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Engr . Jonathan U. NdiagwalukweExecutive Director (S/O), TCN

STRATEGIES FOR MITIGATING INCIDENCE OF SYSTEM COLLAPSE

By

Enugu Power Summit 11th -12th May, 2012

● Introduction

OUTLINE

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● The Grid System

● System Frequency Management

● System Collapses in Retrospect

● System Collapse Mitigation Strategies

● Concluding Remarks

● Causes of System Collapse

● Grid Instability

● A system is an inter-related set of components that work together within an identifiable boundary, as a coherent whole, to achieve an overall goal.

INTRODUCTION

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● In the case of a power system, when all or some of the functional components have failed as a result of perturbations,System Collapse is said to have occurred.

● The scope of failure determines whether the collapse is total or partial.

● System Operation States

INTRODUCTION (CONT’D)

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► Normal State:

  The power system operates in normal state when system

frequency and voltages are close to their nominal values.

There is adequate generation to cope with load demand. ► Alert State:

  It is the state of an electric power system in which an event will result in

loss of load, stressing of system components beyond their ratings, bus

voltages and system frequency outside tolerances, cascading voltage

instability etc.

The Grid Code stipulates that the grid has to be in the normal state

at least 90% of the time, This is hardly the case with our grid

● An electric power grid is a system of power

generation plants, transmission substations and lines

interconnected in a mesh for efficient delivery of

electricity

The Grid System

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TO SAKETE

ONITSHA

KAINJI

JEBBA/GS

JEBBA/TS

SHIRORO

Ikeja

Akure

Uyo

BirninKebbi

Minna

Kaduna

Abuja

Jos

Bauchi

Gombe

Damaturu

MaiduguriKano

IIorin

AdoEkiti

EnuguAkwa

Ibadan

Sokoto

Gusau

Katsina

Hadejia

Jalingo

Yola

Abakaliki

Calabar

JIGAWA

KANO

KATSINA

SOKOTO

ZAMFARA

KEBBI

KWARA

KADUNA

NIGER

NASSARAWA

TARABA

YOBE

PLATEAU

EBONYI

CROSSRIVER

OSUN

BAYELSA

EDO

DELTA

ONDO

OYO

IMO

ADAMAWA

BORNO

GOMBE

BAUCHI

EKITI

LAGOS

ATLANTIC OCEAN

NIGER

REPUBLICOF BENIN

REPUBLICOF CAMEROON

REPUBLICOF

CHAD

SAPELEP/ST.

DELTAPOWER ST.

OGUN

Osogbo

NIGERIA

Potiskum

Niamey

132 kV

Mambila

Bali

AFAM POWER ST.

AsabaBenin

EGBINP/ST.

Lokoja

ABUJA

AJAOKUTA

Lafia

Makurdi

MAKURDI

BENUEKOGI

ENUGU

Aliade

ABIA

AKWAIBOM

Owerri

AN AMBRA

PortHarcourt

RIVERS

Umuahia

2

2

2

22 2

2

4

3

TRANSMISSION LINE LEGEND

BULK SUPPLY POINT

HYDROELECTRIC POWER STATION

THERMAL POWER STATIONS

330 KV

H

330KV LINES (EXISTING) – MULTIPLE CIRCUITS

330KV LINES - EXISTING

2

2

2

330KV LINES (FGN) – MULTIPLE CIRCUITS

330KV LINES (PROPOSED PROJECT) – MULTIPLE CIRCUITS

330KV LINES (NIPP) – MULTIPLE CIRCUITS

330KV LINES - FGN

330KV LINES - NIPP

330KV LINES - PROPOSED PROJECT

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Nigerian Power Grid: Existing 330KV Lines Network

ALAGBADO

Abeokuta

Olorunsogo

B1T

T4A

An electric power grid can be rendered unstable by

the following:• System faults at busbar sections or on Transmission

lines

• Loss of generation

• Loss of large loads

• Switching of large loads

A power system is therefore considered

stable if in the event of any or a

combination of the above factors, the

entire network is able to remain in

synchronism. This is hardly the case with

the Nigerian grid. Any of the above events

can throw the system out of synchronism

and result in the shutdown of the grid.

