Cellulose Based

Introduction

Angle rings and caps are needed in the design of the end insulation of transformers. All voltages and dimensions can be covered by selecting the appropriate individual solution from Weidmann’s wide range of products. These include machine and hand moulded angle rings and caps, pressed sectors, drawn caps/angle rings, flexible crepe paper angle rings for distribution transformers and laminated crepe paper rings.

Field of Application

Angle rings form the barriers of the end of the windings. The products of this category offer a selection between sophisticated and economical solutions, both meeting the technical requirements.

Types

Crepe paper angle rings for distribution transformers
“Flexible crepe angle rings“ are used in distribution transformers only. They are manufactured as reel material. They consist of four layers of crepe paper laminated with a special adhesive. Weidmann provides either 90 degree flexible crepe angles or creased laminated crepe paper rolls that are formed to its required shape during the production process of the transformer. 90 degree flexible crepe angles are available in thicknesses up to 1/8 ” and leg widths up to 4 ” per leg. As a standard, the laminated rolls are built with 4 layers of a 200% elongation crepe, giving an overall thickness of 1.5 mm. We supply them in widths from 18 mm with leg widths from 10 mm.

Drawn angle rings and caps
Drawn caps/angle rings are produced for small transformers as well as for various specific insulation purposes such as protections for metal nuts, etc. This product is manufactured in a specific mould for each dimension and is most appropriate in large production quantities as a standardized product for a certain dimension.

Hand moulded angle rings and caps
The whole range of dimensions can be produced with specific moulds. This allows an unlimited range of all dimensions. Hand moulded angle rings are fabricated from wet sheet material. They can be combined with snouts for high voltage lead exits.

Machine moulded angle rings and caps
360° blanks can be produced for a wide range of diameters. Machine moulded angle rings and caps are fabricated from mouldable sheet material.

Pressed angle ring and cap sectors
Pressed sectors are fabricated semi-automatically from wet sheet material. This product covers the range of larger diameters. Due to the specific properties of the material and the moulds, a wide range of edge radii can be offered.

Field of Application

Clamping rings and beams apply the pressing force to the winding of power transformers. Clamping rings can be manufactured in one piece up to a diameter of 3000 mm, a height of 180 mm and a total area of 6 m². Rectangular clamping plates can have dimensions up to 3000 mm x 3000 mm x 180 mm.

Characteristics

Clamping rings and clamping plates are made of polyester resin-glued laminated board. In comparison to laminated wood they offer very uniform mechanical characteristics and much better electrical values. Moreover, this product does not release acids during drying.

Field of Application

Due to their high strength, cylinders made of Transformerboard TIV can be used as support cylinders for windings of power transformers.

Characteristics

Cylinders are manufactured from high-density Transformerboard TIV. Cylinders of Transformerboard TIV are stable, mechanically strong, electrically reliable and can also serve to divide larger oil gaps into several, smaller oil gaps using the so-called barrier technique. In this way, substantially-increased dielectric strength is achieved at given clearances. By utilizing the good mechanical characteristics and outstanding electrical properties, a compact construction of closely arranged barriers can be assembled. Cylinders can be delivered in different states of fabrication:

• blank cylinder which provides all scarfings needed, but is transported in a space saving flat configuration
• rolled open cylinder which is glued on the winding mandrel
• oil stabilized glued cylinder

Field of Application

This special variant of an angle ring or cap is used as an edge protection in the winding of power transformers. Edge radii from 1.0 mm to 6.0 mm are possible.

Characteristics

Edge protection rings are made from shapeable sheet material. The cost effective fabrication method allows limited sized flanges and collars only.

Field of Application

A wide field of different end rings is offered to support windings of power transformers. The manufacturing method depends on the requirements regarding rigidity and maximum force to be applied. End rings must be able to withstand bias and short-circuit forces in order to protect the winding.

Characteristics

Depending on customer needs end rings can be produced in different types:

• Rounded type, open or closed
• Layered and glued type, open or closed
• Laminated type, open
• Milled type, open or closed
• Saw cut type, open

Field of Application

Weidmann offers a wide range of fixation elements to attach leads at the active part structure of power and distribution transformers. Depending on the requirement a tap lead frame can be assembled using the following elements.

Types

Angle rails
Angle rails are an ideal base for a lead frame in a power transformer or can be used to connect support frames. Angle rails are laminated from Transformerboard TIV. A number of standard sizes are offered. Depending on the customer requirement holes or slots can be milled.

Filament-reinforced Paper Tapes
Tapes are used to fix conductors and tighten coils of transformers, motors and generators. Reinforced paper tapes are widely used in transformers since they impregnate easily and thus are not susceptible to the risk of voids and air inclusions. Filament-reinforced paper tapes are available with imbedded glass fibers and synthetic fibers (rayon).

The diamond dotted version with polyester fibers, shrinking at elevated temperatures during the drying process, ensures additional tightening of the coils. All tapes are available in rolls of 100 m to 200 m length.

