engineering

Load profile

Load profile is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Load profile rather than just read about it. In short: In electrical engineering, a load profile is a graph of the variation in the electrical load versus time. A load profile varies according to customer type (typical examples include residential, commercial and industrial), temperature and holiday seasons.

Load profile — illustration

Key takeaways

Load profile belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Load profile to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Load profile from memory before moving on to harder problems.

Reference excerpt

In electrical engineering, a load profile is a graph of the variation in the electrical load versus time. A load profile varies according to customer type (typical examples include residential, commercial and industrial), temperature and holiday seasons. It involves randomness. Power producers use this information to plan how much electricity they will need to make available at any given time. Teletraffic engineering uses a similar load curve.

Power generation In a power system, a load curve or load profile is a chart illustrating the variation in demand/electrical load over a specific time. Generation companies use this information to plan how much power they will need to generate at any given time. A load duration curve is similar to a load curve. The information is the same but is presented in a different form. These curves are useful in the selection of generator units for supplying electricity.

Electricity distribution In an electricity distribution grid, the load profile of electricity usage is important to the efficiency and reliability of power transmission. The power transformer or battery-to-grid are critical aspects of power distribution and sizing and modelling of batteries or transformers depends on the load profile. The factory specification of transformers for the optimization of load losses versus no-load losses directly depends on the characteristics of the load profile that the transformer is expected to handle. This includes such characteristics as average load factor, diversity factor, utilization factor, and demand factor, which can all be calculated based on a given load profile. On the power market, EFA blocks are used to specify the traded forward contract on the delivery of a certain amount of electrical energy at a certain time.

Retail energy markets In retail energy markets, supplier obligations are settled on an hourly or subhourly basis. For most customers, consumption is measured on a monthly basis, based on meter reading schedules. Load profiles are used to convert the monthly consumption data into estimates of hourly or subhourly consumption in order to determine the supplier obligation. For each hour, these estimates are aggregated for all customers of an energy supplier, and the aggregate amount is used in market settlement calculations as the total demand that must be covered by the supplier.

Calculating and recording load profiles Load profiles can be determined by direct metering but on smaller devices such as distribution network transformers this is not routinely done. Instead a load profile can be inferred from customer billing or other data. An example of a practical calculation used by utilities is using a transformer's maximum demand reading and taking into account the known number of each customer type supplied by these transformers. This process is called load research. Actual demand can be collected at strategic locations to perform more detailed load analysis; this is beneficial to both distribution and end-user customers looking for peak consumption. Smart grid meters, utility meter load profilers, data logging sub-meters and portable data loggers are designed to accomplish this task by recording readings at a set interval.

See also Cost of electricity by source Duck curve Electricity generation Electric power transmission Electric power distribution Load duration curve Peak demand Vehicle-to-grid Unit commitment problem in electrical power production Duty cycle

References

Illustrations

Typical seasonal loads of electric utilities in Eastern New England Division in 1919. United States Geological Survey, 1921. Image courtesy of the National Museum of American History from Powering a Generation of Change

Graphs by hour of California's total electric load, the total load less solar and wind power (known as the duck curve) and solar power output. Data is for October 22, 2016, a day when the wind power output was low and steady throughout the day.

Worked examples

Example 1 — a first encounter with Load profile

Start with the simplest possible case. Write down what Load profile claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Load profile before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Load profile ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Load profile

In research: Load profile appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Load profile in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Load profile is common in secondary-school and first-year university syllabi. It links to neighbouring topics Electric power, Electrical systems, Electronic engineering, so understanding it makes those chapters shorter.
In everyday life: Look for Load profile outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Load profile in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Load profile means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Load profile out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Load profile in simple terms?

Why does Load profile matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Load profile?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Load profile.