Megger OTS 60AF/2, OTS80AF/2, OTS100AF/2 User Manual

OTS 60AF/2, OTS80AF/2 and OTS100AF/2 Oil Test Sets

USER USER

GUIDE D’UTILISATION

GEBRAUCHSANLEITUNG

GUÍA DEL USUARIO

SAFETY WARNINGS

• T

he Oil Test Set must be properly earthed.

• The test chamber must be kept scrupulously clean.

• If the test chamber cover is cracked or damaged in any way, the test set

must not be used, but sent for repair to an authorised agent.

• A routine continuity check between the emc/discharge barrier and the earth

point should be made weekly (see page 9, section 5).

• The correct type of oil test vessel must be used, and correctly positioned on

the support horns

before carrying out any testing (see page 9, section 7).

• Replacement fuses must be of the correct type and rating.

• Safety warnings and precautions must be read and understood before the

instrument is used. They

must be observed during use.

NOTE

THE TEST SET MUST ONLY BE USED BY SUITABLY TRAINED AND COMPETENT PERSONS.

Symbols used on the instrument

Caution: Refer to accompanying notes.

Risk of electric shock.

Equipment complies with relevant EU Directives

Earth terminal

Safety Warnings 2 General Description 4 Applications 6 Specification 7 Accessories 8 Operation

arnings 9 Preparing the test vessel 10 Loading the test vessel 11 Preparing the oil test set 12 Automatic testing sequences 14

5 minute test 15 AS 1767, BS 148, BS 5874, CEI 10 -1, EN60156, IEC 156, IP 295, NFC 27, ΓOCT 6581, SABS 555, STAS 286, UNE21 and VDE 0370 tests 17 ASTM D877 test 18

ASTM D1816 test 18 Custom test 19 Withstand (Proof) tests 21 BS 5370a test 23 Self check tests 25 Calibration check 26 Printer facilities 27 Downloading Results to a PC 28 Print out information 29 Fuse replacement 29 Sampling and Testing Oil for Dielectric Strength 30

Guide de l’utilisation 31

Gebrauchsanleitung 53

Guía del usuario 75

Repair and Warranty 97

Contents

The OTS60AF/2, OTS80AF/2 and OTS100AF/2 are transportable, easy to operate, oil test sets. A voltage selector fitted on the mains supply input panel at the rear permits the test sets to be operated from either 110 V, 120 V, 220 V or 240 V 50 Hz/60 Hz mains power supplies. The casing is made of sheet steel and carrying handles are fitted at each side. The whole construction is very robust.

Incorporated within the casing is the test chamber of moulded plastic construction with a hinged p

olycarbonate cover. Protruding into the chamber from its floor are two horns; through these pass the high voltage transformer output connections, to cradle terminals one at the top of each horn. The test vessel containing the sample of oil to be tested, is placed on these cradle terminals.

Within the test vessel are mounted two electrodes. The shape of the electrodes and the gap set between them is determined by the particular national oil testing specification to be used. The vessel itself is of cast resin construction made in two parts. The electrodes are automatically connected to the cradle terminals when the vessel is placed on the horns.

Inset into the top rear panel of the test chamber is a supply socket. This provides an independent power supply for the optional ASTM D1816 American test vessel which has an impeller type oil stirrer. Oil stirring may also be achieved by a magnetic stirrer bar driven by a rotating magnetic field generated from beneath the test chamber. This magnetic field is only generated when required, under software control.

The hinged cover to the test chamber is fastened by a trapped key interlock switch. This is a safety feature whereby high voltage cannot be applied to the test chamber unless the interlock is closed. Should the interlock be released during an oil testing sequence, the high voltage will be automatically cut off and the test aborted; the display will indicate that this has occurred. However, the mains supply will still be applied and the On/Off switch will still illuminate.

Note:- User settable parameters and test results are stored in non-volatile memory (referred to as

NOVRAM) and are unaffected by the operation of the test chamber interlock or by power failures.

The control panel is to the right of the test chamber. Once the testing specification has been selected and a test initiated (via the control panel) the operator is free to do other work while the test sequence is automatically carried out.

Below the control panel an integral printer is fitted so that a permanent record of any test results may be obtained. A 9 Way ‘D’ type plug is fitted to the test set to enable an external printer to be connected if required.

Control Panel

Test circuitry is controlled by a microprocessor and all the inherent benefits of pre-programmed tests, menu selection of function and memory storage of test results are available.

Panel controls are: (i) An On/Off power supply rocker switch which illuminates in the ‘On’ position. (ii) Three tactile keys for making menu selections and generally controlling the test sequences. (iii) A tactile key for advancing the paper through the internal printer.

The display is a liquid crystal dot-matrix type giving full information in alpha-numeric form. The display shows the tests which are available, allocates names to the tactile control keys according to the programme adopted, shows the voltage being applied during a test and reviews the individual test breakdown voltage results when a test sequence is concluded (plus showing the average breakdown voltage and standard deviation).

An L.ED. on the control panel illuminates to indicate that a high voltage is being applied to the test electrodes.

The menus, and their information shown on the display are straightforward and simple to follow. The text of the operating section of this instruction book gives detailed information which, after the set has been used once, will probably only need to be referred to if difficulties arise, but please ensure you read thesection entitled WARNINGS on page 9.

