Posts · J&K / Uttarakhand power projects
Moving an industrial plant to a 66 kV supply: what changes for the transformer
Published by Jaybee Industries
A higher supply voltage brings a power transformer and a substation into the plant. Plan them as a project, not a purchase.
Industrial plants in the estates of Jammu, Kathua, Haridwar, Dehradun and Udham Singh Nagar often begin with an 11 kV or 33 kV supply and one or two distribution transformers. As the plant grows, the load can reach a level where the utility asks for, or the plant prefers, a connection at a higher voltage such as 66 kV. That move brings a power transformer and its own substation into the plant. It changes the scale of the electrical project, and it is worth understanding before you begin.
Why move to a higher voltage?
A higher supply voltage carries more power with lower current, so losses in the supply line are lower and voltage regulation is often better. Utilities may require it above certain loads. For the plant, it can also mean better supply reliability and room for future expansion. The trade-off is a larger capital investment and more equipment to own and maintain.
What the new substation includes
- Incoming line and outdoor switchyard with isolators, circuit breakers, current and voltage transformers and lightning arresters.
- One or more power transformers stepping down from 66 kV to the plant distribution voltage.
- Protection and control panels, battery and charger, and metering as required by the utility.
- Earthing grid, lightning protection, fencing, lighting and fire precautions.
- Distribution switchgear feeding the plant's existing or new distribution transformers.
A consultant or EPC contractor usually designs and builds the whole substation, with the power transformer as its main item.
Choosing the power transformer
Key points to settle early:
- Rating: present load, growth over the planned period, and whether one large unit or two smaller units suit reliability better.
- Voltage ratio and taps: a 66 kV primary with the plant's distribution voltage on the secondary, and an on-load tap changer where voltage control is needed.
- Impedance: chosen to limit fault levels on the plant's switchgear while keeping voltage regulation acceptable.
- Vector group and neutral earthing: matched to the utility's system and the plant's earthing philosophy.
- Cooling: natural oil and air cooling, with forced-air fans for extra capacity if needed.
- Losses: stated clearly, so the total cost of ownership can be compared.
Check what happens downstream
A new, stronger source changes fault levels across the plant. Review the short-circuit rating of existing switchgear, cables and distribution transformers, and update protection coordination. Existing distribution transformers may remain in service, now fed from the new substation's distribution voltage.
Space, access and civil works
An outdoor switchyard and power transformer need much more space than a distribution substation. Plan the location with clear access for transport and a crane, room for oil containment and fire walls if needed, and space for a second transformer in future. In hill areas, the access road and site levelling can take as long as the electrical work.
Project timeline
Utility approvals, design, manufacture of the power transformer, civil works, erection and testing all take time and depend on each other. Start utility discussions and the transformer specification early. The transformer is usually the longest-lead item, so order it once the rating and ratio are fixed, and run civil work in parallel.
Testing and documentation
Agree on routine tests, any type-test references, and witness inspection at the factory. Keep all test reports, drawings and commissioning records together. Utilities will usually ask for them before connection.
Talk to Jaybee early
Jaybee Industries manufactures power transformers of about 2.5 to 25 MVA up to the 66 kV class at its plants in Bathinda, Nalagarh and Ambala. Bring your load forecast and utility requirements to the team early, and it will help you fix a specification that fits your plant's growth.
Send your enquiry
Call toll-free 1800 309 9948, message us on WhatsApp at +91 98162 95407, or email info@jaybeeindustries.com. Mention this article and your site location so the right team responds. We reply with technical options; we do not publish prices, and every offer is prepared for your specification.
Related pages on this site
- Power transformers
- Power & dry-type range
- Power transformer specification checklist
- For EPCs & industrial buyers
- Power transformer RFQ
Request a quote Call 1800 309 9948 WhatsApp +91 98162 95407 info@jaybeeindustries.com