Product Review - Fluke Earth Testers 1623 and 1625

Fluke has launched two new series of earth testers 1623 and 1625 ground testers.  The testers offer a new kind of earth resistance measurement known as stakeless testing, in addition to the conventional fall-of-potential method used for 3 and 4 pole earth resistance loop testing.

Stakeless testing us particularly useful in earthing grid systems where there are more than one electrodes.  In stakeless earthing, the electrodes do not have to be disconnected from the grid. 

The device has the facility to filter out interference from a specific frequency as it conducts the measurement.  In addition, the instrument also measures earth impedance at 50Hz in addition to the resistance to more accurately visualise a prospective line-to-earth fault. 

The unit can also measure soil resistivity using the 4 pole method.

The Fluke 1625 tester comes with two test leads, 4 ground earth stakes, 3 cable reels with wire, 2 clamps and a set of batteries

Power from the Sahara

The European Union is proposing an ambitious venture to install solar panels in the arid stretches of the Sahara, the world's largest desert.

These solar panels will be of the concentrated solar thermal type. consisting of a parabolic mirror which will focus the light and heat to a central tower.  An engine in the tower( Stirling engine) will convert the heat to mechanical energy which will power a generator.  This method is superior to the photovoltaic type of solar power generation in that it enables the heat energy to be stored and enables power generation during night time as well using the accumulated heat.

The power generated will be transported to Europe through a network of highly efficient underwater cables laid across the mediterranean.  In the next five years, a small test project is to be completed.  It is estimated that by 2050 almost all the power required for Europe will be generated from this solar network.

According to estimates, if only 1% of the Sahara were covered in Solar Panels, there would be enough power to power the entire world.  Food for thought, indeed!

Residual Current Protection

Residual Current Devices are protective devices to safeguard against an electrical shock or any other consequence of a leakage current.  These devices find extensive use in homes, industries and other places.

These devices functioning by measuring the current going into and coming out of an electric circuit.  In the ideal situation, both the currents are the same.   When a current leaks, either as an electric shock to a person or through an earth fault, the current which comes out of the device is lesser than the current entering the device (this difference is called the residual current).  The device senses this and trips the circuit.

These devices are alternatively known as ground fault interruptors or appliance leakage current interruptor.

Electrocution or death due to electric shock requires only small currents in the range of 5 to 50 mA.  Thus these devices are stipulated to operate at a leakage current of 5mA.

Industrial versions of the RCCBs are sometimes used for situations other than electrocution.  These have a higher tripping threshold of the order of 500mA.

RCCBs can also be used for three phase applications. 

Residual Current circuit breakers usually have an inbuilt test function to ensure that the device is functioning.  This test button needs to be operated once a month to ensure a state of readiness.

Residual current circuit breakers should not be used as a substitute for ordinary circuit breakers as they will not operate in the event of an overload or a short-circuit.  This is because the residual current does not rise in these events.  Therefore, an independent overcurrent protection needs to be given.