Rule K and Harmonics

Idaho Power has a responsibility to deliver reliable energy to our customers.

Idaho Power’s Rule K: Customer’s Load and Operations Tariff, approved by the Idaho and Oregon public utility commissions, outlines limitations related to power quality and reliability.

Idaho tariff

Oregon tariff

Knowing your responsibilities under Rule K helps ensure reliable power at your location and for all customers.

What Is Rule K and What Does It Mean to Me?

Idaho Power’s commission-approved “Rule K: Customer’s Load and Operations Tariff,” outlines limitations and responsibilities as they relate to your power quality and reliability, including:

  • Equipment that may interfere with service to other customers
  • Harmonic control of electronic loads that produce higher current and voltage frequencies than our electrical system can allow
  • Requirement for customers to give notice before making significant changes to their electrical equipment
  • The customer’s responsibility for protection of their own electrical equipment
  • Service to motors larger than 7½ horsepower

Knowing your responsibilities under Rule K helps ensure power quality and reliability for your operation and all Idaho Power customers.

Rule K applies to all Idaho Power customers. Harmonics generally affects the large commercial, industrial and irrigation rate classes.

“Harmonics” is a term used to describe a fundamental principle of physics. Harmonic voltage and current distortions have the potential to impact power quality and cause both Idaho Power and customer-owned equipment to fail. Rule K allows Idaho Power to limit the physical effects of harmonics on our system equipment, as well as its effect on other customers’ equipment.

Idaho Power is concerned about harmonic voltage distortion and equipment stresses related to harmonic current distortion. Harmonic voltage distortions occur when a customer’s electronic equipment uses current at frequencies other than Idaho Power’s voltage; these types of currents are called harmonic currents. Harmonic currents interact with Idaho Power’s electrical system and produce harmonic voltage distortion.

Idaho Power’s commission-approved Tariff No. 101 “Rule K” requires all harmonic generating equipment to comply with the Institute of Electrical and Electronics Engineers, Inc. (IEEE) Standard 519-1992, “Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems.” This standard has been approved by the public utility commissions in both Idaho and Oregon.

Many new electronic devices, including those designed to save power, use complicated and rapid electronic switching that causes harmonic interference and disrupts power quality to all customers.

Devices that can cause harmonics include:

  • Variable speed drive (VSD) motor controllers
  • Electrical devices using short duration pulses
  • Static power converters (static power converters of electric power are the largest nonlinear loads and are used in industry for a variety of purposes, such as electrochemical power supplies, adjustable speed drives, and uninterruptible power supplies)
  • Arc discharge devices
  • Induction arc furnaces
  • Saturated magnetic devices
  • Over voltage transformers (rotating machines to a lesser degree)
  • Compact-fluorescent lighting
  • Electronic ballast lighting

In order to comply with Rule K, customers using harmonic generating equipment may be required to install additional filters or other harmonic mitigation methods to avoid damaging their own equipment and Idaho Power’s system. These are available from your electrical equipment supplier.

Idaho Power has a responsibility to limit harmonics on its system and will be testing to ensure customer compliance. Customer cooperation with harmonics rules will help Idaho Power improve power quality at customer locations and meet our commitment to provide reliable, responsible energy services, today and tomorrow.

Testing is scheduled by rate class and electronic load size. Large commercial and irrigation customers often use harmonic-causing electronic devices because of their size and type of operation. These rate classes have been identified for testing. Industrial customers fall into this group as well; the majority were tested in 2008.

Currently, Idaho Power is testing remaining large industrial loads and non-agriculture water supplies of 50 horsepower or greater that are operated with a variable speed drive (VSD, VFD, ASD).

If you fail your test you will be given one year to come into compliance with Rule K. Idaho Power will work with you to accomplish this.

For assistance with a PDF on this page or to request a PDF in an alternate format, please contact Customer Service at 208-388-2323 or 1-800-488-6151