General Description

Cradle terminal

est chamber

Sheet steel case

Carrying handle

Control panel

Internal printer

H.V. transformer output terminal ‘

horns’

E.M.C./ Discharge barrier

Oil test vessel

Hinged polycarbonate cover

Safety interlock on test chamber

H.V. indicator

Printer paper feed key

Liquid crystal display

Control keys

Power supply On/Off switch

External printer connector

Mains supply socket

Fuses

Mains supply voltage selector

Earth terminal (additional)

Figure 2. Oil test set controls etc.

Figure 1. OTS100AF/2 oil test set layout (the OTS80AF/2 and OTS60AF/2 are similar).

Figure 3. Oil test set rear panel.

The OTS60AF/2, OTS80AF/2 and OTS100AF/2 are used for determining the dielectric strength of liquid insulants, such as the insulating oils used in transformers, switchgear and other electrical apparatus. They are transportable and suitable for laboratory use as well as testing on site. A four wheeled trolley is available to assist with on-site transportation.

The test sets are fully automatic. The operator has simply to prepare the test vessel, load it with sample o

il, place it in the test chamber, select the appropriate specification for the tests and then start the test sequence. The test set carries out automatically (and if necessary unattended) the sequence of tests as defined by the pre-selected national specification.

Oil testing specifications, for which the sets are pre-programmed, are as follows:-

International IEC 156 1995 British BS 5874:1980, BS148:1984,

BS 5730a:1979 American ASTM 1816-84a, ASTM D877 German VDE 0370/84 French NFC 27-22:1974 Italian CEI 10-1-1987 Spanish UNE21-309-89 Russian

ΓOCT 658-75 Rumanian STAS 286-81 South African SABS 555-1985 Australian AS 1767-1976 Institute of Petroleum IP 295/83 European EN60156 (1996)

For other specifications, five separate, fully programmable, custom test sequences are available which can be stored within the non volatile memory (NOVRAM). A 5 minute test sequence is also provided so that a user may quickly obtain an idea of the state of an oil sample.

Three types of withstand (proof) testing of an oil sample are available. The principle of these tests is to subject the oil sample to a specified voltage for a defined length of time (1 minute) to see if it will withstand that voltage. Withstand test ‘A’ and Withstand test ‘B’ incorporate a user definable initial stand time period.

Safety features incorporated in the design include the safety interlock on the test chamber cover and an easily operated mains supply On/Off switch. These ensure a high level of safety for operators, provided the set is used in a responsible manner.

Applications

Power cord

If the power cord plug is not suitable for your type of socket outlets (receptacles), do not use an adaptor. You should use a suitable alternative power cord, or if necessary change the plug by cutting the cord and fitting a suitable plug. The colour code of the cord is:

Earth (Ground)

ellow/Green

Neutral Blue

Phase (Line)

Brown

If using a fused plug, a 13 Amp fuse to BS 1362 should be fitted.

Note: A plug severed from the power cord should be destroyed, as a plug with bare conductors is hazardous in a live socket outlet (receptacle).

Output Voltage (max.) OTS60AF/2 60 kV (30 kV - 0 - 30 kV) OTS80AF/2 80 kV (40 kV - 0 - 40 kV) OTS100AF/2 100 kV (50kV - 0 - 50 kV)

(high voltage test frequency is 61,8 Hz)

Display Dot-matrix liquid crystal display giving alphanumeric information

and kV test voltage.

Resolution 0,1 kV

Temperature Range

Operating 0°C to +40°C Storage -40°C to +70°C (in accordance with BS 2011 part 2)

Humidity Range

Operating 80% RH at 40° C (non-condensing) Storage 93% RH at 40° C, 95% RH at 25°C (in accordance with BS 2011

part 2 )

External Printer Socket 9 pin ‘D’ type plug for RS232C interface

Safety The test sets meet the requirements IEC 61010-1

E.M.C. In accordance with IEC 61326-1

Operational uncertainties Refer to www.megger.com

Supply Voltage 220 V ± 10%, 240 V ± 10%,

110 V ± 10%, 120 V ± 10%, (four selectable values), 50 Hz / 60 Hz.

Fuses 2 x 6,3 A (F) ceramic HBC IEC 127/1, 20 mm x 5 mm

3.15 A (T) ceramic HBC IEC 127/5, 20 mm x 5 mm, for 220 V / 240 V 4 A (T) ceramic HBC IEC 127/5, 20 mm x 5 mm, for 110 V/120 V Mains power cord fused plug: 13 Amp fuse to BS 1362

Dimensions 502 mm x 464 mm x 319 mm (193⁄4in x 181⁄4 in x 121⁄2 in approx.)

Weight 41 kg (90 lb) approx.

Cleaning Wipe disconnected test set with a clean cloth dampened with

Isopropyl Alcohol (IPA)

Specification

Accessories

Supplied with Instrument Part Number

User Guide 6172-064

Mains power cord 25424-860

il test vessel fitted with spherical electrodes 12,7 mm diam. 6231-445 Oil test set preparation kit 6121-486 comprising:two magnetic stirrers pair of cylindrical electrodes 1 inch diam. pair of mushroom electrodes 36 mm diam. *electrode spacing gauges for 1 mm (0,04 inch), 2 mm (0,08 inch), 2,5mm, 2.54mm (0,1 inch) and 4,0 mm (0,16 inch)

Protective cover 5340-334

Optional

Voltage calibration meter (0-100kV) OTS/VCM100

Oil test vessel fitted with mushroom electrodes 36 mm diam. 6231-447 Oil test vessel fitted with cylindrical electrodes 1 in diam. 6231-446

Oil test vessel for ASTM D1816 specification (motorised stirrer) 6111-146

A pair of mushroom electrodes 6220-482 A pair of cylindrical electrodes 6220-483 A pair of spherical electrodes 6220-484 A pair of cylindrical electrodes with 0,5 mm edge radius for use with any test vessel 6220-538

Printer paper 57,5 mm wide, 15 m long, 50 mm diam. 25995-001

Printer ribbon Epson part no. ERC-09 (IRC160) 25995-002

Printer lead, 9 pin female ‘D’ connector to 25 way male ‘D’ connector 25955-026

PC Download lead

25955-025

ransportation trolley

6320-224

Note:- Capacity of oil test vessels is 400 ml, except for the ASTM D1816 vessel which is 800 ml.

