Máy điện trở tiếp xúc SKB EP MIKO-2.3 (1000A)

All types of electrical equipment (transformers, electrical machines and electrical switching devices) require different means for full-rate diagnostics. However in case of direct-current resistance measurement the multipurpose instrument MIKO-2.3 can be used.

Resistance range for the above listed equipment is wide and resides within the values from 10^-3 to 600А and more.

For monitoring of a transformer or a sole circuit-breaker, for instance, a microohmmeter, milliohmmeter, thermometer and even kiloohmeter are needed. It means that you have to use three or even four instruments one at a time which is not usually convenient. Increasing of the number of instruments increases not only the total cost of a set, but also its weight which complicates transportation of equipment to remote facilities.

This mode is designed for measuring transfer resistances of any switching devices as well as of demountable and nondemountable contact connections in the range within 1 µOhm  ÷ 10⁵ µOhm. Moreover, this mode allows considering the availability or absence of current in the measured circuit of transformer. 

When measuring transfer resistances of contacts and connections questions regarding the strength of the measuring current arise as in case of dry contacts the result of measurement will be falsely high. That is why the main requirements to microohmeters are the following: provision of quite heavy operating current which allows burning of acidified film forming on contacts and giving significant error at resistance measuring.

MIKO-2.3 surpasses all foreign- and home-produced microohmmeters. The closest foreign analogue microohmeter with the current of 500A has the weight of 7.5 kg and mains supply. At the same time MIKO-2.3 with its weight of only 2.7 kg produces current of 1,000А. It is particularly true about dead-tank circuit breakers of MKP and U type, the contact circuit of which contains up to eight series-connected arcing contacts and two main contacts which means that they are more sensitive to corrosion and repair labour input is bigger due to the great amount of oil in the tank.

MIKO-2.3 complies with the international standard IEC 60694 "Common specifications for high-voltage switchgear and controlgear standards" (International Electrotechnical Commission (IEC)), specifying current strength for microohmmeters from 50А to the nominal current of the measured item which excludes erroneous diagnostics results.

The instrument has an archive for storing the results of measurements in "microohmmeter" mode; meant for storing of 62 measuring results. For each measurement the value of resistance, current strength and measurement date/time are stored in the archive.

Data transmission to the computer and filing of measurement results is performed with the help of a special program developed by the manufacturer.

It is designed for measurement of direct-current resistance in circuits with high inductance (transformers, electromagnets etc.) within the range of 0.1 mOhm-10⁶ mOhm.

Two submodes are used here: measurement of one-phase and three-phase windings. Besides, MIKO-2.3 has a function of automatic recalculation of resistance measurement results for a three-phase winding:

• calculation of relative deviations of resistance values of moving coils between each other;
• recalculation of resistance values of moving coils connected according to the triangle scheme into resistance values of phase windings;
• recalculation of resistance values of moving coils connected according to the star scheme into resistance values of phase windings;
• recalculation of a winding resistance measured at current temperature T into resistance at base temperature Ɵ with due account for the winding material.

The appliance has an archive for storage of results of changing the "milliohmmeter" mode that allows for storing and reading 63 results for electrical resistance of one-phase windings and 21 result for three-phase windings.

A special program by the manufacturer is used for transmission of data to a computer and for keeping archive records of measurements on a PC.

It is designed for measurement of resistance of potential dividers, ballast, closing and other resistors in terms of considerable interference and induced voltage within the range of 0.1 kOhm-3*10² kOhm.

It is designed for measurement of temperatures of windings, oil and air within the range of -20°C to +120°C.

Switching on each of four modes occurs automatically when appropriate input cable from the instrument set is connected.

Versatility and weight of the appliance are especially critical for organizations responsible for facility commissioning that have to constantly carry heavy weights of instruments and equipment for significant distances.

Light weight and self-contained supply (charge time is 3 to 5 min) give an opportunity to use MIKO-2.3 not while standing on ground, but while being on a switch cover or in a cradle scaffold. That is why the length and weight of cables of MIKO-2.3 are significantly lesser, and one can go down and up the equipment only once instead of two times in case of measurement with a ground-based appliance.

MIKO-2.3 instrument is easy to use and maintain, reliable and resistant to electromagnetic field influence.

MIKO-2.3 input cables are equipped with clamps of "alligator clip with ground clamp" type of unique design that has no analogues by other manufacturers of instruments. This design ensures quick and faultless connection to an object that excludes errors of measurement of small resistance values, and ensures reliable contact even in case of oxygenated surfaces of an object.

Besides, there is an option of a four-clamp connection of the instrument cables to circuit-breaker bushings and to transformers through remote potential contacts.