The latest family of instruments for measuring insulation resistance by Sonel S.A. has now been extended with two additional models, including MIC-10k1 which enables insulation resistance measurements up to 10kV.
In the first models of the new series Sonel designers have succeeded in reconciling two apparently contradictory features: a very high resistance to external interferences and the capability to operate on tested objects with the presence of induced voltage. It was also necessary to ensure maximum safety when making measurements.
Most of the insulation testers currently available on the market first check for the presence of voltage on the object before the measurement. When no voltage above a certain value (usually around 25 V) is detected, the proper measurement procedure is started. The MIC-5010, MIC-5005, MIC-5050 and MIC-10k1 meters use a unique algorithm to identify the type of voltage present on the tested object. If mains voltage is detected, no measurement is made while if voltage is generated by electromagnetic field, the measurement is performed and the result is shown on the display. This allows measurements to be made in the presence of very strong electromagnetic fields, which was previously impossible.
MIC-5050, as well as earlier introduced models, MIC-5010 and MIC-5005, ensures the measurements of insulation resistance by using a preset voltage: 100, 250, 500, 1000, 2500 and 5000V, or any voltage chosen by the user from within the range 50V-5000V (every 10 or 25 V). MIC-10k1 has an extended test voltage range of up to 10 kV (also with smooth stepless adjustment within 50V to 10000V). Both new meters are capable of performing the following measurements: DAR, PI, Ab1, Ab2 coefficients, step voltage (SV) insulation resistance and dielectric discharge ratio(DD). They can also measure, similarly to the MIC-5010 model, the continuity of protective connections and equipotential bonding with a current of ≥200 mA..
The new functions and features of MIC-5050 and MIC-10k1 meters include:
• graphic display showing all measured values and settings without toggling between screens, as well as graphical presentation of the measurement over time;
• selectable test current value of 5mA (except 1, 2 and 3 mA, similar to MIC-5010 and MIC-5005 models), to ensure the even faster charging of high capacity objects;
• unique capability of measuring automatically insulation resistance of 3 -, 4 – and 5-core cables by using the AutoISO-5000 attachment, thus eliminating the need to manually switch individual cable conductors to complete the whole measuring sequence required;
• temperature measurement with an additional probe when measuring the insulation;
• fault location (boosting) – in this mode the instrument does not interrupt the measurement in the event of a breakdown, making it easy to locate the damage.
Toggling the screen from the value to graph mode (possible options: resistance and leakage current or resistance and voltage over time) allows the tracking of variations of the resistance and leakage current or voltage during the measurement, as well as to analyse the measurement process afterwards; the graph mode is available for all functions (measurements of insulation resistance, boosting, SV, DD). After the measurement is completed, moving the cursor over the screen displays an accurate measured value for a given time.
In contrast to instruments currently available on the market (including even well-known brands), Sonel meters rely not only on the safety and quality of the instruments themselves, but also on their accessories. Safe test leads with a guaranteed voltage stability up to 11kV have special safe plugs; measuring probes and also “crocodile” clips meet extremely stringent requirements of the PN-EN 61010-031 standard. The accessories are delivered with a portable case. The length of leads used for measurement ranges from 3 m (standard) up to even 20 m – such long leads can be used due to the high resistance to interference of the unit.
Due to their overall dimensions necessitated by the kind of power supply needed to ensure a high current efficiency and electrical safety standards, the devices are enclosed in a portable case ensuring the ability to operate in harsh environmental conditions (IP 67 – with lid closed) and high measuring category of CAT IV 600 V (CAT III 1000 V). In order to carry the instrument in unfavourable conditions an optional backpack case is provided.
Turn the knob to switch test voltages and functions and select options by pressing directly assigned buttons. The menu allows the selection of general measuring parameters and functions. The backlit screen and keypad make it easy to work in limited visibility conditions. The presence of voltage at the terminals when measuring is indicated by LEDs. If necessary, the case lid can be easily removed to facilitate measurements in specific circumstances.
An important advantage of the instruments is their measurement range – the maximum measured value of insulation resistance for MIC-10k1 is 40TΩ (20TΩ for MIC-5050). Each measurement interrupted after timeout or manually ends by the object being discharged by the meter, which is accompanied by the real time display of the voltage drop. The measurement time is user defined up to 99 minutes 59 seconds. MIC-10k1 and MIC-5050 meters stand out from other similar devices in that they also measure DAR, PI coefficients during the insulation resistance measurement (or Ab1, Ab2 – to be chosen by the user; the time of resistance readings for calculating the coefficients may be freely selected by the user – up to 600 s), there is no need to run a separate measurement function. After the measurement is completed, all the results (resistances measured at specific times, absorption ratio, actual voltage during the measurement, leakage current, capacitance of the object) are saved in the memory along with the values of insulation resistance over time to generate a time plot (a characteristic curve).
Two- or three-wire insulation resistance measurement can be performed to eliminate the impact of surface leakage currents. In addition, the meters are equipped with the function of (hardware and software) filters that help stabilize the result in particularly difficult and unstable measuring conditions. Running this function causes the partial values of measured insulation resistances to be filtered within user-selected time intervals.
In addition to traditional insulation resistance measurements, the instruments are also capable of step voltage insulation resistance measurement (SV), when insulation exposure is gradually increased helping to disclose certain types of damage, such as moisture. Each series of SV measurements comprises consecutive tests done within a preset time with a stepwise increasing voltage, for example: 2 kV → 4 kV → 6 kV → 8 kV → 10 kV. After the measurements are finished all the results for individual voltages are saved in the memory.
Another function is the measurement of Dielectric Discharge ratio (DD) – an insulation condition indicator independent of test voltage. DD ratio allows for the assessment of the deterioration (ageing) of insulation parameters and detects moisture or delamination. The measuring procedure consists in charging an object (as during the measurement of insulation resistance), and then, after discharging the object for 60 s, measuring the discharge current. The charge stored in the dielectric can be measured in this way, thus helping to evaluate the condition of the insulation.
Measurement limits (limiting values) can be set when measuring insulation resistance or continuity with MIC-10k1 and MIC-5050 meters (similarly to MIC-5010 model). After the measurement, the display shows an additional message indicating whether the preset limit was exceeded or not. Information about the set limit and the test result is saved in the meter’s memory together with the measurement result.
The capabilities of the MIC-10k1 and MIC-5050 models are supplemented by a tree-structure memory, which makes it possible to record tens of thousands of measurement results, divided according to the structure of the subsequent protocol. Each result can be individually described with an on-screen virtual keyboard or an additional Bluetooth keyboard (after the test, or when viewing the results in the meter’s memory). The results can be arranged according to clients and objects, and it is possible to provide a detailed description for each client, object and measuring point (name, address, etc.). More importantly, it is possible to load the structure of the future protocol, prepared in the “Sonel Electrical measurements” application, and to make measurements one by one for the corresponding points. If necessary, the structure can be changed during the measurements.
The instruments are powered by a high-capacity battery and can also use the mains supply. Charging the battery is done with a built-in charger of optimal charging speed, dependent on the degree of battery discharge.
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