The new spacer gauges are no longer big enough to have the diameter marked on them.

They now

have a series of grooves cut into them to state the difference between them which is as follows:

1 rings - 1mm 2 rings - 2mm 3 rings - 2.5mm 4 rings - 4mm

Guage Indentification

5152-293

5152-294

5152-296 5152-319 5152-296

1mm 2mm 2.5mm 2.54mm 4mm

Rings 1 2 3 4

Warnings

1. Ensure that the oil test set is properly earthed before use. The test set MUST be connected

to a socket outlet with a protective earth conductor. To ensure effective earthing, it is recommended that the green/yellow terminal on the mains input panel at the rear of the test set be separately connected to a known good earth.

2. Before connecting the mains supply, ensure that the mains supply voltage selector is set to the correct value for the power supply to be used. The voltage selector is located on the mains input panel at the rear of the test set.

3. Ensure that the test chamber is always scrupulously clean, particularly prior to a test. Wipe away any spilled oil in the test chamber or on the test vessel when necessary.

The vessel must be properly positioned in the test chamber on the top of the support horns.

4. If the test chamber cover is cracked or damaged in any way, the test set

MUST NOT be used.

The cover must be replaced, by an authorised repairer, before the set is put into service again.

5. The oil test set has a metal emc/discharge barrier on the inside of the test chamber cover which is connected via two springs to the earth pin of the mains supply input plug. The continuity between the metal barrier and the earth pin must be routinely checked at weekly intervals. There are also two touch contacts from the metal barrier on to the casing. The integrity of these contacts should be verified when closing the cover.

6. The test set is fitted with high breaking capacity ceramic fuses to IEC 127. It is essential that any replacement fuses fitted to the test set conform to this specification, (for full details see the Specification section). Glass fuses

MUST NOT be used due to their low breaking capacity.

7. Only test vessels manufactured and supplied by Megger Limited for use with the OTS60AF/2, OTS80AF/2 or OTS100AF/2 sets must be fitted within their respective test chambers.

The correct vessel type is shown in Figure 4. No other vessel or container, (including any which may look similar) must be used.

8. Damage to the test set and loss of warranty may result from the use of the wrong oil test vessels.

9. Casing panels or covers must not be removed while the test set is connected to the mains supply

. T

o do so will expose live parts of the circuit. Internal capacitors may retain their charge even when the test set is disconnected from the mains supply (especially under fault conditions). Any adjustments or repair must be carried out by trained qualified personnel, therefore loss of Warranty may result if work is carried out by personnel other than the manufacturer or one of his approved agents.

10. Whenever it is likely that the test sets protection has been impaired, it must

NOT be used, but

taken out of service and returned to the manufacturer or his approved agent for repair.

The protection is likely to be impaired if, for example the test set shows visible signs of damage; fails to perform the intended measurements; has been subjected to prolonged storage under unfavourable conditions or has been subjected to severe transport stresses.

If the oil test set has been exposed to severe environmental changes i.e. in humidity or temperature, it should be allowed to acclimatise to its new conditions for a period of not less than 12 hours before use.

Preparing the Test Vessel

1. Separate the cover holding the electrode mountings from the container.

2. Ensure that the vessel is thoroughly clean, both inside and out.

. Mount the appropriate electrodes on the sliding arms, if they are not already in place. It may be

necessary to slacken one or both of the clamp screws at the base of the electrode supports and move the sliding arms back. The sliding arms have a threaded stud and the electrodes screw on to these. Screw on and tighten firmly with finger pressure.

4. Set the gap between the electrodes according to the requirement of the testing specification being undertaken. Spacing gauges are provided in the accessory kit for this purpose. The clamp screws at the bottom of both electrode supports should be slackened and the sliding arms moved so that the gap is approximately central between the two supports. Tighten the clamp on one support to hold one side firmly, then adjust the other so that when the gauge is passed between the electrodes it touches both simultaneously. Tighten the clamp screw on the second support. Recheck the gap after it has been set.

list of electrode shapes and gap spacing for standard testing specifications is shown opposite. Each test display screen also shows electrode shape; spacing, and type of stirring for each preprogrammed test specification, where appropriate.

5. Clean the vessel in accordance with the instructions given in the relevant test specification to be used, then fill the container part of the vessel with the sample oil until the level is about 12 mm (

⁄2 in) from the top.

6. If required, drop in a clean magnetic stirrer bar (not for ASTM D877 and ASTM D1816 specifications, or any case where impeller stirring has been selected). Ensure that the stirrer bar is central in the vessel.

Note:- The

ASTM D1816 specification requires continuous stirring.

This is provided by the special

D1816 vessel by the motor driven impeller. See figure 12 on page 19.

