Smart Grid As Smart as the Quality of its Measurements by Linoh - - PowerPoint PPT Presentation

Smart Grid – As Smart as the Quality

• f its Measurements

by Linoh Magagula, PhD, MIEEE, National Metrology Institute of South Africa (NMISA)

• Smart

grid – intelligently integrated electricity network to efficiently deliver sustainable, economic and secure electricity supplies

Improved power quality Smart: communication; sensing; control

• Quality measurements…

– Accurate, precise, traceable.

• Quality measurements are necessary to ensure good

functioning of such a network

– Renewables are intermittent & vulnerable to instability – Can inevitably impact stability of main network if not accurately managed – Quality measurements facilitate good monitoring & controllability

• Very brief background … national quality infrastructure &

metrology

• Metrology covers depths of knowledge that are familiar only to a few – but

everyone makes use of

• National Quality Infrastructure: system needed by

business and governments to optimise production, protect consumer rights, health, environment, security, trade and provision for adequate quality of service

– Metrology is pivotal

• Science of measurement and its application
• Vital part of our everyday life

– Coffee bought by weight – Water, electricity are metered – Police speed traps, surgeon’s laser, hours of sunshine, room temperature, etc.

• Science & engineering completely dependent on measurement

• Metrology includes all practical and theoretical

aspects of measurement & is divided into 3

• verlapping activities:

– Definition of internationally accepted units of measurement (e.g. ampere - The ampere is that constant current which, if

maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 x 10–7 newton per metre of length.)

– Realisation of these units in practice by scientific methods – Traceability (i.e. linking measurements to reference standards: reliable, trusted and accepted internationally)

Quality Infrastructure

• Metrology, standardisation, conformity assessment and

accreditation form independent pillars of essential quality infrastructure – national and international

• In South Africa, we refer to the national quality

system as Technical infrastructure

• Electricity supply industry is evolving

– Prosumers (consumers also producers) → trade – Energy savings & energy efficiency very important – Innovative storage , 2-way comms, integration of different sources, etc. →Accurate & traceable measurements become crucial

• Facilitate seamless integration of different energy sources

(conformance to grid code)

• Facilitate precise monitoring & control of state of the grid
• Quality & safety
• Support technological innovation
• Prevent conflicts in trade, billing, etc.

Accuracy & Traceability

• Accuracy: A measurement is accurate if the average of a set of

repeated measurements is close to the true value of the quantity being measured

• How can we be sure that measuring instruments/devices can

accurately measure?

– Acceptable method to ensure accuracy → calibration (measuring the instrument against a measurement standard, which is of higher accuracy) – determines performance characteristics of the instrument

Voltage & resistance standards are basic references from which all digital voltmeters & calibrators derive accuracy

• Traceability: The value of the calibration standard must be

related to stated references, i.e., national standards through an unbroken chain of transfer comparisons, all having stated uncertainties originating at a national standards laboratory

• Accuracy of national standards validated through

international comparisons

• Specifications of new measuring instruments are usually valid

for 2 – 3 years

– Only through traceable calibration can accuracy of measurements be validated

Which measurement reading is correct? 132 MWh 87 MWh

Power quality issues

• Renewable & alternative energy sources can potentially

degrade the power quality of the supply from the grid

– Cause losses, malfunctioning of equipment, power outages, etc.

• Improving monitoring can alleviate situation

– Requires reliable (accurate & traceable) measurements to enable precise controllability: (the more accurately measured the more the process can be optimised)

• Harmonics, Flicker, Power frequency, ROCOF, Voltage dips & swells, etc.

• The IEC 61000 – 4 – 30 power quality measurement method

standard depends on traceable measurements to achieve its goals

– “all instruments will, when connected to the same signal, produce the same result”

• Calibration of measuring instruments to traceable measurement standards is the
• nly method that can ensure accuracy of measurements

– Power quality measurements are important to system operators to ensure that a connected plant does not cause undue disturbance to their network

• Example aspects requiring accurate measurements in smart

grids:

• Smart grid – as smart as the quality of its measurements

– Accurate measurements improve quality (of life)

Take away…

• 4 main reasons for having an instrument calibrated

– To establish & demonstrate traceability – To ensure readings from the instrument are consistent with other measurements – To determine the accuracy of the instrument readings – To establish the reliability of the instrument, that it can be trusted

• Measurement requirements for your electrical

devices/instruments? (storage, generation, transmission, distribution, RF, etc.) – dclf-rf@nmisa.org – lmagagula@nmisa.org