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DC current resistance measurement in inductive and noninductive circuits in the range from 10 µOhm ÷ 10 kOhm for the currents of up to 10А
OLTC in-place check mode (DRM method)
Automatic measurement data processing
High level of protection and safety conformance in regard to
Output signal power control (0.3; 1; 5; 20; 62)
Power from the mains and external accumulator storage battery
Illustrative and functional measurement data output
History of measurements stored in the instrument and PC connection through USB
Measuring cables of ergonomic design

Milliohmmeter MIKO-8 of the device
is discontinued

Certificates
  • Safety Test Certificate IEC 61010-1:2001
  • EMC Compatibility IEC 61326-1:2005
  • Russian Register of Innovative Products
  • Recommended for use in JSC Russian Railways electric installations
  • PJSC ROSSETI Register of Innovative Solutions
  • Russian State Register Certificates
  • Declaration of Conformity of the Customs Union
DC current resistance measurement in inductive and noninductive circuits in the range from 10 µOhm ÷ 10 kOhm for the currents of up to 10А
  • Windings of power transformers, instrument current transformers, electromagnets and electric motors;
  • Compensatory, current-limiting and other resistors of high-voltage circuit breakers;
  • Contacts and contact connections of power and signal circuits;
  • Cables.

Production of the device is discontinued. A new version of MIKO-8M with be delivered to the warehouse in the second quarter of 2018. Orders are accepted. Comparison of the first version of the device and its modification is at Reference.

OLTC in-place check mode (DRM method)

Measurements in milliohmeter mode and in in-place check mode complement each other and provide a comprehensive picture of the state of transformer.

OLTC "in-place" check mode allows carrying out of in-place check and diagnostics of OLTC with current-limiting resistors without removing the contactor tank covers. This mode involves measuring of instantaneous current passing at first through the transformer cover and then through OLTC contracts at switching from one tap to another. A graph of current variance at contacts switching is drawn up and the time of switching as well as the general technical condition of the instrument is checked on its basis.

Analysis of the acquired graphs provides not only for sorting out of elements by fault-free/faulty criteria but also for defining the nature of the defect allowing eliminating of fault-free OLTCs opening.

  • express diagnostics of OLTC transformer technical condition at any weather environment;
  • construction of assessment diagram of contactors’ operation without OLTC tank opening;
  • review of the graphs of the measured item on the instrument itself;
  • defining of OLTC fault location: for instance, identifying of interruption of current-limiting resistors, poor selector contacts, etc.

For example, for type RS, RNOA, etc., on-load tap changers the correctness of operation of the main and arcing contactor contacts, their condition (burned or not burned contact), current-limiting resistor integrity may be determined. For type RNTA – 35/320 tap changers and in the same on-load tap changers, in which the contactor and selector are changed for a fine control circuit breaker, main and arcing contacts, current-limiting resistor condition, as well as condition of surface of all fixed contacts of the circuit breaker, through which the moving contacts move, can be checked.

Automatic measurement data processing

Milliohmmeter MIKO-8 includes all advantages of service functions of MIKO-7 with the advanced software:

  • Automatic selection of the measuring range and setting of the required measuring current;
  • Automatic compensation of thermal electromotive force in the external circuit of resistance measurement;
  • Automatic inductive load measurement. The instrument automatically defines the moment of resistance and stops the measuring process;
  • Automatic calculation of relative deviations of winding resistance at three phases against each other;
  • Automatic recalculation of linear resistance of windings connected with delta or star connection to the phase winding resistance;
  • Automatic recalculation of winding resistance measured at current temperature to resistance at the certified temperature (with due regard to winding material);
  • Automatic calculation of deviations measured and normalized to the certified temperature of winding resistance in relation to the certified values of resistance;
  • Automatic calculation of winding temperature based on its measured and certified value of resistance and certified temperature;
  • Automatic stopping of measurement process.
High level of protection and safety conformance in regard to
  • exceeding of measuring current;
  • polarity reversal of cable ends in accumulator storage battery;
  • electromotive force (emf) of self-induction.

At disconnection of the measuring cable from transformer bushings or from the instrument as well as at disconnection of the mains cable from the mains or accumulator battery in the course of measurement, emf of self-induction of up to several kV is generated in the disconnected circuit and the electric arc appears in the break point.

MIKO-8 is characterized by the redundant protection against emf of self-induction in case of involuntary disconnection of the measuring cable or power cable protecting users from electric shock and the instrument from being damaged.

