Unitronics electric UM2B User manual

Read this manual before using the equipment.
Keep this manual with the equipment.
UM2B
(Recovery voltage Meter)
User manual

TABLE OF CONTENTS
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TABLE OF CONTENTS
PROLOGUE _____________________________________________________________ 3
SYMBOLS _______________________________________________________________ 4
GUARANTEE ____________________________________________________________ 5
1.- INTRODUCTION ______________________________________________________ 6
2.- DESCRIPTION OF MEASURING METHOD _______________________________ 8
2.1.- Philosophy of the method ________________________________________________ 8
2.2.- Test characteristics _____________________________________________________ 9
2.3.- System behavior and important parameters during measurement ______________ 9
2.4.- ETPRA. Data interpretation_____________________________________________ 13
3.- UM2B EQUIPMENT___________________________________________________ 14
3.1.- Description of the product ______________________________________________ 14
3.2.- System elements_______________________________________________________ 15
3.3.- Physical description of equipment ________________________________________ 19
4.- PREPARATIONS BEFORE TO USE _____________________________________ 21
4.1.- Precautions in the area of installation _____________________________________ 22
4.2.- Equipment connection__________________________________________________ 23
4.3.- Disconnection of equipment _____________________________________________ 26
5.- SOFTWARE DESCRIPTION____________________________________________ 27
5.1.- Introduction __________________________________________________________ 27
5.2.- Hardware dongle. Configuration menu____________________________________ 29
5.3.- Test performance______________________________________________________ 31
5.3.1.- Test identification_______________________________________________________ 33
5.3.2.- Transformer technical data________________________________________________ 38
5.3.3.- Configuration of measurement_____________________________________________ 42
5.3.4.- Connection ____________________________________________________________ 44
5.3.5.- Measurements _________________________________________________________ 46
5.4.- Test analysis __________________________________________________________ 52
5.4.1.- Select test file__________________________________________________________ 53
5.4.2.- Transformer technical data________________________________________________ 55
5.4.3.- Recovery voltage _______________________________________________________ 57
5.4.4.- Peak time _____________________________________________________________ 59
5.4.5.- Insulation resistance_____________________________________________________ 60

TABLE OF CONTENTS
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5.5.- Test duplication assistant _______________________________________________ 62
5.6.- Remarks page_________________________________________________________ 63
5.7.- Reports printing_______________________________________________________ 64
5.8.- About … _____________________________________________________________ 70
5.9.- Exiting_______________________________________________________________ 71
6.- EQUIPMENT MAINTENANCE _________________________________________ 73
6.1.- Cleaning of equipment _________________________________________________ 74
6.2.- Care of cables_________________________________________________________ 75
6.3.- Check of high voltage cables_____________________________________________ 76
6.4.- Replacing fuse ________________________________________________________ 78
6.5.- Storage and transport __________________________________________________ 79
7.- TROUBLESHOOTING_________________________________________________ 80
8.- TECHNICAL SUPPORT________________________________________________ 83
8.1- Return for calibration/repair_____________________________________________ 83
8.2.- Ordering spares _______________________________________________________ 86
8.3.- Observations__________________________________________________________ 86
8.4.- Authorized representatives and technical services___________________________ 89
9.- SPECIFICATIONS ____________________________________________________ 90
9.1.- Electrical. ____________________________________________________________ 90
9.2.- Technical characteristics: _______________________________________________ 91
9.3.- Measurement Scales. ___________________________________________________ 91
9.4.- Minimum control PC requirements_______________________________________ 92
9.5.- Additional specifications ________________________________________________ 92
APPENDIX A.- “CE” CONFORMITY DECLARATION ________________________ 93
APPENDIX B.- CONTROL SOFTWARE INSTALLATION______________________ 94
APPENDIX C.- OTHER UNITRONICS EQUIPMENT _________________________ 95
C.1.- Available applications__________________________________________________ 96
APPENDIX D.- GLOSSARY ______________________________________________ 101

PROLOGUE
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PROLOGUE
This instructions manual contains all the information required to start-up and
maintain the UM2B metering system. The objective is to provide all the information required
for a correct operation.
IMPORTANT: Read the entire instructions manual before starting up
the UM2B unit.
The information contained in this manual is considered to be as accurate as possible.
In any case, UNITRONICS will accept no responsibility for direct or indirect damage arising
as a result of misinterpretation, inaccuracies or omissions therein.

SYMBOLS
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SYMBOLS
DANGER: This symbol indicates a highly dangerous procedure that
might cause serious damage to the equipment or to persons, or even
death, if not correctly performed.
ATTENTION: This symbol indicates a dangerous procedure that
might cause serious damage to the equipment or to persons if the
appropriate precautions are not taken.
UNITRONICS, S.A.U. is an ISO9001 certified company.
The equipment meets the requirements of the EU Directives.
UM2B. Recovery Voltage Meter
User Manual
June 2008 (Fifth Edition) UM2B User Manual V3_0CE.doc
Copyright 2008, UNITRONICS. URL: http://www.unitronics-electric.com
All rights reserved. The reproduction of any part of this manual is prohibited without authorization.
The contents of this manual may be changed without prior notice.

