Rating of Transformers supplying Harmonic-Rich Loads David Chapman - PowerPoint PPT Presentation

Rating of Transformers supplying Harmonic-Rich Loads David Chapman Copper Development Association david.chapman@copperdev.co.uk Copper Development Association

Losses in Transformers No-load loss (‘iron loss’) – energy consumed in eddy current and hysteresis loss – present 100% of the time Load losses Resistive loss (‘copper loss’) – dependent on square of load current – most important during high load periods Eddy current loss Copper Development Association www.leonardo-energy.org www.cda.org.uk

Distribution transformer efficiency standards HD 428 & 538 Load Losses for Distribution No-Load Losses for Distribution Transform ers Transform ers OI L-FI LLED ( HD4 2 8 ) UP TO DRY TYPE OI L-FI LLED ( HD4 2 8 ) UP TO DRY TYPE RATED 2 4 kV 2) 2 4 kV 2) ( HD5 3 8 ) ( HD5 3 8 ) POW ER LI ST A LI ST B LI ST C 1 2 kV LI ST A’ LI ST B’ LI ST C’ 1 2 kV PRI MARY 3) PRI MARY 3) kVA W W W W W W W W 5 0 1 ,1 0 0 1 ,3 5 0 8 7 5 N/ A 1 9 0 1 4 5 1 2 5 N/ A 1 0 0 1 ,7 5 0 2 ,1 5 0 1 ,4 7 5 2 ,0 0 0 3 2 0 2 6 0 2 1 0 4 4 0 1 6 0 2 ,3 5 0 3 ,1 0 0 2 ,0 0 0 2 ,7 0 0 4 6 0 3 7 5 3 0 0 6 1 0 2 5 0 3 ,2 5 0 4 ,2 0 0 2 ,7 5 0 3 ,5 0 0 6 5 0 5 3 0 4 2 5 8 2 0 4 0 0 4 ,6 0 0 6 ,0 0 0 3 ,8 5 0 4 ,9 0 0 9 3 0 7 5 0 6 1 0 1 ,1 5 0 6 3 0 / 4 % 6 ,5 0 0 8 ,4 0 0 5 ,4 0 0 7 ,3 0 0 1 ,3 0 0 1 ,0 3 0 8 6 0 1 ,5 0 0 6 3 0 / 6 % 6 ,7 5 0 8 ,7 0 0 5 ,6 0 0 7 ,6 0 0 1 ,2 0 0 9 4 0 8 0 0 1 ,3 7 0 1 0 0 0 1 0 ,5 0 0 1 3 ,0 0 0 9 ,5 0 0 1 0 ,0 0 0 1 ,7 0 0 1 ,4 0 0 1 ,1 0 0 2 ,0 0 0 1 6 0 0 1 7 ,0 0 0 2 0 ,0 0 0 1 4 ,0 0 0 1 4 ,0 0 0 2 ,6 0 0 2 ,2 0 0 1 ,7 0 0 2 ,8 0 0 2 5 0 0 2 6 ,5 0 0 3 2 ,0 0 0 2 2 ,0 0 0 2 1 ,0 0 0 3 ,8 0 0 3 ,2 0 0 2 ,5 0 0 4 ,3 0 0 Source: CENELEC Copper Development Association www.leonardo-energy.org www.cda.org.uk

