MEPS 2 - The Next Stage of Efficiency Regulation for Distribution Transformers
Trevor BlackburnSchool of Electrical Engineering
UNSW
The Role and Purpose of MEPS Regulations
• Improve power and energy efficiency levels• Reduce electrical energy waste and CO2 emissions• Done by regulating minimum efficiency levels• Applied to locally-manufactured and imported items• Electrical equipment regulated by MEPS include:
– Distribution transformers– Large electrical drives– Air conditioners– Fluorescent ballasts– Compact fluorescents
The MEPS regulation process
• Public domain technical report issued• Discussions with manufacturers and users• Regulatory Impact Statement generated• Australian Standard developed and published• Applications for registration and approval for
specific classes of transformers• Compliance testing process
Distribution Transformer Range
• Single phase and three phase• Ratings: 10 kVA – 3100 kVA (2500 now)• Includes: oil-filled, dry-type and SWER units• MEPS 1
– Introduced in 2004 – Two minimum power efficiency levels specified
• Standard [Regulated minimum levels]• High efficiency [Voluntary levels]
• MEPS 2• Proposed implementation date of no earlier than
– 2012– One regulated minimum efficiency level is specified
• Identical to the MEPS 1 high efficiency level
Why Transformers?
• Network losses are significant– Represent about 5-10% of overall T & D energy
transfer
• Network Transformers – Cause up to 40% of total network losses
• Between the generator and consumer at 400/230 V, electrical energy may pass through: – 2 transmission transformers– 2 or 3 distribution transformers
Distribution losses in Australian utilities2009 [ESAA – EGA data]
7
Transmission & Distribution transformer regulation ?
• Transmission transformers– Usually one-off design– Usually very energy efficient– Very small numbers– Give only limited energy saving benefits
• Distribution transformers– Mass produced to an economic design– Losses may be sacrificed for low capital cost– Very large numbers in use– Potentially large energy saving benefits
Number of utility-owned Distribution Transformers in Australia: 2010
• 33 kV 7,544• 22 kV 213,373• 11 kV and below 337,759• SWER 113,248
• TOTAL 661,934
• Usually relatively lightly loaded (25-30%)• Long life expected
9
Number of privately owned transformers (commerce, industry, mines)
• Difficult to determine• Large numbers of imported units• Based on international numbers, about
25% of utility numbers• Generally shorter life than utility trafos• More heavily loaded:
– About 40-50% on average
Transformer loss and
greenhouse gas mitigation
MEPS for Transformers
AS 2374.1.2 - 2004Power transformers – Part 1.2Minimum efficiency Performance Standards (MEPS) requirements for Distribution Transformers
Specifies minimum (power) efficiency levels for oil and dry-type transformers under specific test conditions
Existing MEPS efficiency LevelsLiquid-immersed transformers
(at 50% rated load)
Existing MEPS Levels Dry-type transformers
[at 50% rated load]
Effect of loading on losses
Targosz_2007(Leonardo)
MEPS 2 Levels
Why do we need to increase MEPS1 efficiency levels to MEPS2?
• Need the most efficient transformers that are available to minimise the effect on climate change
• Power electronic loads on transformers will increase losses due to harmonic content:– Increasing harmonic levels arise from use of:
• Adjustable speed drives (IGBT switching)• Switch mode power supplies (Computers and IT equipment)• Compact fluorescent lamps• Any other non-linear loading
– Transformer losses scale as the square of harmonic number
• May require de-rating of transformers in some applications to avoid overheating
• K-factor transformers
1000 kVA oil filled transformer
• Daily load cycle– 8 hours @ full load, unity PF– 6 hours @ 50% load, unity PF– 6 hours @ 25% load, unity PF– 4 hours @ no load
• MEPS 1 power efficiency = 99.27%• MEPS 2 power efficiency = 99.37%
Energy savings with MEPS 2
Energy savings potential
• MEPS 1efficiency– Daily energy efficiency: 99.07%– Daily energy loss: 117 kWh
• MEPS 2 efficiency– Daily energy efficiency: 99.24% – Daily energy loss: 100 kWh
• Daily energy saving with MEPS2 17 kWh• Annual saving with MEPS 2: 6.21 MWh• Annual CO2 saving: 6.42 tonnes
Effect of non-linear loads
• Both core loss and load loss are increased by harmonic frequency content of the load current and/or supply voltage
• Core loss– Hysteresis loss scales as (f)1.8
– Eddy current loss scales as (f)2
• Copper eddy current loss scales as (f)2
20
Adjustable speed induction drive harmonics
21
CFL Current Harmonics
Effect of harmonic loss 150 kVA transformer supplying PCs
Requires de-rating to 125 kVA to maintain normal life
Can the efficiency levels of transformers be increased?
