Integrating Smart Transformers (SST) Into Distribution Substations December 2015 by Shaban Awili Cigré SCB1 Page 1
Agenda SST Research Motivation Smart Transformer Technology Overview System Integration Requirement Impact on Distribution Substation Cost Implications System-oriented analysis summary Identify Understand Develop (SST) Advantages (SST) Challenges Comparison Framework Cigré SCB1 Page 2
The Inevitable Change ��������� ����� Transmission HV Distribution MV Distribution LV “Our aim is that by 2027 we will have an active Electricity Network That Maximises Renewables Usage ” Said John Byrne ESB Cigré SCB1 Page 3
The Smart iFuture Add Benefits Add Control Add Functions Consumer Control Smart Transformer Potential Issues Cigré SCB1 Page 4
Smart Transformer Overview Dual Active Bridge (DAB) “It is a box that can take energy in any form – it doesn’t care whether it is AC or DC AC-DC Rectifier DC-AC Inverter Converts Uses HF Transformer & – and it will provide energy on the secondary side with very few losses and to the Converts HV-AC (LF) LV-DC into Switches to Convert HV-DC specifications set by the client.” By Dr: Aedan Kernan into HV-DC voltage LV-AC (LF) voltage into LV-DC voltage Cigré SCB1 Page 5
SST Components/Applications Source: http://www.marketsandmarkets.com/PressReleases/solid-transformer.asp Cigré SCB1 Page 6
SST Based Distribution System FREEDM system SST Section3 REL 38 kV F CL E 10 kV FID FID D REL REL REL SST Section2 SST REL REL REL REL C 10 kV CL A B FID FID REL HV/MV (SST) Based Substation SST Section1 MV/LV (SST) Based Substation 400V Distributed Energy Storage Distributed Renewable Energy LOAD DRER DESD Devices (DESDs) Resources ( DRERs) Cigré SCB1 Page 7
SST Fault Scenarios SST Section3 REL Current in Ter C and D Does not 38 kV F CL E Exceed Maximum 10 kV FID FID D current REL REL REL SST SST Section2 REL REL REL C 10 kV CL A B FID FID REL Current is limited to 2 pu at Terminals SST Voltage below 0.8 Pu Section1 IGBTs contained SST is removed in the SST by the Under rectifier are blocked Voltage Protection 400V The over current DRER/DESD keep does not occur on the primary feeding the load as backup side of the SST LOAD DRER DESD Cigré SCB1 Page 8
Overloading Capabilities (LFT) IEC 60076-7 Loading Guide Long–Time Emergency Short-Time Emergency Normal Cyclic Loading Cyclic Loading Loading � � � A higher ambient temperature Loading resulting from the Unusually heavy loading due or a higher than rated load prolonged outage of some to the occurrence of one or current is applied during part of system elements that will not more unlikely events which the cycle. be reconnected before a seriously disturb normal steady state. system loading. � 100 % for normal operation � � 180% for temporary half 150 % for temporary overload load hour overload � � Current (p.u.) up to 1,5 Current (p.u.) 1,5 � Current (p.u.) 1,8 � � Top-oil temperature 105 ( o C) Top-oil temperature 115 ( o C) � Top-oil temperature 115 ( o C) � � Hot-spot temperature 140 ( o C) Hot-spot temperature 140 ( o C) � Hot-spot temperature 160 ( o C) IEC 60076-5, Specifies The required short-circuit current withstand duration to be 2s. Cigré SCB1 Page 9
Overloading Capabilities (SST) The power electronics components reduces the overload capability during load peaks. The control action could provide a solution to the overloading problem during the transients faults In contrast with the grid components requirement of bearing currents higher than the rated values for longer periods. The SST higher realization costs do not allow to oversize The SST needs new procedures for dealing with the over loading conditions Cigré SCB1 Page 10
Overloading Control Concept (SST) Photovoltaic (PV) plant equipped with a Battery Energy Storage System (BESS). The BESS contributes to limit the power fluctuation in the feeder. Manage a possible overload without derating the SST. This will reduce the current and enhances the SST security against the overload situation. Cigré SCB1 Page 11