GUARANTEE
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GUARANTEE
All equipment produced by UNITRONICS has a standard warranty period of 12
months as from the date of delivery to the customer.
The warranty is against defects in materials and workmanship. UNITRONICS‟
obligation shall be to repair or replace defective products within the warranty period. The
warranty covers the equipment. It does not cover accessories such as cables, etc.
In order to benefit from this warranty, the purchaser should inform UNITRONICS or
his closest representative (see section 8) of the defect prior to the completion of the warranty
period.
This warranty does not cover any defect, fault or damage caused by misuse or
inadequate maintenance by the purchaser, nor non-authorized modifications or use outside
the specifications. Neither does it cover faults caused by natural disasters, including fire,
flood, earthquake, etc.
Any opening of the equipment, modification, repair or attempt to repair performed
without authorization shall invalidate this warranty, which shall automatically be left void.
This warranty is effective only for the original purchaser of the product and is not
transferable in the event of resale.
Warranty extensions and maintenance contracts are available for both the hardware
and software. Please ask for information from the commercial department of your nearest
representative (see section 8).

1.- INTRODUCTION
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1.- INTRODUCTION
This unit has been especially developed to facilitate the measurement of recovery
voltage in dielectrics. This measurement is especially significant in the case of transformer
dielectrics, where the equipment provides an interpretation of the possible degree of
humidity in the insulation and its evolution with time. In paper-oil dielectrics, the quality of
the insulation is influenced to a large degree by it‟s humidity content. In any case, the unit is
capable of evaluating the status of dielectrics of all types, both in rotating machines and in
transformers, cables and other devices.
Gaining insight into the status of transformers is a complex problem. For this reason,
different techniques have been developed, allowing in-depth studies to be performed on the
different parts into which transformers may be divided.
One of the methods used consists of measuring the recovery voltage of transformers,
this allowing problems such as the following to be detected:
degradation of solid dielectric
degradation of liquid dielectric
contamination of the insulation
Almost all these methods have a peculiarity: the absolute values of the parameters
measured are not usually sufficiently indicative for the results to be evaluated. Rather, it is
their evolution that provides the best information on the status of the winding, as a result of
which it is particularly useful for the results to be memorized and incorporated into databases
for correlation.
This leads to the definition of a predictive maintenance policy consisting of the
scheduling, at a suitable frequency, of a series of routine and easily performed tests that
provide sufficient information on the evolution of the assembly through the analysis of
certain parameters. When these analyses detect rapidly evolving situations, or when average
values considered to be potentially hazardous are reached, other more complex testing
techniques will be applied, which may imply the unavailability of the machine for long
periods or even some risk for the integrity of the winding.
The objective of this type of maintenance is to gain accurate insight into the actual
status of the equipment or component and, depending on its condition, to determine what
course of action would be most appropriate: continue normal operation, impose certain
limitations, undertake service or repairs or, finally, undertake replacement. In other words,
the aim is not only to limit unnecessary actuations but also to complete the information
available on the actual status of the equipment, such that suitable decisions may be taken.

1.- INTRODUCTION
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Predictive maintenance is applied successfully and with the greatest frequency to
major items of equipment subjected to complex ageing or degradation phenomenon and on
which a large number of variables act. In most of these cases there is no formula available
allowing the status of the equipment to be estimated, as a result of which tests are required to
obtain the values of different significant parameters and, on the basis of these, to undertake
interpretation.
Consequently, start-up goes hand in hand with the definition and performance of tests
and the interpretation of their results. For the first, it is necessary to have in-depth knowledge
of the equipment and techniques involved, while for the second there is a need for specialist
technical personnel.
As a complement to the UM2B unit and it‟s associated software of Recovery Voltage
measurement, it exists a software application for Insulation Resistance measurement. This
application will allow us to carry out a quick evaluation of the machine insulation test
without executing Recovery Voltage software.

3.- UM2B EQUIPMENT
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2.- DESCRIPTION OF MEASURING METHOD
2.1.- Philosophy of the method
The UM2B is an automatic system designed to determine the recovery voltage of
transformers. It is designed to be a predictive maintenance system, for which it meets the
following requirements:
Automatic measuring system. In order to avoid errors due to acquisition times,
manipulation and corrections caused by the ambient conditions and the conditions
of the machine at the moment of measurement.
Repeatability of the measures. The system warranties that the readings obtained
over time have been acquired in the same way and under the same degree of
accuracy and tolerance. This will allow the evolution of the readings to be
studied.
Automatic and organized storage of results. This allows the information obtained
to be handled in a very simple manner.
Updateable system. The system has been developed such that whatever new
software development might arise, it may be implemented with the same
hardware elements.
Acquisition of key parameters. The system automatically calculates certain
parameters and graphics for the diagnosis of machine status.
Non-destructive testing. If suitably handled, there is no risk of damage to the
winding during testing.

