UTILITY GIANT CAN'T FULLY EXPLAIN WHY POWER GRID FAILED.

Byline: Jaxon Van Derbeken Daily News Staff Writer

Officials with utilities throughout the West were assured Monday that steps were being taken to prevent another massive power outage, but Los Angeles officials said they would rely on local power plants for now.

``We're not sharing as much, until we understand what is wrong with our sharing system,'' said Marcie Edwards, director of bulk power for the Los Angeles Department of Water and Power.

Authorities from across the Western United States converged on Portland, Ore., on Monday to hear a report from the Bonneville Power Administration on what triggered Saturday's outage that cut power to 4 million people from Canada to the Mexican border.

``The purpose of the meeting was to address how we could keep this from happening in the future - we feel that we can meet that objective,'' said Perry Gruber, Bonneville spokesman.

The giant utility provides power to Idaho, Oregon, Washington and Montana and oversees the Pacific Intertie connection to Southwestern states that was shut down in the blackout.

Authorities acknowledged that the interstate system - designed to isolate power outages - failed to perform properly and said the meeting helped pinpoint equipment and system failures.

But while they have isolated sagging power lines that touched trees as a key cause of the outage, Bonneville officials say they have yet to pinpoint just why the loss of power from the five lines triggered the massive shutdown.

What they do know is that the sagging lines coming into contact with trees somehow triggered a generator shutdown at the McNary Generating Facility on the Oregon-Washington border.

That failure touched off a shutdown in the power flow on the major power-sharing line, or intertie, that feeds the Southwest, including California.

However, the exact cause of the generating plant failure is not known.

``Everything operated how it was supposed to after the generator failed,'' Gruber said. ``We can't figure out why it tripped.''

``We believed the McNary generation facility should have been able to handle the instability,'' he said.

The failure was similar to a smaller outage that occurred in July when a tree fell into a power line in Idaho, causing a power cutoff to 2 million people in 15 states and part of Mexico and Canada.

Bonneville announced Monday that it has begun a four-step program to improve the system. Between 300 and 400 trees have been pruned or cut down because of the risk to power lines should they sag from heat and heavy usage.

Bonneville also has cut by 25 percent the amount of power carried on the Pacific Intertie feeding the Southwest.

On Sunday, Bonneville sought and was granted temporary suspension of measures designed to protect Pacific salmon from injury as they pass through Dalles Dam because the safeguards limit the dam's generating capacity.

Bonneville is also doing a complete review of how it interrelates with other power providers.

Los Angeles power officials said they will continue to rely on local generating plants as much as possible until the experts figure out what happened and why.

``We are relying on our own internal resources at this point,'' Edwards said. She said the city's power is coming from power plants in Castaic, San Pedro and El Segundo and others.

The DWP has an in-house generation capability of 4,250 megawatts. On Monday, peak demand was 4,930 megawatts, so the utility had to import 680 megawatts.

The peak demand Monday was far from the record peak for the DWP, which soared to 5,312 megawatts on June 27, 1990. Southern California Edison officials noted that their record peak was 18,413 in 1992, compared with a peak demand of 17,000 forecast for Monday.

Also on Monday, authorities began a review of what went wrong at the Hyperion waste treatment plant, and why the power backup system failed to prevent discharge of 6 million gallons of partly treated sewage.

The discharge triggered the shutdown of a 10-mile stretch of beach that reopened Monday after tests showed the bacteria levels in water from Venice Beach to Redondo Beach were far below the danger level.