NRS 097-series / Grid Code Discussion:

Transcription

1 SASGI Meeting: NRS 097-series / Grid Code Discussion: Gerhard Botha Research, Testing and Development 2014/04/16

2 Overview Introduction What is NRS 097? What do we have? What do we want? Comparison of international documents Proposed amendments Conclusions 2014/05/06 2

3 Introduction Requests from residential (municipal) customers to install PV Key drivers: personal, local, regional or national objectives to increase the renewable energy component of electricity utilized; a whole range of drivers including sustainability, climate change, future fossil price volatility risk aversion, utility energy shortages, etc.; changing dynamics of electricity generation costs, with embedded generation close to the source of consumption becoming economically or financially viable; and in particular contexts where embedded generation may help alleviate localized network capacity constraints or improve power reliability to key circuits on the customer premises (particularly if it can be dispatched or coupled with energy storage). 2014/05/06 3

4 Introduction Why do we (utilities) require standards? Key drivers: Safety Safety Safety 2014/05/06 4

5 Introduction Key drivers: LV networks designed for power flow downstream; Incorrect interfacing can affect network performance and quality of supply; Overvoltages, voltage dips and spikes, interruptions, harmonics, etc; Safety: Equipment incorrectly rated both utility and customer; Equipment damaged due to SSEG not meeting requirements; Utility network energised Maintenance personnel; Customer network energised Reclosing operations; Emergency personnel, e.g. fire brigade. 2014/05/06 5

6 What is NRS 097-1? Does not exist yet Planned to be based on Eskom Standard for Interconnection of Embedded Generators Complements the SA Grid Code (RPP, NC) Protection details Anti-islanding details SCADA details Metering details Applicable to units connected to MV and higher voltages 2014/05/06 6

7 What is NRS 097-1? 3 REQUIREMENTS 3.1 General Requirements 3.2 Legal And Regulatory Requirements 3.3 Operational Safety 3.4 Generator Capabilities And Operation 3.5 Requirements For The Utility Network Interface 3.6 Requirements At The PUC And PGC 3.7 Metering 2014/05/06 7

8 What is NRS 097-1? 4 SUPERVISORY CONTROL AND DATA ACQUISITION 4.1 Gateway Equipment 4.2 Protocols For Information Exchange 4.3 Telecommunication Interface Requirements 4.4 Minimum Data Exchange Requirements 5 TESTS 5.1 Pre-commissioning And Commissioning Tests 5.2 Maintenance Tests 2014/05/06 8

9 What is NRS 097-2? Set of industry standards that define technical requirements: the utility interface, generator requirements and utility implementation guidelines for the interconnection of small scale embedded generators to LV distribution networks of a utility. The standards cover: Utility interface requirements (NRS published, being reviewed) Embedded generator requirements (NRS draft) Utility framework (NRS being published) Procedures for implementation and application (NRS ) 2014/05/06 9

10 What is NRS 097-2? Reviewed international documents: EA ER G83/1-1: Recommendation for the connection of SSEG (<16 A per phase) in parallel with the public LV networks. IEC , Electrical installations of buildings Requirements for special installations or locations Solar PV power supply systems. IEC 61727, PV systems Characteristics of the utility interface. IEC 62116, Test procedure of islanding prevention measures for utilityinterconnected photovoltaic inverters. NRS 048-2, Electricity supply Quality of supply Part 2: Voltage characteristics, compatibility levels, limits and assessment methods. SANS , The wiring of premises Part 1: LV installations. SANS /IEC , Low-voltage switchgear and controlgear Part 2: Circuit-breakers. 2014/05/06 10

11 What is NRS 097-2? WG requirements/decisions: Generic document (i.e. generation source/device independent) < 1 000kVA (vs. 100kVA) > 4.6kVA must be balanced units > 13.8kVA must be three-phase units (vs. 10kVA) Safety requirements (including redundancy) Anti-islanding, disconnection for abnormal network conditions Metering (examples) NOTE: not for tariffs, but technical requirements 2014/05/06 11

12 What do we have? NRS : Published December 2010 Standard Conditions for Small Scale (less than 100kW) Embedded Generation within Municipal Boundaries; 22 September 2011; Municipalities need to keep proper records and report to NERSA, what, where, how much etc.; Comply with requirements from NRS ; Update proposed to NERSA by AMEU/ESKOM; Grid code Renewable Power Plants version 2.6 published Nov 2012; 2014/05/06 12

13 What do we want? NRS (Type Testing) draft: Review international standards again International exposure No single document that will fulfil the requirements for SSEG connection and type testing for LV networks in South Africa Specific comparison for utility interface: VDE 4105 EN IEC 61727, series, other ER G83/1-1 and G59/2 IEEE 1547 / UL 1741 Align with international best practices! 2014/05/06 13

14 Document Comparisons NRS X: <100kW, LV only, 50Hz connection requirements IEEE 1547: <10MVA, Typically MV, 60Hz type testing IEEE ER G83/1-1: <3.66kW per phase per installation (3ph : 11kW), LV only, 50Hz connection requirements and type testing ER G59/2 applies to everything else. VDE 4105: <100kVA on LV network, 4.6kVA per phase per installation (3ph : 13.8kVA), LV only, 50Hz connection requirements and type testing UL1741: relaxed requirements in some instances for <30kW detailed testing 2014/05/06 14

