SKB-EP MIKO-21 Micro-Ohmmeter Features:
Adjustable test current up to 200 A
One of the problems during transient resistance measurement with permissible error is availability of oxide films between contact surfaces.
According to international standard IEC 60694: General Specifications for High-Voltage Switch Gears (International Electrotechnical Commission), to control this type of error test current amperage during testing the electric resistance in the main circuit of a HV circuit breaker shall be between 50A and its rated value.
The Australian version comes with 5 metre Test Lead with Clamps (and not the 2 metre lead set as stated in Datasheet).
Test current in foreign circuit breakers is often limited by specific values: 100 A and 200 A.
The amperage in MIKO-21 can be set in several ways:
- By selecting from a number of specified values: 10 A, 50 A, 100 A, and 200 A;
- By setting the automatic mode for selecting test current;
- Manual mode for setting test current in the range from 1 to 200 A at a step of 1 A.
Special algorithms for contact resistance measurement of HV circuit breakers with in-built current transformers (CT)
SKB EP microohmmeters are the only instruments enabling to measure contact resistance of live tank and dead tank circuit breakers using separate automatic modes optimized for those circuit breakers.
- Mode 1 makes it possible to carry out measurement in the circuits without CT;
- Mode 2 enables to operate measurement in the circuits with CT with minimal battery power consumption;
- Mode 3 enables to operate measurement in the circuits with CT using 100 A or 200 A current (set by a user) without saving the battery power.
Current transformers of bulk-oil circuit breakers form an extended transition process when test current is applied. Due to that measurement time is determined by parameters of CTs, their number, and test current. For example, for HV oil circuit breaker measurement time may be up to 30 seconds.
MIKO-21 special algorithms with automatic measurement stop prevent subjective errors and increase number of measurements per one battery charge.
Four ways to start resistance measurement
Four ways are programmed in the instrument to start resistance measurement:
- Single is launched once the cable clamps are contacted to the tested object and followed by pressing the START button.
- Auto single circuit is initiated by pressing the START button. The instrument will start measurement when the electric contact between the tested circuit and the test cable contacts is set. The test can be repeated by pressing the START button again.
- Periodic is used in pre-specified time intervals when both hands are occupied with cable probes pressing against the test points. The user can choose time interval between the tests. The instrument will work continuously until the user stops the mode.
- Auto periodic circuit is initiated by pressing the START button and used for continious measurements. The user connects the current cable, and as soon as the potential contacts are connected, the measurement will start automatically. To repeat a test, simply break contact with potential probes and reconnect.
Colour graphic display of high brightness ensures easy reading on a sunny day, whereas intuitively understandable interface with a multi-sensor display simplifies the instrument use.
The Instrument can be manipulated either from the film keyboard or from the multi-sensor display, as suits.
Communication with PC via USB or a flash card facilitates data transfer from the Instrument to the Company’s data base.
The device can be integrated into measuring systems under PC control of diagnostic laboratories and companies producing electric equipment.
Independent power supply, light weight and size
Availability of an energy-independent memory and a mode of “automatic storage of the results of measurements” considerably reduces the full time of the circuit breaker test owing to transfer of the data obtained from the substation area to the Company’s office.
The above peculiarities ensure complete independence and high mobility of the instrument over the vast substation or workshop territory as you avoid troubles with a power cable, extension rod to the socket, and grounding.
Test cable of unique and ergonomic design
For convenience the standard kit includes only one type of a test package (Kit 3 includes two t metre test cables with crocodile clips for high-voltage circuit breakers up to 110 kV).
Suitable cable or a set of cables can be selected from a large range of additional accessories:
- Test cable, the instrument should be placed near a circuit breaker:
One set with spring-loaded contacts for measurements in busbars or in arc extinguish chambers. Two other kits with crocodile clips (with current and potential wires) for circuit breakers of up to 10 kV, circuit breakers of up to 110 kV, and a part for circuit breakers of up to 220kV.
- Test cable, the instrument should be placed in the lifter cradle:
Three kits that include cables with crocodile clips (with current and potential wires), a cable with a G-clamp (with current and potential wires). They differ in length and purpose, namely: for HV circuit breakers of up to 220kV, for HV circuit breakers of up to 330kV, some for 500kV, and for HV circuit breakers of up to 750kV.
- Test cables for precision measurements and measurements on the circuit sections with the test current is applied to their end points.