Smartening the grid: the challenges for power engineers


Anoop Gangadharan, Yokogawa Europe, spoke to Electrical Review

As the world makes the transition from fossil fuels to renewable energy, the impact on our existing energy infrastructure is significant. 

With developments such as renewable energy power stations, energy-positive buildings and infrastructures, electricity no longer has a unidirectional flow across the power grid. As local energy generation and private storage facilities increase, greater demands and newer challenges are imposed. As a result, to ensure a stable and reliable power grid, not only are the existing standards for power consumption and harmonic influences becoming stricter for consumer products, but also new standards are starting to appear for all energy sources connected to the grid.

Balancing act

Keeping a balanced grid poses several challenges to power engineers. The power output from different sources have different levels of distortions, with those from switched-mode suppliers (e.g. solar, wave and wind) usually greater than those in constant-mode supply (coal, gas and nuclear). With the multitude of different power stations feeding the grid, engineers in charge of ensuring a balanced grid need robust testing and accurate measurements to reduce the impact of noise, distortions and harmonics from multiple sources. Similarly, operators of power generation stations and large consumers also need to quantify the effects of their inputs to and outputs from the grid. Infographic: Getting started with electrical power measurements.

Understanding and characterising power

As a result, there is a growing need for power engineers to correctly and accurately characterise the behaviour of all power system components in the constantly evolving smart grid, taking into account questions such as:

* What is the level of AC/DC voltage and current to be evaluated?

* At what frequency range/bandwidth do measurements need to be made?

* What wiring will be used: single-phase, 3-phase or a combination of both?

* What is the shape of the signal: sinusoidal, PWM or a more complex waveform?

* Is the power repetitive, stable, intermittent, continuous or fluctuating?

* Are cycle-by-cycle or sub-cycle power transients required to be measured?

* How distorted are the waveforms? Are the signals noisy?

* What is the power factor?

The testing technologies used for these measurements needs to be robust enough to ride through disturbances such as soft switching and soft starting that occur during and after power outages or responses to peak demands. Choosing the power measurement solution that is right for you

Greater certainty required

Engineers are facing a growing network complexity and therefore the number of measurements and tests they must carry out in their role. They must be able to accurately measure more than just voltage or current uncertainty and take power uncertainty, as a whole, into consideration. Once engineers know what accuracy they need to achieve they can decide on the appropriate measurement technology to use. The technology needs to match the application in terms of operating bandwidth, voltage, current, accuracy and number of inputs.

In addition, depending on waveform complexity, types of computation, and electromechanical measurement requirements, one or more of the following requirements may have to be satisfied:

* Fast and automatic updates of measurement range or update rate to measure input signals fluctuating in amplitude or frequency

* Specifications not only at a power factor of unity but also at power factors applicable to the needs of the application - while accounting for uncertainty contributions from internal phase shifts

* Harmonic and flicker analysis capabilities based on IEC standards

* Measurement ranges with high crest factors to capture distorted signals or large, unexpected peaks

* The ability to compute electrical parameters in star, delta and other wiring configurations

* Functionality and sampling rates for analysing PWM and other complex waveforms

* Measurement of physical parameters such as torque, mechanical power, slip, rotation speed, temperature, pressure, strain etc.

* Time-domain measurements for analysing cycle-by-cycle or sub-cycle power transients.

Selecting the right power measuring instrument based on these criteria can play a key part in shaping the power infrastructure of the future to meet the challenges outlined above. Are you achieving the levels of accuracy you need?