Sensor Accuracy and Data Management Issues

Transcription

1 8/2/21 1 Sensor Accuracy and Data Management Issues Panel on Experiences and System Requirements for Power Quality Data Analytics 1PESGM912 Jan Meyer Robert Stiegler Etienne Gasch Max Domagk Technische Universität Dresden, Germany 2 Agenda Major design aspects for measurement campaings 1. Measurement site and duration 2. Transducers and instruments 3. Selection of Parameters 4. Data management. Data analysis and reporting Different objectives require different specifications (more information in the final report of CIGRE WG C4.112) 1

2 8/2/21 Motivation Voltage measurements: Requires always sensors (e.g. instrument transformers) except in LV networks Current measurements: Always sensors (e.g. instrument transformers or Rogowski coils) required Harmonic voltages measured with different instrument transformers at the same busbar and phase at a 4 kv substation 3 Voltage magnitude in V VT A VT B VT C Significant differences due to different frequency responses 4 Present status of standardization 1. Standards related to harmonic measurement methods (IEC , IEC ) Accuracy limits only for measurement instruments 2. Standards related to instrument transformers (IEC /3) Accuracy limits only at rated frequency 3. Suitability of instrument transformers for Power Quality applications (IEC TR ) Reflects increasing interest of all stakeholders and suggests introduction of accuracy classes Ongoing standardization work in IEC TC38 to close the gap in accuracy definitions 2

3 8/2/21 Measurement methods Non-invasive Parallel measurement of the same voltage by a sensor with known frequency response Advantages: Conditions close to reality Possible during normal operation of transformer Disadvantages: Depends on existing voltage distortion Invasive Excitation of sensor at primary side with single or multifrequent signals Advantages: Full coverage of the considered frequency range Disadvantages: Less realistic conditions in case of mobile measurement system Access to the transformer itself required Mobile test system for measurements up to 3 khz 6 Characteristic of frequency response ratio error ε U / % I II III frequency / khz Ratio error U () f U ( ) ε = sm s f r r U() f -1 U () f U ( f ) pm p r r Distinction of 3 qualitative different ranges: I ε U (f) = II ε U (f) > III ε U (f) < Phase displacement Measured value equals real value Measured value larger than real value Measured value smaller than real value ( f) ( f) ( f) Δϕ = ϕ ϕ sek pri 3

4 8/2/21 7 VT: Impact factors (1) Ratio error in % Frequency response of VTs for different voltage levels 22-kV-VT, 11-kV-CVT, 66-kV-VT 3-kV-VT, 2-kV-CVT, 1-kV-VT Ratio error in % frequency in khz Decreasing first resonance with increasing rated primary voltage Different damping behavior and sequence of series and parallel resonance Impact on full spectrum 8 VT: Impact factors (2) Ratio error ε V Frequency response of two 2-kV- VTs from different manufacturers Frequency / khz Different internal designs Impact on full spectrum Ratio error ε V in % Impact of temperature on first resonance +4 C +2 C C -2 C -4 C Δnr(f) ε V ) 1% -1, 6 6, 7 7, 8 Frequency in khz Impact around resonance frequency 4

5 8/2/21 9 Burden VT: Impact factors (3) Manufacturing tolerances Ratio error ε in % V keine Bürde 68Ω,1µF 68Ω,1µF Ratio error ε V in % Δε U (f) 1% Frequency in khz Signal cables can change the frequency response Impact on full spectrum Frequency in khz 1 VTs of the same type and from the same batch Impact around resonance frequency Calibration based on frequency response from manufacturers can be dangerous 1 VT: Proposal of application bandwidth Definition of application bandwidth 1-%-application bandwidth for about 1 VTs of different type Ratio error ε in % V f1% f% f1% -2, 1, 1, 2, 2, Frequency in khz Corresponds to the concept of accuracy classes in Primary voltage in kv Decreasing bandwidth with increasing rated primary voltage

6 8/2/21 11 VT: Indicative suitability ranges Voltage level 2nd 7th order 8th 2th order 21th th order MV 1 kv Yes Yes Yes 2 kv Yes Yes Uncertain 3 kv Yes No No HV 6 kv Yes Yes Uncertain 11 kv Yes Uncertain No EHV 22 kv Uncertain No No Source: CIGRE/CIRED Joint Working Group C4.112 Design-dependent deviations possible Conventional voltage transformers should not be used for measurement of supraharmonics No resonances up to 1kHz for MV-CTs CT: Impact factors High dependency of accuracy from burden type: Sufficient accuracy only for pure resistive burden Significant increase of ratio error and phase displacement error already for small values of inductive burden parts CT s with voltage output can be the solution for high accuracy harmonic measurements Source: Henze C., OMICRON ITMF 211 nr δ i in f in Hz f in Hz a) b) a) % S r (pure resistive burden) b) % S r (mixed resistive reactive burden) 12 6