Grid Instability

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SYSTEM FREQUENCY MANAGEMENT

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● A nominal frequency of 50Hz is achieved when active power generation in the system equals the total demand.

● In practice, we seek to achieve this balance through manual load shedding/generation scheduling or by the appropriate application of under-frequency relays.

● The SCADA/EMS facility, through its Load Frequency Control (LFC) function, offers an automated means for frequency management.

SYSTEM COLLAPSES IN RETROSPECT

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YEAR GENERATION TRANSMISSION

INDERTERMINATE

2000 2 9 02001 9 10 02002 19 22 02003 14 39 02004 20 32 02005 15 21 02006 8 22 02007 3 24 02008 8 32 22009 8 31 02010 9 29 42011 0 17 2

10

20002001

20022003

20042005

20062007

20082009

20102011

0

5

10

15

20

25

30

35

40

45

GENERATION TRANSMISSION INDERTERMINATE

SYSTEM COLLAPSES IN RETROSPECT………

2012 SYSTEM COLLAPSES TO DATE

SUMMARY OF MAJOR SYSTEM DISTURBANCES IN 2012

S/NoDATE/ MONTH

TYPE OF DISTURBANCE IN

THE GRID IMMIDIATE CAUSE/REMARKS

TOTAL PARTIAL

116/03/201

2X  

The tripping of Benin/Onitsha 330KV line (CCT B1T) at both ends

223/03/201

2  X

(1) Explosion of the red phase CT of the primary side of 150MVA 330/132/33kV transformer at Benin TS.

325/03/201

2  X Bus Zone protective relay operation at Benin T/S

428/03/201

2X   The tripping of Benin/Onitsha line (cct B1T)

502/04/201

2  X Tripping of Benin - Onitsha line (CCT B1T) at both ends.

603/04/201

2  X Tripping of Benin - Onitsha line (CCT B1T) at both ends.

712/04/201

2X  

The simultaneous tripping of Benin/Onitsha 330kV line (cct B1T) and Onitsha /Alaoji 330kV line (cct T4A)

8 30/04/12

  X The tripping of Onitsha/Alaoji 330kV line (cct T4A)

907/05/201

2X   (1) Tripping of Jebba Units (2G1 & 3) on fault

1009/05/201

2X    Indeterminate

1110/05/201

2X   Indeterminate

Graphical representation of 2012 system collapses to Date

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Transmission Generation Indeterminate0

1

2

3

4

5

6

7

8

9

No.

Causes of system collapse

System collapse can result from: • Generation• Transmission• Load Management

GENERATION:• Grossly inadequate generation• Sudden loss of generation • Absence of/or inadequate operating reserveTRANSMISSION:• Tripping of critical 330KV lines (especially the single circuit lines)• Indiscriminate operation of line protection relays• Transmission equipment failure

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Causes of system collapse........contd.

• LOAD MANAGEMENT– Grid indiscipline - Reluctance to adhere to load

allocation– Lack of a functional SCADA/EMS system,

necessitating manual operation which is fraught with human error

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Generation Profile (Mar’11 – April’12)

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MONTH AVERAGE ACTUAL GEN. CAPABILITY

(MW)

PEAK GEN.(MW)

AVERAGE GEN.(MW)

MAR 2011 4450.14 3851.60 3324.62APR 2011 4627.51 3943.60 3501.11MAY 2011 4195.03 3635.90 2945.25JUN 2011 4359.04 3354.00 2790.33JUL 2011 4571.53 3607.00 2970.51AUG 2011 4421.46 3839.70 3363.06SEPT 2011 4684.33 4003.80 3352.65OCT 2011 4899.55 4054.20 3078.07NOV 2011 5039.38 3627.77 3280.36DEC 2011 4768.91 4089.30 3338.36JAN 2012 4788.26 4162.20 3531.69FEB 2012 4959.01 4086.20 3465.29MAR 2012 5171.00 3744.20 3096.49APR 2012 5338.68 3698.30 2936.67

Collapse Free Months with average Spinning Reserve of 280MW

System Collapse Mitigation Strategies

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● Elimination of all encumbrances on all Transmission lines.