Laminated Clamps
Laminated clamps are used for various purposes in power transformers, e.g. fixation of oil tubes or even lead exits. Laminated clamps are manufactured from Transformerboard TIV according to customer specification.

Perforated Beams
Perforated beams are an ideal base for a lead frame in a power transformer. Beams with holes are milled from laminated Transformerboard TIV.

Threaded Rods and Nuts
Threaded rods and nuts made of Transformerboard TIV are used for the connection of various components. These elements are made of Transformerboard TIV and are applicable for electrical fields under comparable high stress.

U-channels
U-channels are used as protection of leads in the tank. They are manufactured according to customer drawings.

Introduction

Weidmann offers a variety of lead exit systems which form shielded barrier systems to lead conductors through tank walls from the winding to the bushing or tap changer.

Field of Application

Lead exit systems are used mainly in power transformers of high voltage. The range starts from 220 kV up to 1200 kV AC or in HVDC applications up to 800 kV according to Weidmann’s design criteria.

Types

Barrierboard
A Barrierboard forms a drip-proof partition between the core and coil assembly and the tap changers. Barrierboards are manufactured from laminated Transformerboard TIV of the thickness appropriate for the size and pressure applied. Weidmann offers several kinds of connectors depending on the needs. As an additional service Weidmann can perform a hydraulic pressure test to measure deflection.

Faltenbalg
A Faltenbalg is a special Weidmann component that separates the lead exit turret from the tank of power transformers. This offers not only protection for the winding but also the possibility of separating the tank and turrets during transportation. The design of Faltenbalgs must take the field conditon of AC or DC application into consideration. Depending on the requirement the design is pressure tested up to 2.5 bar. As an additional service Weidmann can perform a hydraulic pressure test to measure leakage and deflection.

Lead Exits
Lead exits are supplied not only in a cost efficient and reliable modular version for 400 kV or 500 kV but also in customized designs for higher voltages up to 1200 kV or even for HVDC. As a business partner Weidmann may take responsibility not only for manufacturing but also for field studies and design. The standard design is based on a metallic core insulated with shaped Transformerboard. A number of barriers depending on the design voltage subdivide the oil gap between base insulation and tankwall. The result of our design is a minimized size of the turret at maximum safety.

Linkboard
Planned changes of service voltages or usage at different sites are occasionally reasons for specifying transformers with dual voltage. Weidmann offers several kinds of connectors depending on the needs.

Introduction

The following solutions are offered for any kind of shielding needs.

• Shield rings
• Open tapered shield ring
• Closed, wound metalized shield rings
• Flexible core shields and yoke shields

Field of Application

Shielding elements are used to define areas of uniform electrical potential at the end of the winding, around the magnetic core or in some cases within windings.

Types

Core Shields / Yoke Shields
Flexible shields provide an economical means of electrostatic shielding around magnetic cores and inside winding structures. Moreover, center terminal exits through the tap winding can be shielded. Flexible shields are used in power and traction transformers. With these shields, the conductive layer is bonded between two Transformerboard TIV boards under high pressure. Because of this strong construction, the metal layer is effectively protected against mechanical damage.

Closed, Wound Metalized Shield Ring
Metalized shield rings control and smooth the electrical field at the axial winding ends of power transformers. They generally consist of a hard core of Transformerboard TIV covered with a layer of metal-foil tape. The outer insulating layer of the metalized shield ring consists of crepe paper tightly wrapped around the ring by machine.

Open, Wound Tapered End Compensating Ring (Core Wound)
Metalized shield rings control and smooth the electrical field at the helical winding ends of power transformers. Wound, metalized tapered end rings are used for spiral windings (often regulating windings) to compensate for axial length.

Rigid Metalized Carbon Paper Shield
The Rigid Metalized Carbon Paper Shield is designed to be used in conditions where there is a high magnetic field, like in high voltage devices such as Series and Shunt Reactors with air gap core.

The rigid cylindrical shielding comprises a metalized layer sandwiched between two cylinders. The semi-conductive carbon paper layer, connected to a copper chord, prevents local higher electromagnetic losses, when exposed to the magnetic flux, typical of the Reactor design.

Learn more about the Rigid Metalized Carbon Paper Shield here.

Field of Application

Snouts and flange tubes insulate the lead out of the windings and are part of the end insulation of power transformers.

Characteristics

Snouts and flange tubes are manufactured according to customer drawings. They are produced in a wet moulding process. The possibilities for the design of snouts are virtually boundless, but the necessity of manufacturing a new mould could be reflected in longer delivery times. Snouts can be combined with corresponding angle rings and caps. Together they offer a one piece end insulation which perfectly meets the technical requirements of the unit.

Introduction

Various forms of spacing elements are used to create space radially in between winding conductors as well as axially in or between windings.

Field of Application

Spacing elements are used in the HV-LV gap as well as within the winding in power and distribution transformers.