Carefully reassemble the two parts of the test vessel.

Operation

Figure 4. Oil Test Vessel

Electrode support

Shrouded connector arm

Container

Electrodes

Sliding arm

Clamp screw

Cover

Loading the Test Vessel

1. Open the test chamber cover by turning the trapped key interlock knob a 1⁄4-turn anticlockwise and pulling it outward.

2. Place the test vessel in the chamber so that the ends of the connector arms rest on the cradle terminals at the top of the support horns. Clean away any spilled oil.

Note:- For an ASTM D1816 vessel connect the paddle stirrer motor lead to the supply socket in the top

rear of the test chamber.

Caution:- Visually confirm that the two spring earth contacts linking the metal emc/discharge

barrier on the test chamber cover to the back of the chamber are intact (see Figure 5).

3. Close the test chamber cover, pushing in and turning the interlock knob clockwise to secure it.

tandard

test

specification

selected

Electrode

shape

Electrode

spacing

ASTM D1816

ASTM D877

2,5 mm

1 or 2 mm

2,54 mm

EN60156 AS 1767 BS148 BS 5874 CEI 10-1 IEC 156 IP 295 NFC 27 ΓOCT 6581 SABS 555 VDE 0370 UNE 21 STAS 286

Figure 5. Spring earth contact on test chamber cover.

Preparing the Oil Test Set

1. Adjust the mains voltage selector if necessary and connect the oil test set to a suitable supply. It is recommended that the green/yellow earth terminal is connected to a known good earth.

2. Switch on both the supply and the test set. The copyright message appears on the display for a b

rief time and is followed by the main programme menu screen. The options available from the

main menu are:-

AS 1767-1976 ASTM D877 ASTM D1816-84a BS 148:1984 BS5730a:1979 BS 5874:1980 CEI 10-1-1987 EN60156 - 1996 IEC 156 1995 OPTIONS IP 295/83 NFC 27-221: 1974 ΓOCT 6581-75 SABS 555-1985 STAS 286-81 UNE21-309-89 VDE 0307/84 5 MINUTE TEST SELF CHECK CHECK CALIBRATION CUSTOM WITHSTAND (PROOF)

The main menu display allocates labels to the three control keys, as their function changes. On switch on, these will be (from left to right)

s, t, and SELECT. The left and centre keys control scrolling up and

down through the menu options, and the SELECT key activates the highlighted option.

Note:- The display shows only five menu options at any one time and those in view will depend upon

the last option used. When scrolling, the highlighted option is the one ready for selection.

Select the required option and follow the display instructions.

Selecting OPTIONS from the main menu

The OPTIONS sub-menu allows you to set up and retain customised preferences for the following:-

DISPLAY CONTRAST DISPLAY BACKLIGHT LANGUAGE PRINTER CONTROL TIME / DATE

Note:- All of the settings will remain in the internal memory when the instrument is switched off or the

test chamber cover interlock switch is opened.

Scroll through and select as before. Highlight MENU and press SELECT

to return to the main menu.

Display Contrast

When DISPLA

CONTRAST is selected, the centre and left arrow keys can be used to adjust the

readability of the display screen. Press SELECT to return to the OPTIONS sub-menu.

Note:- A quick way to bring the display contrast into view on the screen is to press the centre key while

switching the test set on. The key must be held for approx. 1 second after switching on.

Display Backlight

When DISPLAY BACKLIGHT is selected, the centre and left arrow keys can be used to switch the display backlight ‘On’ or ‘Off’ as required. Press SELECT to return to the OPTIONS sub-menu.

Operation

Language Select

The display screen and print-out can be set to read in any one of six languages:-

ENGLISH FRANCAIS DEUTSCH E

SPANOL PORTUGUES ITALIANO

Scroll through and select as before. Pressing SELECT returns to the sub-menu.

Note:- A quick way to bring the language screen into view on the screen is to press and hold the right

hand key while switching the test set on. After making the selection proceed through the remainder of the OPTIONS sub-menu.

Setting the printer options

Scroll through the OPTIONS sub-menu to PRINTER CONTROL and press SELECT. A further sub-menu is displayed as follows:

PRINT LAST RESULTS AUTO PRINT NO. OF COPIES BAUD RATE QUIT INT. PRINTER ON EXT. PRINTER OFF

Where applicable, the status of each option is given (e.g. NO. OF COPIES 1), and this can be altered as required by successive pressing of the SELECT key. For example, to change the ‘On’/‘Off’ mode of the internal printer, scroll through this sub-menu to INT PRINTER, and press SELECT. It is expected that the internal printer will normally be on.

Note:- Successive pressing of the SELECT key toggles the internal printer between the ‘On’ and ‘Off’

mode. This automatically switches the EXT PRINTER (external printer option) to the opposite mode. It is not possible to use both the internal printer and an external printer together.

If an external printer is to be used, the Baud rate of the the test set must be adjusted to match that of the printer. To do this, scroll through the menu until BAUD RATE is highlighted. Successive pressing of the SELECT

key will scroll between standard Baud rates available i.e. 9600, 4800, 2400, 1200, 600, 300 and

150. Leave in view the one to be chosen. The data transfer format is:-

1 start bit 8 data bits 1 stop bit no parity

One or two copies of the results print-out may be made. Scroll through to No. OF COPIES and press SELECT to toggle between the selection of 1 or 2. Leave the required number displayed. The PRINT LAST RESULTS option causes the last set of test results to be printed when the SELECT key is pressed.

