Peter Vaessen en Marc Achterkamp, KEMA
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1) Increased loading of existing grid assets is possible through end-of-pipe solutions to gain 15% efficiency, tailor-made solutions for bottlenecks, reassessing continuous load capabilities, and additional dynamic and cyclic load tests. 2) Thermal limits of equipment must be considered, as time constants for cooling are on the scale of seconds to hours and hot spots are crucial at high currents. 3) Metering and protection equipment can be impacted by temporary overloads if current and thermal limits are exceeded, which could cause measuring errors, compliance issues, and protection relay operation.
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Peter Vaessen en Marc Achterkamp, KEMA
- 2. Peter Vaessen • KEMA Laboratories • Innovation manager • Lab development • TU Delft • Electrical Sustainable Energy Department • Head of High Voltage Technologies
- 3. Increased loading of existing grid-assets, HOW? 1. Use end-of-pipe solutions to gain 15% 2. Tailor made solution for specific bottlenecks 3. Reassessment of capabilities for continuous load 4. Perform additional tests for cyclic and dynamic load Losses per meter: ~ 17mW J2A copper conductor (20°C) with J in A/mm2 and A in mm2
- 4. Thermal, can it (continuously) deal with the heat? Load 1 Load 2 Load 3 unstable stable What about Ambient?
- 5. Thermal, can it (dynamically) deal with the heat? • Typical maximum current densities 1-2 A/mm2 for large conductors, up to 4-5A/mm2 in transformers and small diameter cables • Time-constants of thermal phenomena are in the range of seconds to hours, needs to be determined → overall and hot-spot (when appropriate) • The higher the current, the more the details become crucial, e.g., a bend in a conductor but also its shape and orientation • Some typical figures: - melting energy copper 0.6kJ/g - increase of resistance 0.4%/K - elongation 20µm/m/K Problem area current → overheating Problem area voltage → spark
- 6. Temperature rise/cycle tests according to IEC standards 1. Cables 60502-2 2. High voltage switchgear 62271-1 3. Distribution transformers 60076-2 4. Instrument transformers 61869-2 Not enough for dynamic loading, additional thermal time constants and hot- spot (when appropriate) must be determined + accurate measurement and protection needed
- 7. Marc Achterkamp • KEMA Laboratories • Metering, Protection & Substation Automation Laboratory • Type Testing and Certification • Notified Body MID 2014/32/EU
- 8. Impact (temporary) overloading on Metering and Protection • Metering • Measuring CT saturate >120% rated current Measuring error • Compliance “Meetcode”?
- 9. Impact (temporary) overloading on Metering and Protection • Protection • Protection relay • CT inputs protection relay 4 x In continuously • Protection CT’s • CT secondary winding rated continuous thermal current
- 10. Impact (temporary) overloading on Metering and Protection • Protection • Settings • Wide range • Electromechanical versus Digital protection relays • Communication to switch between setting groups • Selectivity