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ABB began to re-design its OVR (Out-

door Vacuum Recloser) in 2000. Using

an international design team, the end

result is a “small” power switch princi-

pally used in power distribution net-

works.

The integrated current sensor and

communication units permit the use

of remote control and the immediate

location and identification of faults. A

compact lightweight housing, devel-

oped in the course of the re-design

process, facilitates fast and easy instal-

lation of the device as a unit. It con-

sists of a housing with three poles, a

drive, position indicators and a con-

trol and remote communication unit.

The main component of the recloser

is the vacuum interrupter chamber,

encapsulated in outdoor epoxy resin.

The chamber enables all necessary

switching operations. Such chambers

are capable of completing a very large

number of switching cycles without

the need for maintenance, and pres-

ent no ecological threats. The resin-

molded enclosure reduces the number

of moving components and extends

maintenance intervals. It also im-

proves the resilience to acts of vandal-

ism. Polyurethane has been replaced

as an insulating material by Cy-

cloaliphatic epoxy resin. This material

is suitable for outdoor applications

and ensures longer fault-free opera-

tion of the device.

Two types of devices were developed:

One for operational voltage levels

ranging between 15.5 and 27 kV; and

the second one for voltage levels up

to 38 kV. The higher voltage levels

required a different type of vacuum

chamber, and hence larger dimen-

sions. The structure of the OVR, how-

ever, for both types remained basical-

ly the same .1

The reactive molding simulation

(based on the Automated Pressure

Gelation (APG) process) used tech-

niques developed by ABB Corporate

Research during the RAMZES project.

RAMZES (ReActive Molding ZEro-de-

fects Solution) is a 3-D computer sim-

ulation tool that provides information

to identify what happens during the

critical molding and gelation process.

The data can be applied to the design

of the mold itself, and to key variables

like resin temperature, injection pres-

sure, mold temperature scheme, posi-

tion of inlet channels and the initial

temperature of internal parts. This in-

formation helps overcome common

molding problems, such as premature

gelation, undesired weld-lines and air

traps.

These simulation methods are based

on the commercial, three-dimensional

FLUENT software. They incorporate

two models: the Macosko viscosity

model and the Kamal curing kinetics

model - both describing the ther-

mosetting material (epoxy resin).

14

ABB Review 1/2005

The perfect cast

Development of ABB’s new generation of outdoor reclosers using

advanced simulation methods

Helmuth Leskoš ek, Oliver Claus, Marek Florkowski, Robert Sekula, Kurt Kaltenegger, Hoan D. Le

New types of outdoor vacuum reclosers.

1

The design was supported by simula-

tions for electric field strength and

distribution, molding and curing

processes and for the assessment of

mechanical deformations and stresses

occurring during these processes.

Application of numerical methods in the

development of epoxy products

The popularity of simulation tech-

niques is shown by their use in a

wide range of applications.

The simulation tasks for ABB’s OVR

re-design project included:

Simulations supporting the electric

system design (dielectric properties,

electric field strength and potential

distribution).

Simulations of the reactive molding

process (mold filling, the curing

process, post-curing), thus provid-

ing important data such as tempera-

ture distributions, curing degree,

potential stresses and deformations.

The simulations to determine the dis-

tribution of electric fields were com-

pleted before the simulation of the

reactive molding process was begun.

15

ABB Review 1/2005

The commercial ABAQUS software

rounded off the simulation phase by

modeling chemical shrinkage using

the models developed by ABB Corpo-

rate Research.

The simulation software results helped

determine important parameters for

the overall manufacturing process,

from mold filling, through the curing

process to the final heat processing of

the product. The simulation took into

consideration the full complex struc-

ture of the process (injection of liquid

material, polymerization, chemical

and thermal shrinkage, heat exchange,

stress build-up).

The mold filling process was generated

with the use of a visualization method.

When this phase of the process was an-

alyzed, it was possible to identify and

locate areas in which the mold might

remain unfilled so that the positions of

the injection inlets could be adjusted.

