International Journal of Scientific & Engineering Research, Volume 4, Issue 4, April-2013 434

ISSN 2229-5518

POWER DEMAND OF TRANSFORMERS IN COMMERCIAL NERVE CENTRES IN NIGERIA – BENIN CITY AS A CASE STUDY.

BY

G. I. Ighalo & B. Omatahunde Ambrose Alli University, Ekpoma Nigeria ighawin@yahoo.com

ABSTRACT

Since independence, Nigeria has never known constant power supply and smooth distribution of power. Power demand is of paramount interest to the electrical engineer concerned with the generation, transmission, and economic implications of electric energy. This situation is so due to the technical and economic implications of electric energy production/consumption. Benin City as one of the load infested areas in Nigeria could provide a solution to the problem of stabilizing power supply in Nigeria if carefully studied. This study reveals that the power demand in Benin Cit y has been on the increase. This is an eye opener to the PHCN (Power Holding Company of Nigeria), which must take appropriate measures necessary to accommodate this increasing power demand. The study further reveals that the Brewery factory in Guinness injection substation has the highest load density with a
value of 102.0 VA/m2 this is due to the running of motors for 24/7 hours. The lowest
load density is that from the Dam feeder in Ikpoba Dam., with a value of 0.3VA/m2.

Keywords: injection, power demand, substation, transformers, transmission.

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INTRODUCTION

Electrical energy demand in Nigeria is on the increase due to the ever increasing population and the attendant increase in commercial and industrial activities. This is even worse in urban centres where the population is concentrated due to rural to urban drift in populations. [Michael, 1972]
As power demand grows with population growth the generation, transmission and distribution networks must be strengthened to cope with the consequent technical and economic shortfalls. With increasing power demand, the loading of the generators, transformer, transmission lines and all the associated switchgear also increase. Hence, concerted efforts must be made to monitor the pattern of this power demand so that appropriate financial and technical measures can be taken to enhance the status of the power distribution/transmission network equipment..
A load survey of this nature is necessary because, with increasing demand for power all the distribution network equipment will have to handle larger normal and fault current levels, hence complexity and cost of protective gear required will also increase. [Theraja, 1995]
This study will help the power utility engineers to plan for and forecast future trends in power demand, and thus be able to take appropriate techno-economic measures necessary to forestall power outages. This will make for a stable power supply and improve the standard of living of the citizenry (consumers). A network diagram for Benin City is shown in Fig 1.0

MATERIALS AND METHODS

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This study being rather a load survey is a statistical problem. In this case injection sub-stations in Benin Cit y with their distribution transformers were surveyed, in order to achieve a good estimate of power demand, the KVA rating and KVA readings for every one hour for one week were taken and recorded. Some consumer loads were also measured and recorded.
Certain performance factors such as average demand, maximum demand
factor, diversity factor, load factor, load density and coverage area, were investigated

in this study, where

Average Load

=

Kwh consumed during the period considered

Hours in the period considered

Demand Factor

=

Maximum demand (usually < 1) Total Connected Load

Diversity Factor

=

sum of individual maximum demand

Maximum demand of the entire load

Load Factor

=

Average power per year (or per month or per day

Maximum demand
Load Density = Capacity of transformer in KvA Area Covered by transformer in m2
= Load
Area Covered by Load
The various classes of consumers surveyed include the residential consumers, commercial and industrial consumers. The seven injection substations selected for the purpose of this study are Etete, Nekpenekpen, Ugbowo, Ikpoba dam, Guinness, Siluko and GRA injection substation, the rated powered and voltage ratios of transformers, and load reading were taken

