Voltage spikes, also known as transients, are a constant danger to people working with electrical systems. Transients are short bursts of energy that last for just microseconds or milliseconds.
Transients can be created by lightning strikes, but they also occur at lower energy levels and are more typically caused by inductive load switching. They are harmful in a number of ways:
- They deteriorate solid state components. Sometimes a single high energy transient will puncture a solid state junction; repetitive low energy transients can accomplish the same thing.
- Their high-frequency component (fast rise times) cause them to be coupled into adjoining conductors.
The impact of transients can be devastating, especially for anyone taking measurements on electrical equipment when the transient occurs. For example, when an inductive load such as a motor or transformer is switched off, it generates an inductive voltage spike. And because the circuit is a high energy source, it can supply current to the voltage spike until the surrounding air breaks down into conductive plasma, causing a major fault or arc fault incident.
If you’re taking measurements on electrical systems, these transients are "invisible" and largely unavoidable hazards. They occur regularly on low-voltage power circuits, and can reach peak values in the many thousands of volts. In these cases, you’re dependent for protection on the safety margin already built into your meter and other safety measures you’ve undertaken.
Protecting yourself from the threat of electrocution, arc-flash events and transients is critical. For electrical workplace safety, the key to staying safe is following the National Fire Protection Association standard known as NFPA 70E – The Standard for Electrical Safety in the Workplace. Whether you’re a professional electrician, an apprentice or a supervisor, it’s your responsibility to read and fully understand this standard. It could save your life. Outside the United States, the electrical standard may be different. Many countries reference IEC 60364, The Canadian Electrical Code published by CSA or German Din VDE.
In addition to using a multimeter rated for the appropriate measurement category, anyone working on live power circuits should be protected with flame resistant clothing, wear safety glasses or, better yet, a safety face shield, and use insulated gloves and shoes.
For more information on Electrical Safety, see our online course available at the Fluke eLearning Center.