One of the most important simulation

results of the reactive molding process

was a description of the temperature

distribution and curing propagation .2

The process of developing a new

product usually involves several eval-

uation cycles. This is costly and usu-

ally increases time to market, and it

does not eliminate the possibility that

faults may be discovered later.

Simulation is now successfully em-

ployed by many companies to opti-

mize design, shorten the development

process and improve the manufactur-

Curing propagation (38 kV OVR).

2

The results obtained by using the

FLUENT software were transferred to

ABAQUS, and structural analyses were

performed. These covered the time in

which a component is left in the mold

(approx. 150s) and the duration of the

entire cooling process (approx.

33 hours). Sample stress distribution

in the component is shown in .

To optimize the manufacturing

process, several simulation runs were

3

Stresses in a recloser.

3

ing process. Of course no simulation

can fully replace physical testing, but

powerful simulation tools can signifi-

cantly speed up the process and im-

prove fault detection.

This line of thinking was applied when

ABB decided to develop the new gen-

eration of outdoor reclosers. In fact,

the design process relied heavily on

simulations. Simulation determined

the dielectric performance of the

device and helped select the best

geometry. It also supported the man-

ufacturing process by simulating the

filling of the mold and the curing of

the epoxy.

The result: a very reliable device in a

very short time to market!

16

ABB Review 1/2005

The perfect cast

performed using varying parameters

sets.

Production began after the process

parameters had been set in accor-

dance with the simulation data .

This 3-D simulation approach had the

following advantages:

A shorter development period for

the product.

Reduced costs of mold design.

Shorter manufacturing cycles.

Improved process efficiency.

Test Procedure

Extensive prototyping tests were per-

formed to ensure the technical func-

tionality of the products and to meet

the quality requirements in the course

of mass production. The most impor-

tant included the electrical , me-

chanical and visual tests and inspec-

tions. Prototype tests were performed

in accordance with ANSI C37.60 at

several testing laboratories in Mexico,

Sweden, Italy and Germany.

Stable operational voltages and cur-

rents, the surge-current performance

5a

4

and the ability to switch-off capacitive

and inductive loads are the most sig-

nificant advantages of the recloser.

Randomly selected devices were

checked for their performance under

varying temperature conditions

–

down to –60°C – to verify their resist-

ance to crack formation. The rate of

temperature change applied was 10°C

per hour.

The future

The modern design incorporates the

results of advanced simulation tech-

niques that: make the development

process significantly shorter; optimize

5b

the design; and minimize the risk of

defects occurring in the manufacturing

process.

Suitable APG molds can now be pre-

pared based on reliable simulation

data. The application of a special tool

surface coating method (nanotechnol-

ogy-Nanogate) improves the APG

manufacturing process. After special

treatment, a cleaned mould surface is

covered with a nano-lacquer – charac-

terized by strong chemical bonds with

the substrate – and thus forms an ex-

cellent base-layer with antistick prop-

erties.

The knowledge obtained by transfer-

ring the simulation data to the APG

mold design process implies a signifi-

cant method improvement or even a

“quantum leap” that revolutionizes de-

sign processes. The number of design

faults have been significantly reduced

and manufacturing processes and

tools are now easier to control.

Helmuth Leskoš ek

Oliver Claus

ABB Calor Emag, Ratingen, Germany

helmuth.leskosek@de.abb.com

oliver.claus@de.abb.com

Marek Florkowski

Robert Sekula

ABB Corporate Research, Krakow, Poland

marek.florkowski@pl.abb.com

robert.sekula@pl.abb.com

Kurt Kaltenegger

ABB Power Technologies Management Ltd,

Zurich, Switzerland

kurt.kaltenegger@ch.abb.com

Hoan D. Le

ABB Inc., Raleigh, USA

hoan.d.le@us.abb.com

Testing of reclosers: electrical tests (a) and low-temperature tests (b).

5

Casting of the reclosers (ABB Calor Emag Mittelspannung, Ratingen).

4

Suitable APG molds can

now be prepared based

on reliable simulation data

with relatively few design

modifications. In addition,

manufacturing processes

and tools are easier to

control.