Electricity + Control February 2018
TRANSFORMERS + SUBSTATIONS
Liquid
Cast
Dry
Total losses (kW)
6,76
12,18
12,25
KWH billing rate x
R0,55
R0,55
R0,55
Annual hours x
8760
8760
8760
Annual cost of energy due to Losses @ 50% load: =
R32 569,68
R58,683,24
R59 020,50
Excess annual energy costs
R26 113,56
R26 450,82
Base
10-Yr* excess energy costs:
R261 135,60
R264 508,20
Base
*Simple costs, assumes no interest rate or escalat- ing energy costs
3 Feature: Liquid filled transformers have a small- er footprint. Materials and Resources Benefit: Smaller equip- ment reduces building size demand. Constants: Assume Industrial space rental at R55,00 per square metre Typical cost per square metre
Additional cost of transformer losses – air-conditioning energy consumption Energy consumption by the transformer is not the only energy factor. Transformer losses are dissipated as heat, which must be removed from a controlled tem- perature environment by air conditioning. Illustrat- ed below are calculations to convert transformer losses into increased air conditioning energy con- sumption.
Liquid (FR3)
Dry Differ- ential
KVA
R55,00 per m 2
Depth: m 1,402 1,676 Width: m 1,402 2,438 m 2 1,966 4,088 Depth: m 1,585 1,676 Width: m 1,463 2,438 m 2 2,319 4,088 Depth: m 1,920 1,676 Width: m 1,341 2,438 m 2 2,575 4,088
750 kVA
Constants 1 kW = 3 415 BTU/Hr
2,12
m 2
R116,70 per m 2
1 Ton Air Conditioning = 12 000 BTU/Hour 1 Ton Air Conditioning = 1,7 kW power use
1 000 kVA
1,77
m 2
R97,29
per m 2
Liquid
Cast
Dry
Total Losses (kW)
6,76
12,18
12,25
1 500 kVA
BTU/HR/KW x
3 415
3 415
3 415
1,51
m 2
R83,19 per m 2
BTU/HR =
23 085
41 595
41 834
BTU/HR per ton A/C ÷
12 000
12 000
12 000
A smaller building also has the benefit of requiring less lighting and ventilation. 4 Feature: Liquid filled transformers have superi- or operating life, maintainability, and repairability. Materials and Resources Benefit: Less waste/ disposal/replacement/labour.
A/C (tons) =
1,92
3,47
3,49
kW power usage per ton A/C x
1,7
1,7
1,7
kW
=
3,27
5,89
5,93
Annual hours of operation(h) x
8 760
8 760
8 760
Annual energy usage (kWh) =
28 649
51 619
51 916
kWH billing rate x
R0,55
R0,55
R0,55
Annual cooling costs =
R15 756,95
R28 390,45
R28 553,80
Operating life: Typical dry-type lifespan: 15 - 25 years Typical liquid-filled lifespan: 25 - 35 years
Excess annual cooling costs
base
R12 633,50
R12 796,85
10-Yr excess energy costs
base
R126 335,00
R127 968,50
2 Feature: Liquid filled transformers have a lower operating sound level. Indoor environmental quality benefit: Less noise pollution. Decibels is a logarithmic function, and sound pres- sure doubles for every three decibel increase. Research shows that decibel levels over 60 can reduce a person's attention span. A study by the American Society of Interior Designers showed that office productivity would increase if workspaces were less noisy [2] [3].
The retirement age of transformers removed from service for a variety of reasons ranges from 14 to 35 years; the average is 25 years. However, the average life of liquid- immersed transformers that remain in service is 30 years or more [1]. Because liquid-filled transformers last longer than dry-type, they save on material, labour to replace, and oper- ational impact due to outage to replace.
Maintainability Recommended annual maintenance for a typical
34 Electricity + Control
FEBRUARY 2018
Made with FlippingBook - Online catalogs