Page 17 - SPARKS APRIL 2013 1-28 LOW RES

sparks
ELECTRICAL NEWS april 2013
NEARLY every factory, shopping mall, airport,
office complex and high-rise apartment has
and electrical room providing power distribu-
tion throughout the facility. Most of these
electrical equipment rooms are in the base-
ment or lower floors, out of sight and in many
cases out of mind… until there is a failure, says
R&C Instrumentation’s Steve Edwards.
“The power distribution system usually
includes high voltage metal-clad switchgear,
cast resin transformers, low voltage switch-
gear and panel-boards. A fault or failure in any
one of these components can result in power
outages, loss of productivity, and even fire or
explosions,” he explains.
“Routine checks of these components nor-
mally consist of current and voltage measure-
ments and, most recently, thermographic
‘snapshots’ of the temperature distribution
in the switchgear. Safety procedures greatly
restrict direct access to these components,
hence the new practice of installing Infrared
Windows to allow Infrared Cameras to take
images without opening the doors.
“IRISS has approved windows and panels al-
lowing thermal images may be taken through
a special polymer material whilst not reducing
the integrity of the panel.
“With approved IR windows and panels it is
not necessary to isolate, remove covers, switch
on with open doors to live connections and
then switch off replace covers and put the
plant back into service. Simply take the read-
ing through the IR transparent material.
This will save plant downtime and labour,
which both save money and workers’ safety is
Busbar temperature monitoring the safe way
17 motor control centres and motor protection
PRIMARILY aimed at thepumpmarket, this newmicroprocessor
range ofmotor protection relays go a longway inmeeting the
protectiondemands ofmost, if not all, electricmotor applications.
Important physical considerations include compactness, inte-
grated CTs all the way to 50A, and a door-mountedMMI fitted
with an infrared sensor that permits accessing the relay settings,
as well as faults and events records without opening the cubicle
door or flameproof enclosure. These features alone contribute to
improved operational safety and better time efficiency.
The protection relays can account for up to 2 000 event
records and 60 last faults complete with values of current inter-
rupted, time, date, voltage at the time of trip and circuit interrup-
tion time. They can also provide information on apparent power
and actual power consumption of themotor.
Improved protection benefits include:
• Earth insulation lockout (prior to starting themotor);
• Earth leakage protectionmay be selected as instantaneous or
IDMT with sensitivities in the range from30 to 1 000mA;
• Frozen contactor back-tripping facilities; and
• An array of features related to dry-run protection such as user
selected priming time, dry run detection by power factor
measurement or current only and user selectable automatic
motor re-start with delay timer.
Advanced features include harmonic filtering, frequency
monitoring, start and run stall protection parameters and up to
nine control logic parameters that may be allocated either to the
main trip contact or the on-board auxiliary relay.
Enquiries: (012)327-1729
Motor protection relays
with benefits
enhanced,” he says.
Why is temperature such a
critical measurement?
“Overload, phase imbalance,
power factor, corrosion and
poor electrical connections all
result in the generation of heat.
Any generation of heat is an
indication of loss of energy and
wasted power. Heat also contrib-
utes to a shortening of the life
of the equipment by up to 85%.
The conditions may develop
slowly over time and can result
in a catastrophic fault.
“A ‘snapshot’ using a thermal imager only
provides an analysis for less than one second
out of a 24-hour operational period and may
only be taken once per year. If the system is
critical for total plant operation this once per
year check may not be adequate. On plant
service units, such as large air compressors,
we always measure bearing temperatures and
vibration to attempt to predict failures; we
can do the same with the busbar connections
to ensure the correct temperature and limit
outages due to busbar and cable connection
burning. Continuous monitoring of the busbar
within a switchgear cabinet can provide both
instantaneous alarms for fault conditions and
trend analysis for predictive maintenance,” he
explains.
Predictive maintenance is a most effective
tool to prolong the life and efficiency of the
equipment and to minimise shutdowns. A
trend detected during continuous monitoring
will allow for maintenance of the equipment at
your choosing to minimise downtime.
The most effective solution to busbar
temperature monitoring is the use of infrared
point sensors. Infrared sensors provide safe
non-contact measurement of real-time busbar
temperatures.
“The latest development from Raytek is the
Mi3 series and is ideally suited for this monitor-
ing function. The different op-
tics between types of sensors
allows the sensor to be safely
mounted within the cabinet at
a distance from the busbar to
avoid flashover to the sensor
and electrical magnetic inter-
ference (EMI). The sensor head
and mounting bracket do not
require any special insulating
material for mounting to the
equipment structure.
“The sensor electronics are mounted
remotely from the sensor head and outside
the switchgear enclosure. The ability to have
multiple heads to one electronics and for the
electronics to give normal analogue outputs as
well as communicate over Profibus or Modbus,
makes this range totally suited for this applica-
tion,” says Edwards.
Enquiries: 086 111 4217
WAGO’s new 2273 Series terminal blocks are
more than 50% smaller than the 273 Series
that have proven themselves inmillions of
applications, saving substantial space in elec-
trical installations.
The individually combined cross-sections
from 0.5 to 2.5mm², a nominal current up to
24A and clear, unique colour coding for quick
access provide perfect installation conditions.
TheWAGOmodules connect all different
sizes of wires. New highly transparent con-
nector housings enable visual inspections; for
New series of compact push-wire connectors
example, checking if all conductors have been
fully inserted, or if the test probe has been
pushed deep enough into the test point.
In addition, an integrated inspection win-
dow helps to clearly identify if the conductors
have been stripped properly, ensuring protec-
tion against accidental contact.
The connectors have a permissible current
rating of 24A for a maximumwire size of
2.5mm² (AWG 14). The permissible nominal
voltage of 450V allows the connectors to be
used in all 230V / 400 V power networks.
They are VDE tested andmarked with the
ENEC approval mark. The new connectors are
available as two-, three-, four- five- and eight-
wire connectors.
The terminals of two- to five-connectors
are arranged in a row, while the eight-wire
connector terminals are arranged in superim-
posed rows. Each type of connector features a
different cover colour for easy identification.
WAGO is represented locally by Shorrock
Automation.
Enquiries: (012) 345-4449