Harmonics Studies Needed to Assess Vulnerabilities
By David Mueller, Director of Energy Systems Studies
On March 13, 1989, a geomagnetic disturbance, GMD, caused by solar activity affected bulk power systems in North America.
The most serious impact led to the shutdown of static compensators on a network essential to control of Hydro Québec’s grid. This caused voltage to drop, frequency to rise, tripped transmission lines and, seconds later, knocked out power across most of the utility’s grid.
Concerns over GMD events have led the North American Electric Reliability Corporation, NERC, to study GMD’s threat to transmission systems. It also caused NERC to recently issue reliability standards for transmission organizations, in response to the potential for GMDs and geomagnetically induced currents, GIC, to disrupt operations and possibly damage assets.
Transmission utilities and regional transmission organizations have five years to comply.
The new NERC standards wisely advise transmission organizations to assess the threat to their transformers, expensive assets with long lead times for replacement. But the new standards do not require these organizations to perform detailed harmonic simulations.
These harmonic situations are required to evaluate phenomena similar to the 1989 event that hobbled Hydro Québec. NERC has cited a concern that commercially available harmonic simulation packages do not currently have enough capability for this analysis.