◊ This is part of the ‘history’ series of articles ◊
In the early 1900s, the electrical grid in the Niagara area and parts of northern Ontario began as 25-cycle developments. Anyone old enough to have experienced 25 cycle power will remember the annoying flicker it caused with incandescent lighting. It was produced for over 100 years on parts of the grid.
When alternating current electricity was invented, frequency was referred to as ‘cycles per second‘ or ‘cycles‘ until the term Hertz (named after Heinrich Hertz) was adopted as part of the International System of Units (SI) in 1930.
It rarely occurs to most people that today, our electrical system in North America operates on alternating current (ac) at a fixed frequency of 60 Hertz (Hz). That means our voltage alternates between positive and negative polarity in a sinusoidal wave pattern that repeats 60 times every second. The electrical grid in Ontario began with 66⅔ Hz and 25 Hz systems.
The system frequency is highly significant for generators, motors, transformers and reactive components.
Systems of different frequencies are not compatible. Separate infrastructure is required for each frequency.
In 1900, there were no accepted standards for frequency. Lower frequencies or dc worked well with electric motors because they produced better torque characteristics than ac at higher frequencies. Industrial processes and urban transportation were best served by direct current (dc) or low frequency ac at 16 or 25-cycle. Without any collaboration independent power producers developed systems that operated at 25 Hz, 60 Hz and 66⅔ Hz in Ontario and neighbouring jurisdictions.
The Adams Power Station
The Adams Power Station built in 1895 in Niagara Falls New York was originally intended to produce compressed air for industrial processes. With the emerging interest in polyphase ac electricity it was decided to make the power station electric. The hydraulic portion of the plant had already been designed when the decision was made to go electric. The design speed of the water turbine system determined that the electric generators would produce 25-cycle polyphase alternating current. That is how the 25 Hz system started in Niagara.
In New York, where 25 Hz generation was born, it was finally decommissioned in 2006.
Historical references for 25 Hz in the United States:
‘History of 25 Hz in New York State‘ by IEEE – Part 1. Part 2 is available here
‘The Schoellkopf Disaster – Aftermath in the Niagra River Gorge‘ by IEEE
Ontario’s 25 Hz 104-year lifecycle
Ontario’s 25 Hz Niagara System development began with the construction of the Canadian Niagara Power Generating Station (also known as the Rankine Generating Station) and the Ontario Power Company Generating Station on the Niagara River in 1905. The 25 Hz frequency was adopted for Rankine and Ontario Power because of the existing Adams Power Station in the U.S.
Canadian Niagara Power Generating Station (Rankine Generating Station) 1905
Ontario Power Company Generating Station 1905
Credit: Canada. Dept. of Interior / Library and Archives Canada / PA-043423
Credit: By Skyden67 – Own work, CC BY-SA 3.0
The goal of the Niagara development was to supply power approximately 130 km to Toronto, even though transmission of electricity across that distance was not yet possible because of voltage limitations. The longest transmission line in Ontario was built in 1898 from the DeCew hydroelectric generating facility in St. Catharines to Hamilton. It was 54 km long and operated at 22,500 volts (22.5 kV).
Recognizing the opportunity for economic growth, Adam Beck, an Ontario politician, championed the creation of a government not-for-profit organization to design, build, operate and maintain the infrastructure required. The organization was created through an act of parliament in 1906 known as ‘The Power Commission Act‘. The newly created company would be called the Hydro-Electric Power Commission of Ontario (HEPCO), commonly referred to as The Commission.
By 1908 transformation of voltages up to 110 kV was made possible by Canadian General Electric. The high voltage made the transmission of power over long distances possible. Transmission towers and line hardware rated for the high voltage were successfully tested and deployed in southern Ontario to build the first 25 Hz system. The first actual operation of the Niagara System occurred on May 18th, 1910.
Image: HEPCO 1911 Annual Report
The Commission began an aggressive expansion through constructing transmission and generating facilities across the province. There were many privately owned facilities that were purchased by the Commission and integrated into the expanding electrical system. In the early days of electricity development there were pockets of 25 Hz, 60 Hz and 66⅔ Hz in Ontario. The 25 Hz system was the largest for decades until it became apparent that 60 Hz had economic advantages over the lower frequency and was growing in popularity in North America.