Overloading Capabilities (SST) Concept of the Coordinated Frequency and Voltage Overload Control. Voltage and frequency of the master controller are set to nominal values (OS I). The Master controller changes the frequency thought the DG droop controller ( OS II). After 35s Insufficient power contribution is reached and DG is not sufficient to control frequency. Master controller starts changing the voltage level at LV terminal of SST The transformer overload is avoided for total of 60 sec (OS III). Cigré SCB1 Page 12
Impact on Substation Design (Physical Design) (LFT) Fire Protection Transformer Design consideration 5m Horizontal Separation (a) Vertical Separation (b) [m] [m] 5 15.2 Table 16 : IEC 61936-1 2002 Recommendations for separation distances between outdoor transformer and buildings Transformer Liquid To To Type Volume (l) Other Transformers or non Combustible 5m 5m Combustible Building Building Surfaces [m] Surfaces [m] Oil Insulated > 2,000 < 5 10 Transformers 20,000 ABB 10 MVA 6,156 5 10 5m Cigré SCB1 Page 13
Impact on Substation Design (Physical Design) (LFT) Transformer Substation Layout Up to 50% SST Reduction In Volume In Volume 18% Potential Reduction Reduction 10 MVA Oil LFT System Size Substation (LFT) (LFT) (SST) Potential Area Original Area clearance Area Required Area Area m 2 m 2 m 2 m 2 Reduction m 2 1500 12 302 6 290 Cigré SCB1 Page 14
Cost Implications (LFT) Total ownership cost consist of several components: � Purchase price � The Installation Costs � Value of the Energy Losses � Maintenance Costs Factors A, B (€/kW), that depend on transformer type, size, loading conditions, as well as cost of capital, energy market forecasts, expected transformer life. � Decommissioning Costs Life Cycle Cost Breakdown Cigré SCB1 Page 15
Cost Implications (SST) Costs are estimated by means of component cost models for high-volume production � Approximately factor of five more expensive purchasing price. � Produces roughly two to three times higher losses. � It offers reduction in the footprint, weight and volume. Weight Breakdown Material Cost Breakdown � It eliminates all associated costs with using oil. � Offers savings in the civil, transport and installation costs. � TOC will be higher due to the higher purchasing price and higher losses. “Solid State Transformer Market worth $204.3 Million by 2020” MarketsandMarkets : Market Research Consulting Firm Cigré SCB1 Page 16
SST System Benefits Unlike the conventional (LFT) the (SST) offers additional system benefits that should be considered when comparing to (LFT) Universal Provides ability to utilise input or output in AC or DC power. Fault Isolation Protects the load from power supply disturbances Eliminates the tap changer Instantaneous Voltage requirement Regulations Provides backup and reduces Integrates Energy Storage outages length Control voltage and frequency levels will Actively Change Power Characteristics reduce the system losses Provide reactive power compensation and Improve Power Quality system harmonic filtering Provide DC Power In substations it could be used to feed control equipment or to feed DC micro grid Cigré SCB1 Page 17
Summary Identify Understand Develop (SST) Advantages (SST) Challenges Comparison Framework � Protection Integration � Functionality � Flexibility, Requirement � Reliability � Intelligence / Controllability � Overloading Capability � Size, Wight and Volume � Significant Potential in Smart � Additional losses implications Grid applications � Efficiency / Cost � New Asset Reliability � Reduction in Footprint � LFT Represents a truly � SST can only be judged in the Experienced Competitor context of a given application � Eliminating Fire Hazardous and to (SST) the use of oil. Cigré SCB1 Page 18
So What Shall we Do ? Cigré SCB1 Page 19
Any Questions Cigré SCB1 Page 20
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