LOAD-FLOW ANALYSIS OF CUET CAMPUS

ABSTRACT

Load flow study is essential for a system of multiple load centers. It explains the effects of new loads, new stations, new lines, new. It is especially effective for reliable and continuous safe flow of power. Through this thesis we have tried to evaluate the existing power system in our CUET campus.

Load-flow study-

1. Analyses system capability to supply the connected load.
2. Provides useful information about real and reactive power flow, bus voltages and power factor in each branch of the system.
3. Plans the future expansion of power system.
4. Determines the best operation of existing system.

OBJECTIVES

1. To know the existing campus distribution.
2. To know the sources of power in CUET campus.
3. To calculate the connected load, bill payable to REB, useful load, power factor- then the difference between connected load and actual load as per bill i.e. percentage error.
4. To draw the load curves on the basis of yearly load variations.
5. To propose some methods for improving the stability of the power system.
6. To propose some methods for economic utilization of electric power.
7. To have a proposal for an electrical master plan for the next 25 years.

SOURCES OF POWER IN CUET CAMPUS

The campus is mainly provided power by Pomra substation of REB. Besides this, there are 3 generators for emergency power supply during load shedding. A manually operated generator of 75 KVA. An auto-back up source of 19 kVA. A manually operated generator of 30 KVA.

EXISTING POWER DISTRIBUTION IN CAMPUS

A transformer of 500 kVA in our substation steps down the 11 kVA into 0.415 kV. For future use there is a transformer of 200 kVA. There are 12 circuit breakers to control the power supply in CUET campus. Two of them are Oil Circuit Breaker (OCB) ,one is MCCB and others are MCB. A main MCCB of 800 A controls other circuit breakers.

TRANSMISSION LINES ON THE MAP OF CUET CAMPUS

ONE-LINE DIAGRAM OF THE EXISTING POWER SYSTEM

Existing Connected Load (in kW)
EME building	103.79
CE+ CSE building	126.72
Pre-engineering building	126.99
Academic Section	51.38
Workshop	3.22
Library, Gallery, Medical       Center, Post Office, Bank,       Transport Section, Mosque	42.34
CUET School  & College	9.92
Student Halls + Extensions	631.44
Residensial Areas	269.94
Anser Camp, Guard Sheds, Street Lights & Water Pumps	70.64
Tweleve stored building(under construction)	2.64
Overall connected load in CUET Campus	1439.02

CALCULATION OF USEFUL LOAD

Total connected load in CUET Campus = 1439.02 kW
Therefore,
Useful load = One fourth of the connected load=359.75kW
PERFORMANCE REPORT
We have justified the accuracy of our calculation through the term “Performance Report” of residential areas and entire CUET campus.

Overall Performance Report in CUET Campus
Types of load	No of load	Calculated Average load		Actual load (As per bill)kWh	Error
Fan	3157	189.42 kW*12hr*0.5*30	34095.6kWh	152400	(154948.26 -152400)/152400*100%
Tube	2879	115.16 kW*9hr*0.5*30	15546.6 kWh
Bulb	3162(60W)+ 18(100W)+ 2(400W)+ 16(200W)	195.52 kW*9 hr*0.5*30	26395.2 kWh
PC	1466	557.08 kW*6 hr*0.5*30	50137.2 kWh
AC	33+17	244 kW*4 hr*0.5*30	14640 kWh
TV	116	12.53 kW*4 hr*0.5*30	751.68  kWh
Fridge	118+7	55.2 kW*10 hr*0.5*30	8280 kWh
Water Pump	3	52.22 kW*6 hr*0.5*30	4699.8 kWh
Washing machine	21	31.5 kW*0.5 hr*0.25*30	118.13 kWh
Photo copy	7	7.56 kW*1 hr*0.5*30	113.4kWh
Oven	29	43.5 kW *0.25hr*0.5*30	163.13 kWh
Heater	1	2 kW*0.25 hr*0.5*30	7.5 kWh
Total			154948.26 kWh	152400	1.7%

Overall Performance Report in CUET Campus (Considering types of use)
Building Name	Calculated connected load		Actual load (As per bill)	Error
EME Building	103.79 kW*8hr*0.3*30	7472.9 kWh	152400 kWh	(156715.9 -152400)/152400*100%
CE+CSE Building	126.72 kW*8 hr*0.3*30	9123.84 kWh
Pre-Engineering   Building	126.99 kW*8 hr*0.4*30	12191.04 kWh
Academic Section	51.38 kW*8 hr*0.5*30	6165.6 kWh
Workshop	3.22 kW*1hr*0.5*30	48.3 kWh
Library, Gallery, Medical enter, Post Office, Bank, Transport Section, Mosque	42 .34kW*8 hr*0.3*30	3048.48 kWh
CUET School &  College	9.92 kW*8 hr*0.3*30	714.24 kWh
Student Halls + Extensions	631.44 kW*10hr*0.4*30	75772.8 kWh
Residential areas	269.94 kW*10 hr*0.4*30	3092.8 kWh
Ansar Camp, Guard Sheds, Street Lights	70.64 kW*6 hr*0.4*30	5086.08 kWh
Water Pumps	52..22 kW*6 hr*0.5*30	4699.8 kWh
Total	156715.9 kWh		152400 kWh	2.8%

POWER FACTOR

Power factor is the cosine of the angle between voltage and current in an ac circuit. Power consumption depends upon this factor. Low power factor is not expected due to some reasons-

1. It requires large kVA rating of equipments.
2. Greater conductor size is needed.
3. It causes large copper losses.
4. It provides poor voltage regulation and poor efficiency.

