close, raise, lower )

Indications(position, status )

Alarms (protection trips, alerts, warnings)

Metering(current, voltage, power, temperature )

Synchro-check

OLTCvoltage control

Katampe 330/132 kV s/sCONTROL BOARD


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Specific characteristics of Power system of Nigeria

Still in development

Waste area with very different population density and consumption

Still unable to supply the nations demand for electricity needs to build new

generating plants and rehabilitate existing but not operational capacities

Hydro generation in middle belt (Kainji, Jebba and Shiroro)

Thermal generation on south (Egbin, Sapele, Afam, Delta)

Total energy loses are still very high (about 30 %) Long lines needs to build new substations

Radial lines needs to build new lines to close the loops

Parallel SC lines, double circuits lines

Low reliability of plants due to insufficient maintenance

Low security and transient instability

Persistent and frequent black-outs

Deregulation and privatization in power sector goes very slow


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KAINJI HPP

JEBBA HPP

JEBBA SHIRORO HPP

OSHOGBOKATAMPE

KADUNAKANO

JOS

GOMBEBIRNIN KEBBI

157 km 3 x SC

5,6 km DC

AIYEDE

IKEJA WEST

EGBIN TPP

251 km SC

280 km DC

62 km DC

119 km SC

137 km

2 x SC

BENIN

AJAOKUTA

195 km 2 X SC

SAPELE TPP

AKANGBA

AJA

50 km DC

ONITSHA NEW HAVEN

ALAOJI

25 km DC

AFAMALADJA

DELTA IV TPP

G

G

81km 2XSC

310 km SC

244 km 2XSC

G

230 km SC

197 km SC

265 km SC

96 km 2XSC

144 km DC

G

G

G

G

137 km 2 X SC

95 km SC

138 km

SC175 km

SC

107 km

17 km

63 km

5 x 90 MVA

2 x 150

MVA

4 x 150

MVA

2 x 150 MVA

G

6 x 220 MW

60 MVA

90 MVA150 MVA

90 MVA

2X60 MVA

2 x 90

MVA

2 x 150

MVA

2 x 150

MVA

2 x 150MVA

2 x 150

MVA

2x150 MVA

4 x 150 MW

4 x 200 MVA

2x 120 MW

2 x 100 MW

4 x 80 MW

6 x 90 MW

2 x 150

MVA

6 x 120 MW

4 x 71.25 MW

6 x 140 MVA

2 x 168.5 MVA

3 x 50

MVA

2 x 150

MVA

2 x 150

MVA

2 x 90

MVA

150 MVA

90 MVA

60 MVA

17 km DC

16 km DC

256 km SC

330 kV Transmission Power Network of Nigeria


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Historical growth of NEPA generation

Not suppressed power demand is 12,000 MW (unofficially)


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Generated energy in NEPA Power plants


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Status of NEPA Hydro power plant (2004)

89 %


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Status of NEPA Thermal power plant (2004)


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Status of NEPA Thermal power plant (2004)


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New power plants up to 2007

Okpai Power Project(Agip) 450 MW

Afam VI (Shell) 700 MW

Geregu (Siemens) 414 MW

Papalanto (Chinese Gov.) 335 MW

Omotosho (Chinese Gov.) 335 MW

Alaoji 400 MW Shell PDC Afam 700 MW

3334 MW

By Plan in 2007

8500 MWIn total will be connected on network

Documents

ETC GDPR 01a Power System Design