In 1922, the Hydro Electric Power Commission of Ontario was the largest, most powerful utility in the world, with a demand for electricity of 496,000 kilowatts
In 1928 transmission voltages reached 220 kV which enabled a 323 km connection from Ottawa in the east to Toronto Leaside.
The use of 25 Hz power expanded until the 1950s when the Commission embarked on a standardization program which moved the system to 60 Hz. The 25 Hz system was largely replaced by the early 1960s with the exception of a few industries that did not want to make the investment in equipment modification.
Delivery infrastructure had to be maintained for each frequency for over 100 years.
The final 25 Hz equipment at Sir Adam Beck GS #1 (formerly called Queenston – Chippawa) remained until 2009 when G1 and G2 were finally removed.
The Niagara System
In the early 1900s the generation in the Niagara Falls area was predominantly 25 Hz for compatibility with the Adams Generating Station in New York. Following construction of Rankine and the Ontario Power Company stations in 1905, it expanded through the addition of Toronto Power GS (Niagara Falls 1906), Queenston – Chippawa GS (Niagara Falls 1921), DeCew Falls II GS (St. Catharines 1943) and the first two units at R.L. Hearn Generating Station (Toronto 1951). Sir Adam Beck #1 (formerly named Queenston – Chippawa) also hosted a relocated frequency changer from Chats Falls in 1960.
Credit: Ronny Jaques / National Film Board of Canada. Photothèque / Library and Archives Canada
Image: Ronny Jaques, Public domain, via Wikimedia Commons
Southwestern Ontario (Toronto-Niagara Falls–Windsor) operated as a large 25 Hz island until the early 1950s when it began to migrate to 60 Hz. Rotating frequency changers were used to optimize 25 Hz infrastructure by enabling power transfer to the growing 60 Hz system. When the need for 25 Hz was eliminated in some areas the changers were used as synchronous condensers until they reached end-of-life.
The Niagara System generation began conversion to 60 Hz beginning with DeCew Falls #1 from 1950 to 1951.
The two 25 Hz units at R.L. Hearn were converted to 60 Hz in 1953/54.
The two units at DeCew Falls #2 were converted by 1955.
Sir Adam Beck #1 ten 25 Hz generating units were converted to 60 Hz or modified as follows:
- Units 9 and 10 to 60 Hz in 1956
- Unit 3 to 60 Hz in 1970
- Unit 4 to 60 Hz in 1984
- Unit 5 to 60 Hz in 1985
- Unit 8 to 60 Hz in 1990
- Unit 6 to 60 Hz in 1996
- Unit 7 to 60 Hz in 2009
- Units 1 and 2 were decommissioned in 2009.
Toronto Power GS ceased operation in 1974 and the water flow redirected to the 60 Hz generators at Sir Adam Beck GS.
The Ontario Power Station was decommissioned in 1999 to accommodate the construction of a casino.
Rankine Generating Station was decommissioned in 2005 and converted to a museum after operating for 100 years at 25 Hz.
Eastern Ontario
In eastern Ontario, Chats Falls Hydroelectric Generating Station went in service as 25 Hz in 1931 with four units. The next year, an additional four 25 Hz units came on line. A 220 kV line connected Chats Falls to Toronto and the 25 Hz Niagara System. In 1934 a vertical axis 25/60 Hz frequency changer was built at Chats Falls.
Image: HEPCO 1931 Annual Report
In 1954 four of the 25 Hz units at Chats Falls were converted to 60 Hz. The remaining four units were converted by the end of 1958. The frequency changer operated until 1960 when it was moved to Sir Adam Beck #1 Generating Station.
Northern Ontario
Pockets of 25 Hz generation and load developed in the Commission’s Northern Ontario Properties in the early 1900s which would remain until 2008. The key elements of the areas 25 Hz infrastructure were five hydroelectric sites and two frequency changers. Three hydroelectric stations were developed on the Mattagami River beginning with Sandy Falls in 1911. Wawatin Falls and Lower Sturgeon followed in 1912 and 1923 respectively. Upper Notch Generating Station was completed on the Montreal River in 1932 and Abitibi Canyon Generating Station went in service in 1933. The frequency changers were installed in Kirkland Lake in 1920 and Sudbury in 1955.
