Mechanical Technology April 2015

Mechanical Technology — April 2015

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Special report

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ontextualising the Zest WEG

and Shaw Controls’ offerings,

Knihs says that we are living

in an electrical world. Since

Thomas Edison developed the first viable

incandescent lamp, electricity use has

spiralled, first due to the increased use

of lighting and electrical machines, then

through the electronic revolution and

today due to the ever-increasing use of

digital devices.

In consequence, many ways of gen-

erating, distributing and using electric-

ity have emerged with the Zest WEG

Group offering solutions at every level:

WEG electric motors, components and

VSDs from Zest WEG; plant installation

services from EnI, transformers from

WEG Transformers Africa; cogeneration

and renewable energy solutions from

Zest Energy; backup generators from

Generator Set Division; and the electri-

cal panels, switch gear and sub-station

solutions from Shaw Controls. “We even

offer complete industrial automation

solutions,” adds Knihs.

Shaw Controls manufactures switch-

board panels and control systems from

24 V up to 36 000 V (36 kV) for the

industrial, mining and infrastructure sec-

tors, having recently extended its product

offering to encompass low voltage (LV)

and medium voltage (MV) applications.

Introducing the importance of thor-

ough design and quality manufacturing to

achieve the safety requirements for elec-

trical panels, Knihs shows a few videos

highlighting the potential consequences

of arc-flash faults.

“Electricity is invisible, but when

something goes wrong it can cause seri-

ous problems, injuries and fatalities,”

he says, before showing a video of a

substation experiencing arc flash. We

see the bright light associated with arc-

ing for a few moments before the whole

substation explodes into a ball of flame.

Arc flash occurs when the air be-

tween electrical conductors changes

from being an insulator into a conduc-

tor, providing a short-circuit path for

current between electrical connections.

Once initiated, the severity of an arc

flash increases because the electrical

resistance of the air decrease as the arc

temperature rises. The arc, therefore,

draws more and more current causing

the conducting path to get hotter and

hotter, until something melts or explodes

to break the circuit.

“An arc flash releases an enormous

amount of energy,” says Knihs, before

showing another video of a pair of techni-

cians opening a panel to do maintenance.

Just as the one walks away and while the

other is disconnecting a breaker, an arc

flash occurs that engulfs the technician

in flames. Knihs follows this with a video

showing an arc flash underway behind

an enclosed panel. After a few moments,

an explosion occurs blasting the door off

the front of the panel. “Here we see that

the arc flash blew out against everyone

around them.”

As a result of real events such as those

shown, Knihs reveals that, two year ago,

legislation was passed forbidding any

electrical work to be done with the door

of an energised electrical panel open. The

door must be kept closed to shield people

in front of the equipment from the effects

of an arc flash.

In addition, manufacturers must

prove that electrical panels can resist a

gas explosion without allowing anything

to be projected into the space in front

of and around the panel. All explosive

pressure must be channelled upwards

and out through the top of the panel.

“Shaw Controls’ products conform to

these standards and are tested to prove

that they do,” Knihs adds, showing one

last video of a panel under test. Once

the arc flash is initiated, we see a burst

At a Shaw Controls media breakfast function on March

10, 2015 Valter Luiz Knihs (left), Zest WEG Group

automation and systems director, along with the

Shaw Controls team, showcased the company’s

local design and manufacturing capability at

its Robertsham premises in Johannesburg.

MechTech

reports

Shaw Controls showcases local

of flame projected safely out of the roof

of the panel.

Moving on to Shaw Controls’ efforts

to prevent arc flash and cope with its ef-

fects, Knihs says: “Shaw Controls offers

a complete product line from MV switch-

gear to LV withdrawable motor control

centres (MCCs), which are all locally

manufactured and independently certified

in accordance with IEC 62271‑200 and

IEC 61439-1/2 standards.” According to

IEC specifications, LV covers applications

of up to 690 V, while the MV range is from

1.0 kV up to 52 kV. In addition, Shaw

Controls has recently received ISO 9001

accreditation from Bureau Veritas.

LV switchboard panels include

SC 100, SC 200 to SC 300 models,

which can be configured for various

applications at different fault levels and

current ratings. This gives Shaw Controls

the flexibility to be able to offer fit-for-

purpose solutions. A recent addition to

the Shaw Controls product range is the

CCM 03 ZA withdrawable MCC, which

is an already well-established product

of WEG Brazil. This highly successful

MCC solution will now be manufactured

in South Africa.

All electrical panels include both a

mechanical and electrical interlock sys-

tem to ensure maximum safety, while the

construction itself is robust. Switchgear

panels are manufactured using bent steel

profiles and enclosed on all sides by steel

plating. Over-pressure relief devices in

the top provide for pressure relief in the

event of internal arcing. Shield-type MV