7 8/2/21 13 Rogo: Introduction Accuracy specification from manufacturer applies for reference condition (centered position of phase conductor, no external interference) Difference between reference condition and real setups Placement and shape of coils Overlapping of multiple coils Closeby of other phase conductors High signal dynamic and frequency range (especially for supraharmonics) Junction box Distribution panel in substation 14 Rogo: Accuracy and bandwidth Reference position (coil center, perpendicular conductor) 2 Amplitude Error 1 Phase Displacement Amplitude Error in % Coil 1 Coil 2 Coil 3 Phase Displacement in Coil 1 Coil 2 Coil Frequency in khz Frequency in khz Bandwidth determined by analog electronics Minor problem for coils delivered with PQ instrument (Match of bandwidth of PQ instrument and coils is ensured by manufacturer) Attention in case PQ instrument and coils are bought individually 7

8 8/2/21 1 Rogo: Impact of conductor position Error in % Position dependent error (Simulation) Error > Error < - x / cm y / cm Amplitude Error in % Comparison of measurement and simulation Simulated Measured Position Error significantly depends from length of gap in the lock X-Ray photo of analysed coil 16 Rogo: Impact of signal dynamics 1A/Hz + x ma/2hz (reference position) Significant differences between manufacturers (mainly determined by resolution of A/D-conversion) Dynamic range varies between 2 and 2 (for uncertainty of better than %) 8

9 8/2/21 17 Future trends Ratio error ε V [%] Inductive VTs optimized for harmonic measurements 2-kV-VT with extended frequency range 2 2 Conventional VT 1 Optimized VT Frequency [khz} Source: RITZ Instrument Transformers GmbH Ratio error ɛ V [%] Non-conventional sensors with improved frequency response Frequency response of a RC-divider Frequency f [khz] Source: Pfiffner Instrument Transformer Ltd. 18 Agenda Major design aspects for measurement campaings 1. Measurement site and duration 2. Transducers and instruments 3. Selection of Parameters 4. Data management. Data analysis and reporting Different objectives require different specifications (more information in the final report of CIGRE WG C4.112) 9

10 8/2/21 19 Joint working group CIGRE/CIRED C4.112 Guidelines for Power Quality Monitoring Measurement Locations, Processing and Presentation of Data Final report available since 11/214 at Survey on international industry practice on Power Quality monitoring (34 TSO, 73 DSO from all continents) Identification of key challenges for future PQ monitoring 2 (1) Performance at increasing device amount Number of Responses Number of Portable Monitors Distribution Transmission Tranmission Number of Responses Number of Fixed Monitors Distribution Transmission Tranmission More than 2% of the participants have more than 1 permanent installed devices Growing number of larger monitoring campaigns with permanent installed devices Increasing importance of system aspects 1

11 8/2/21 21 (1) Future aspects of system design Distributed storage and processing More intelligence on device level increases performance and scalability Transfer of data with different level of aggregation (raw data only on request) Database vs. file-based storage approaches Multi-level approaches Zero-configuration Consistent setups for comparable data sets Easy replacement of instruments Storage of additional data about site configuration and location Increase of selective queries (e.g. short circuit power, customer types) Regional analyses and inclusion in GIS systems 22 (2) Easy exchange of data and devices Number of different types of devices Number of Responses Almost 9% of the participants use devices of more than one brand/type Limitations in the efficient exchange of data between different devices and device-independent analysis Requirement of standardized interfaces and device-independent storage 11

12 8/2/21 23 (2) Possibilities for standardized interfaces Data storage must be independent from device type File level (lower efficiency) Often manual data export/import necessary Use of common file format definitions (PQDIF, NEQUAL,...) Knowledge of native formats for development of individual filter applications Database level Based e.g. on stored procedures Device level (higher efficiency) Idea of IEC (logical nodes allow diverse implementation) Implementation guide required to ensure conformity with IEC Example 24 (2) Swiss national monitoring system (NEQUAL) XML-based file format for data exchange Uniform, device-independent reporting for single or multiple sites 12

13 8/2/21 2 (3) Analyse and compare large data amounts Used analysis software Percentage of Respondants 1% 8% 6% 4% 2% % 86% 2% Bundled Software Web Application Non monitor-specific software 13% 16% Other Most participants use the standard software provided by the device manufacturer Limited comparability between analyses and reports from different manufacturer-specific software Need for device-independent analysis tools and easy-to-understand, flexible indizes Example (3) Analysis of Swiss measurement campaign 26 Analysis of about 4 out of 7 weekly measurements in LV networks Query based on site characteristics Application of PQ index that reflects the remaining PQ reserve Utilization of limit in % Urban areas Minimum quality index (No measurement has less reserve than...) RMS THD UNB PLT H H H H H H H H H H H H H H H

14 8/2/21 27 (4) Increase level of information usage Percentage of Respondants 1% 8% 6% 4% 2% % Reason and frequency of reporting 72% For Investigations into Specific Events 1% For Requested Specified Periods 32% Regularly (weekly or monthly) 14% Other One third of the participants frequently generate only standard reports Very limited use of the valuable information in the continuous growing data amounts (Dark Data) Need for automated data mining methods ( agents ) to use the information in the data as best as possible Example (4) Analysis of long-term measurements Analysis of long-term trends 28 Analyses based on weekly 9th-percentiles of almost 4 years Application of methods for time-series analysis Analysis of seasonal variations 14

15 8/2/21 29 Thank you for your attention! 1