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The IESO to Resume Routine Voltage Reduction Tests in July 2023

June 22, 2023

Routine voltage reduction tests will take place on Tuesday, July 18, 2023, as part of mandatory testing of the IESO’s emergency operating measures. The tests are an important tool for ensuring the reliability of Ontario's electricity grid.

Voltage reductions lower demand quickly and minimize the likelihood of service interruptions, helping the IESO maintain the reliability of Ontario’s power system during a variety of unplanned occurrences.

A three per cent reduction is expected to occur from 9:00 a.m. to 10:00 a.m. EST. A five per cent reduction is planned for 1:00 p.m. to 2:00 p.m. EST. Voltage reduction tests have not been held since July 2019 owing to the impacts of the COVID-19 pandemic. These tests are normally conducted every 18 months as per North American reliability requirements.

Voltage reduction tests have three key purposes:

  • To determine how much power can be reduced through the two levels of reduction
  • To identify equipment problems so they can be addressed
  • To help keep IESO and market participant staff familiar with procedures to execute voltage reductions and identify any deficiencies in the procedures that may need to be corrected

Voltage reductions have minimal or no noticeable impact on the general public as the voltages are still expected to be within established industry standards for electrical equipment used by residential, commercial and industrial consumers.

More information about voltage reduction tests is available on the IESO website.

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