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The Basics of Power Failures and Their Solutions

Session 3 - How We Use Electricity

In the previous session, we defined the three types of power disturbances, namely “dips,” “interruptions,” and “power outages.” Though these problems originate on the supply side of the electrical network, many problems can, in fact, originate on the receiving end without us being aware of them. In this session, we’ll look at some of these demand-side problems.

Types of Electrical Equipment

Certain power disturbances stem from the type of electrical equipment used by the consumer. Let's split the types of electric equipment into two by the fluctuation of power consumption.

1. Equipment with regular energy consumption

Household goods, lighting, computers, and other consumer electronics consume a relatively stable supply of electricity. With minimal fluctuation in power consumption, utilities have little difficulty selecting the appropriate configurations of transmission equipment, making it relatively easy to supply power to such electrical equipment.

2. Equipment with irregular energy consumption

Motorized equipment such as elevators and trains that repeatedly start and stop consume high amounts of electricity. As a result, transmission equipment with large capacity, wiring, and high resistance is required. Such kinds of electrical equipment are said to present utilities with various problems.

1. Equipment with regular energy consumption 2. Equipment with irregular energy consumption

Electrical equipment with regular energy consumption do not typically cause any major problems. Motorized equipment with irregular energy consumption, however, can affect the supply side of electrical systems. Next, we’ll look at some examples of power disturbances caused by motorized equipment.

Power Disturbances Caused by Motorized Equipment

Above we touched on how motorized equipment like trains and elevators. The motor, a primary component in these applications, is a source of problems.
The moment the motor starts, it requires a large amount of electricity. This is called an “inrush current.” Following this initial phase, the motor runs at a constant speed and stabilizes the energy consumption. This is referred to as “rated current.” Inrush current consumes several times more energy than at rated current but in a very short time. Power transmission facilities must be equipped to handle inrush current.

Relationship between inrush current and rated current

In addition, motors tend to emit a noise-like electronic phenomenon known as harmonics. Servo motors, in particular, are known for generating harmonics. These harmonics can have detrimental effects on electrical equipment. Harmonics from a motor can flow back into the power supply, causing malfunctions in other electrical equipment within the same facility. Worse-case scenarios can see harmonics cause overheating in electronic components and lead to fires.

Harmonics

In this session, we looked briefly at how we use electricity.
In the next sessions, we’ll introduce how to avoid power disturbances that can occur on both the supply and demand sides by utilizing devices that specialize in protecting electrical equipment. These power supply devices can be selected with the knowledge of the abovementioned types of electrical equipment and the kinds of power outages introduced in the previous session. In session four, we’ll look at how these specialized power supply devices work and what types are available.

Revised: 11/1/2016

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