Note:- The last set of test results remain in the internal memory when the instrument is switched off or

the test chamber cover interlock switch is opened.

The test set will automatically print the results

of a test when completed if the

AUT

O PRINT

option is set to ‘On’. Scroll through as before until the option is highlighted and, if necessary, press SELECT until the required status is displayed. If this option is set to ‘Off’ then a PRINT option will be given at the end of a test sequence.

To move back into the OPTIONS sub-menu scroll through until QUIT is highlighted, then press SELECT.

To move back to the main menu from the OPTIONS sub-menu scroll through until MENU is highlighted and press SELECT.

TIME / DATE

The correct time and date are pre-set and will not normally need to be adjusted. The internal 24 hour clock is powered by a LITHIUM battery with a life of 10 years.

When TIME / DATE is selected, a further sub menu is displayed as follows:

DATE FORMAT VIEW QUIT SET DATE S

ET TIME

Scroll through and select as before.

DATE FORMAT offers the choice of U.K. date style (dd-mm-yy), or U.S. date style (mm/dd/yy). Successive pressing of the SELECT key will select the alternate style.

To adjust the date, scroll to SET DATE, and press SELECT. Set the date with the left and centre arrow keys, and press SELECT. Then set the month, followed by the day of the month, in the same way.

To adjust the time, scroll to SETTIME, and press SELECT. Set the hour with the left and centre arrow keys, and press SELECT. Then set the minutes in the same way.

Selecting VIEW will display the time, together with date in the chosen format. To return to the sub menu, scroll to highlight QUIT and press SELECT.

To return to the main menu, scroll to highlight MENU, and press SELECT.

Automatic Testing Sequences

Choose the appropriate pre-programmed oil testing specification programme from the main menu by scrolling through using the s, t keys until the required specification is highlighted. Then press SELECT.

When a test specification has been selected in this way, the display screen changes to show the name of the test (this remains in view throughout the test sequence) and gives an option to START the test sequence with the left hand key, or return to the main menu with the right hand key. For each separate test specification, the display will indicate appropriate choices of electrode shape and spacing, if the specification stipulates these. The appropriate method of stirring is also shown. If the STIR MODE option is displayed, the user may vary the mode of stirring between MAGNETIC (magnetic stirrer bar), IMPELLER (stirrer test vessel), or NONE as is appropriate to the selected test.

When started, each test sequence is carried out completely automatically.

Note:- The microprocessor software contains routines which monitor the operation of the oil test set. In

the unlikely event of a problem occurring (whether caused by the test set or an external event), the test currently in progress will, when resumed continue from the point at which the problem occurred. If this is not possible the test set will be placed in a safe condition and a situation status message will be displayed.

Operation

Calculations

After an automatic test sequence is completed, the average is calculated from the following formula:

verage

x =

∑

where

Standard Deviation

The sample standard deviation s(also known as σ

n-1

) is given by:-

s = ∑

n x

√

n - 1

Where s= sample standard deviation.

Data Dispersion

The ratio of standard deviation upon mean (

s / x )

also known as the co-efficient of variation is used to determine whether the spread of a set of test results is within acceptable limits. This value may be expressed as a percentage.

i = n

i = 1

= mean (average) of results

individual results

= number of results

i = n

i = 1

5 MINUTE TEST

Note:- This is a non-standard test, designed to provide a rapid assessment of the oil condition.

1. To commence the test, highlight 5 MINUTE TEST on the main menu and press select. The display will appear similar to figure 6.

Repeated pressing of the centre key marked STIRMODEchanges the stirring choice through MAGNETIC, IMPELLER or NONE. Press the right hand key marked MENU to return to the main menu.

2. On pressing the START key the display appears similar to figure 7.

The display indicates that the one minute initial stand time is being undertaken, and the remaining time is shown in seconds.

3. After the initial stand time is complete the high test voltage is automatically switched on and applied to the sample. The display showing ‘TEST 1’ appears similar to figure 8.

The high voltage indicator light is illuminated, and the display shows the voltage rising at the rate of 2kV/s being applied to the oil sample. This voltage rise continues until break down occurs (or up to maximum). The number of the test in the sequence is displayed, together with the words ‘IN PROGRESS’.

Figure 8. Applied voltage display screen.

Figure 7. Initial stand time display screen.

TIME REMAINING

01:00

INITIAL STAND TIME

STOP

5 MINUTE TEST

XX kV

TEST 1

IN PROGRESS

STOP

5 MINUTE TEST

STIR MODE

START

STIRRING: MAGNETIC

2.5

Figure 6. Initial Stir Mode selection display screen.

4. When breakdown occurs (or if the maximum voltage is reached) the test voltage is cut off, the high voltage indicator light goes out and the test set begins its oil sample stirring period. The stirrer rotates for a period of 30 seconds and the breakdown voltage value of the previous test is retained on the display. The display screen appears similar to figure 9.

Stirring time remaining is shown, alternating with the word ‘STIRRING’.

5. When stirring has finished the display indicates that the 30 seconds intermediate standing period is being undertaken and time remaining is shown, alternating with the word ‘STANDING’. The breakdown voltage is retained on the display, which appears similar to figure 10.

6. When step (5) is finished the test voltage then begins to rise again as in step (3), this time for ‘TEST 2’, and the cycle of events repeats.

