General Specification for Three-Phase

General specification for three-phase

oil-immersed in the vegetale oil HV/LV distribution transformers

100 to 2500 kVA

1 - Scope

Three-phase oil-immersed transformers, hermetically sealed with integral filling, insulation system with vegetale oil natural air natural (KNAN) cooling for indoor or outdoor installation, destined for use in three-phase HV/LV distribution systems .

The transformers have reduced losses , type BoAk ( table of EN 50464 standarts)

following the specification of synergrid ( march 2011 )

2 - Standards

These transformers will be in compliance with the following standards :

- NBN C52 101 à 105

- IEC 60076.01 to 60076.05

- NBN EN 50464

- IEC 354 edition dated 1991- Loading Guide for oil-immersed type power transformers.

These transformers will be manufactured in accordance with :

- a quality system in conformity with ISO 9001

- an environmental management system in conformity with ISO 14001, both certified by an official independent organisation.

3 - Description

3.1 - magnetic core

This will be made from laminations of grain oriented silicon steel, insulated with mineral oxide; the method of cutting and stacking will be "step lap", so as to optimise the level of no-load losses.

3.2 - LV windings

These will be made from copper profile wire or aluminium or copper foil (according to the manufacturer's preference ) .

3.3 - HV windings

These will be made of copper profile wire or aluminium or copper round wire (according to the manufacturer's preference) .

3.4 - HV connections

The standard HV connections will use porcelain bushings on the top of the transformer.

Fixed HV plug-in bushings 24 kV 250A, with HV mobile plug-in bushings - straight or elbow according to the orientation of the incoming cables - may be provided as an option.

3.5 - LV connections

The LV connections will be made using porcelain bushings up to 500 kVA, and flat-bars from 630 kVA onwards.

LV porcelain bushings from 630 kVA are also available on request.

A LV air-insulated terminal cover may be provided as an option.

3.6 - HV tapping

The tapping which act on the highest voltage adapting the transformer to the real supply voltage value, will be provided with an off-circuit tap-changer switch with a padlocking facility on the top cover of the transformer.

4 - Accessories and standard equipment

These transformers will be equipped with :

- 4 bi-directional flat rollers

- 2 lifting and untanking lugs

- 2 earthling terminals

- 1 filling plug

- 1 draining device

- 1 rating plate

- 1 routine test certificate

5 - Protection

These transformers will be equipped in option with a protection relay , DMCR or similar , these including :

· 1 gas detector/flow level indicator with one contact (for gas discharge and drop in liquid level)

· 1 over-pressure contact (for internal pressure increase)

· 1 thermostat with 2 contacts for alarm and tripping (for internal temperature increase)

· 1 dial type thermometer without contact.

6 - Main characteristics of construction

6.1 - tank

The tank of the transformer will be made with flexible cooling corrugations, in order to absorb the expansion of the dielectric due to temperature variations.

The cover will be bolted on top of the tank.

The tank will be built in such a way as to avoid any water accumulation.

6.2 - dielectric and component material

The dielectric will be vegetable oil of natural ester type with high fire point in according to IEC 60156 and to IEC 61100.

The concentration in PCB (polychloriphenyl) has to be lower than the minimum detection rate of 2 ppm (parts per million).

The components of the transformer such as insulation material, varnish, painting, etc. have to be new and PCB-free.

The filling of the transformer will be made under vacuum, in order to guarantee the maximum preservation of dielectric properties.

The live part of the transformer will be previously oven dried so as to remove all residual humidity.

6.3 - gaskets

All the gaskets (in general made of elastomer) have to be resistant against the action of the vegetale oil, at the working temperature.

6.4 - protection against corrosion

The main characteristics of the coating guarantee following norm ISO 19444-2

Category C3 , medium durability RI 3 – 5 year

Colour : RAL 7033

7 - Electrical tests

7.1 - routine tests

These tests will be carried out on all the transformers after the manufacturing, enabling an official test certificate to be produced for each one :

- applied voltage dielectric test

- induced voltage dielectric test

- measurement of no load loss and no load current

- measurement of windings resistance

- measurement of impedance voltage and load loss

- measurement of the transformation ratio and vector group

(All these tests are defined in the IEC 60076-1 to 60076-5 standards).

7.2 - type tests or special tests

These tests can be requested as option, but are subject to prior agreement of the supplier :

- temperature rise test

- lightning impulse test

- measurement of partial discharges.

- short circuit test (implemented in an approved laboratory)

- noise level measurements in accordance with IEC 60076-10.

(All these tests are defined in the IEC 60076-1 to 60076-5 standards).

Technical Data