Image from HEPCO 1935 Annual Report
Abitibi Canyon Generating Station was the largest 25Hz development in the area, located on the Abitibi River, 74km north of Smooth Rock Falls (near James Bay). It began generating with two units at 25 Hz in 1933. The station expanded to five 25 Hz generators in 1936. Lines were constructed to connect to Sudbury and eventually to the Toronto area. The distances involved required high voltage transmission at 110 kV in 1933, increased to 230kv and eventually to 500 kV in 1966. In 1943 unit 3 at Abitibi was relocated to DeCew Falls #2 to offset the increased load during World War 2. That same generator unit was returned to Abitibi Canyon, converted to operate at 60 Hz and put back in service in 1959. As 25 Hz load declined, Abitibi Canyon converted to 60 Hz. Unit 5 was converted to 60 Hz in 1966 with the remaining units converted by 1981.
Upper Notch GS was eliminated in 1971 when the Lower Notch GS construction flooded the area out. Sandy Falls GS. Lower Sturgeon GS and Wawatin GS were converted to 60 Hz in 2010.
Frequency standardization
There were approximately 800,000 customers on 25 Hz before The Commission embarked on a 10 to 12-year Frequency Standardization Program to move to 60 Hz.
In 1949, the Commission began the conversion of an estimated:
- 1,800,000 motors,
- 550,000 washing machines,
- 300,000 refrigerators,
- 400,000 electric clocks,
- 100,000 furnace blowers,
- 167,000 industrial motors,
- 175,000 commercial motors.
Some industries refused to convert because of the cost and remained on the lower frequency until 2009 when the last 25 Hz generator units (G1 & G2) at Sir Adam Beck Generating Station were removed from service.
Frequency Management using frequency changers and converters
In the early days of electricity many applications emerged with different voltage and frequency requirements. Transformation provided the solution for voltage management of ac systems and rotary conversion was used for dc systems. Electric railway systems for example, required either dc or low frequency ac to provide motors with the torque for moving heavy loads. Since ac emerged as the solution for delivery of electricity, municipal systems required frequency changers/converters to supply ac or dc motor loads. Frequency conversion relied on the use of rotating machines which were predominantly implemented as part of the delivery infrastructure.
Electrical systems operating at different frequencies cannot be directly connected to each other. Direct connection of ac systems requires them to be the same frequency, voltage and synchronized.
Converters
Converters produce a dc output from an ac input.
Port Arthur utilized a 750 kW motor-generator set in 1912 for their street-railway system converting 2,200 V 60 Hz ac to 600 Vdc.
In 1915, London Station utilized 500 kW 920 V ac rotary converters to supply dc load at 1.5 kV.
Changers
Frequency changers are used to change input power at one frequency to output power at a different frequency.
A growing need emerged to interconnect the isolated ac power systems in Ontario which were operating at the three different frequencies of 25 Hz, 60 Hz and 66⅔ Hz. Moving energy between the different systems required a large scale frequency-changer solution. The frequency changer of this era was basically a horizontal-axis synchronous motor-generator set. One machine acts as a motor to drive another machine as a generator.
Frequency changers provided electrical isolation through mechanical coupling of rotating machines and made large energy transfers between systems possible. From 1920 until 2009 over a dozen frequency changers ranging in size from 1.2 MVA to 45 MVA were operated in various locations across Ontario with all but one of them being located within the delivery infrastructure. A single vertical-shaft 45 MVA frequency changer was operated at two different generating stations from 1935 until 2009.
One of the first implementation of a frequency changer was at Cooksville Transformer Station in 1920. The 1.2 MVA changer was used to enable power flow between the 60 Hz Erindale Hydroelectric Generator Station and the 25 Hz Niagara System. The Erindale Generating Station was built around 1910 and decommissioned in 1923. The frequency changer was relocated to Mount Forest where it operated until 1943. The Mount Forest location provided support for the increasing load in the Eugenia Division of Georgian Bay’s 60 Hz System from Niagara. A 26.4 kV line from Stratford Transformer Station of the Niagara System provided a connection to Mount Forest.
In 1930 a 5 MVA frequency changer was installed at Hanover to add to the Mount Forest capacity installed in 1923. It provided additional support from the Niagara System. The additional capacity required an 89 km single-circuit, twin-pole 110 kV 25 Hz line to Hanover from the Kitchener Transformer Station of the Niagara System. A second 6.75 MVA unit was added at Hanover in 1940. Both converters were relocated to R. H. Martindale (Sudbury) in 1955.
