Protection equipment manufacturer NewElec reports that it is common practice to utilise earth leakage protection relays having a sensitivity of 375 mA or greater for use on three-phase induction motors over 75 kW, while the tendency is to fit 250 mA sensitivity relays on smaller motors. The logical conclusion that can be drawn from this is that engineers appear to be less concerned about earth leakage faults occurring on the larger motors than on the smaller ones! This does not make for good engineering. Luc Dutrieux of NewElec says: "Most design engineers will tell you that it has always been like this in the past - they really do not know the reason."
It emerges that design specifications have been written in this manner to resolve the problem of nuisance trips during motor starts. These trips are caused by short duration harmonics or sustained harmonics and are experienced when starting large motors by means of direct on-line methods, and more lately, variable speed applications. However, elevating the sensitivity trip threshold in this way to overcome shortcomings in the earth leakage protection devices being used diminishes the protection to the motors.
NewElec's GA range of earth leakage modules obviates the need to elevate sensitivity trip thresholds because it includes harmonic filtering as a standard feature. In addition the tripping curve characteristics are user selectable between IDMT or instantaneous so that systems grading can also be achieved when this is required.
Four-digit multifunction instrument Vepac Electronics
Electrical Power & Protection
The OM 403 model series comprises four-digit panel programmable instruments designed for maximum usefulness and user comfort, while maintaining their fair price.
Read more...New function/arbitrary waveform generator Vepac Electronics
Electrical Power & Protection
Siglent has released the SDG1000X Plus series Function/Arbitrary Waveform Generator, providing engineers with a more flexible and efficient signal generation solution.
Read more...World’s fastest 14-bit arbitrary waveform generator Vepac Electronics
Electrical Power & Protection
The ARB Rider AWG-7000 is the world’s fastest 14-bit arbitrary waveform generator, with a 20 GS/s real time update rate and 14-bit vertical resolution. Thanks to Simple Rider software, it offers best-in-class performances and an easy to use interface.
Read more...Steam on demand
Electrical Power & Protection
Rental boilers are increasingly popular, offering the convenience of on-demand power and heat without the commitment of a permanent installation. They are an ideal solution while a customer awaits repairs, or only needs a boiler for a particular period, or does not have the capital to invest upfront.
Read more...High-voltage backup power solutions
Electrical Power & Protection
Businesses are facing increasing pressure to rethink their approach to power. As a result, there’s been a significant uptick in interest in high-voltage installations, either as standalone battery energy storage systems, or as solar installations feeding into battery storage.
Read more...Rotary friction welding – a first for Tutuka power station
Electrical Power & Protection
Steinmüller Africa has successfully used rotary friction welding in a project with engineering consultant, eNtsa. This innovative technique was applied to fabricating four headers used for high-pressure water heater boiler units installed at Tutuka power station in Mpumalanga.
Read more...Why it is vital to size soft starters carefully WEG Africa
Electrical Power & Protection
The application of soft starters has become a well-established strategy to improve the uptime and lifespan for motors and mechanical equipment driven by motors, but they need to be chosen carefully.
Read more...Changeover switch between two power supplies Schneider Electric South Africa
Electrical Power & Protection
Schneider Electric South Africa has unveiled the Resi9 Changeover Switch product range which provides the perfect solution to switch manually between two power supplies or circuits.
Read more...Partial discharge monitoring solution for MV switchgear Schneider Electric South Africa
Electrical Power & Protection
Schneider Electric South Africa has unveiled its PowerLogic PD100 Partial Discharge Monitoring Solution, designed to be installed on MV switchgear to detect anomalies early, to prevent unplanned downtime.
Read more...Boiler update at food processing plant transforms production process
Electrical Power & Protection
The replacement of 78 year-old boilers at a Western Cape food processing plant by Associated Energy Services has not only proven to be a worthwhile investment for the client, but has transformed its entire production process.
printer friendly version