7. Steps (3), (4), (5) and (6) are repeated so that the test voltage is applied for a third time. After the test voltage has been cut of

f on the third test, the display shows the average breakdown

voltage value of the three tests in the sequence. The display appears similar to figure 11.

The three control keys now assume different functions. Press the left hand key labelled VIEW to sequentially display the breakdown voltage value of each individual test, followed by their standard deviation value. If the automatic print option is pre-selected, the results will be printed automatically at the conclusion of a test sequence. If not, press the centre key, labelled PRINT to obtain a print-out of the results. When the printer is in operation, the display shows ‘PRINTING PLEASE W

AIT’.

Press the NEW key to return to the start of the 5 MINUTE test, followed by the left hand START key to repeat a test sequence, or the MENU key to return to the main menu.

Figure 9. Stirring mode display screen.

Figure 10. Intermediate stand time display screen.

Figure 11.

Average breakdown voltage display screen.

Operation

XX kV

TEST 1

5 MINUTE TEST

00:30

STOP

XX kV

TEST 1

STANDING

5 MINUTE TEST

STOP

XX kV

5 MINUTE TEST

AVERAGE VOLTAGE

VIEW

NEW

Note:- At any time during a test sequence the right hand control key labelled STOP can be used to end

a test and return to the test option display screen. Similarly during printing the left hand key labelled STOP can be used to stop the print function and return to the average breakdown display screen.

AS 1767, BS 148, BS 5874, CEI 10-1, EN60156, IEC 156, IP 295, NFC 27, ΓOCT 6581, SABS 555, S

TAS286, UNE 21 and VDE 0370 tests.

Note:- These specifications give the option of using spherical or mushroom shaped electrodes.

1. To commence, highlight the selected test on the main menu and press SELECT. The display will appear similar to figure 6. Press the right hand key marked MENU to return to main menu. Repeated pressing of the centre key labelled STIR MODE changes the stirring choice through MAGNETIC, IMPELLER or NONE.

2 On pressing the START key, TEST 1 is initiated. The display appears similar to figure 7. The

display indicates that the initial stand time is being undertaken and time remaining is shown in minutes and seconds.

3. After the initial stand time is complete the high voltage is switched on and applied to the oil sample. The screen display appears similar to figure 8.

The display shows the voltage rising at the rate of 2kV/s being applied. This voltage rise continues until breakdown occurs (or up to maximum). The number of the test in the sequence is displayed together with the words ‘IN PROGRESS’.

4. When breakdown occurs (or if the maximum voltage is reached) the test voltage is cut off, the high voltage indicator light goes out and the test set begins its intermediate stirring period. The stirrer rotates for a period of 1 minute and the previous breakdown voltage is retained on the display. The display screen appears similar to figure 9.

Time remaining for stirring is displayed, alternating with the word ‘STIRRING’, unless stirring is continuous (see page 7).

5. When stirring has finished the display indicates that the intermediate standing period is being undertaken. Time remaining is shown, alternating with the word ‘STANDING’. The previous breakdown voltage is retained on the display, which appears similar to figure 10.

6. The test voltage then begins to rise again as in step (2), this time for TEST 2, and the cycle of events repeats.

For these specifications there are 6 consecutive tests.

After the test voltage has been cut off on the last test, the display shows the average breakdown voltage value from the 6 tests in the sequence. The display appears similar to figure 11.

Note:- (1) NFC27, STAS286 and UNE21 test specifications differ from the above in that the last 5 of the

6 results are used to calculate the average and standard deviation. (2) The programme for the BS 148 test sets a pass limit of 30 kV

, as required by the specification for this standard.

, labelled PRINT

to obtain a print-out of the

results. When the printer is in operation the display shows ‘PRINTING PLEASE W

AIT’. Press the NEW key to return to the start of the selected test, followed by the left hand START key to repeat a test sequence, or the MENU key to return to the main menu.

Note:- At any time during a test sequence pressing the right hand key labelled STOP will end a test and

return to the test option display. Similarly during printing, the left hand key labelled STOP can be used to stop the print function and return to the average breakdown display screen.

ASTM D877 test

Note:- This specification does not require stirring. Do not fit a magnetic stirrer bar.

1. To commence the test, highlight ASTM D877 on the main menu and press SELECT.

he display will appear similar to figure 7.

2. On pressing the START key, TEST 1 is initiated and the display appears similar to figure 7.

The display indicates that the 2 minute 20 second initial stand time is being undertaken, and time remaining is shown. After the initial stand time is complete the high voltage is switched on and applied. The display appears similar to figure 8.

The high voltage indicator light is illuminated, and the display shows the voltage rising at the rate of 3 kV/s being applied. This voltage rise continues until breakdown occurs (or up to maximum). The number of the test in the sequence is displayed together with the words ‘IN PROGRESS’.

3. When breakdown occurs (or if the maximum voltage is reached) the test voltage is cut off, the high voltage indicator light goes out and the display indicates that the 1 minute intermediate standing period is being undertaken. Time remaining is displayed, alternating with the word ‘STANDING’. The previous breakdown voltage is retained on the display, which appears similar to figure 10.

4. When the intermediate stand time has finished the test voltage begins to rise again as in step (2), this time for TEST 2, and the cycle of events repeats.

5. For this specification there are 5 consecutive tests. After the test voltage has been cut off on the last test, the display shows the average breakdown voltage value of the 5 tests in the sequence. The display appears similar to figure 11.