Canadian Niagara Power built a 9MVA frequency changer in 1924 at Niagara Falls to connect the 25 Hz supply from Toronto Power GS to the Dominion Power System’s 66⅔ Hz infrastructure in St. Catharines and Hamilton. The Commission purchased the changer in 1930. The facility became redundant in 1951 when the 66⅔ Hz system was converted to 60 Hz. There are no records indicating precisely what happened to the frequency changer after 1951. The historic building that once housed the changer still exists today. It was repurposed as a service centre and is now owned by Ontario Power Generation, located off Murray St. near the intersection with Main St. in Niagara Falls.
As the need for 60 Hz power grew, Chats Falls Generating Station was equipped with a 45 MVA vertical shaft frequency changer in 1935 to support Eastern Ontario and the Ottawa area. The changer fed into the 110 kV 60 Hz transmission at the Ottawa Transformer Station by a short wood-pole line.
In 1960 the Chats Falls frequency changer was relocated to Sir Adam Beck #1 Generating Station. The changer was used to transfer energy to the 60Hz system as the Niagara 25 Hz system load diminished. By 2003 the 25 Hz generating capacity was 3 times greater than the load. The frequency changer did not have the capacity to transfer excess generation to the 60 Hz system, creating constraints which were subject to market financial compensation. Load surges in the Hamilton area required more than one generator at Sir Adam Beck #1 to be on-line for spinning reserve to avoid frequency excursions. The situation was inefficient and costly with reliability risks resulting in the Independent Electricity System Operator’s (IESO) decision to decommission the 25 Hz system in 2009. Only two customers remained with 25 Hz load by 2007. All 25 Hz infrastructure was decommissioned in 2009 according to plan. The obsolete equipment was removed from Sir Adam Beck #1 over the following decade.
In 1947 additional integration of the Niagara, Georgian Bay and Eastern Ontario Systems was provided through a 25 MVA frequency changer installed in Scarborough. The Scarborough Frequency Changer No. 1 was connected to Georgian Bay and Eastern Ontario by new 110 kV lines to supply the increasing peak loads and better manage surplus generation capacity. A 130 km 110 kV tie-line was added between Oshawa and Barrie to interconnect Georgian Bay to Eastern Ontario. 110 kV circuits were built from Scarborough to Leaside and Oshawa to Barret Chute to complete the plan. Second and third 25 MVA frequency changers were installed at Scarborough in 1949 and 1951. By 1960 only two of the frequency converters remained at Scarborough. They were rebuilt and operated as four synchronous condensers for voltage support as frequency conversion was no longer required.
Image: HEPCO 1947 Annual Report
South of London, the Westminster Frequency Changer and Transformer Station went into service in 1948 with a 25 MVA changer. A new 106 km 115 kV line from Westminster to Sarnia was constructed to facilitate power flows from the new Polymer Corporation 60 Hz thermal generating station in Sarnia onto the 25 Hz Niagara System. Over the next two years a second and third frequency changer were installed bringing the Westminster capacity to 75 MVA in 1950. In 1950, the Westminster station was renamed the E. V. Buchanan Transformer Station. Buchanan would also be connected by 115 kV circuits to J. C. Keith Generating Station and by 230 kV circuits to Des Joachims and Otto Holden Generating Stations by 1951, making it an essential tie point between 25 Hz and 60 Hz systems. There are no historical records on the decommissioning dates of these frequency changers.
In Northern Ontario, a privately owned frequency changer was installed in 1920 at Kirkland Lake. The Kirkland Lake Frequency Changer Station connected the Timiskaming and Abitibi districts. It was initially equipped with two sets of changers rated 1.25 MVA and 2.5 MVA. A third 4.25 MVA set was installed in 1926. Kirkland Lake Frequency Changer Station was purchased by the Commission in 1944. An additional 3.1 MVA frequency changer was placed in service in 1948.
R.H. Martindale Transformer Station (Sudbury) was equipped with two 25-60-Hz frequency-changers in 1955. The changers were relocated from Hanover Transformer Station, each with a capacity of 5,000 kVA. Frequency changing provided a solution for increasing the utilization of 25 Hz generation on the 60 Hz system as load shifted to the standard of 60 Hz. After the final 25 Hz generating stations on the Mattagami River was removed from service in 2008 for frequency conversion to 60 Hz, the Martindale converter was no longer required.
