Engineering News — December 08, 2017

36 ENGINEERING NEWS | December 8–14, 2017 LO

I

was in a courtroom the other day and the

public prosecutor was asking questions.

Unfortunately, they were not engineer-

ing questions and I am an engineer. Thus,

I did not understand the questions or why

they were being asked. As a true engineer, I

would say, “Ah, if you mean.. .”, and I would

go on and the prosecutor would just ask the

question again and ask me to say “yes” or

“no” when, in fact, the answer to the ques-

tion, the way he put it, was “it depends”. So,

finally he said: “When you say the informa-

tion changes, how can you tell?” So I said,

oh, you can see the change in the phase angle.

This stopped the flow of questions. Yay.

A phase angle is the relative difference

between the peaks of two sine waves. Oh,

darn. Sine waves? Okay, like this: the tide

goes in and out every day. Between high

tides is 12 hours and 25 minutes. An observer

will note that the rise and fall of the tide is

not a constant – as the tide comes in, the

rise will become slower and slower until the

peak, and then the tide retreats slowly and

then more rapidly. The graph of the tide rise

and fall is a sine wave.

The same happens with the voltage in

a power line. The longer the power line

becomes, and the more power it supplies,

and the greater the phase angle between the

voltage at one end and the voltage at the other

end. When the phase angles get too large,

then the power line can no longer effectively

deliver power and it shuts down.

One can insert phase angle correctors at

points along the line, which will keep the

transmission and receiving-end voltages in

step, but you risk tripping the whole line if

these fail. In general, one designs that one

phase angle corrector can trip and the line

will still operate.

An alternative solution is to design the

power line to operate on direct current (dc)

instead of alternating current. This was done

for the connection to the Cahora Bassa Hydro

scheme, in Mozambique. These lines are

expensive – a dc line to Cape Town will be

about R2-billion.

Another way to deal with the problem is to

reduce the load on the line by having a power

station at the receiving end of the power line

and just use the line to link the transmission

and receiving ends. This was the rational

for the construction of the Koeberg nuclear

power station (which also gave a handy rea-

son for making enriched uranium to blow

things up if needed).

Koeberg is 33 years old and the reason

for its construc-

tion has re-arisen,

to wit: how to keep

the power system

to the Western and

Southern Cape

stable.

The answer

• build another
  Koeberg, but only
  bigger – is not
  popular and is
  widely criticised
  for political reasons. Renewable-energy
  supporters think the job can be done by
  renewable technologies, which they cannot.
  In point of fact, renewable wind energy makes
  the whole matter of stability worse, not better.
  It is very difficult to explain all this to envi-
  ronmentalists, since they really do not seem
  to want to be educated – they just want to
  argue, which, naturally, is their right.
  However, one cannot be, or should not be,
  against oil tankers crossing the ocean if you
  yourself drive a car and, in the same way, if
  you want a reliable power supply and you
  live in the Cape, the fact of a new reliable
  power station has to be part of the occasion.
  I was a power systems engineer and it is very
  clear to me. I put it out there: if any environ-
  mentalist can offer a valid, viable alternative
  I will gladly print it. But I will add my com-
  ments, if necessary.

ELECTRICALLY SPEAKING

Phase angles

OPINION&ANALYSIS

THROUGH innovation in the energy
sphere, Africa is slowly starting to
overcome historical blockages that have
prevented the continent from achieving
economic growth and creating sustainable
jobs, according to energy consultancy
Africa House director Duncan Bonnett.
Speaking at a PowerGen and
DistribuTECH breakfast in Sandton,
Bonnett noted that such blockages as a
lack of urbanisation masterplans in cities, a
lack of finance and market access, a lack of
reliable power and transport utilities in the
continent’s industrial sectors, and a lack of
finance and ancillary infrastructure in the

information and communication technology,

telecommunications and power sectors, still

held back many countries on the continent.

He added, however, that the continent

could look forward to continued massive

infrastructure spend, and highlighted that,

over the next ten years, it was set to grow by

10% a year, or roughly $180-billion by 2025.

Bonnett said he believed that Nigeria

and South Africa would dominate the

infrastructure market, but noted that

countries such as Ethiopia, Ghana, Kenya,

Mozambique and Tanzania were also

“looking good”.

Overall infrastructure spend in Nigeria

is expected to grow from $23-billion to

$77-billion by 2025. “A more investor-

friendly environment towards oil

investment is also likely to boost this

projection further,” stated Bonnett.

In South Africa, this figure is set to

reach $60-billion.

This, Bonnett explained, is where the

electricity sector and its providers would

come into play. However, he said that

companies needed to work on a local

presence.

“Companies prepared to make the

necessary commitment to these

developments will be best placed to take

advantage of them through their proximity,

partnerships and position as local players.

“The time is ripe for South Africa-

based companies to adopt a new way of

interacting with the region,” he added,

stating that these companies needed to

develop local skills across the oil and gas,

mining and power value chain.

Meanwhile, PowerGen and

DistribuTECH Africa have called for

the submissions of abstracts for its 2018

conference.

The advisory board has opened

submissions for topics concerning the

electricity sector in all parts of sub-Saharan

Africa, inclusive of electricity industry

strategy, fossil fuel-based generation,

nuclear power, renewable energy and

power delivery.

The deadline for submissions is

January 8, 2018.

PowerGen and DistribuTECH Africa

2018, which had over 3 000 attendees

and 75 exhibitors in 2017, will take place

from July 17 to July 18, in Johannesburg,

next year.

ELECTRICITY

Building

Momentum

Local presence key to

capitalising on African

infrastructure opportunity

Terry Mackenzie-Hoy

Mackenzie-Hoy is a consulting acoustics and electrical

engineer – [email protected]

MEGAN VAN WYNGAARDT
CREAMER MEDIA
SENIOR CONTRIBUTING EDITOR ONLINE