• What are the ultimate efficiency limits?• What are the manufacturing constraints?• New materials?• What are the operational constraints?• Industrial use and impact on losses• Total life cycle cost of the transformer
The ultimate efficiencies[US DOE determination : MAX-TECH levels]
25
Comparison of MEPS1 with other international efficiencies for liquid immersed three phase transformers
Efficiency Comparison: 3 phase liquid
97.8
98
98.2
98.4
98.6
98.8
99
99.2
99.4
99.6
99.8
100
50 100 160 250 400 630 1000 1600 2500
Transformer rating (kVA)
Po
we
r e
ffic
ien
cy (
%)
MEPS1
US benchmark
US proposed
EU existing
EU proposed
Japan top runner
26
Comparison of MEPS1 [12 and 24 kV] with other international efficiencies for dry-type three phase transformers
Efficiency comparison: 3 phase Dry type (12 kV)
96.5
97
97.5
98
98.5
99
99.5
100
50 100 160 250 400 630 1000 1600 2500
Transformer Rating (kVA)
Tra
nsf
orm
er e
ffic
ien
cy (
%)
MEPS1 12 kV
US Benchmark
US Proposed
EU HD528
Japan top runner
MEPS1 24kV
Australian ESI Aug 07 27
Comparison of MEPS1 And MEPS2 liquid immersed transformer efficiencies with international standards
Oil Tx comparison
97.8
98
98.2
98.4
98.6
98.8
99
99.2
99.4
99.6
99.8
100
1 2 3 4 5 6 7 8 9
MEPS1
US benchmark
US prop
EU C-C'
EU pr
Japan
MEPS2
New MEPS comparison
Australian ESI Aug 07 29
MEPS1 and MEPS2 efficiencies for all transformer types and ratings
MEPS1 and MEPS2 Transformer Efficiencies
96
96.5
97
97.5
98
98.5
99
99.5
100
10 16 25 50 25 63 100 200 315 500 750 1000 1500 2000 2500
Transformer Rating (kVA)
Po
wer
Eff
icie
ncy
@ 0
.5 p
u (
%)
Oil 1ph_MEPS1
Oil 3ph_MEPS1
Oil 1ph_MEPS2
Oil 3ph_MEPS2
Dry(12kV) 1ph_MEPS1
Dry(12kV) 3ph_MEPS1
Dry(12kV) 1ph_MEPS2
Dry(12kV) 3ph_MEPS2
30
Increase in transformer numbers and installed capacity for the 30 year modelling period [2006 – 2036].
Increase in Transformer Number and capacity 2006-20036
0
200000
400000
600000
800000
1000000
1200000
1400000
6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Year
Nu
mb
er a
nd
MV
A
Utility Tx no.
Utility Tx MVA
Private Tx no.
Private Tx MVA
31
Annual loss of the three phase oil-immersed transformers with MEPS1 and MEPS efficiency and the difference in annual loss [at 25% load]
Annual energy loss @ 25% load for 3 ph oil units with MEPS1 and MEPS2
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
25 63 100 200 315 500 750 1000 1500 2000 2500
Rating (kVA)
En
erg
y lo
ss (
kWh
)
3 ph MEPS1
3 ph MEPS2
MEPS1-MEPS2
Timeline for MEPS 2
• Dec/Jan2008: Broad elements of new standard containing revised figures
• April 2012: Likely Public Comment Draft of new Standard to be produced
• 2013: MEPS 2 to be implemented no earlier than this
33
Efficiency determination
• NATA registered labs for MEPS for Transformers
• TCA (Sydney)• CalTest (Port Elliott, SA)
• CalTest also test Motors to MEPS
Australian ESI Aug 07 34
Manufacturer Tests
• Australian Manufacturers perform loss measurements and efficiency determination as a type test.
• Main manufacturers for utilities are– Wilsons (Wodonga)– Schneider (Benalla)– Tyree (Mittagong)– ABB (Brisbane and Perth)– TMC (Melbourne)– Ampcontrol (Newcastle)
Australian ESI Aug 07 35
Imported transformers
• Very large numbers• Mainly for the private sector• Difficulty in regulating• Testing is difficult because of size• Need mobile test sets
– Caltest have mobile facility– Excite from LV side– Problems with OHS constraints
36
Efficiency determination
• Method used in the Standard is from the main power trafo standard: based on loss compliance tests
• Requires only 1-2% accuracy in loss determination
• But efficiency is specified to a 0.01% variation• Uncertainty of the efficiency determination is
thus questionable• US Dept of Energy has a much more rigorous
test method specified
Conclusions
• Transformers are a significant contribution to overall network loss
• There is significant potential for reduction of transformer losses
• Modern load types increase losses due to the high harmonic content
• Harmonics should be included in some form in testing
• Testing methods as specified need some improvement
Top Related