Tracing the history of privately owned and operated frequency changers is next to impossible due to the lack of public records, however, they did exist. The Canadian Westinghouse Company in Hamilton provides an example of privately owned frequency changing capacity. Publicly available records indicate Westinghouse played a role in frequency standardization by utilizing its own capacity in 1949. The specifics have unfortunately been lost over time.
There are many stories within the stories behind the history of 25 Hz power in Ontario. Thankfully, many libraries and archives still have information available if you care to spend the time to look.
A special thanks to Mark Wilkinson (OPG – Retired) for providing information on Sir Adam Beck GS.
Derek
25 Cycle power served us in NYC Transit since the late 1890s. With the construction of our gargantuan “Manhattan” piston steam engines in our 74th and 59th street plants, we started down a 100+ year trek of operations. In December 1999 I was part of the team shutting down 25 cycle operations, and tripped the last breaker, thus ending an era of 25 Cycle generation and transmission. BUT as Casey Stengel said, “It ain’t over till its over!” While we no longer use 25 cycle power to operate the rotary converters and energizing the rails with DC, 25 cycle power is still alive and well in our own 25 cycle system. The old signal systems in certain older areas of the BMT and IRT subway still requires 25 cycle power for operations. Transit engineering saw that contractually we had to be clear of the Edison 25 cycle system, so we started installing solid state frequency converters in 18 strategically located substations. When the December 1999 date was reached, our manual rotary substations went off line and the frequency converters took over supplying 25 cycle power at 600v for the IRT and 2500v for the BMT. As time goes on and more funding for signal system upgrades appear, the older 25 cycle signals will be removed and new communications based train control installed. (October 4, 2024)
Robert W. Lobenstein Retired General Superintendent – NYC Transit Power Operations
Thanks for the information on the 25 cycle system in New York Robert!
A fascinating subject indeed! It is worthy of further reading for anyone interested in electric transportation and its rich history.
Regards
Derek
Hi Derek
very interesting article
the Brandon with the 25Hz fan
there are technical solutions, however buying a modern 60Hz fan would be far more economical
25Hz or just about any frequency can be obtained from AC Power sources, (Google it). They are AC power supplies instead of DC power supplies
for the purpose of running a fan (about 50W) an audio amplifier can be used with a 24V to 240V regular 60 Hz transformer (as opposed to 12V to 120V, this is because of the lower frequency)
A 12V 60Hz transformer may overheat on 25 Hz, 24V to 240V 60Hz should do
a 25 Hz source such as an audio signal signal generator would be needed to generate the signal, and the volume control to adjust the voltage. This signal can also be obtained on Internet just Google play 25Hz tone
Thanks for the positive feedback Jacques!
I’m going with buying the 60hz fan solution
The insulation on a fan motor that old is probably too frail to withstand much practical use.
Regards
Derek
in response to a comment from Andrew (which was mysteriously converted to spam and deleted) I have the following observations.
The conversion to 60hz was before my time, however based on my research, I will speculate…
The conversion to 60hz involved customer side equipment replacement, generator conversion and converter deployment. It was a broad strategy that involved economic and technical considerations.
I can speculate that the converters served to move energy from 25 to 60hz in the early days when there was an abundance of 25hz capacity. As the 25hz capacity diminished, the support shifted to move energy from 60 to 25hz as with the final units at Sir Adam Beck GS.
I can’t be absolutely certain about how synchronizing was carried out with the converters, however, I suspect that the units were used to supply isolated load. The capacity of the converters were small enough that they would not be suitable for connecting the 25 and 60hz systems. I don’t think there was any clutch mechanism on the converters. Operators would need to isolate load from the system and then restore it via the converter. It would interrupt customers but would be the safest way to shift the load.
Regards
Derek
Great article! It’s astonishing that 25 Hz lasted until 2009. It just goes to show how no one wants to fix things that aren’t broken!
I just visited the Rankine Power Station Museum, and can highly recommend it. They’ve done a great job in turning this vast plant into a museum. They cleaned up the long outflow tunnel that took water from the bottom of the turbines and dumped it below Niagara Falls, and have made it into a striking walk. There’s a viewing platform at the end that gives a great view of all the Falls!