  • a set of required protective means against superheat of the measuring unit;
  • protection grounding contact in the mains plug and safety earthing terminal on the case of the measuring unit.
Output signal power control (0.3; 1; 5; 20; 62)

In the range of 0.3 ÷ 70 W (0.3; 1; 5; 20; 62) for the avoidance of excessive resistance of low-power windings of electric motors, electromagnets, etc.

Power from the mains and external accumulator storage battery

The instrument can be powered from the mains (≃ 110÷220, 330V) and external accumulator battery, for instance, car battery of 12V, providing for mobility and flexibility in application.

For powering the instrument from a car battery, a special cable supplied on order is required.

Illustrative and functional measurement data output

The results of measurements and calculations are shown on a big color graphic display.

History of measurements stored in the instrument and PC connection through USB

The history of measurements stored in the instrument is designed for viewing, copying and deleting measurement results, stored in the non-volatile memory of the instrument as well as for performing various calculations.

Personal computer connection through USB allows for:

  • controlling the instrument with the help of PC;
  • systematizing and storing the results on computer;
  • drawing up of measurement reports.

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

Measuring cables of ergonomic design

Cables of different length and the grip of alligator type clamps allowing performance of ground measurement as well as the measurement from the cover of transformers of all voltage types.

Specifications Value
Resistance range, Ohm 10µOhm ÷ 10kOhm
Maximum permissible intrinsic error of resistance measurement ±(0.1%+0.5µOhm)
Measuring current intensity, А 0.015 ÷ 10
Relative drift of measuring current intensity, %/s ±0.002
Set output power limits, W 0.3; 1; 5; 20; 62
Power supply voltage from the external accumulator storage battery, V 11 ÷ 14
Maximum consumed power, W 120
Type of data transmission channel USB
Operation temperature range, ºС -20 ÷ +50
IP for transportation IP64
IP rating in operating state IP20
Maximum measuring unit weight, kg 3.2
Dimensions, mm 270х250х130
Interface language English
User manuals language English
Calibration interval, year 3
Standard complete set
Photo Item, Index Application
MIKO-8 measuring unit MIKO-8 measuring unit СКБ032.00.00.000 The instrument and accompanying documents: calibration certificate, operation manual and record book.
Measuring cables <br><b>on order</b> Measuring cables
on order
As a matter of convenience for the user, measuring cables are not included in the standard complete set. Each user can select a cable to his/her own requirements.
Select at least one measuring cable (see "additional complete set on order" below).
Mains cable Mains cable СКБ031.23.00.000 For connecting the instrument to the power line. Temperature range -25°С ÷ +120°С. Rubber insulation (length – 2 m).
Ground wire Ground wire СКБ010.01.00.000 For instrument case grounding. Equipped with a ground clamp and screw end cap. Rated current – 50А.
Zero resistance equivalent Zero resistance equivalent СКБ023.15.00.000 Resistance zero point accuracy check. Value – 0.000 µOhm.
Shunt 75ШСММ3 Shunt 75ШСММ3 Performance check. Value – 1 MOhm ± 0.5%.
VP2B-1V-2А cut-out (2 pcs.) VP2B-1V-2А cut-out (2 pcs.) For power source protection.
Cable USB 2.0 A-B Cable USB 2.0 A-B For connecting the instrument to the computer and its control from PC (length – 1.8 m).
Attachment devices set kit Attachment devices set kit СКБ126.06.02.000
Additional complete set (on order)
Photo Item, Index Application
Measuring cable Measuring cable СКБ032.18.00.000 Cable for ground measurement of TS – 35kV. Allows control from transformer cover (35kV ÷ 500kV). The cable is made in the form of elastic silicone tube resistant to low and high temperatures and corrosive media. Alligator type clamps with the jaw of up to 40 mm (length – 8.5 m).
**Complete set can include 3 cables for connection to three phases simultaneously.
Measuring cable Measuring cable СКБ032.12.00.000 Cable for ground measurement of TS – 35kV. Allows control from transformer cover (35kV ÷ 500kV). The cable is made in the form of elastic silicone tube resistant to low and high temperatures and corrosive media. Alligator type clamps with the jaw of up to 80 mm (length – 8.5 m).
**Complete set can include 3 cables for connection to three phases simultaneously.
Measuring cable Measuring cable СКБ032.19.00.000 Cable for resistance measuring in four-terminal winding in inductive and noninductive circuits. Cable is complete with 2 probes and 4 isolated alligator-type clamps А25С. The cable is made in the form of elastic silicone tube resistant to low and high temperatures and corrosive media (length - 3 m).
Measuring cable with a fast-switching ground clamp Measuring cable with a fast-switching ground clamp СКБ032.26.00.000 Cable for measuring the resistance of transformer windings with the pins at inputs of no more than 80 mm. Cable clamp is coupled with a fast-switching ground clamp providing for instant connection to the pins of the inputs with the help of the button at its bottom. By pushing this button you can immediately set the clamp on the pin and fix it securely by screwing the ground clamp until tight (clamp jaw of up to 103 mm).
Measuring cable extension Measuring cable extension СКБ031.20.00.000 For ground measurement of all TS (35kV ÷ 500kV) Recommended for application together with measuring cables SKB032.18.00.000 (throat of up to 40 mm) and SKB032.12.00.000 (throat of up to 80 mm). The extension is made in the form of elastic silicone tube resistant to low and high temperatures and corrosive media (length – 6.5 m).
Potential clip contact Potential clip contact СКБ23.21.00.000/-01 For convenient connection to the pin of the input. Recommended for application together with the cable SKB032.12.00.000 (jaw of up to 80 mm).
Short-circuiting cable with a ground clamp Short-circuiting cable with a ground clamp СКБ032.13.00.000/-01/-02 Secondary circuit shorting. For in-place check of the transformer OLTCs (DRM method).
G50 (ground clamp jaw opening – 45 mm), G75 (ground clamp jaw opening – 70 mm) and G100 (ground clamp jaw opening – 85 mm) at option.
Short-circuiting cable Short-circuiting cable СКБ035.31.00.000 Short-circuit cable for short-circuiting the secjndary circuits. To be used for LTCs of power transformers and auto transformers. Consists of 3 short-circuiting the same length of 12 m.
Additional resistor Additional resistor СКБ032.25.00.000 For in-place OLTCs monitoring at apparent resistance of the winding of no more than 0.5 Ohm
Battery power cable Battery power cable СКБ031.17.00.000 The cable for powering the instrument from external accumulator battery (for instance, car battery). The cable is made in the form of elastic silicone tube resistant to low and high temperatures and corrosive media (length - 5 m).
Reference inductor adaptor Reference inductor adaptor СКБ023.12.00.000 For verification laboratories: inspection / calibration of the instrument.
Software Software For remote control of the analyzer.
Cable and documentation bag Cable and documentation bag СКБ126.06.00.000 Handy, sturdy and wear-resistant bag for carrying cables, documents and other additional component parts to MIKO-8.
Manipulating rod Manipulating rod СКБ010.41.00.000
СКБ010.41.00.000-01
СКБ010.41.00.000-02
The rod is designed to ensure convenient connection to contacts of a transformer inputs.

