Overvoltage Protection Basics

January 23-24, 2024 | Live Streaming Online

Click Here to register $1195

If you are unable to attend at the scheduled date and time, we make recordings available to all registrants for three business days after the event

This course focuses on transmission to distribution substations and electric distribution circuits (15kV, 25kV and 35kV) arrester applications.

Every year the power delivery industry suffers millions of dollars in losses caused by overvoltage events. Equipment and system related failures are isolated by circuit breakers, fuses or reclosers and create a permanent outage to large areas serving many electric utility customers. This adversely affects the electrical utility’s reliability indices.

This course begins with a discussion of Ohm’s Law components (voltage, current & impedance) regarding surge currents and traveling wave theory then moves to insulating systems. A presentation outlining dielectric clearances and insulating materials provides a basis of understanding as to withstand capability within the electric system. The agenda moves on to an overview of surge arrester classification which includes those used at distribution and substation locations. Attendees will work through application examples that emphasize the various selection criteria. Overvoltage mitigation strategies, including shielding and arrester placement will be explored.

Learning Outcomes

  • Define Ohm’s Law components and their relationship to overvoltage issues
  • Classify, explain & discuss various types of overvoltage events
    • Sustained
    • Temporary
    • Transient
  • Analyze the propagation of transient surge currents and the resulting voltage
  • Interpret surge arrester catalog information
  • Contrast and evaluate overvoltage mitigation techniques
  • Calculate protective margins of arrester discharge voltage to equipment withstand voltage capability
  • Formulate a nominal protective solution based on effectiveness and economics



9:00 a.m. – 5:00 p.m. Central Time

Electricity Basics

  • Ohm’s Law
    • Voltage
    • Current
    • Resistance/Impedance

Electrical Equipment Insulation Systems

  • Extermal Clearances
    • Phase to Grid
    • Between Phases
    • Source to Load
  • Internal Insulating Material
    • Air
    • Oil
    • Paper impregnated with dielectric fluid
    • Polymer – silicon rubber, epoxy

Equipment Voltage Withstand Rating

  • 50/60Hz Wet/ Dry
  • Basic Insulation Level (BIL)
  • Vacuum Interrupters

Overvoltage Categories

  • Sustained Voltage Control
    • ANSI C84.1 – operating voltage range
      • Voltage Regulation
  • Temporary Overvoltage
  • Transient Overvoltage < Course Focus
    • Transient Overvoltage
      • Switching Surges
      • Lightning < Focus
        • Lightning

12:30 – 1:15 p.m. :: Lunch Break

Temporary Overvoltage Characteristics

  • Gapped vs. MOV

Surge Arrester Application

  • Distribution Class Arresters
  • Placement on the Distribution Systems
    • Overhead Distribution Systems
      • Equipment
      • Continuous Lines
      • End of radial line
      • Failed Arrester Isolator
    • Underground Distribution System
      • Riser/Dip Pole
      • End of Radial Line
      • Open point of Underground Loop
      • MOVE Arrester
        • Failed Arrester Disconnect System


9:00 a.m. – 12:00 p.m. Central Time

Substation Surge Protection

  • Dielectric clearances per NESC Part 1
  • Lightening Sheild Wire
  • Lightening Mast
  • Transmission Line Discharge Energy
  • Station Class Arresters
    • Porcelain vs. polymer housed
    • Energy handling capability
  • Surge Arrester Cantilever Strength


Insulation Coordination

  • Formula
  • Acceptable margin
  • Example Problem

Substation OVP Design Strategy

  • Ground Grid Design
  • Placement of Arresters
  • Arrester Monitoring System