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 load current to prevent excessive voltage distortion on the power system
• Requirement for customers to give notice before making significant changes to their electrical equipment
• The customer’s responsibility for protection of their electrical equipment
• Service to motors larger than 7½ horsepower

Knowing your responsibilities under Rule K helps ensure the power quality and reliability of electric service 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” refers to voltage and current at frequencies that are multiples of the normal 60Hz voltage and current supplied by Idaho Power. Certain electronic loads produce harmonic currents. Harmonic current generates additional heating in electrical equipment and produces distorted voltage in the power system. This distorted voltage is then supplied to other loads, where it can also produce extra heat and may interfere with the operation of some electronics.

The extra heating caused by harmonic current and voltage can lead to the failure of Idaho Power and customer-owned equipment. Rule K allows Idaho Power to limit harmonic current produced by customer loads to limit the impact of harmonics on our system and their effect on other customers’ equipment.

Idaho Power’s Tariff No. 101, “Rule K,” requires all customers to comply with the current edition of the Institute of Electrical and Electronics Engineers (IEEE) Standard 519, “Standard for Harmonic Control in Electric Power Systems.” The public utility commissions in Idaho and Oregon have approved this Tariff.

Many electronic devices, including those designed to save energy, can be a source of harmonic current. The electronic power supplies in these devices modify the supplied voltage level or frequency and will produce harmonic current as a byproduct of their operation.

Devices that can cause harmonics include:

• Variable frequency drives (VFDs) used to control electric motors
• Static power converters (any device that converts AC voltage to DC voltage or changes the voltage’s frequency magnitude using solid-state electronics)
• Arc discharge devices
• Induction arc furnaces
• Over voltage transformers (rotating machines to a lesser degree)
• Compact-fluorescent lighting
• Electronic lighting ballasts

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

Idaho Power is responsible for limiting harmonics in its system. We monitor our system and customer loads and will test to ensure customer compliance. Customer cooperation with harmonics rules will help Idaho Power improve power quality at customer locations and meet our commitment to providing reliable, responsible energy services today and tomorrow.

If you fail your test, you will typically be given one year to comply with Rule K. Idaho Power will work with you to accomplish this.