The rod is completed with a clamp with current and potential contacts connected by wires with the measurement platform. Test cables are connected to the measurement platform from the ground.

  • Manipulating rod for equipment of up to 35kV (2.2 m);
  • Manipulating rod for equipment of up to 110kV (3.7 m);
  • Manipulating rod for equipment of up to 220kV (5.1 m);
Safety Test Certificate IEC 61010-1:2001 on the MIKO-8
EMC Compatibility IEC 61326-1:2005 on the MIKO-8
MIKO-8 is included in Russian Register of Innovative Products under #241, valid until 12.10.2018.
MIKO-8 is included in Russian State Register under #59506-14, valid until 24.12.2019.
MIKO-8 - ТС № RU Д-RU.ME97.B.00019; valid until 06.07.2019.
Testimonials about Milliohmmeter MIKO-8
OJSC IRKUTSKENERGOREMONT

In December 2015 OJSC IRKUTSKENERGOREMONT procured the MIKO-8 analyzer for DC resistance measurements of windings of oil and dry transformers from 0.4 to 220 kV, capacity of up to 80000 kW with OLTC and NLTC devices of different types. The instrument is used during overhauls of transformers both in OJSC IRKUTSKENERGOREMONT, at transformer substations of OJSC IESK, and at PAO Irkutskenergo.

MIKO-8 meets all the requirements to transformer testing instruments. During the entire period of MIKO-8 use we diagnosed about 150 transformers (both for testing the transformer winding state prior to overhaul (without and with winding replacement) and after the transformer overhaul). 

The main merit of the instrument is its convenient design, light weight, reliability, easy operation, user-friendly menu, an in-built archive of measurements for further analysis of the results and for calculation, and ability to automatically convert the data. The instrument is powered from the 200 V main which eliminates the use of internal and external DC power sources.

DRM-test of OLTC devices of transformers allows non-destructive control and diagnosis of OLTC device condition. During measurements the instruments builds up a graph of amperage at the moments of contacts changeover which allows assessment of general state of the tested equipment. 