► Short Term Strategies: 

● Review of the operation of Under-frequency Load Disconnection scheme.

● Procurement of additional operating reserve capability for effective frequency management.

● Timely completion of on-going SCADA/EMS reactivation project for real-time Grid management and supervisory control.● Review of the entire system protection scheme is required to ensure proper and reliable operation

● Manpower shortage in system operations is now acute needs to addressed.

System Collapse Mitigation Strategies (Cont’d)

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● It is imperative to strengthen the Grid to satisfy N-1 reliability assessment criteria.

► Long Term Strategies:  

● Increased generation is an absolute necessity for stable grid operation.

● Creation of closed loops in the network.

● Network compensating devices, such as the Static Var Compensators (SVC) should be deployed for efficient voltage control.

Nigerian Power Grid: Existing, On-going and Proposed 330KV Lines Network

TO SAKETE

ONITSHA

KAINJI

JEBBA/GS

JEBBA/TS

SHIRORO

Ikeja

Akure

Uyo

BirninKebbi

Minna

Kaduna

Abuja

Jos

Bauchi

Gombe

Damaturu

MaiduguriKano

IIorin

AdoEkiti

EnuguAkwa

Ibadan

Sokoto

Gusau

Katsina

Hadejia

Jalingo

Yola

Abakaliki

Calabar

JIGAWA

KANO

KATSINA

SOKOTO

ZAMFARA

KEBBI

KWARA

KADUNA

NIGER

NASSARAWA

TARABA

YOBE

PLATEAU

EBONYI

CROSSRIVER

OSUN

BAYELSA

EDO

DELTA

ONDO

OYO

IMO

ADAMAWA

BORNO

GOMBE

BAUCHI

EKITI

LAGOS

ATLANTIC OCEAN

NIGER

REPUBLICOF BENIN

REPUBLICOF CAMEROON

REPUBLICOF

CHAD

SAPELEP/ST.

DELTAPOWER ST.

OGUN

Osogbo

NIGERIA

Potiskum

Niamey

132 kV

Mambila

Bali

AFAM POWER ST.

AsabaBenin

EGBINP/ST.

Lokoja

ABUJA

AJAOKUTA

Lafia

Makurdi

MAKURDI

BENUEKOGI

ENUGU

Aliade

ABIA

AKWAIBOM

Owerri

AN AMBRA

PortHarcourt

RIVERS

Umuahia

2

2

2

2

2

2

2

2

2

22

2

2

2

2

2

2

2

2

2

1

11

4

22

22

2

2

2

2

2

2

2

2

2

2

22 2

2

4

3

ALAGBADO

Abeokuta2

Olorunsogo

TRANSMISSION LINE LEGEND

BULK SUPPLY POINT

HYDROELECTRIC POWER STATION

THERMAL POWER STATIONS

330 KV

H

330KV LINES (EXISTING) – MULTIPLE CIRCUITS

330KV LINES - EXISTING

2

2

2

330KV LINES (FGN) – MULTIPLE CIRCUITS

330KV LINES (PROPOSED PROJECT) – MULTIPLE CIRCUITS

330KV LINES (NIPP) – MULTIPLE CIRCUITS

330KV LINES - FGN

330KV LINES - NIPP

330KV LINES - PROPOSED PROJECT

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CONCLUDING REMARKS

Increased Generation,expanded grid network with redundancies and functional grid management tools will launch the system into an era of stability and a collapse free operation.

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THANK YOU

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