The Ontario Electrical Grid is operated by Hydro One. It consists of Transmission Lines, Switching Stations, Transformer Stations, and Distribution Lines. It is the power broker’s bank for the Electricity Market. Some wholesale participants deposit, while others withdraw. The power broker controls who makes deposits and who makes withdrawals.
The power broker is the Independent Electricity System Operator, actually a team of brokers who schedule Wholesale Suppliers (generators) to meet the anticipated needs of the Wholesale Users (large industrial customers and municipal utilities), one day in advance, in order to set the spot market price of electrical energy in $’s per MWh.
No matter how electrical energy is made, be it via hydraulic turbines, wind turbines, steam turbines, air turbines, or photovoltaic (solar) farms, it has to be contracted to be sold and made available to the Bulk Electrical System.
Wholesale End Users contract to buy the electrical energy for the price established yesterday. Backup generation is also contracted for single-contingency unforeseen conditions that arise from time to time.
If a large generator shuts down for some unexpected reason, then the system frequency will drop for a few seconds until the water gates at a few hydraulic stations open wider to generate more power. The make-up power will raise the system frequency back to 60.000 Hertz (cycles per second). This will cause a momentary spike in the spot market price. The surcharge is then passed on to small users such as retail stores, farms, and others who get a monthly Hydro Bill, like you and me. When supply = demand, then f = 60.000 Hz.
In the 1980’s, a comparison was made between all of the kilowatt-hours generated and all of the kilowatt-hours consumed by end users at a specified time. The heat losses of all the conductors, transformers, circuit breakers, and disconnect switches was calculated to be 13.8% of the power generated. Seems to support a case for a distributed power system.
Redundancy was built into the system. Two sets of lines, two transformers, and multiple circuit configurations were installed. Most of the equipment would only carry about 40% of their rated capacity. This allowed ‘A’ equipment to be taken out of service, isolated, maintained, perhaps repaired or replaced, tested, and returned to service, while ‘B’ equipment carried all of the load.
Redundancy ensured the lights stayed on, should a piece of equipment fail, by switching load to the other intact equipment. And redundancy allowed a buffer of capacity for future growth. That was then, but the future is now, and the buffers are being squeezed.
Peter Nicholas is a former Ontario Hydro (now Hydro One) Protection and Control Technologist, Electrical Instructor, and Agricultural Energy Advisor. He was a Systems Designer (28 kV Pole Lines & Substations) with Elecsar Engineering, and finally an Electrical Manager/ Safety Manager with C & C Construction Group. He is a member of SCAN!
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