## Why Do Traditional Line Distance Protection Relay Testing Procedures FAIL on Digital Relays?

Traditional line distance relay testing procedures (MTA, Reach, and Timing) are a great way to test electro-mechanical relays and learn how line impedance relays operate; but they are inefficient, ineffective, and frustrating when applied to modern digital relays. This post will show you why your traditional tests are probably failing,

Why Do Traditional Line Distance Protection Relay Testing Procedures FAIL on Digital Relays?

## I Want to Know How a High Impedance Differential Scheme Works

We received this question from the Ask Chris form at relaytraining.com. Follow this link to ask your own question and it might appear in a future blog post. High Impedance Differential Scheme Testing High impedance differential relays are some of the easiest relays to test. Isolate the relay from the

I Want to Know How a High Impedance Differential Scheme Works

## Distance or Impedance Protection (21) Video

Line distance (21) protection is primarily used to protect transmission lines or other electrical equipment where the equipment’s impedance characteristic can be calculated or modeled with software applications. The protective relay calculates the ratio of measured voltage and current and uses Ohm’s Law to continually monitor the measured impedance while energized. The measured impedance

Distance or Impedance Protection (21) Video

## High Impedance Busbar Differential Protection

We covered the basic operating principles of high impedance busbar differential protection in our previous post, I Want to Know How a High Impedance Differential Scheme Works. You should read that post first before we dig deep into the calculations and considerations that explain how high impedance busbar differential schemes function.

High Impedance Busbar Differential Protection

## 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 series explains Line Distance Protection. This bonus animation was created to help relay testers understand distance relay principles. See if you can

Can You Predict What Happens Inside a Distance Protection Relay?

## Finding the Direction in Directional Overcurrent Relays

A reader recently asked a question about the forward and reverse directions described in the Directional Overcurrent Relay section of The Relay Testing Handbook series.  I used electro-mechanical directional relays as an example, which may have been a mistake.  Let’s take another look at the Directional Overcurrent (67) element from a

Finding the Direction in Directional Overcurrent Relays