15 Document Comparisons IEC 61727: <10kVA, PV only connection requirements IEC 62116: No size indications specific mention of 61727, PV only anti-islanding testing IEC : No size indications, building installations, PV only wiring standard IEC 62446: No size indications, seems to be aimed more at house installations, PV only documentation, commissioning tests and inspection requirements wiring verification 2014/05/06 15

16 Comparisons (Basic Requirements) Description NRS :2010 IEC VDE-AR-N-4105 UK (ER G83/1-1) EN Purpose Utility interface Utility interface Utility interface / type approval Utility interface Utility interface Technologies All PV All All All Frequency [Hz] 50 N/A Size (A/phase) Separate limits for <16A, <75A, > 75A Size (kw/kva) <11kW, <52kW, > 52kW Voltage levels 400 LV LV Power Factor Standard curve: lagging at >50% power output >20% output power Lagging >0.9 (0.98/ new) (<13.8kW), 0.9 (>13.8kW) (<13.8kW), Leading (0.98/ new) (>13.8kW) % (units 10% (units Max step sizes >100kW) >100kW) 1% of rated current 1% of rated DC current injection (0.5%) current Not provided 20mA 0 (Not allowed) Inform and Fit allowed Yes Various Max short-circuit current Not defined Not defined Synchronous generators 8 Asynchronous generators 6 Inverters 1 Times rated current Not defined Not defined 2014/05/06 16

17 VDE 4105 Standard power factor characteristic curve 2014/05/06 17

18 Comparisons (Protection) Description NRS :2010 IEC VDE-AR-N-4105 UK (ER G83/1-1) EN Protection Islanding No No Not defined If required Disconnect time <2.0s <2.0s <5s <0.5s Not defined Abnormal voltage Range 1 V < 0.5pu V < 0.5pu V < 0.8pu V < 0.9pu < 0.85pu Disconnect time <0.2s <0.1s <0.2s <1.5s <1.5s Range 2 0.5pu-0.85pu 0.5pu-0.85pu Disconnect time <2.0s <2.0s Range pu-1.1pu 0.85pu-1.1pu 0.8pu-1.1pu Disconnect time Continuous Continuous Continuous Range 4 1.1pu-1.2pu 1.1pu-1.35pu >1.1pu Disconnect time <2.0s <2.0s <0.2s Range 5 >1.2pu >1.35pu >1.15pu >114.7pu >1.15pu Disconnect time <0.16s <0.05s <0.2s <1.5s <0.2s Abnormal frequency Range 1 <47.5Hz 50Hz±1Hz <47.5Hz <47Hz <47Hz Disconnect time <0.5s <0.2s <1s / <0.2s <0.5s <0.5s Range Hz<f<52Hz (new) 50.2Hz<f<51.5Hz Disconnect time 50% P_M per Hz (new) 40% P_M per Hz Range 3 >52Hz >51.5Hz >50.5Hz >51Hz Disconnect time <0.5s <1s / <0.2s <0.5s <0.5s 2014/05/06 18

19 VDE 4105 Power curtailment Included in RPP Grid Code 2014/05/06 19

20 Comparisons (Protection) Description NRS :2010 IEC VDE-AR-N-4105 UK (ER G83/1-1) EN Reconnection time Ramp rate 60s 10% of power (new) 20s to 5min (system dependent) 5s for short disturbances 10min of stable power 10% of power 3min Disconnection time can be increased to 5s if generator can withstand network reconnection at 180 out of phase 3 min for mech, 20s for inverters 2014/05/06 20

21 Comparisons (Synchronising) Description NRS :2010 IEC VDE-AR-N-4105 UK (ER G83/1-1) EN Synchronising parameters Automatic Angle 20 ±10 Frequency 0.3 Hz ±500mHz Voltage 5% / 11.5V ±10% Earthing According to SANS According to BS 7671 According to Short-circuit protection According to According to Isolation and switching According to SANS According to /05/06 21

22 Comparisons (Quality of Supply) Description NRS :2010 IEC VDE-AR-N-4105 UK (ER G83/1-1) EN QOS Measured POC POC/PCC POC/PCC Seems to be POC Seems to be POC Flicker NRS (combined effect) 0.5 max due to all generation is in conflict with IEC /11 IEC IEC Pst NRS (new) Plt NRS (new) RVC NRS (new) 3% 4.00% 3.30% 6kW - 10kW Unbalance (4.6kVA - new) Desirable <4.6kVA ER P29 Commutation notches 5% (new) 5% Current distortion (per harmonic) IEC (IEEE519) IEC /12 + listed IEC , class A IEC , class A 2014/05/06 22

