IAEA Technical Meeting on Flexible (Non-Baseload) Operation for Load Follow and Frequency Control in New Nuclear Power Plants Erlangen, Germany, 6-8 October 2014 NPP Grid Interface Key Areas David Ward UK
Operating a grid system? 2
IAEA Milestones Guide NG-G-3.1(2007) Milestones in the Development of a National Infrastructure for Nuclear Power 3
Phases and Milestones Source: Figure from IAEA NG-G-3.1(2007) 4
IAEA Technical Report NG-T-3.8 (2012) Electric Grid Reliability and Interface with Nuclear Power Plants 5
Mutual Dependence NPP Export power The Grid System Import power for start-up and shutdown 6
Mutual Dependence NPP Reactor trips Voltage control Frequency control The Grid System Transients Abnormal Voltage Abnormal Frequency Loss of supply 7
NPPs Prefer a Reliable Grid Frequency well controlled (+/- 1%) Voltage well controlled (+/- 5%) Reactor trip does not cause abnormal voltage or frequency Abnormal voltage or frequency is rare Loss of grid supply to NPP is rare System collapse/blackout very rare 8
Organisations Involved Grid System Operator Transmission System Owner NPP owner/operator Owners/operators of other generation Electricity or Energy Regulator Nuclear Regulator Often same organisation 9
Grid System Operator Responsible for real time secure operation of the transmission system: Forecasts demand Instructs power plants to change output to match demand Monitors and controls power flows Monitors and controls frequency & voltage Must satisfy the energy/electricity regulator 10
NPP Operator Responsible for operation of the nuclear plant Has the primary responsibility for nuclear safety Must satisfy the requirements of the nuclear regulator Has commercial incentive to maximise output and income Has incentive to maximise life of the plant 11
Grid System Operator Carries out long term studies of the system Designs modifications to the transmission system Plans maintenance outages on the transmission system Establishes the technical requirements for the grid and for generators 12
Grid Code (Technical Rules) A document that defines the technical requirements for equipment and its operation 13
Grid Codes - Examples GB Nordic Nigeria http://www2.nationalgrid.com/uk/industry-information/electricitycodes/grid-code/ https://www.entsoe.eu/news-events/formerassociations/nordel/planning/pages/default.aspx http://www.nercng.org/index.php/document-library/codes-standards-and- Manuals/ Jordan http://www.ideco.com.jo/portal/otherfiles/library/gcmcjune2009.pdf 14
Grid Code Contents Usually specifies Normal performance of the grid Frequency, voltage, harmonics, phase imbalance, fault clearance times Required performance of generating units Planning information to be exchanged Operational information to be exchanged Operational procedures 15
What Types of Flexible Operation? Planned load changes to match forecast demand Load changes to balance renewables Load changes on instruction or automatically Within hours Within minutes Within 10-30 seconds (AFC) Emergency load drops or trips 16
Baseload and Flexible Operation Source: Drawn by author for draft IAEA publication 17
Planned or instructed load changes It is important to specify the load changes that will be required: How large? How quickly? How often? How much notice? Will requirements for NPPs be the same as other generators? 18
Frequency Response (AFC) Source: GB Grid Code 19
Emergency Actions Transmission fault near a NPP may cause: Stability problems Need for reactor trip within seconds Or: Overloading of transmission circuits Need for rapid load reduction within minutes Source: Internet photo 20
Grid Code Requirements It needs to be clear and unambiguous It must be capable of change It must be compatible with capability of nuclear plant If it applies to nuclear, it must also apply to other generators 21
MILESTONES - GRID ISSUES IN THE THREE PHASES 22
Grid - Phase 1 Consider Expected growth of grid capacity Historical grid performance Potential to improve grid characteristics Capacity of grid compared with unit size of available NPPs Grid connections to suitable sites Need for nuclear to be flexible Adapted from IAEA NG-T-3.8 (2012) 23
Grid Phase 2 Carry out detailed studies Decide suitable site for NPP Plan grid connections to the NPP site For Bid Invitation Specification: Define grid characteristics Define performance requirements for NPP Adapted from IAEA NG-T-3.8 (2012) 24
Grid - Phase 3 Complete grid connections to NPP site and grid upgrades and enhancements Monitor growth and performance of the grid Establish formal agreements between grid company and NPP Establish good communications Train grid operators in NPP characteristics Adapted from IAEA NG-T-3.8 (2012) 25
A POTENTIAL PROBLEM - LOW INERTIA 26
Inertia Problem 50.4 50.2 Rate of Fall Depends on System Inertia 50 49.8 49.6 49.4 49.2 49 48.8 Minimum 48.8 Hz 48.6 11:30 11:31 11:32 11:33 11:34 11:35 11:36 11:37 11:38 11:39 11:40 11:41 11:42 11:43 11:44 11:45 11:46 11:47 11:48 11:49 11:50 11:51 11:52 11:53 11:54 11:55 11:56 11:57 11:58 11:59 12:00 Source: National Grid publication 27
Inertia Problem Turbine generators contribute inertia to the grid (stored energy about 5MWs/MVA) But Variable-speed wind turbines Solar panels HVDC inverters Contribute no inertia to the grid Source: Microsoft graphics 28
Inertia Problem - conclusion If you replace turbine generators with: Large wind turbines Solar panels HVDC inverters Frequency control becomes harder: Frequency changes faster Generators need to respond faster Source: Microsoft graphics 29
Thank you for your attention Comments and questions? 30