The three control keys now assume different functions. Press the left hand key labelled VIEW to sequentially display the breakdown voltage values of each individual test, followed by their standard deviation value.

If the automatic print option is pre-selected, the results will be printed automatically at the conclusion of a test sequence. If not, press the centre key, labelled PRINT to obtain a print-out of the results. When the printer is in operation the display shows ‘PRINTING PLEASE WAIT’.

Press the NEW key to return to the start of the

ASTMD877 test followed by the left hand STAR

key to repeat a test sequence or the MENU key to return to the main menu.

Note:- At any time during a test sequence, pressing the right hand control key, labelled STOP will end a

test and return to the test option display. Similarly during printing the left hand key labelled STOP can be used to stop the print function and return to the average breakdown display.

ASTM D1816 test

Note:- This test requires continuous stirring by a paddle type stirrer, using the special vessel available

for this specification. See figure 12. The test can be performed with standard oil test vessels but this will not conform to the specification. The magnetic stirrer may be selected if required. The paddle stirrer is connected to the socket in the rear of the test chamber at the time the test vessel is placed on the high voltage horns.

1. To commence the test, highlight ASTM D1816-84a on the main menu and press SELECT. The display will appear similar to figure 6. Repeated pressing of the centre key labelled STIRMODE changes the stirring choice through MAGNETIC, IMPELLER or NONE. Press the right hand key labelled MENU to return to the main menu.

2. On pressing the START key, TEST 1 is initiated and the display appears similar to figure 7.

If selected, the stirrer operates and continues to do so throughout the test sequence.

The display indicates the stirring mode selected and that the 3 minute initial stand time is being undertaken. Initial stand time remaining is shown in minutes and seconds.

Operation

3. After the initial stand time is complete the high voltage is switched on and applied to the oilsample. The display appears similar to figure 8.

The high voltage indicator light is illuminated, and the display shows the voltage rising at the rate of 0,5 kV/s being applied. This voltage rise continues until breakdown occurs (or up to maximum). The number of the test in the sequence is displayed together with the words ‘IN PROGRESS’.

4. When breakdown occurs (or if the maximum voltage is reached) the test voltage is cut off, the high voltage indicator light goes out and the display indicates that the 1 minute intermediate stirring period is being undertaken. Stirring time remaining is shown in seconds, alternating with the word ‘STIRRING’. The previous breakdown voltage is retained on the display, which appears similar to figure 9.

5. When the intermediate stir time has finished the test voltage begins to rise again as in step (3), this time for TEST 2, and the cycle of events repeats.

6. For this specification there are 5 consecutive tests. After the test voltage has been cut off on the last test, the display shows the average breakdown voltage value from the 5 tests in the sequence. The display appears similar to figure 11.

AIT’.

Press the NEW key to return to the start of the ASTM D1816 test, followed by the left hand START key to repeat a test sequence or the MENU key to return to the main menu.

Note:- At any time during a test sequence, pressing the right hand key labelled STOP will end a test

and return to the test option display

. Similarly during printing the left hand key labelled ST

can be used to stop the print function and return to the average breakdown display.

Figure 12. Oil test vessel for ASTM D1816 specification.

CUSTOM Test

This option is included so that users can program their own test parameters. Custom test is therefore ideal for setting up other oil testing specifications. Up to five separate CUSTOM tests can be programmed, and once established are stored in memory for use on future occasions.

rogramming a CUSTOM test

1. From the main menu select CUSTOM. The display will appear similar to figure 13.

The three control keys have the functions NEXT, SELECT and MENU.

Pressing the NEXT key moves on to the next (of the 5 available) CUSTOM tests.

Pressing MENU moves back to the main menu. Pressing SELECT moves into the programming and testing options for that particular CUSTOM test. The control key functions changes to START, PROGRAM and QUIT. Pressing QUIT moves back to the previous display. Pressing START initiates a test sequence based upon the parameters displayed. Pressing PROGRAM enables the test parameters to be altered.

2. To alter the test parameters, press the centre key labelled PROGRAM. The function of the three control keys now become CHANGE, PRINT and QUIT. Pressing QUIT moves back to the previous sub-menu and pressing PRINT provides a print-out of the test parameters in view on the display.

3. Press the left hand CHANGE key to enter the sub-menu for setting the INITIAL STAND TIME. Use the left and centre keys to decrease and increase respectively, the minutes and seconds shown on the display

. Press SELECT when the desired value is set on the display; this makes

the selection and moves into the sub-menu for the next parameter to be set.

Note:- Repeated presses of a key changes the value in 5 second steps. Pressing and holding a key

changes the value in 5 second steps to the next minute value and thereafter in 1 minute steps. (Maximum value 99 minutes 55 seconds).

4. The number of individual tests in a sequence may now be set; again using the the left and centre keys to make the selection. Press SELECT

when the desired value is displayed; this makes the

selection and moves into the sub-menu for the next parameter to be set.

Note:- Repeated presses of a key changes the value in steps of one. Pressing and holding a key

changes the value in steps of one to the next five values and thereafter in steps of five. (Maximum value 99).

5. The rate of rise of the test voltage may now be set; again use the left and centre keys to set the desired rise rate and press SELECT when the desired value is displayed.

Note:- A press of a key changes the value by 0,5 kV/s and there is no rapid change facility. (Maximum

value 5 kV/s).

6. The display now changes to offer oil stirring options. Repeated pressing of the centre key marked MODE changes the stirring choice through MAGNETIC, IMPELLER, or NONE.