High precision and shot time of measurements are also worth mentioning.

On the average one measurement takes from 15 to 30 seconds.  MIKO-8 allows measurements of transformer winding resistance with NLTC and OLTC without its shutdown and without interrupting the resistance measurement. It is a very important fact as it accelerates the equipment testing.

Following the results of the instrument operation, we can conclude that it fully corresponds to the performances declared and meets the operating requirements of companies. 

Testimonials about Milliohmmeter MIKO-8
NALADKA GEM Limited Liability Company

Specialists of Naladka GEM, LLC have been dealing with adjustment and tests of electric equipment of all classes of voltages (from 0.4 to 500kV) at large energy facilities and at substations for more than 20 years.

Our Company has been using your MIKO-1 and MIKO-8 instrument for adjustment and tests of generators, electric motors, power transformers, and high-voltage circuit breakers.

The MIKO-8 is used for measuring the resistances of windings in power transformers, voltage transformers, secondary windings of current and voltage measurement transformers.

ИResistances are measured with high accuracy. Time of measurements is short, which is very important for measurements at power transformers with a large number of LTC positions as winding temperature with time tends to decline that leads to errors in measurements.

Technicians of Naladka GEM, Llc highly appraise the instruments as they allow high quality and rapid measurements. These instruments can be recommended to commissioning and operating companies, as well to manufacturers of high-voltage equipment.

Testimonials about Milliohmmeter MIKO-8, PKR-2, PKR-2M
Irkutsk State Technical University

In the period between August 9-11 the Research Laboratory for Electric Equipment Testing of the Irkutsk State Technical University performed diagnosis of a block-type TDTNG 75000/110 transformer at a thermal power plant TPP-9 of OJSC Irkutskenergo using your instruments. Resistances of transformer windings were measured using the MIKO-8 microohmmeter. Circular diagrams of LTC transformer were obtained using PKR-2 instrument.

It should be noted that the instruments are of high quality, they are compact and have a number of advantages over similar instruments of other firms (particularly, user-friendly interface, ability to review curves of the instrument signal on site).

On the whole the instruments were highly appraised by our specialists.

Testimonials about Milliohmmeter MIKO-8, Micromillikilloohmmeter MIKO-2.3
OGUEP OBLKOMMUNENERGO

In 2010 OGUEP Oblkommunenergo procured MIKO-1 micro ohmmeter for measuring the transient resistance of high-voltage circuit breaker contacts. It should be noted that capacity of the battery ideally fits the instrument, its charge is sufficient for the whole working day of heavy operation.

In 2011 we procured the MIKO-2.3 instrument for measuring the ohm resistance of high-voltage transformer windings. The instrument has advantages similar to those of MIKO-1 but capacity of the battery is sometimes insufficient for making measurements on a high-voltage transformer if it cannot be charged on site.

After positive experience of operating the MIKO instruments, in 2013 we procured five MIKO-8 devices.

MIKO instruments ideally suit companies that deal with maintenance, adjustment and testing. The instruments have high precision, are simple in operation, compact and have low weight. During operation of MIKO 2-3 and MIKO-8 when measuring the DC resistance the transformer windings are rapidly saturated and, as a result, the time of measurements reduces. Current output by the instrument allows burning the oxide and oil films occurring between contacts thus giving regular records of transient resistance. Another advantage of the instruments is ability to combine potential and current circuits in two terminals and account of proper resistance of wires included into the kit.

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The Company moves forward and continuously updates its products, that is evidenced by three new milliohmmeters to be manufactured in 2018: MIKO-7M, MIKO-8M, and MIKO-9.
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The SKB EP Company moves forward and continuously updates its products that is evidenced by two new versions of milliohmmeters to be manufactured in 2018: MIKO-7M and MIKO-8M.
Demonstration of the operation Milliohmmeter MIKO-8
Demonstration of the operation Milliohmmeter MIKO-8
You have got a unique chance to undergo an on-line test-drive of Milliohmmeter thanks to demonstration of the main functions and modes presented on the website.
Comparison technical characteristics of milliohmmeters MIKO-7 and MIKO-8
Comparison technical characteristics of milliohmmeters MIKO-7 and MIKO-8
The company "SKB EP" manufactured  three types of instruments for the winding resistance measurement of transformers, motors, solenoids, cables and other circuits containing inductance and electrical resistance in non-inductive circuits: MIKO-7 with basic and advanced software and MIKO -8.
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Main features and technical advantages that differentiate milliohmmeters  MIKO-7 and MIKO-8 production "SKB EP" of similar equipment.
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