IEE Southern California Centre - Field Trip Review

Author: IEE Member - Mr. John Mack

With the advent of an open market for electrical energy, the ability to store large quantities has become a valuable asset.   We have heard of prices as low as one cent per kilowatt-hour and as high as $6 for the same commodity.

The Los Angeles Department of Water and Power owns a very large pumped storage system located on and operated in co-operation with the California aqueduct and located about fifty miles north of the city.

An enthusiastic group of members, spouses and friends of the IEE Southern California centre were treated to an excellent and exciting tour of the facility on a fine Saturday morning, September 19th.

The trip through wild and hilly countryside covered in browning grasses with yet some green in the larger bushes is some six or so miles off the main North-South California highway (Interstate 5).

The tour started by ascending to the roof of the massive building, most of which is hidden under the ground, from which we had a great view of the six main penstocks.  Though they are some sixteen feet in bore it was hard to appreciate the scale from our position.  A thirty-foot tunnel over six miles long connects Lake Pyramid to the portal a thousand feet above us.  A manifold and a green steel surge tower looked to us like a large can of peas sitting on the mountainside.

Transformers, one for each of the six generators are on the roof and raise the voltage from 18 kilovolts to the transmission level of 230 kV and from this point on the power is carried by aerial lines to a switchyard with busses and sulfur hexafluoride filled circuit breakers.

Crossing the roof to the other side we looked down on the tailrace lagoon.  Since the modified Francis turbine/pumps are below the bottom of the pond a means of shutting off the water is required so that maintenance can be performed.  Large panels with rubber sealed edges are stacked on the roof and lowered into place by a travelling crane are used for this purpose.

We walked down to the control room floor to view a fine scale model of the plant and another rather different and well-worn replica, which looked like a pile of children's blocks.  It turns out that each block represented a single concrete pour and it was used so that everyone involved in the construction could clearly understand the procedure.

A broad window allowed us to see the operator and his assistant who monitor a large number of alarms.  There is a control bay for each of the six major machines with a corresponding console for its auxiliaries.

Taking the elevator down to the maintenance level, some 20 feet below water level, we could see the circular covers of the generators.  Two overhead travelling cranes are required to lift some 800 tons of rotor and turbine.  Rated at 250 Megawatts with 28 poles and synchronized at 128.57 rpm the total station is rated at 1.2 Giga watts.

The facility can absorb and supply this much power for over eight hours.  Down one more level we saw that each stator is contained in its own chamber, which can be flooded with CO₂ in case of fire.

Descending by metal stairs a real treat was waiting for us.  Our hosts Had arranged to operate some of the major components of one of the idle machines.  We were looking down on the largest ball valve I ever expect to see.  The 16-foot penstock terminates into this valve which was in closed position.

A 10-inch line bypasses the ball valve and as its own valve opened we heard the rush of water under high pressure in full stereophonic sound.  Then as hydraulic balance restored quiet to the chamber the next event began with a bang as oil entered a giant ram.  Very soon the enormous ball valve rotated 90 degrees.  Once again the water was still, held back only by the closed wickets in the Francis turbine.

We moved to the chamber on top of the turbine and with a phone call to the control room the wickets were opened to the full thousand-foot head above us.

As the shaft, at first slowly, then rapidly accelerated to synchronous speed, about two revs per second, we learned that since there was no load on the turbine it was only "consuming" water at ten percent of the maximum flow rate.

This was certainly the high point of our visit after which we took the elevator to ground level and thanked our guide.

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Document last updated - October 25, 1998