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Category Archives for Electrical Basics

Use Sequence Components To Make Sure Your Relay Isn’t Disabled By Incorrect Phase Rotation

Did you know that a relay connected to, or set with, the incorrect phase rotation can disable its higher level functions? Did you know that the wrong phase rotation can make your relay testing worthless?

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How to Perform an In-Service Protective Relay Meter Test

In-service protective relay meter tests are THE MOST important tests that should be performed on every digital relay. All of your offline relay testing is meaningless if: The CT/PT ratios are incorrect. The

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Why Does My Open-Delta Connected Phasor Diagram Look Weird?

Meter tests on protected relays connected to open-delta connected PTs can be very confusing. I know I spent a LOT of time trying to figure out the values reported by my first open-delta connected relay

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How to Understand and Determine Phase Rotation in a Power System

Understanding phase rotation is vital when connecting two systems together because the results can be catastrophic if someone doesn’t understand how to interpret phase rotation drawings. You would think

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How to Measure Phase Angles with a Phase Angle Meter

I’ve noticed that many students don’t seem to have experience with phase angle meters, and they can’t guess what a phase angle meter would measure in simple circuit. This knowledge is CRITICAL if

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Frequency Response and the Power System

Here’s an excellent video on frequency response in the grid from NERC. I often tell my students that renewables are making the power system less stable and this video explains part of the issue....

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What Was Your Electrical Epiphany?

The next generation of relay testers need your help! We’re almost finished our “How to Test Protective Relays” Online Seminar and we’re starting to write the next online training

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What is DC Offset? Ask Chris

I was recently asked about DC Offset during a paper I presented at the 2015 Hands-On Relay School and struggled with an answer because I know what it looks like and I know it exists, but I’ve never heard

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Drawing Phasor Diagrams for Relay Testers

Waveform diagrams contain every detail of an electrical system, but that information can be difficult to understand without a lot of effort. Phasor drawings take the complex information embedded in waveform

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We Need Your Help with Our Next Protective Relay Online Training Class: Electricity 101!

We’re wrapping up our upcoming protective relay online training class: Understanding and Drawing Phasor Diagrams, and we are ready to get started on the next course about the electrical fundamentals

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Calculation of Short-Circuit Current from Silent Sentinels 1924

Silent Sentinels 1924 Excerpt #6 This excerpt from the 1924 version of Silent Sentinels discusses how electrical engineers calculated short-circuit currents operated in 1924. This is the 6th in the

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Methods of Clearing Ground Faults from Silent Sentinels 1924

Silent Sentinels 1924 Excerpt #5 This excerpt from the 1924 version of Silent Sentinels discusses how electrical engineers understood how alternating-current systems (AC) operated in 1924. This is the

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Methods of Clearing Short Circuits from Silent Sentinels 1924

Silent Sentinels 1924 Excerpt #4 This excerpt from the 1924 version of Silent Sentinels discusses how electrical engineers understood how alternating-current systems (AC) operated in 1924. This is the

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Methods of Applying Relays to Circuit-Breakers from Silent Sentinels 1924

Silent Sentinels 1924 Excerpt #2 This excerpt from the 1924 version of Silent Sentinels discusses how electrical engineers were applying relays to circuit-breakers in 1924.  This is the 2nd in the series.

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Can You Predict What Happens Inside a Distance Protection Relay?

Distance Protection (21) has many names (Line Protection, Line Distance Protection, Impedance Protection) and is one of the more complicated elements used in protective relaying. The Relay Testing Handbook

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