Small Three Phase Oil Immersed Distribution Transformer

Product Overview

CNHK’s Pole mounted small Transformers HKS11 (>10KVA, <250kVA) are suitable for air distributionnetworks in rural and surrounding areas of cities.
The CNHK high pole series is characterized by strongresistance to atmospheric erosion and environmentalconstraints (high humidity and salt spray) due to athoroughly modified surface treatment and painting process

Type Designation

Constitution

Core

The magnetic circuit is of the three column type with mired joints. It is manufactured with first-rate, grain oriented silicon iron sheets insulated with calcite. The mounted core is camped down in order to reduce vibrations and minimize noise levels.

Windings

The windings are made of either copper or aluminium; they are insulated with either pure cellulose or double enamel Furthermore, the complete columns are manufactured to withstand short circuit stresses.

Off-circuit tap changer

The tappings (2x 2.5%) of the MV winding, are connected to the off-circuit tap changer located horizontally between the yoke and the tank cover. The handle is located on the cover and should be operated when the transformer is deactivated. The design prevents setting the off-circuit tap changer to intermediate positions.

Insulating oil

The mineral oil with its electrical and chemical characteristics is in compliance with the EC Standards and is P.C.B. free.

Tank and cover

The sides of the tank are made of corrugated cooling surfaces. The bottom plate, side and frames are of a weldedconstruction. The welds are tested for oil tightness. The thermometer pockets, bushings, tap switch drive and lifting lugsare fitted on the tank cover. The cover is bolted to the tank frame. The undercarriage is welded to the bottom plate and the rollers are suitable for either longitudinal or transverse movements.

Painting and surface treatment

Transformers tank is taken with anti-corrosion treatment or painted. The metal parts are carefully sandblasted. Thepainting system is a spray coat with thickness of 130um. The top coat is RAL 7033 or customized.

Specification Table

Typical Data for Small Oil immersed Distribution Transformer HKS11-10kVA to 250kVA, Up to38.5kV, NLTC

* Provide +5% or +2×2.5% tap changer
* Tank Type: H: Hermetically sealed with corrugated tank
* NLTC: No-load Tap Changer

Typical Data for Higher Effiency Small Oil Immersed Transformer HKS18, HKS20, HKS22, Up to38.5kV, NLTC

*Provide +5% or +2×2.5% off-load tap changer
*NLTC: No-load Tap Changer