3.- UM2B EQUIPMENT
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2.2.- Test characteristics
The test to be used should be performed, with a view to the following:
The tests should be easy to perform, allowing for performance by suitably trained
personnel from the facility, without the need for specialists.
The tests should not imply any risk for the equipment to be tested.
The tests should not imply excessive unavailability (and if possible none).
The data and results obtained should offer at least some information allowing the
operator performing the test to make an immediate interpretation.
The set of data obtained should allow for storage on data-processing media, such
that they be simple to transmit for in-depth study by specialists, who will obtain
the maximum information from the data acquired and take the appropriate
decisions through comparative studies with other cases.
2.3.- System behavior and important parameters during measurement

3.- UM2B EQUIPMENT
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The UM2B unit is designed to output a direct current voltage of up to 2 kV to the
element to be tested, carry out the loading and discharge intervals on the dielectric as
described for the specific test and, finally, measure the voltage and current.
The unit will examine the status of the dielectric of the equipment being tested, as
shown electrically in figure 2.1. The different elements in this figure are as follows:
-Cg, Geometric capacity of the equipment being tested. This will be determined by
the physical characteristics of the armatures of the equivalent condenser, surface,
properties of intermediate dielectric and separation between armors.
-Ra, Insulation resistance. In measuring, this is related to the final leakage current
following the transitory loading period of the dielectric.
-Rpx and Cpx are the electrical elements used to describe the recovery voltage
characteristic. In an equivalent circuit there will be a multitude of such elements, in
order to reflect the distributed nature of this behavior.
The test to be performed aims to determine the equivalent time constants Rp/Cp, the
measure and evolution of which are determining factors as regards the current and future
status of the dielectric. The test consists of inserting over a time T a previously established
voltage of up to 2 kV. Following this time, a short-circuit is performed on the sample for a
time T/2, and finally the evolution of the recovery voltage appearing is recorded. This
process (cycle) is repeated for multiples of T, and the maximum recovery voltages associated
with each interval or cycle are used to graph a curve on which would be shown in a T time
axis of application and maximum tension in the other axis. Above the mentioned dots a
fitting curve is drawn. Then, each time constants Rp/Cp should appear as a maximum on the
graph.
Figure 2.1: Dielectric equivalent circuit.
When a high voltage generator DC voltage is applied to a dielectric, the current
across the insulation shows the following behavior, as plotted in figure 2-2.

3.- UM2B EQUIPMENT
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Figure 2-2: Description of the test procedure.
1) Application of H.V. voltage to the sample. The current starts with a high value that
gradually decays with time and finally remains stable. The low initial insulation
resistance is caused in part by the high initial loading current of the associated
condenser Cg. This capacitive current rapidly decays to a low value as the insulation
is charged. Furthermore, the low initial insulation resistance is caused by another
phenomenon, which is the dielectric absorption current, Rp/Cp. This current also
decreases with time, albeit more gradually, until it reaches an insignificant value.
The final leakage current does not change with the time of voltage application, and is
a fundamental parameter for judging the insulation, this is Ra. The insulation
resistance varies directly with the thickness of the insulation, and inversely with the
area tested.
2) Short-circuiting of the sample. At this moment the current is initiated with a high
value in inverse direction to the period before corresponding to the rapid discharge of
Cg, while Ra does not actuate due to the short-circuit having a lower resistance.
There will be a weak current associated with the discharge of the Cp‟s across the
Rp‟s, but the most likely thing will be that if the short does not last too long, these
Cp‟s will maintain part of their charge.
3) The short-circuit is removed and the measurement performed. During this phase,
and with the Cp‟s remaining charged, if the voltage is recorded at the terminals of the
sample, the Cp‟s will be observed to charge the capacitor Cg across the Rp, and
finally both will discharge via Ra. This gives a curve with a maximum that, as
commented before, is the one registered for every cycle.

