Indicating the conditions of the insulation of electrical networks and equipment is an important element for ensuring efficient protection against electric shocks. Recently, the company, SONEL S.A., has been working hard on the development and production of state-of-the art devices for such testing. A number of models with test voltages up to 5 kV and to 10 kV have been implemented. Due to extended measurement functions and immunity to electric fields and other interferences, they are one of the leading products used in professional power engineering for complex and advanced insulation resistance testing. Common insulation resistance tests carried out in receiving end of the electrical grids do not require such extended measurement functions, as this leads to an increase in the overall dimensions of the device. Therefore, with a large group of electricians in mind who test receiving end electrical systems in the broadly defined municipal infrastructure, industries, office buildings or private housing – Sonel MIC-2501, a new insulation resistance tester has been designed and launched onto the market.
Figure 1: Sonel MIC-2501 insulation resistance tester.
Measuring insulation resistance
This kind of testing is most often carried out by small or even one-man electrical service companies. Therefore, the main objective was to design such a device where the high technical parameters would be maintained, while its manufacturing costs would be optimised and reduced compared to those of previous models. It should be emphasized that both the functionality and ergonomics result from collaboration with the present users of meters manufactured by Sonel S.A. The device has been designed in compliance with PN-EN 61557- 2 and allows insulation resistance testing to be performed as described in, amongst others, PN-HD 60364-6 and PN-EN 04700.
Sonel MIC-2501 basic measurement functions
• two- or three-lead insulation resistance measurement.
• selectable measurement voltage from the range 100 to 2500 V in100 V steps
• acoustic determination of five-second periods of time.
• measuring T1, T2 and T3 times to determine absorption coefficients for 15, 60 and 600 s,
• indication of actual test voltage during measurement,
• protection against measuring live objects .
• low voltage measurement of circuit continuity and resistance:
• leakage current measurement during insulation resistance testing.
• DC and AC voltage measurement within the range 0…750 V.
• memory: 990 cells (11880 records); data transmission to the PC through the USB cable.
• battery-powered insulation tester .
• it is possible to power and charge the meter from an external power supply, car lighter socket or external battery – the so called “power bank”.
Researching the market about user expectations and taking into consideration their comments led to a slightly different approach to designing the case for the new meter model. It has been designed so that the meter can be used without removing it from the case. The meter can be hung around the neck with straps, which means that the user has two hands free, thus enhancing safety at work and improving the operator’s manual abilities. An additional bag, which is detachable from the main case, is to be used to attach the meter to the belt, thus reducing the weight of device hanging from the neck, and thus enhancing working comfort, especially during measurements lasting a long time.
Figure 2: Sonel MIC-2501 meter in a specially designed case with suspenders
An innovative idea is to enable meter powering from external sources of energy. So called “power banks” are commonly available and they work very well in emergencies when no other power supply is accessible (insulation resistance testing is often carried out in systems that have not been connected to the mains yet).
Figure 3: Sonel MIC-2501 being charged from the “power bank”.
The kit contains the device complete with necessary leads, probes, crocodile clips and a charger. All of these things are stowed in the handy case mentioned above.
Figure 4: Standard equipment
Sonel MIC-2501 is a universal meter with a very wide field of applications for measuring insulation resistance. It can be used for the measurement of cables, receiving end electrical systems, electric motors and transformers. By connecting the Sonel PRS-1 probe, which is part of the accessories, to the meter, it is possible to perform resistance measurements for floors and walls. By combining many applications, ergonomics, a large readable display, a handy case allowing measurements to be made without having to remove the meter and an affordable price, Sonel MIC-2501 is very attractive item for all electricians who perform electrical measurements, working both in professional power engineering as well as in industry or electrical service companies.
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