Distribution transformer efficiency standards HD 428 & 538 Load Losses for Distribution No-Load Losses for Distribution Transform ers Transform ers OI L-FI LLED ( HD4 2 8 ) UP TO DRY TYPE OI L-FI LLED ( HD4 2 8 ) UP TO DRY TYPE RATED 2 4 kV 2) 2 4 kV 2) ( HD5 3 8 ) ( HD5 3 8 ) POW ER LI ST A LI ST B LI ST C 1 2 kV LI ST A’ LI ST B’ LI ST C’ 1 2 kV PRI MARY 3) PRI MARY 3) kVA W W W W W W W W 5 0 1 ,1 0 0 1 ,3 5 0 8 7 5 N/ A 1 9 0 1 4 5 1 2 5 N/ A 1 0 0 1 ,7 5 0 2 ,1 5 0 1 ,4 7 5 2 ,0 0 0 3 2 0 2 6 0 2 1 0 4 4 0 1 6 0 2 ,3 5 0 3 ,1 0 0 2 ,0 0 0 2 ,7 0 0 4 6 0 3 7 5 3 0 0 6 1 0 2 5 0 3 ,2 5 0 4 ,2 0 0 2 ,7 5 0 3 ,5 0 0 6 5 0 5 3 0 4 2 5 8 2 0 4 0 0 4 ,6 0 0 6 ,0 0 0 3 ,8 5 0 4 ,9 0 0 9 3 0 7 5 0 6 1 0 1 ,1 5 0 6 3 0 / 4 % 6 ,5 0 0 8 ,4 0 0 5 ,4 0 0 7 ,3 0 0 1 ,3 0 0 1 ,0 3 0 8 6 0 1 ,5 0 0 6 3 0 / 6 % 6 ,7 5 0 8 ,7 0 0 5 ,6 0 0 7 ,6 0 0 1 ,2 0 0 9 4 0 8 0 0 1 ,3 7 0 1 0 0 0 1 0 ,5 0 0 1 3 ,0 0 0 9 ,5 0 0 1 0 ,0 0 0 1 ,7 0 0 1 ,4 0 0 1 ,1 0 0 2 ,0 0 0 1 6 0 0 1 7 ,0 0 0 2 0 ,0 0 0 1 4 ,0 0 0 1 4 ,0 0 0 2 ,6 0 0 2 ,2 0 0 1 ,7 0 0 2 ,8 0 0 2 5 0 0 2 6 ,5 0 0 3 2 ,0 0 0 2 2 ,0 0 0 2 1 ,0 0 0 3 ,8 0 0 3 ,2 0 0 2 ,5 0 0 4 ,3 0 0 BA’ Source: CENELEC Copper Development Association www.leonardo-energy.org www.cda.org.uk

Distribution transformer efficiency standards HD 428 & 538 Load Losses for Distribution No-Load Losses for Distribution Transform ers Transform ers OI L-FI LLED ( HD4 2 8 ) UP TO DRY TYPE OI L-FI LLED ( HD4 2 8 ) UP TO DRY TYPE RATED 2 4 kV 2) 2 4 kV 2) ( HD5 3 8 ) ( HD5 3 8 ) POW ER LI ST A LI ST B LI ST C 1 2 kV LI ST A’ LI ST B’ LI ST C’ 1 2 kV PRI MARY 3) PRI MARY 3) kVA W W W W W W W W 5 0 1 ,1 0 0 1 ,3 5 0 8 7 5 N/ A 1 9 0 1 4 5 1 2 5 N/ A 1 0 0 1 ,7 5 0 2 ,1 5 0 1 ,4 7 5 2 ,0 0 0 3 2 0 2 6 0 2 1 0 4 4 0 1 6 0 2 ,3 5 0 3 ,1 0 0 2 ,0 0 0 2 ,7 0 0 4 6 0 3 7 5 3 0 0 6 1 0 2 5 0 3 ,2 5 0 4 ,2 0 0 2 ,7 5 0 3 ,5 0 0 6 5 0 5 3 0 4 2 5 8 2 0 4 0 0 4 ,6 0 0 6 ,0 0 0 3 ,8 5 0 4 ,9 0 0 9 3 0 7 5 0 6 1 0 1 ,1 5 0 6 3 0 / 4 % 6 ,5 0 0 8 ,4 0 0 5 ,4 0 0 7 ,3 0 0 1 ,3 0 0 1 ,0 3 0 8 6 0 1 ,5 0 0 6 3 0 / 6 % 6 ,7 5 0 8 ,7 0 0 5 ,6 0 0 7 ,6 0 0 1 ,2 0 0 9 4 0 8 0 0 1 ,3 7 0 1 0 0 0 1 0 ,5 0 0 1 3 ,0 0 0 9 ,5 0 0 1 0 ,0 0 0 1 ,7 0 0 1 ,4 0 0 1 ,1 0 0 2 ,0 0 0 1 6 0 0 1 7 ,0 0 0 2 0 ,0 0 0 1 4 ,0 0 0 1 4 ,0 0 0 2 ,6 0 0 2 ,2 0 0 1 ,7 0 0 2 ,8 0 0 2 5 0 0 2 6 ,5 0 0 3 2 ,0 0 0 2 2 ,0 0 0 2 1 ,0 0 0 3 ,8 0 0 3 ,2 0 0 2 ,5 0 0 4 ,3 0 0 C-C’ Source: CENELEC Copper Development Association www.leonardo-energy.org www.cda.org.uk