3.- UM2B EQUIPMENT
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For the measurement to be performed under optimum conditions, there are certain
details that should be taken into account:
Conditions of the surfaces. Any dust accumulating on the surface of the sample tested may
alter insulation resistance measurements if there is associated humidity, for example in the
case of rainfall.
Temperature. The resistance of insulating materials changes with temperature.
Consequently, the result of a test will be comparable to that of another only if both are
performed at the same temperature. For this purpose, it is habitual to refer tests to certain
reference temperatures, with the appropriate correction parameters, in order to allow for
comparison. It is of interest that the tested machine has his temperature stabilized (let settle
after switched off from service) and his temperature be measured from the inside with
appropriate accuracy. Temperature has a large influence in dielectric evaluation as insulation
resistance is directly related to temperature variations. To figure out, each 10ºC of thermal
increment for the same increment to the same dielectric, his resistance is halved.
Test voltage. Insulation measurements will be performed at test voltage values agree with
the working voltage of the machines to be tested, in order not to cause degradation to their
insulations.
Previous charge effect. A factor that affects insulation and dielectric absorption
measurements is the preliminary presence of a previous charge in the insulation. This charge
may come from the normal operation of a generator with its neutral not grounded or from
previous insulation resistance measurements. A lot of time may be saved if the generator
winding is grounded until such time as the test is to be performed. The duration of this
grounding should be around four times the charge period of the previous test.
Measuring cables. In view of the weak currents involved in the measurement and its special
characteristics, it is important to take into account the following as regards the cables:
–Do not tread on cables or knock or move them during testing.
–Locate the cables extended, without bending or folding, as close as possible and in
parallel throughout their entire length.
–Should be in perfect condition and checked for use.

3.- UM2B EQUIPMENT
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2.4.- ETPRA. Data interpretation
It follows interesting details if you have available the Insulation Resistance
Measurement Software (ETPRA).
From the exam of the circuit of figure 2-1, it states that to discharge Cg, you only
need to short-circuit the dielectric terminals, but to discharge Cpx, it will be required a time
proportional to the time constant Rpx*Cpx. This means to say that if a transformer has not
been phase-grounded the required time to discharge that Cpx, it will exist some residual
charge that make hard to compare consecutive test of Insulation Resistance performed in the
dielectric.
The software developed for UM2B unit accounts for this effect and let you perform a
discharge period previous to the test, that will make consecutive test easy to exactly
compare. Anyway, in some case it could be appreciated slight differences between the
insulation measurement performed with the Recovery Voltage software and the one
performed with the Insulation Resistance software (ETPRA). This is due to that the
Recovery Voltage measurement software uses one of the charging cycles longer than 10
minutes to measure insulation. In this software the discharge conditions of that Cpx have
been restricted enough not to make the test last too long and give accurate results. This limit
could offer slight measurement differences between both applications.
It is therefore recommendable to begin the test with the unit UM2B after having
shorted the machine to test. If it had been made previous test, that short should last at least
around four times the charge time of the last test.

3.- UM2B EQUIPMENT
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3.- UM2B EQUIPMENT
3.1.- Description of the product
The UM2B unit has been especially designed to determine the recovery voltage of
single and/or three-phase transformers and autotransformers of any type. It is based on the
measurement of a series of simple parameters by means of a data acquisition system and a
computer application for the performance of calculations.
Figure 3-1: Appearance of the measurement system.
Once the data have been obtained, enough information is available for diagnosis of
the current status of the transformer, and for assessment of the trend curves. The advantages
that characterize the UM2B method may be summarized as follows:
minimum risk for the machine.
reduced unavailability times.
simple performance.
high degree of test automation.

3.- UM2B EQUIPMENT
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3.2.- System elements
The equipment may be fitted with the following elements and / or accessories:
NOTE: The XX nomenclature indicates different versions, depending on the characteristics
of the equipment. Please consult with your sales person.
REF No
DESCRIPTION
UM2BXX
UM2B measuring equipment with serial number.
Figure 3-2: Measuring unit.
BEL00
Measuring equipment transport bag.
Figure 3-3: Transport bag.

3.- UM2B EQUIPMENT
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CR00
Mains supply cable with ground terminal.
CRS23200
Shielded series cable with DB9 terminal connectors for
communications between the PC and the unit. The cable must be
shielded.
Figure 3-4: Serial cable.
M8AT0L
8-metre long high voltage shielded measuring cables with wide
opening clip pincers at one end and high voltage connectors at the
other. The polarity is indicated by the color of the clips and
connectors: red for positive and black for negative. These must be
shielded.
Figure 3-5: High voltage cables with power clips.

3.- UM2B EQUIPMENT
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BCL00
Cable transport bag
Figure 3-6: Transport bag.
SOFUM2BRBWXXX
1CD with equipment control software.
UM2BMUXX
The present user manual.
RAFVDM00
Four power sockets protected against voltage surges, differential
currents and overcurrent. This incorporates a voltmeter for direct
verification of the supply voltage indicator of ground connection and
terminals for ground connection.
Figure 3-7: Power Socket.

3.- UM2B EQUIPMENT
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MM00
Rigid transport case with reinforced external protection and internal
padded lining of high-density foam rubber.
Figure 3-8: Transport Case.