American-Assembled Oil-Filled Shunt Reactor Built for North Dakota Wind Energy Center

Pennsylvania Transformer Technology completes commissioning of a three-phase, ONAN-cooled shunt reactor for reactive power compensation at a North Dakota wind integration substation, strengthening the company's growing footprint in the domestic EHV reactor market

50 MVAr

Reactive power rating

230 kV

System voltage

900 kV BIL

HV terminal insulation

73.1 dB

Tested sound level

50 pC

Partial discharge level

PTT Successfully Tests a 50-MVAr, 230-kV Three-Phase Shunt Reactor

CANONSBURG, Pa. -- Pennsylvania Transformer Technology (PTT), a Quanta Services company and the only American-assembled provider of extra high voltage shunt reactors, recently completed testing of a 50-MVAr, 230-kilovolt three-phase shunt reactor for a mid-June delivery to a southeastern North Dakota wind energy center -- marking a significant milestone for PTT as it expands its footprint in the domestic EHV shunt reactor market, a segment historically dominated by overseas manufacturers.

The project required PTT engineers to meet a rigorous performance specification calling for a 900kV line end BIL, vibration and sound level limits at elevated voltage level, operation across a wide ambient temperature range -- from minus 20 degrees Celsius in the harsh North Dakota winter to a maximum of 40 degrees Celsius -- and suitable for full outdoor installation at an elevation of 3,300 feet.

PTT’s engineering, sales and assembly team with the completed 50-MVAr, 230-kV shunt reactor at the company's Canonsburg, Pa., facility. Sample text. Click to select the Text Element.

The reactor must maintain the winding temperature rise within 65 degrees Celsius by resistance, with hottest-spot temperature rises not to exceed 80 degrees Celsius with ONAN cooling.

The finished reactor, built at PTT's Canonsburg, Pa., factory, features a 900-kV basic impulse level on its high-voltage line terminals, a 150-kV BIL neutral terminal, and a conservator-type oil preservation system equipped with a nitrile rubber air cell. The unit weighs approximately 240,000 pounds in assembled configuration, holds 9,262 gallons of Type II inhibited mineral oil, and generates a sound level of 78 decibels at 245 kVs rated voltage -- meeting IEEE C57.21 acoustic requirements.

three-phase 15/20/25/28 MVA ONAN/ONAF/ONAF power transformers

Factory-Tested High-Voltage Reactor Equipped with Advanced Protection and Monitoring Systems

The reactor was furnished with bushings rated at 900 kV BIL on high-voltage terminals and 150 kV BIL on the neutral, along with multi-ratio bushing-type current transformers of C800 relaying accuracy. A recloseable mechanical pressure relief device, sudden pressure relay, winding hottest-spot temperature detection equipment, magnetic liquid level gauge, and NEMA 4 weathertight control cabinet round out the accessory package.

The specification required a demanding suite of factory acceptance tests conducted in accordance with IEEE C57.21 and witnessed by the customer's representatives. The test program included lightning impulse and switching impulse dielectric tests, partial discharge measurements, temperature-rise tests, frequency response analysis, positive-sequence saturation curves to 150 percent of rated excitation, zero-sequence impedance measurements, audible sound and vibration evaluations, and insulation power factor tests, among others.

The tested sound level of 73.1dB and average vibration level of <40 microns is much lower than the limits confirming mechanical integrity of the unit. The very low partial discharge level of 50pico coulombs is proof of good insulation design and quality.

The reactor was shipped without oil and pressurized with breathable dry air, accompanied by two three-dimensional digital impact recorders to monitor longitudinal, horizontal and vertical forces during transit.

"Development of this EHV shunt reactor widened our engineering capability in ways that directly benefits the next customer. The work on this project challenged our team on critical mechanical aspects of design to limit vibration with advanced core packet design and the external tank profile while assuring thermal design, insulation coordination and acoustic performance at an elevated voltage level -- all under the rigorous scrutiny of a full witnessed test program.

That accumulated experience is now embedded in our design processes and in our people. As utilities across the country face growing reactive power management demands driven by renewable integration and grid modernization, PTT is positioned to deliver American-assembled solutions with the lead times, technical depth and post-delivery support that imported units simply cannot match."

Sandeep Chakravarty, Executive Board Member, Pennsylvania Transformer Technology

PTT Expands U.S.-Built Shunt Reactor Line Up to 765 kV to Support Renewable Grid Reliability

PTT's shunt reactor product line covers ratings up to 150 MVAr and voltages through 765 kV, with advanced gapped-core, oil-filled construction fully compliant with IEEE C57.21. The company says American manufacturing provides utilities with greater supply chain security, faster access to engineering support, and simplified warranty administration compared with units sourced from overseas manufacturers.

Grid operators nationwide are deploying shunt reactors at an accelerating pace as long transmission lines serving wind and solar generation facilities create overvoltage conditions that require reactive power compensation to maintain grid reliability and voltage stability. North Dakota -- home to extensive wind generation assets -- represents a key market for such infrastructure investment.

PTT holds ISO 9001:2015 with certification from Smithers Quality Assessments, Inc., covering the design, manufacture and test of small, medium and large power transformers at its Canonsburg, Pa., and Raeford, N.C., facilities.

For information on PTT's shunt reactor capabilities or to request a proposal, contact the company at [email protected] or complete

Shunt Reactor Technical Specifications

Shunt Reactor Specification	Value
Reactive power rating	50 MVAr (65 deg C)
System voltage	230,000 V
Cooling class	ONAN (oil-natural, air-natural)
Frequency	60 Hz, three-phase
Grounding	Solidly grounded wye
HV line terminal BIL	900 kV
HV neutral terminal BIL	150 kV
Switching impulse level	745 kVp
Winding temperature rise limit	65 deg C by resistance
Hottest-spot temperature rise limit	80 deg C
Total assembled weight	236,290 lb
Oil volume (main tank)	9,262 gallons, Type II inhibited
Tested sound level	73.1 dB at 245 kV
Partial discharge level	50 picocoulombs
Applicable standard	IEEE C57.21

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