APP 411L: 87L Functions in the SEL-411L Relay

Course Length: 2 Days (PDHs: 15)
Course Based Fees: $1,000*
* Plus Applicable Tax


APP 411L is an advanced hands-on course that builds on the introductory configuration and protection principles taught in CBT 101, and APP 421 and on the logic configuration principles taught in CBT 104. Students in APP 411L will complete hands-on exercises to configure differential protection and advanced logic. SELogic, distance elements, directional elements, etc., are not covered in this course; students interested in learning about all functions other than 87L should take APP 421 or APP 411L in conjunction with APP 421.


This course is intended for utility and industrial transmission protection engineers and power system consultants who want to understand the line current differential (87L) functionality in the SEL-411L Line Differential Protection, Automation, and Control System in detail.


Day 1

  • Introduction
  • Example System One-Line Diagram and Parameters: Two-Terminal, 345 kV Line Example
  • Introduction to SEL-411L Relay Communications and acSELerator QuickSet SEL‑5030 Software
  • SEL-411L Setting and Applying 87L Line Differential Elements Hands-On Exercise
  • SEL-411L Channel Requirements: Logic, Master, Slave, and Loss of Protection
  • SEL-411L Communications Channel Verification Hands-On Exercise
  • SEL-411L Metering Test Hands-On Exercise
  • 87L Element Logic
  • Three-Pole Trip Logic
  • SEL-411L Internal Faults Hands-On Exercise

Day 2

  • Theory of the Generalized Alpha Plane
  • Disturbance Detection Logic
  • External Fault Detection Logic (includes a hands-on exercise)
  • Testing the SEL-411L: 87L Test Modes
  • Data Alignment, Clock Offset Calculations, and Time-Fallback Logic
  • Channel Monitoring, Alarming, and Hot Standby Logic
  • User-Programmable Communications Bits and Reports
  • SEL-411L Setting and Applying 87L Line Differential Elements for a Two-Terminal, Two-Channel System Hands-On Exercise
  • SEL-411L-1 Fault Location Methods and Settings

Learning Outcomes

At the conclusion of this course, students can:

  • Navigate QuickSet.
  • Identify settings calculation formulas and terminology for 87L applications.
  • Determine effective line differential protection settings for example systems.
  • Configure 87L for serial and Ethernet applications.
  • Create SEL-411L Relay logic equations for 87L protection functions.
  • Monitor system performance with real-time metering using HMI tools.
  • Test 87L protection schemes and verify proper relay operation.
  • Retrieve and analyze events using COMTRADE files and the Sequential Events Recorder (SER).
  • Configure traveling-wave fault location.

Student Background and Knowledge

Before you attend this class, we recommend that you:


  • Have basic familiarity with protective relaying, SELogic control equations, acSELerator QuickSet SEL-5030 Software, front-panel controls, and communications settings.
  • Have a working knowledge of trigonometry, basic calculus, and complex numbers.

Course Preparation

Install or update the following software/files on the laptop you are bringing to class:

Please ensure that your laptop does not have any installation blocks before you come to class.

Additional information is on the Course Policies and FAQ pages.

Available Courses

Request onsite training for your company.