RESULTS

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Table 1: Rated Power And Voltage Ratios Of Injection Substation Transformers

s/no

Name of Injection substation

Rated Power

Rated Voltage Ratio of Transformer

1

Etete

20.5MW

33/11KV

2

Nekpenekpen

13.5MW

33/6.6KV

3

Ugbowo

13.5MW

33/6.6KV

4

Ikpoba Dam

6.6MW

33/11KV

5

Guinness

12.3MW

33/11KV

6

Siluko

20.5MW

33/11KV

7

GRA

13.5MW

33/11KV

TABLE 2: Reading Of The Rated Capacity Of Injection Substation

Transformers

S/no

Name of Injection

Substation

Rated Capacity

1

Etete

22.5MVA

2

Nekpenekpen

15MVA

3

Ugbowo

15MVA

4

Ikpoba Dam

7.5MVA

5

Guinness

15MVA

6

Siluko

22.5MVA

7

GRA

15MVA

TABLE 3: Feeders In Each Injection Substation

Name of Injection

Substation

Names of Feeders

Etete A

Sapele road A1, Ihama Road A2, Ugbor A3 Dumez Road A4

Nekpenekpen B

Feeder 1, B1, Feeder 2, B2, Feeder 3, B3, Feeder 4, B4

Ugbowo C

Federal Girls Road, C1 Uselu Road, c2 Edaike C3 Ugbowo, c4

Ikpoba Dam D

Okoro Road, D1, Uselu Road D2, Edaike D3, Dam D4

Guinness E

Brewery E1, New Benin E2, Auchi Road E3 Asaba Road E4

Siluko F

Uwelu Road F1, Edo Textile F2, Oliha F3, Upper Siloko Road

F4

GRA G

Palace G1, Sapele Road G2, GRA G3, Reservation G4

The total individual load in KVA and the coverage area in m2 of each injection substation were estimated and tabulated as shown in table 4, the coverage area being
the space of land inhabited by consumers.

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Table 4: Calculated Total Load

s/no

Injection substation

Feeders

Load

(KVA)

Area (m2) (space of

land covered by

consumers

Total load

Total Area

(m2)

1

Etete

Sapele road Ihama road Ugbor road dumez road

7300

13315

700

1200

86180

453440

578730

62500

38.815

1180850

2

Nekpenekpen

Feeder 1

Feeder 2

Feeder 3

Feeder 4

5400

7900

9750

3600

2654060

9433610

6823410

28887080

26.650

51279040

3

Ugbowo

Okhoro road Upper lawani Dam

2300

2300

900

73540

10506320

38899780

1708940

13.600

42454100

4

Guinness

Brewery

New Benin Auchi Road Asaba road

7500

57600

2650

7115

459900

1046710

1551690

358780

23.025

161178580

5

Siluko

Uwelu road Edo textile Upper Siluko Oliha

1900

7000

4100

7900

1667370

231000

5888610

3477900

20.900

6646140

6

Gra

Palace Sapele GRA Reservation

7650

800

9000

7400

24.850

11265080

From table 4, the individual load density can be determined for each feeder. Considering, for example the Sapele Road feeder in Etete injection substation, we have:
Total load = 7300 KVA Total area = 86180m2
Therefore load density = load/Area Covered by load = 7300 KVA/86180m2 = 0.0847
KVA/m2 = 84.7VA/m2

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Repeating the above procedure for all the feeders in table 4 result in table 5 shown blows with an additional column for load density in KVA/m2

Table 5: Load Densities of the Injection Substation.

Injection substation

Feeder

Total Load

(KVA)

Coverage

Area (m2)

Load Density

(KVA/m2)