METHODS OF POWER FACTOR IMPROVEMENT
Power factor can be improved by 3 methods:

1. Use of static capacitor bank in parallel with the equipment operating at lagging power factor.
2. Using synchronous condenser in parallel with the supply.
3. Phase advancers can be used to improve power factor of induction motor.

In our CUET campus capacitor bank has been used to improve power factor.
CALCULATION OF POWER FACTOR
From substation we get,
CT ratio =1:120
Power, P =1.7*120 kW=204 kW
Voltage, V = 238*1.732V=412.22 V
Current, I = 3.1*120 A=372A
Therefore,
Power Factor = Power/ (1.732*Voltage*Current) = (204*1000) / (1.732*412.22*372) = 0.768
LOAD CURVES

The curve showing the variation of load on the power station with respect to time is known as a load curve. Now we will represent daily load curve, load duration curve, annual load curve of CUET campus . Here we will also represent the annual consumption pattern of CUET as per bill of the financial year June 2008-May 2009.

LOAD CURVE OF CUET

LOAD DURATION CURVE OF CUET

ANNUAL LOAD CURVE OF CUET AS PER BILL

CALCULATION OF SOME TERMS FROM ANNUAL LOAD CURVE

·         Demand Factor	=	Maximum Demand/Connected Load
	=	462.5/1439.02
	=	0.322
·         Average Load	=	No. Of units (kWh) generated in a year/8760 hrs
	=	{(462.5*24*30) + (172.88*24*31) + (173.06*24*31) + (106.7*24*30) + (142.63*24*31) + (69.33*24*30) + (113.71*24*31) + (78.84*24*31) + (109.82*24*28) + (204.84*24*31) + (189.83*24*30) + (165.64*24*31)}/8760
	=	1452608.64/8760
	=	165.82 kW
·         Load Factor	=	Average Load/Maximum Load
	=	165.82/462.5
	=	0.36

ANNUAL CONSUMPTION PATTERN OF CUET AS PER BILL (June 2008 –May 2009)
TOTAL CONSUMPTION: 1452100 kWh

STABILITY
Stability is the ability of a system to reach stable condition after being disturbed.
Two types of stability are:

1. Transient stability
2. Steady state stability

Stability limit is important term which is the maximum power transferred in a network between sources and loads. Transient stability limit is less than steady state stability limit. Methods of improving stability:

1. Use of double circuit line
2. Use of bundled conductors
3. Series compensation of the lines
4. Use of parallel feeders.

ECONOMIC UTILIZATION OF POWER

1. Consciousness is required to reduce power loss.
2. High load factor is required for better utilization of power.
3. Proper time scheduling.
4. Using two part tariff.
5. By prohibiting the use of heaters in student’s halls.
6. Use of compact fluorescent lamp.
7. Improving power factor.

PROJECTED CAMPUS LOADS

Particular Respects	Present status	Status after 25 years
1.No of Departments	4	Near about 12
2.Students Capacity	Near about 1500	4 or 3 times from that of present i.e. about 6000.
3.Teachers Capacity	Near about 100	Almost 3 times from that of present i.e. 300.
4.Other Employees	About 200	About 1000.
5.Connected Load	1439.02 kW	3 times from that of present. i.e., about 4317.06 kW.
6.Transformer Rating	500KVA	Almost 2500 KVA.

PROPOSED ONE-LINE DIAGRAM FOR INCREASED LOAD DEMAND AFTER 25 YAERS

The demand of electric power is increasing gradually. To meet up the future requirement of CUET, the infrastructure of electric system has to be improved. Substation capacity, its protection system and distribution system must have to be upgraded.

It is reported from different media that the power generation crisis is greatly affecting our national distribution system. As a result, about 1400 MW load shedding is expecting in the forthcoming summer peak hours which will greatly affect our university students and teachers. To overcome these sorts of problem, establishment of a permanent power supply source in CUET has to be considered. For this purpose, a generating capacity of 2 MW with two units have to be installed in the CUET campus and authority of CUET may please propose to the competent authority for getting approval of the work, otherwise students and teachers of the CUET will have to face a lot of problems in future.

Submitted by JOBEDA JAMAL KHANAM and JOHORA BEGUM in July, 2009