Full load losses in a 100kVA C-C’ transformer 12% Winding Magnetic 88% Total loss = 1685 W Copper Development Association www.leonardo-energy.org www.cda.org.uk

Full load losses in a 100kVA C-C’ transformer 12% Resistance 9% Magnetic Eddy current (10% ) 79% Total loss = 1685 W Copper Development Association www.leonardo-energy.org www.cda.org.uk

Full load losses in a 100kVA C-C’ transformer 12% Resistance 4% Magnetic Eddy Current (5% ) 84% Total loss = 1685 W Copper Development Association www.leonardo-energy.org www.cda.org.uk

Current waveform for a typical PC 2.0000 1.5000 1.0000 0.5000 Current (A) 0.0000 0 90 180 270 360 -0.5000 -1.0000 -1.5000 -2.0000 Degrees Copper Development Association www.leonardo-energy.org www.cda.org.uk

Harmonic profile of a typical PC 0.6000 0.5000 0.4000 Current (A) 0.3000 0.2000 0.1000 0.0000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Harmonic Copper Development Association www.leonardo-energy.org www.cda.org.uk

Typical harmonic profile - 6 pulse converter 25 20 15 % 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Harmonic number Copper Development Association www.leonardo-energy.org www.cda.org.uk

Effect of harmonics on transformers There are two issues that affect Transformers supplying harmonic-rich loads: • Triple-n harmonic currents circulate in delta windings, increasing resistive losses, operating temperature and reducing effective load capacity • Harmonic currents, being of higher frequency, cause increased magnetic losses in the core and increased eddy current and skin effect losses in the windings Copper Development Association www.leonardo-energy.org www.cda.org.uk

Effect of triple-n harmonics in transformers Triple-n harmonic currents circulate in delta windings - they do not propagate back onto the supply network Copper Development Association www.leonardo-energy.org www.cda.org.uk

Harmonic mitigation by transformer Delta-star transformers Copper Development Association www.leonardo-energy.org www.cda.org.uk

Effect of harmonics on transformers There are two issues that affect Transformers supplying harmonic-rich loads: • Triple-n harmonic currents circulate in delta windings, increasing resistive losses, operating temperature and reducing effective load capacity • Harmonic currents, being of higher frequency, cause increased magnetic losses in the core and increased eddy current and skin effect losses in the windings Copper Development Association www.leonardo-energy.org www.cda.org.uk

Increased Eddy current losses in transformers Increased eddy current loss can be calculated by: = h h max = ∑ 2 2 P P I h eh ef h = h 1 where: P eh is the total eddy current loss P ef is the eddy current loss at fundamental frequency h is the harmonic order I h is the per unit RMS current at harmonic h Copper Development Association www.leonardo-energy.org www.cda.org.uk

K-Rating of Transformers There are two approaches to rating transformers supplying harmonic rich load: - • Designing for the anticipated duty - e.g.the American system, established by UL and manufacturers, which specifies harmonic capability of the transformer - known as K-factor . • De-rating to survive the anticipated duty - e.g. the European system, developed by IEC, which defines de-rating factor for standard transformers - known as factor K . Copper Development Association www.leonardo-energy.org www.cda.org.uk

K-Rating of Transformers - US System First, calculate the K factor of the load according to: = h h max = ∑ 2 2 K I h h = h 1 where: h is the harmonic order I h is the RMS current at h in per unit of total current Copper Development Association www.leonardo-energy.org www.cda.org.uk

K-Rating of Transformers - US System p y 0.6000 0.5000 0.4000 ) Current (A 0.3000 0.2000 0.1000 0.0000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Harmonic For this typical PC load, the K factor is 11.6 (For worked examples see LPQI AN 3.5.2 or IEE 1100 1992) Copper Development Association www.leonardo-energy.org www.cda.org.uk

K-Rating of Transformers - US System Next, a transformer with a higher K rating is selected from the standard range: 4, 9, 13, 20, 30, 40, 50 Copper Development Association www.leonardo-energy.org www.cda.org.uk