Comparison of SKB EP transformer OLTC diagnostic systems

One of the causes of OLTC damage are contactor and switching device malfunctions, contact burning of contactors, contactor mechanisms jamming, loss of mechanical strength of steel parts and paper-bakelite shaft.

To identify the cause of OLTC fault and to automate the diagnostic process, SKB EP implements 2 specialized instruments for OLTC devices' diagnostic: PKR-2M and PKR-2, as well as 2 milli-ohmmeters: MIKO-9A and MIKO-8M(A) that has an auxiliary mode for OLTCs diagnostic.

	PKR-2М	PKR-2	MIKO-9А	MIKO-8М(А)
Electrical resistance measurement in the windings of power and instrument transformers
Resistance measurement of internal contacts and connections of OLTC devices
Resistor type OLTC contactor switchover oscillography
Oscillogram recording by three phases simultaneously
Oscillogram recording phase by phase
"Demountable" diagnostic (with removing contactor tank)
Equipped with special probes for operation without complete or partial oil drain from contactor tank (on order)	improved design for OLTCs of RS and RNT types with elastic grips	improved design for OLTCs of RS and RNT types  with elastic grips	-	-
Non-demountable diagnostic of resistor type OLTCs (DRM method)		Additional option - DRM-test mode can be activated upon request
Supplied with a special cable for secondary winding terminals short-circuiting	standard and optional complete sets	standard and optional complete sets	optional	optional
Measurement of test current when checking the contactor with non-demountable method	1 - 4А	1 - 4А	до 10А	до 10А
Type of oscillogram recorded with the non-demountable DRM method	Three types of display, similar to the appearance of oscillograms recorded with direct connection to contactor	Three types of display, similar to the appearance of oscillograms recorded with direct connection to contactor (after activation of DRM mode)	Current oscillogram of contactor switchover process	Current oscillogram of contactor switchover process
Method for generating/placing oscillograms in the measurement protocol	Automatic protocol generation in software for PC	Automatic protocol generation in software for PC	Transfer to cloud service on PC via USB cable	Transfer to cloud service on PC via USB cable
Maximum oscillogram recording time, min	20	20	15	15
Static checking of OLTC devices (when the drive shaft is rotated by the handle, the points of contacts closing/opening, voltages, currents and resistances on each tap are shown on the display)
Circular diagram recording of the resistor type OLTCs
Circular diagram recording of the reactor type OLTCs
Circular diagrams recording simultaneously in three phases			-	-
Circular diagrams recording phase by phase			-	-
Graphical representation of full-fledged circular diagrams			-	-
Table representation of data indicating the moment of switching of even and odd contacts (contactor and voter)	in degrees for resistor OLTC devices and in revolutions for reactor OLTC devices	in degrees for resistor OLTC devices and in revolutions for reactor OLTC devices	-	-
Display size and type	color multi touch display 640 x 480 pixels	color multi touch display 640 x 480 pixels	TFT color multi touch display, 800 x 480 pixels	TFT color multi touch display, 800 x 480 pixels
Number of data transfer channels, pcs.	2 (USB; USB host)	1 (USB)	2 (Bluetooth, USB)	2 (Bluetooth, USB)
User Interface (set up before measurement)	2-3 parameters must be set	2-3 parameters must be set	2-3 parameters must be set	2-3 parameters must be set
Mains power supply
Power supply by built-in battery		Additional option - a built-in battery is available on request		MIKO-8MA modification
Dimensions, mm	360х290х165	360х290х165	270х250х130	270х250х130
Instrument weight, kg	5,1	6,1	4,0	2,7 MIKO-8M modification 4,0 MIKO-8MA modification
Operating temperature range, ºC	-20 ÷ +40	-20 ÷ +40	-20 ÷ +55	-20 ÷ +55