DESIGN, MANUFACTURING, TESTING, …

1 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance design , MANUFACTURING, testing , installation AND COMMISSIONING OF. LARGE RECTIFIER TRANSFORMERS. FEEDING MW RECTIFIER UNITS FOR. NUCLEAR RESEARCH APPLICATIONS. by BHABHA ATOMIC RESEARCH CENTRE. February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 1. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Outline of Presentation Working of Typical Nuclear Power Plant Simulation of Safety Related R&D Studies in Experimental Facilities Specifications of High Power Rectifier Units Single Line Diagram of Electrical Power System feeding Rectifier Units Schematic Block Diagram of MW Rectifier Unit Approach for design of High Power Rectifier Transformer Simulation of 12 Pulse.

2 MW Rectifier Unit Factors considered for the design of High Power Rectifier Transformer Parametric values of rectifier transformer and mineral oil testing methodology of Rectifier Transformer testing , site installation and commissioning of rectifier transformer Conclusions February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 2. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Working of Typical Nuclear Power Plant February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 3. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Simulation of Safety Related Studies in Experimental Facilities 3-D view of ITL Phase-II.

3 February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 4. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Simulation of Safety Related Studies in Experimental Facilities Old FRCS. New FRCS. February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 5. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Specifications of High Power Rectifier Units Input: 33 10% kV, 3 Phase, 50 3% Hz, AC. Output: Maximum 10,000 kA at 340 Volts DC. Output Power: 3,400 kW. Current/power stability: of set value Response time: < 100 milli second from 10% to 100% of set value Type of control: Secondary control incorporating phase angle control method using SCR as a control element in a closed loop manner Mode of control: CC/CP adjustable from 10% to 100% of rated value Type of load: Resistive (Direct heating of Inconel tubes of Fuel Rod Cluster Simulator (FRCS) of NPP).

4 Cooling: Step down Power Rectifier Transformer is ONAN, Inter Phase Transformer is forced air cooled & SCR assemblies are DM water cooled Circuit configuration: Twelve pulse, fully controlled bridge rectifier system DC current sensor: Clamp-on type DCCT to sense, monitor, control current Power monitor: Incorporation of isolated, true RMS power transducers February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 6. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Single Line Diagram of Electrical Power System feeding Rectifier Units February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 7.

5 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Schematic Block Diagram of MW Rectifier Unit February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 8. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Approach for design of High Power Rectifier Transformer Rectifier transformer supply DC load currents. Secondary windings of rectifier transformers interfaced with rectifier circuits based on semiconductor devices and thus, generate harmonic currents. Secondary current is highly discontinuous and flows part of the cycle.

6 Transformer primary current is continuous, however, THD exceed the limit mentioned in IEEE: 519 guidelines and hence need attention. Harmonic currents causes overheating, induce voltage stresses, core saturation and offer serious problems if they are not evaluated properly. design of magnetic circuit parameters- operating flux density. Calculation of true RMS magnitude of voltage & current Sizing of copper conductor of windings Modeling/software simulation of the transformer and rectifier together to extract the harmonic spectrum of the current. Designer use this approach for optimal design of rectifier transformer. IEEE standard No. verifies usefulness of this methodology.

7 February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 9. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Simulation of 12 pulse, MW Rectifier Unit February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 1. 0. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Simulation Result of DC Output Current Waveform February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 1. 1. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Simulated Result of Secondary Current Waveform February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 1.

8 2. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance FFT Analysis of Secondary Current Harmonic Content in Secondary Current Harmonic Order Frequency Magnitude (Hz) (% of Fundamental). Fundamental 50 100. 3rd 150 5th 250 7th 350 11th 550 13th 650 17th 850 19th 950 23rd 1150 25th 1250 29th 1450 31st 1550 35th 1750 37th 1850 47th 2050 49th 2150 February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 1. 3. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Simulated Results of Primary Current Waveform February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 1.

9 4. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance FFT Analysis of Primary Current Harmonic Content of Primary Current Harmonic Order Frequency (Hz). Magnitude (% of Fundamental). Fundamental 50 100. 3rd 150 5th 250 7th 350 9th 450 11th 550 13th 650 15th 750 17th 850 19th 950 21st 1050 23rd 1150 25th 1250 27th 1350 29th 1450 31st 1550 35th 1750 37th 1850 47th 2350 49th 2450 February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 1. 5. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Problems caused due to harmonics Generally, transformers are designed to operate at rated frequency.

10 The effects of harmonics on transformers are commonly unnoticed and disregarded until over heating & pre-mature failure happens. Transformers that have operated adequately for long periods have failed in a comparatively short time. Main causes are: Overheating of windings Over - stressing of the insulation of the windings Core deformation and extra vibration Skin effect Nuisance tripping of circuit breaker Triple-n harmonics currents circulate in delta windings February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 1. 6. 6th International Conference on Large Power Transformers Modern Trends in Application, installation , Operation & Maintenance Effect of harmonics on losses February 22nd - 23rd , 2017, Scope Complex, Lodhi Road, New Delhi, India 1.