Etete

Sapele Road Ihama Road Ugbor Road Dumez Road

7300

13313

6700

1200

86180

453440

578730

62500

0.0847

0.0294

0.0168

0.0192

Nekpenekpe

Feeder 1

Feeder 2

Feeder 3

Feeder 4

5400

7800

9750

3600

6254060

6326670

40359200

1939110

0.0020

0.00012

0.0002

0.00019

Ugbowo

Federal Girl Road

Uselu Road

Egua Edaken

Ugbowo

2900

5400

2500

8400

4469060

6326670

40359200

1939110

0.0006

0.0007

0.00016

0.0004

Ikpoba Dam

Okhoro Road Upper Lawani Dam

2300

2300

9000

6743610

6823410

28887080

0.0003

0.0007

0.0003

Guinness

Brewery

New Benin Auchi Road Asaba

Road

7500

5760

2650

7115

73540

10506320

3889780

1150450

0.1020

0.0005

0.0007

0.00062

Siluko

Uwelu Road Edo Textile Upper Siluko Road Oliha

1900

7000

4100

7900

459900

104710

1488690

358754

0.00041

0.0067

0.0022

0.0028

GRA

Palace Sapele GRA

Reservation

7600

800

9000

7400

1687570

231060

5888610

3477900

0.0045

0.0035

0.0015

0.0021

Daily Observation of maximum KVA Power demand was carried for 21 Consecutive days at each of the injection substations and the result were recorded as shown in
table 6

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From table 6, the load and demand factors can be calculated for each injection substation as follows:

For Etete injection substation: Day 1

Total KVA m. d = 9248 KVA
Average demand = 9248/42 = 389.5 KVA Maximum demand per 30 minutes = 510 KVA Total connected load = 38815 KVA
Load factor = Average demand/Maximum demand = 38915 / 510 = 0.7637 = 76.4% Demand factor = Maximum demand / Total connected load = 510 / 38815 = 0.01321
= 1.31%
The same procedure is repeated for other injection substations.

CONCLUSION

The Brewery injection substation feeder has the highest load density of 0.102
KVA/m2 and the dam feeder at Ikpoba dam injection substation, the lowest at
0.003 KVA/m2. The heavy industrial and commercial activities around the brewery area could have motivated PHCN to supply more of its available power to this area, considering the enormous financial returns on invested capital.

RECOMMENDATIONS

(a) There should be a map showing the connectivity of the houses in the various substations in Benin metropolis
(b) Any new house connected to the grid should be recorded for effective tariffs
(c) Records of Updated appliance in use by consumers should be sent to PHCN to enable them upgrade the various substations.
(d) To enable corrective repairs, all tariffs should be paid promptly

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(e) Proper computerization should be encouraged.

REFERENCES

Cogdell J.R. (1990) Foundation of Electrical engineering; Prentice Hall, Inc Michael N. (1972) Electrical Installation Technology, 1st edition McGraw Hill Publishers New York.
Paddlock J. O. And Garvin R. A. (1982) Electrical Installation Technology and
Practice 13th edition Macmillan Ltd; London
Theraja B. J. ; (1995) Electrical Technology, 2Nd edition, schad and co. New Delhi
Pp1002 – 1015
Uppal S. L. (1998) Electrical Power, 13th edition Khanna Publishers New Delhi

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Table 6 Maximum Power demand

S/N

Injection

Substation

Day

1

Day

2

Day

3

Day

4

Day

5

Day

6

Day

7

Day

8

Day

9

Day

10

Day

11

Day

12

Day

13

Day

14

Day

15

Day

16

Day

17

Day

18

Day

19

Day

20

Day

21

1.

ETETE

510

480

520

516

576

560

540

520

514

490

510

550

520

522

515

510

485

520

550

510

515

2.

NEKPENEKPEN

400

390

400

410

450

440

440

420

400

410

420

452

420

405

450

410

440

425

440

450

440

3.

UGBOWO

410

410

410

420

440

430

420

410

420

410

410

430

430

440

420

420

410

420

440

430

420

4

IKPOBA DAM

550

460

500

492

504

570

480

500

460

480

520

520

500

500

480

550

560

490

504

500

480

5.

GUINESS

440

464

480

480

540

520

520

520

510

480

480

540

430

440

460

480

520

510

500

540

500

6.

SILUKO

530

510

540

540

560

570

570

520

530

530

520

510

540

540

540

510

510

560

560

560

570

7.

GRA

270

336

300

300

312

330

330

280

285

280

300

310

320

330

328

300

270

300

330

330

335

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132/33 KV

33KV

33/11 KV

33/11 kv 33/6.6 KV

33/11 kv

33/11 kv

33/ 11

Kv

33/ 11

Kv

ETETE

GRA

NEKPENEKPEN

UGBOWO

IKPOBA

GUINNESS SILUKO

Fig. 1.0 Network diagram for Benin City

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