Tag Archives: power transformer

Skipper successfully type tests 33MVA, 161kV Power Transformer for Short Circuit & Impulse

Skipper is always committed to serve its customers by meeting the stated as well as implied standards for the products and providing them with solutions exceeding their satisfaction levels. In our bid to provide high quality and reliable products, our product designs are continuously optimized and validated through various routine, special and type tests.

Skipper after all manufacturing operations, conducted all routine tests on a 33 MVA, 161/11.5 kV EHV Transformer.
To verify and validate its Design, to withstand Lighting Impulse voltages and Mechanical forces resulting from Short circuit faults, Skipper sent the Transformer to CPRI Bhopal, a well reputed, NABL accredited independent laboratory for the following tests:
• Lighting Impulse Test
• Dynamic short circuit Tests

The above tests were conducted from 8th-11th June, 2015 as per IEC 60076 P 3, by applying Lighting and Chopped wave shots to all HV and LV terminals including the Neutral Short circuit shots were applied to each of the HV terminal while LV terminals were shorted. The test was witnessed by our valued client M/s GRIDCo, a Power Transmission Company of Republic of Ghana. These tests proved that Design and manufacturing was robust to withstand above test application at CPRI.

IEC standard specifies Lightning and Chopped wave Tests at different voltage levels depending upon safety and reliability requirement of the installation. However, this transformer was subjected to the highest among the choice of test levels specified by IEC standard for the voltage class of Transformers.
Earlier, Skipper type-tested its 60MVA, 132/33kV Power transformer at CPRI by conducting Lighting Impulse and Short Circuit Tests.

With these tests the capability of transformer to withstand high stresses due to Lightning Impulse and Dynamic Short circuit forces over the long periods (in excess of 30 years) of service is ensured.


Skipper Announces Successful Commissioning of World-Bank funded Mararaba Substation, Nigeria

Skipper proudly announces the successful commissioning of 1 X15 MVA substation of LOT 4 Project Management Unit (PMU) in Mararaba, Nigeria. This World-Bank funded project for Transmission Commission of Nigeria (TCN) will enhance the power requirements of Mararaba town and nearby areas and ensure increased power availability and fewer power cuts for residents.

Skipper Team Commissioning Panel Boards for the project
Skipper Team Commissioning Panel Boards for the project

Project Details are as follows:

Total No. of Feeders : 4

HT – 12.7 km

LT – 57.5 km

500kVA Transformer – 42 nos.

Project Value: On- Shore: 193.199 NMN, Off -Shore: 3.273 MUSD

1 X15 MVA Skipper Power Transformer On-site
1 X15 MVA Skipper Power Transformer On-site

We congratulate Mr. R. Sanjeev Kumar (Project Head), Mr. Hardip (Testing & Commissioning Expert), Mr. Mani Kankan Prabhu (Project Engineer) and other members of the LOT 4 team to complete this landmark project in 9 months. We also take the opportunity to congratulate Mr. B. Srinivas, COO – Skipper Nigeria and Mr. Praveen Gupta, Head – Commercial who mentored the project team team as well as the SCM, Accounts and Admin teams in Nigeria who made the timely delivery of this project possible.

Mr. R. Sanjeev Kumar (Project Head), Mr. Hardip (Testing & Commissioning Expert), Mr. Mani Kankan Prabhu (Project Engineer) and other members of the LOT 4 team
Mr. R. Sanjeev Kumar (Project Head), Mr. Hardip (Testing & Commissioning Expert), Mr. Mani Kankan Prabhu (Project Engineer) and other members of the LOT 4 team

Setting Another Milestone: Successful Manufacturing and CPRI Type Testing of 60 MVA 145 kV class Transformer at Skipper’s Bhiwadi Plant

Skipper manufactures the entire range of products required in a HV substation namely: Transformers, Circuit breakers, CTs, PTs, Isolators and HT and LT Control and Relay Panels.
We also manufacture special duty products namely:
Rectifier Transformers, Furnace transformers, Earthing transformer and distribution transformer using CRGO steel or Amorphous steel.
All products are, at present, meant for LV and HV applications. A newly-built, modern plant is under construction at Bhiwadi India for manufacture of products in Extra High voltage classes, on a plot of Land measuring 40,000 sq. m.

Manufacture and Type Testing of Power Transformer
Skipper secured an order for a turnkey project at Gurada in Nigeria. Supply, erection and commissioning of 2 Nos. 60 MVA transformers as per specifications given hereunder was included in the awarded contract.

Rating : 40/50/60 MVA
Cooling : ONAN/ONAF/ONAF, Vector Group :
Voltage Ratio : 132/34.5 kV
Taps : on HV for Variation of HV Voltage

The Challenge

The application of the transformer is to evacuate power from a gas/hydro generating station for local distribution load at 33kV which calls for a very sturdy and reliable design of transformer. The client expectation was to supply the product duly type-tested for a high fault current capacity with a high operating reliability.

Important aspects of Design

Skipper 60 MVA Transformer
Skipper 60 MVA Transformer

The design has to provide for
• adequate dielectric strength,
• adequate SC strength, and
• adequate thermal ability,
• taking into consideration challenges imposed by local & climactic conditions (temperature, humidity etc.)

Most common arrangement and type of coils

The arrangement of coils most commonly employed for this specification of design is :

• LV (double disc type) as innermost coil concentric with limb
• HV (interleaved / partially interleaved type), 2 coils in parallel with main lead at the centre
• Regulating (discs type), 2 coils in parallel, placed outermost

Main lead take-out poses some threats to dielectric design. Also the SC strength suffers due to axial gap in regulating winding.

Skipper 60 MVA transformer
Winding process

Skipper’s Choice of Position of Regulating Winding

We chose the following coil positions :

LV : Double disc type as innermost coil concentric with limb
Regulating : Multi-start spiral concentrically placed between LV and HV
HV (interleaved), 2 coils in parallel with main lead in centre

No other factor influences the overall strength of transformer as much as the choice of position of the regulating winding viz. a viz. HV and LV windings.

The multi-start regulating winding placed concentrically between LV and HV offers the best dielectric and the highest SC strength. However, since this winding is placed in high leakage field, it results in high eddy losses. This was taken care of through the use of CTC.

Design Verification/Review of Design : This was carried out as per plan.

Emphasis on QC : This was carried out religiously at all stages of production right from selection
of Vendors.

Commitment to Set Goals

Executives staff and employees were fully committed to see by body during the all process of design and manufacture. There was no hesitation in stepping back to see if the process was carried out as planned.

Satisfaction of Achievement

When the unit passed all the Routine, Type and Special tests, the satisfaction of Skipperites surely surpassed any physical award. These transformers are successfully installed on site to the complete satisfaction of the client.