Thanks for taking the time to read the article and the positive feedback John!
I’d like to take that tour of Rankine as well. It’s on my bucket list.
Regards
Derek
Why the frequency all of a sudden jumped from 25Hz to 60Hz? I couldn’t find any reason. Is lamp flickering a factor of the change?
Based on what I understand from researching this topic, the decision to increase system frequency was driven largely by economics.
Without getting too technical, the higher frequency system components are cheaper to manufacture and still provide adequate performance for end use. In particular, transformers and motors require less material to perform within acceptable limits.
Lighting flicker was also a consideration in the decision to increase in frequency, however I can’t say how heavily it weighed in the determination of the new standard.
Regards
Derek
The world still cannot standardize between 50 Hz and 60 Hz and for that matter between 120 volts and 240 volts. I wonder if there will eventually be another conversion movement. It’s apparent that 240 volts at 60 Hz would be the most efficient combination. A few countries like Peru are already there. In the United States, many homes and businesses already have 240 volt 60 Hz service to their circuit breaker boxes.
Changing the frequency standard at this point in time is unlikely without a solid economic or technical case. Let’s not forget that dc has advantages over ac. Hydro Quebec has had a dc link to the US since 1986 with additional connections in the works.
A typical residential service up to 200 amp in Ontario is split phase 120/240. Major appliances like oven ranges, clothes dryers, water heaters and central air conditioners operate at 240. Legacy services may be different.
Regards
Derek
Very good read! I have recently acquired an antique general electric fan c.1917 that still works (previous owner tried it in the wall for a split second), after further inspection i noticed that it says 25cycles! I would really like to be able to have it function is there an “adapter/converter” that would i would be able to use? Preferably small if possible?
Thanks Brandon!
Glad you enjoyed the article.
Regarding your 25 cycle fan, if you don’t want to touch the original motor, you need a 25 cycle AC source that can supply the load current required. I don’t have any experience with your specific application, however I believe a suitably rated variable frequency drive, set at 25 Hz output may work. Good luck!
Derek
Your history of the Ontario frequency is wonderful. My father was a power systems engineer and I know that he would have enjoyed your history too. I wish he was still around to correct me on the details, but here is my attempt at a brief related connection. In 1949 he graduated from the University of Manitoba — into the teeth of post-war recession. He told me that Dean Featherstonhaugh assembled the newly-minted electrical engineers and told them that because Ontario was converting from 25 cycles, there would be jobs for all of them in Ontario! During my summers as a trainee civil engineer, I stayed in Taché Hall, across the road from the Featherstonhaugh High Voltage Laboratory. Thanks again for your work.
Thanks for taking the time to read the article and sharing the fascinating background of your own family! It’s always great to hear about the rich history from those who have lived the experience.
Cheers
Derek
Thanks for the wonderful article! The “25 cycle” electric Telechron clock (made in Ashland, Mass., USA) that was converted to 60Hz sometime after WWII still keeps perfect time on my desk!
Thanks for the positive feedback Matt!
It’s amazing that you still have a clock from the 25 cycle era and it still works!
Clocks that still use 60hz motors should keep very accurate time as system operators still regulate frequency to minimize cumulative error over intervals determined by the appropriate authorities. Here is a link to a NERC document that touches on time accuracy:
https://www.google.ca/url?sa=t&source=web&rct=j&url=https://www.nerc.com/comm/OC/ReferenceDocumentsDL/Reference_Document_NERC_Balancing_and_Frequency_Control.pdf&ved=2ahUKEwj2rNeQ1r38AhX2jIkEHTrOCAEQFnoECBUQAQ&usg=AOvVaw2jjpSEDZHXiK4qZk6Zt2Xw
Cheers
Derek
I remember in 1949 in Cayuga when we had our refrigerator and washing machine changed from 25 to 60 Hz. Flickering lights in downtown Toronto were still in service in the mid ’50s.
As a U of T Mech Eng graduate and later power system planner and economist I enjoyed the article. Well done.
Thank you for reading the article Joe, I’m glad you enjoyed it!
Regards
Derek
Congratulations on your informative, well-written & illustrated article “the-rise-and-fall-of-25-cycle-hz-electricity-in-ontario”.
Thanks for reading the article and your kind comment!