Precision AC Current Measurement Technique Guildline Instruments Limited

Presentation Presenter, Author Richard Timmons, P.Eng., MSc President, Guildline Instruments Acknowledgements Tom Barczyk, McSEE R&D Product Manager, Power Instruments Guildline Instruments Dr. Petar Miljanic

Overview Introduction Current Transformer Measurement Results Stationary Signals Quasi-Stationary Signals Applications and Conclusion

Need for More Accurate Power Measurements Higher Electricity Costs Demand for Better Efficiency Government Mandated Measure Quasi-Stationary Signals Grids are More Noisy Multiple, Alternate Energy Sources Smart, Unpredictable Loads Introduction

Current Transformer Guildline Instruments Limited

Current Transformer Circuit Modified Design Error Correcting Circuit N I Primary Winding N O Output Winding N E Error Correction Winding Single or Multi-Stage Inexpensive to Implement Very Accurate

Current Transformer Manufacture

Measurement Results Guildline Instruments Limited

Source - Fluke 5520 Calibrator Measurement – Guildline 7220 Power Analyzer (Patent Pending) 8 Independent Channels Current and Voltage (3-Phase + Ground) Current – 4 Channels in Series Voltage – 4 Channels in Parallel Measurement Setup

Power Analyzer Current Error Correcting Transformer Voltage Resistive Voltage Divider A/D kHz 8 Independent Channels Processor PC Based Tablet

0.5 A 50 Hz Stationary Sinusoidal Signal AC Current from 5520 in Series I RMS (1) From 4 Independent Channels One Measurement per Period 500 Samples 10 Seconds x 50 Hz Max Noise per Channel About 30 ppm Includes Noise from Fluke 5520 Stationary Signal (1a)

Stationary Signal Current Noise Current Noise < 30 ppm

0.5 A 50 Hz Stationary Sinusoidal Signal AC Current from 5520 in Series I RMS (0.2s) From 4 Independent Channels Measurement Based on Average (i.e. Aggregate) of 10 Adjacent Periods 600 Reported Measurements 120 Seconds x 50 Hz / 10 (Averaging) Max Noise per Channel About 15 ppm Averaging Acts Like a Filter Includes Noise from Fluke 5520 Stationary Signal (2)

Stationary Signal Averaging Filter Aggregation / Average of 10 Measurements Noise Reduced to About 15 ppm

Same 0.5 A 50 Hz Stationary Sinusoidal Signal IRMS (1) From 4 Independent Channels Moving Sample Window of 30 Measurements Used to Calculate Standard Deviation Standard Deviation About 3 ppm for Each Current Measurement Suggests Most of the Type A Uncertainty is from the Source Maximum Standard Deviation Spread on All 4 Current Measurements About 3 ppm High Level of Measurement Consistency Stationary Signal 1(b)

Stationary Signal Standard Deviation Standard Deviation Each Channel About 3 ppm Max Std Dev Spread 4 Channels About 3 ppm

Same 0.5 A 50 Hz Stationary Sinusoidal Signal I RMS (3s) From 4 Independent Channels Measurement Based on Average (i.e. Aggregate) of 150 Adjacent Periods 3 Seconds x 50 Hz 500 Reported Measurements (i.e. 10 Min) Max Noise per Channel About 10 ppm Longer Period of Averaging Improves Filter Includes Noise from Fluke 5520 Reported Signal Very Similar on 4 Channels Implies Signal Noise Dominated by Source Stationary Signal 3(a)

Stationary Signal Long Averaging Filter Aggregation / Average of 150 Measurements Noise Reduced to About 10 ppm

Same 0.5 A 50 Hz Stationary Sinusoidal Signal IRMS (3s) From 4 Independent Channels Moving Sample Window of 30 Measurements Used to Calculate Standard Deviation Standard Deviation on 4 Independent Channels has Almost Identical Traces Again Suggests Most of the Type A Uncertainty is from the Source Suggests Type A Uncertainty of Current Transformers is < 4 ppm Also Shows Very Good Measurement Consistency Stationary Signal 3(b)

Stationary Signal - Standard Deviation with Filtering Standard Deviation of 4 Independent Channels < 4 ppm

50 Hz 0.45 / 0.5 Amp Stationary Sinusoidal Signal Fluke 5520 Generated 0.45 and 0.5 Amps Measured by the Same Current Transformer Signals ‘Pasted’ at Zero Crossing Signal with Current Transient Input into Power Analyzer Represents a 10% Change in Current Amplitude in 1 Period (i.e. 100,000 ppm) IRMS (1) Shows Power Analyzer Settled Within 3 Measurements to < 10 ppm (i.e. 60 msec) 10 ppm Includes Fluke 5520 Noise 0.05 Amp (10%) Transient

10% Current Transient Rising Edge (100,000 ppm) Settled Within 3 Periods < 10 ppm

0.5 Amp 50 / 60 Hz Sinusoidal Signal Fluke 5520 Generate 50 Hz and 60 Hz Measured by the Same Current Transformer Signals ‘Pasted’ at Zero Crossing Signal with Frequency Transient Input into Power Analyzer Represents a 20% Change in Frequency in 1 Period IRMS (1) Shows Power Analyzer Settled Within 1 Measurement to < 10 ppm (i.e. 20 msec) 10 ppm Includes Fluke 5520 Noise 10 Hz (20%) Frequency Transient

20% Frequency Transient Settled Within 1 Period < 10 ppm

Applications and Conclusions Guildline Instruments Limited

Applications Current Transformer AC Current Meter Power Analyzer (Patent Pending) 7220 Power Analyzer Engineering Prototype

Conclusions-1 Asynchronous Sampling With Modern Electronics Equivalent to Phase Locking Averaging Filter Improves Performance by 100% - 300% Comparing Standard Deviation on Different Channels with Same Signal Helps Identify Type A Uncertainty Contribution from Source

Conclusions-2 Implemented Into Power Analyzer with Current Measurements < 10 ppm Error Correcting Transformer Fast Wide-Band A/D Converters Improved Processing Algorithms Measures Both Stationary and Quasi- Stationary Signals Goal is to Improve to < 5 ppm

Providing Precision Measurement Solutions Guildline Instruments Limited