Electrical Load Characteristics and Curves

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Questions and Answers

What does the maximum demand of a system refer to?

The load at receiving terminals averaged over a specified interval

The ratio of maximum demand to rated capacity

The greatest of all demands during a specified time period (correct)

The average load over a designated period of time

How is the utilization factor of a system defined?

The ratio of diversified demand to the total system demand

The ratio of the total energy produced to the maximum rating

The ratio of maximum demand to the rated capacity of the system (correct)

The ratio of average load to the peak load

What is the purpose of the diversity factor?

To measure the total energy consumed over time

To calculate the load at any given time

To assess the individual maximum demands in relation to the whole system's demand (correct)

To determine the ratio of average load to peak load

What does the demand factor express?

The relationship between motor demand and motor capacity Signup and view all the answers

What can the load factor indicate about a system?

The ratio of the actual load to the peak load Signup and view all the answers

In terms of demand, what is meant by diversified demand?

Load from multiple unrelated systems combined Signup and view all the answers

How is the plant factor used in energy production analysis?

To compare energy produced to possible energy if at max capacity Signup and view all the answers

Why might the 15-minute and 30-minute demands be identical?

There is no change in load during these intervals Signup and view all the answers

What is the coincidence factor used to quantify?

The total demand of a group of consumers Signup and view all the answers

How is load diversity defined?

The difference between the sum of individual peaks and the peak of the group load Signup and view all the answers

What does the contribution factor of the ith load signify?

The contribution of the ith load to maximum demand Signup and view all the answers

What is defined by the loss factor?

The ratio of average power loss to peak load power loss Signup and view all the answers

What is indicated by the diversity factor in the context of electrical loads?

The ratio of coincident load to individual load Signup and view all the answers

In Example 2.3, what is the diversified demand of the group of six houses, given a demand factor of 0.65?

5.85 kW Signup and view all the answers

What time period is the industrial load observed in Example 2.5?

Only between 8 AM and 11 PM Signup and view all the answers

How is copper loss defined at the system peak in Example 2.4?

The power lost due to electricity flow resistance Signup and view all the answers

Study Notes

Load Characteristic

Demand: The average load at the receiving terminals over a specified time interval.
Demand Interval: The period over which the load is averaged (e.g., 15 min, 30 min, 1 hr).
Maximum Demand: The highest demand recorded during a specified period of time.

Load Curve

Visual representation of the load variation over a period of time.

Load Duration Curve

Shows the amount of time a load is equal to or greater than a given value during a specified period.

Diversified Demand

The combined demand of a group of unrelated loads over a specific time interval.

Utilization Factor

The ratio of the maximum demand to the rated capacity of a system.

Plant Factor

The ratio of the actual energy produced or served to the energy that could have been produced or served if the plant operated continuously at maximum rating.
Also known as capacity factor or use factor.

Load Factor

The ratio of the average load to the peak load over a designated period of time.

Diversity Factor

The ratio of the sum of individual maximum demands to the maximum demand of the whole system.

Demand Factor

The ratio of the maximum demand of a system to the connected load.
Often confused with the load factor, but the denominator in the demand factor is fixed based on the system's capacity.

Coincidence Factor

The ratio of the maximum coincident total demand of a group to the sum of individual maximum power demands.

Load Diversity

The difference between the sum of individual load peaks and the peak of the combined load.

Contribution Factor

The contribution of an individual load to the group maximum demand, expressed as a percentage of the individual load's maximum demand.

Loss Factor

The ratio of the average power loss to the peak-load power loss during a specified period.

Example 2.3: Residential Customers on a Distribution Transformer

Six residential customers are connected to a distribution transformer (DT).
Each house has a connected load of 9 kW.
The demand factor (DF) for the group is 0.65.
The diversity factor (FD) for the group is 1.10.

Example 2.4: Feeder Copper Losses

A feeder has a system peak of 3000 kVA per phase and a copper loss of 0.5% at the system peak.
The copper loss of the feeder in kilowatts per phase can be calculated.
The total copper losses of the feeder in kilowatts per three phases can be calculated.

Example 2.5: Industrial Load on a Primary Feeder

Two primary feeders are supplied by a transformer at a substation.
One feeder supplies an industrial load with a peak of 2000 kW at 5 PM.

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Description

Explore the concepts of electrical load characteristics, including demand intervals, load curves, and utilization factors. This quiz will test your understanding of terms such as maximum demand and load factor in electrical systems. Perfect for students of electrical engineering or energy management.