Types

Block Washers
Washers and block washers provide mechanical support and insulation from winding to ground. End insulation with spacers and pressure ring block washers are supplied as standard products or according to customer drawings for power transformers.
Washers and blocks are made from Transformerboard TIV or laminated Transformerboard TIV.

Clackband
Clackband is produced from a kraft paper and TIV bevel strips. When used directly in the winding, clackband facilitates ideal cooling by guiding the oil flow. It is made of trapezoidal blocks and two layers of paper. Because it is already assembled, clackband avoids the possible shearing of spacing blocks and is accordingly easy and safe to handle during the winding process.

Corrugated Board
A wide range of profiles is offered for our corrugated board. Besides electrical application corrugated board is also used for decorative application. The large size of this material and special surface films offer almost unlimited possibilities.
Corrugated board is mainly manufactured from Transformerboard TIV. There are also other materials used such as vulcanized fiber from TOYO (Japan).

Duct Strip (Thermoflow)
Duct strip, called Thermoflow, is used as a spacer element in the construction of oil filled distribution transformers.
It is manufactured from thermally upgraded kraft paper with Transformerboard strips bonded to one side. A variety of configurations (paper thickness, strip dimensions, and overall width) is available.

Ladders
Ladder band is used as a spacer element in the construction of oil filled distribution transformers.
It is manufactured from thermally upgraded kraft paper tapes with Transformerboard strips bonded to one side. The kraft paper base is not continuous through the entire width of the product. A variety of configurations (paper thickness, strip dimensions, and overall width) is available.

Radial Spacers
Radial spacers are used in power transformers to space the individual conductor layers in the windings.
Weidmann spacers for the radial spacing of windings are made from calibrated strips. Those milled spacers are free of burrs and available in an almost limitless range of thicknesses. One or two slots in the various shapes of rectangular, trapezoidal or T-slots spacers are milled according to our customers needs. Combined with strips these spacers offer an excellent system for spacing copper wires.
Spacers are milled from Transformerboard TIV or laminated Transformerboard TIV. Depending on the requirements the surface screen pattern can be removed (>0.5 mm) in order to reduce the compressibility of the spacer.

Spacer Strips
Spacer strips are milled from Transformerboard TIV or from laminated Transformerboard TIV. Depending on customer needs the surface screen pattern can be removed in order to guarantee lowest compressibility. This semi-finished product can be punched as well as milled depending on the thickness and customer requirements.

Strips
Strips have various functions such as spacing HV-LV, guiding the copper layers and supporting the spacers. This product group contains different shapes such as rectangular, bevel key and T-strips. Strips are milled from TIV and from polyester or casein laminated Transformerboard TIV. For thicknesses of 8 mm and more, polyester-glued Transformerboard TIV is the standard base material. These strips fulfill highest electrical and mechanical requirements.

Introduction

Rigid or flexible, made from paper or from Transformerboard, tubes are used for a wide field of applications in power transformers as well as distribution transformers.

Field of Application

The use of tubes can vary as widely as the many forms of these elements. They can be used to guide oil in a transformer, to insulate conductors or even to take the form of a winding cylinder.

Types

Tubes and Corrugated Tubes (made of wet sheet)
Tubes are used for the insulation of leads, traction rods or for guiding the flow of oil in the tank. The various purposes require various different shapes, such as: straight, S- or T-shaped. A wide range of dimensions is possible.
Tubes and corrugated tubes are moulded from wet sheet. Certain diameters are produced as standard parts. In addition, flexible connections can be made with corrugated tubes that are also produced in several standard dimensions.

Crepe Paper Tubes
The main application of crepe paper tubes is to insulate conductors but they are also suitable to build oil guides.
In metric dimensions we provide crepe tubes with a minimum inside diameter of 2 mm, a minimum wall thickness of 0.50 mm and a maximum length of 1828 mm. In imperial dimensions, the minimum inside diameter is 3/16″, the minimum wall thickness is 1/32″, and the standard length is 6 feet (1828 m).

Wound paper tubes
Paper tubes usually insulate conductors but with big inside diameter and wall thickness they also serve as winding cylinders in distribution transformers. Depending on the apparatus involved tubes made of different raw materials are required.
Weidmann provides tubes made of insulating paper, diamond dotted paper and bakelite paper (phenolic resin/paper combination) in all diameters required.

Field of Application

Washers and block washers provide mechanical support and insulation from winding to ground. End insulation with spacers and pressure ring block washers are supplied as standard products or according to customer drawings for power transformers.

Characteristics

Washers are manufactured from Transformerboard TIV.

Field of Application

Pre-mounted winding packages allow users to decrease throughput time as well as reduce material stock in the winding production area. That is why winding packages contribute to the decrease of overall manufacturing costs.

Characteristics

Depending on the requirements winding packages feature different degrees of pre-fabrication.The picture above shows a package with a high level of pre-fabrication, including metalized shield rings and washers with blocks.