DC in the LV network: cable challenges. Antonios Tzimas Dimitris Antoniou Simon Rowland

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Barry McLaughlin
5 years ago
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1 DC in the LV network: cable challenges Antonios Tzimas Dimitris Antoniou Simon Rowland

driven by exploitation of diversity in renewable sources and diversity in load is expected.

2 UK Government s 2050 reduction in CO2 emissions target. Top of the network describes the HV transmission where transcontinental energy exchange in Europe, driven by exploitation of diversity in renewable sources and diversity in load is expected. Tail of the network is the so-called last mile. The challenge is to re-engineer the way the last mile assets are used without changing the cables and pipes in the ground.

3 The challenge Top : HVDC transmission are driving HV technologies and products No identified benefits in MV networks Tail : End user DC products increase in the home and office The increasing number of electric vehicles/charging stations are DC Electric climate control units Demand cycle is changing Can we better utilise the existing cable infrastructure for DC distribution?

4 if DC is prevalent in the transmission system, and omnipresent in the office and home, might it offer opportunities in the distribution network?

5 The Tail challenge Endless variety of products in the ground Local installation varies Lack of transparency and records LVDC ageing unknown

6 Our approach Learn from considering our local campus network Develop links into local distribution utilities Agree a network system to consider with them Source old cable? Develop steady state thermal cable models using FEA in COMSOL multiphysics. Agree a system to study at the Tail.

r=9.75 2. 0.5 3. 2.8 4. 0.5 5. 0.1 6. r=30 7. 0.15 8. 1.8 9. 3.15 10.3.5 Inside buildings 415V; 1 core x 300mm 2 Layers 1.

8 Cables under study Underground 6.6kV; 3 core x 300mm 2 Layers 1. Copper conductor 2. Conductor screen 3. XLPE insulation 4. Insulation screen 5. Copper screen 6. String fillers 7. Tape binder 8. Sheath 9. Steel armouring 10.Oversheath Dimensions (mm) 1. r= r= Inside buildings 415V; 1 core x 300mm 2 Layers 1. Copper conductor 2. XLPE insulation 3. LSZH sheath 4. Alum. wire armour 5. LSZH jacket Dimensions (mm) 1. r=

9 Thermal distribution: single core cable

10 Thermal distribution: triple core cable

11 Single core 415V AC cable Current through each cable (A): (25%) (50%) (100%) Building Power requirements: 800kW Maximum power is delivered through a total of twelve cables, six from each transformer. DC Voltage (V) Building Power requirements (%) What voltage can the cable withstand?

12 EMerge Alliance Standard A family of DC power distribution standards to create microgrids meeting evolving commercial building needs. 24 VDC Large number of participating members Many products have been registered for the standard ETSI EN VDC standard Requirements for the interface between ICT equipment and its power supply IEC SMB SG4 LVDC distribution systems up to 1500 VDC SCOPE To address the IEC standardisation needs on systems and products to be used with dc voltages up to 1500 V and to indicate to SMB the directions for future standardisation in this field NTT (Nippon Telegraph and Telephone) Use of 380 VDC system

13 What s different/similar AC/DC, LV/HV Processes 50 Hz DC Dielectric heating Water trees (2) Corona (3) Electrical trees (500) Joule heating Partial discharges (1) Dig-up Corrosion Tracking Space charge injection (15) LV 400V HV 400 kv

14 What s different/similar AC/DC, LV/HV Environment 50 Hz Power quality - harmonics Lightning impulse Switching impulse Moisture/pollutants Dig-up Electric field DC LV 400V HV 400 kv

15 Conclusions We can develop models of capacity (AC and DC) This depends on DC voltage limits of old AC cable This requires reliability models We need to develop our relationship with DNOs We will benefit from a shared LV network across the Tail to consider We will link the in-building research to this LV network research with Imperial.

OFFSHORE WIND FEASIBILITY STUDY APPENDICES Appendix C.2 Subsea Cable Data Sheets

OFFSHORE WIND FEASIBILITY STUDY APPENDICES 10-7 10.3.2 Appendix C.2 Subsea Cable Data Sheets Design data for TFVA 36 kv 3x1x240 mm 2 KQ Metallic Laying up Inner sheath Bedding Armor Diameter of conductor