23 Comparisons (Quality of Supply) Table 1 Current distortion limit as a function of harmonics (Source: IEC 61727:2004/IEEE519) Odd harmonics Distortion limit 3 rd through 9 th Less than 4,0 % 11 th through 15 th Less than 2,0 % 17 th through 21 st Less than 1,5 % 23 rd through 33 rd Less than 0,6 % Even harmonics Distortion limit 2 nd through 8 th Less than 1,0 % 10 th through 32 nd Less than 0,5 % Interharmonics? 2014/05/06 23

24 Key decisions: NRS Review Revision of NRS : Applicable up to 1MVA connected on LV Additional requirements for larger units, e.g.: Must be balanced multi-phase units Must be able to receive generation inhibit signals Incorporate VDE 4105 where appropriate, e.g. Overfrequency curtailment requirements, Power factor requirements. 2014/05/06 24

25 NRS : Type Testing This was where the fun started Various documents: Basic descriptions and requirements, to UL 1741 Traceability Testing environment descriptions Testing monitoring and accuracy Repetitions of tests Test certificates 2014/05/06 25

26 NRS : Type Testing The following type tests are required: Anti-islanding / Loss of mains; Synchronising to grid; Short-circuit protection; Short-circuit / fault current contribution; Tripping requirements for abnormal voltage and frequency; DC current injection; Power factor; Reconnection after trip; QOS emissions; Step size/ramp rate adjustments (if included in requirements); Different tests from different documents 2014/05/06 26

27 NRS : Type Testing Environment Basic Test requirements: Test result accuracy as per main doc and manufacturer spec Testing environment as per manufacturer spec Measurement accuracy and calibration of the testing equipment suitable accuracy to confirm conformance and traceable calibration Product information manufacturer to provide all requirements for correct installation as well as specified performance Test reports ensure repeatability Simulated utility detail, e.g. THD < 2.5%, system impedance etc. Measurement system requirements uncertainty <50% of EUT accuracy and capable to confirm manufacturer s stated performance 2014/05/06 27

28 NRS : Simplified Connection In line with international practices and CIGRE recommendations; Simplified connection decision tree: Less than 25% of NMD (ADMD); Dedicated connections; Less than 75% of upstream transformer size; Less than 15% of MV feeder peak load; Size vs. distance limitations. 2014/05/06 28

29 NRS : Simplified Connection 2014/04/16 29

30 NRS : Simplified Connection 2014/04/16 30

31 NRS : Simplified Connection Research: UCT similar analysis to Herman-Beta Method for LV network design; 6 case studies; Voltage rise considered; Indications are that the simplified requirements are appropriate until further investigation; QOS impact not considered. 2014/05/06 31

32 NRS : Policies and Procedures Eskom draft documents: General matters that require attention to facilitate EG Metering will need to be upgraded All staff working on LV feeders will need to be trained Networks may need suitable notification Short-term policy for LV Connected EG: Safety of line men and contractors Performance of the system Single Customer To Single Transformer Connection Lockable isolator Multiple Customers Connected To a LV Feeder Not allowed at present 2014/05/06 32

33 NRS : Policies and Procedures SANS section 7.12: NOTE 2 This part of SANS does not cover the supply to an installation that functions in parallel with the main supply (co-generation). Amdt 6 Aspects not covered by SANS is not not allowed. It is just outside of the jurisdiction of SANS and the authority of a registered person. Other bodies such as Professional Engineers and Professional Technicians operate in this space that is not explicitly defined by the Electrical Regulations or SANS Standards. The UK wiring code is explicit in the meaning around not covering embedded generators, it state that it has to be done with the approval of the grid provider. The SANS does not state this explicit but discussions with the drafters of the text indicate that it is the intent of the code to allow the grid provider and the embedded-generator owner to come to an agreement on the matter. 2014/05/06 33

34 NRS : Policies and Procedures List of basic technical requirements: Compliance to NRS Compliance to NRS or equivalent Utility accessible lockable isolation switch to prevent the embedded generator feeding back onto the utility installation. Suitable notification at the Eskom point of supply and metering installation Basic tests to verify the normal safety function of the installation with the embedded generator installed. The balance of the customer installation carries a valid COC Sign-off by suitably qualified person, i.e. Professional Engineers or Professional Technicians 2014/05/06 34

35 Wiring Code SANS : Parallel connection not covered; SANS : Does not conflict or supersede SANS ; Only cover from the generator terminals to the customer DB; DC requirements in SANS to be upgraded; SABS discussion on adoption of international documents/wording. 2014/05/06 35

36 PLEASE NOTE SAFETY!!! Anti-islanding extremely important for utility personnel as well as public Australia rumours of several PV installations that caused fires at residential homes; Also safety of emergency personnel, e.g. fire brigade Firemans switch (over and above current definition) Potential conflict identified in SANS series Insurance implications Make sure your unit complies with all relevant specifications! 2014/05/06 36

37 Conclusions We have come a far way since 2007: NRS is being updated in line with international documents, based on international experience NRS is being drafted in line with international documents NRS being published We still have a lot to do Policy aspects, e.g. tariffs, application processes, incentives, licensing vs. registration, data requirements etc. Type testing of generators no SA laboratory equipped to do so. Wiring requirements: SANS in beginning stages. 2014/05/06 37

38 Thank you