If NONE is selected, there will be no intermediate stir. Repeated pressing of the left hand key marked CONT. turns continuous stirring ‘On’ or ‘Off’. If CONT. is selected, there will be no intermediate stand. Press SELECT

when the desired options are showing on the display

Figure 13. CUSTOM Test display screen.

Operation

NO. OF TESTS 1 RISE RATE 2:0 STIR TIME 0:30 STAND TIME 0:45

CUSTOM TEST

SELECT

7. If selected, the intermediate stir time between 0 seconds and 99 minutes 55 seconds may now be set on the display. Increment to the desired time using the left and centre keys and press SELECT.

8. If selected, the intermediate STAND TIME between 0 seconds, and 99 minutes 55 seconds may now be set on the next display. Increment to the desired time using the left and centre keys, and p

ress SELECT.

9. The average start number may now be set by operating the left and centre keys.

Note:- The arrow keys increment to set the number of tests to be used in calculating the average

breakdown voltage and standard deviation. The averaging of the breakdown voltages will start from the number set. For example, if 1 was set all the results will be used to calculate the average. If 3 was set then the first two breakdown voltage values will be ignored when the average is calculated.

10. Press the SELECT key to set the average start and move out of the set-up mode. The parameters that have been set for the CUSTOM test are now displayed. Press the QUIT key to move back to the sub display giving the option to START a test, or press QUIT again followed by NEXT to enable another CUSTOM test sequence to be set.

Performing a CUSTOM test

1. Obtain the START option and press the key. The oil test set will now automatically perform a sequence of individual tests according to the customised programme. The average value and standard deviation will be given at the end, together with the options to review and print the results.

2. Pressing the NEW key followed by the QUIT and then the MENU key is the route back to the main menu.

WITHSTAND (PROOF) TESTS

There are three types of Withstand (proof) test available. Following an optional, selected stand time, the tests subject the oil sample to a selected withstand voltage for one minute, to see if breakdown occurs.

Withstand test ‘A’ causes the voltage to rise to a set value, remain there for one minute and then be removed (if breakdown does not occur beforehand).

ithstand test ‘B’

causes the voltage to rise to a set value, remain for one minute and then be further

increased to maximum or the breakdown point whichever occurs sooner.

BS5730 test causes the voltage to rise to 22kV, 30kV or 40kV (depending on the selected installation category and electrode gap) for 1 minute. If breakdown occurs, another 2 tests are automatically carried out. Both these tests must pass for the sample to be accepted.

Withstand test ‘A’

1. From the main menu select the WITHSTAND option. On the display the function of the three

control keys changes to A, B and MENU. (Pressing MENU returns to the main menu options screen).

2. Press the left hand key labelled A. The display changes to appear similar to figure 14.

Figure 14. Withstand test initial stand time selection display screen.

INITIAL

STAND TIME

00:30

ENABLED:YES

WITHSTAND A

YES/NO

SELECT

s t

Initial stand time is displayed. Repeated pressing of the left hand key changes ENABLED: to YES or NO. To accept the displayed initial stand time, choose YES and press SELECT. To alter the displayed initial stand time, press the centre arrows key. The display then moves to a sub display to alter and set the initial stand time between 0 seconds and 99 minutes 55 seconds.Increment to the desired time using the left and centre keys, and press SELECT.

ote:-Repeated presses of a key changes the value in 5 second steps. Pressing and holding a key

changes the value in 5 second steps to the next minute value and thereafter in 1 minute steps.

3. The display now changes to show the Withstand voltage level and allow it to be altered as required. The display appears similar to figure 15.

Use the left and centre keys to increase or decrease the withstand test voltage to the required level.

Note:- Repeated individual presses of a key changes the value in 1 kV steps. Pressing and holding a

key changes the value in 1 kV steps to the next 5 kV value and thereafter in 5kV steps.

4. Press SELECT to move to the test option display as shown in the example of figure 16

5. The QUIT option moves back to the withstand test choice display.

6. Press and hold the STIR key to stir the oil sample if required.

7. Press the START key to begin a test. The test voltage will increase at 2 kV/s to the level set and remain there for 1 minute (unless breakdown occurs first). The display shows the time for which the voltage is applied.

8. The test voltage is automatically removed after 1 minute and the result of the test displayed. Options are now displayed to PRINT the result or to perform a NEW test.

9. Press NEW to go back to the test option screen ready for a repeat test. From this option press QUIT followed by MENU to return to the main menu.

Figure 16. W

ithstand test option display screen.

Figure 15. Withstand test voltage level display screen.

Operation

WITHSTAND

STIR

START

QUIT

30kV

WITHSTAND A

SELECT

Withstand test ‘B’

Follow the procedure for Withstand test ‘A’, but note that after the test voltage has been maintained for 1 minute it will continue to rise at 2 kV/s to the breakdown point or to the maximum value, before it is automatically removed.

BS5730a test

1. With reference to BS 5730a, adjust and set the appropriate electrode gap of 2,5mm or 4,0mm.

2. From the main menu highlight and select BS5730a. The display will appear similar to figure 17.

3. Pressing MENU moves to the main menu. With reference to BS 5730a, select the appropriate EQUIPMENT CATEGORY by pressing the left or centre key.

4. The display now changes to appear similar to figure 18. Press the left or centre key to select the electrode gap setting of either 2,5mm or 4,0mm. Pressing QUIT returns to the previous sub display.

5. The display will now change to show the correct withstand voltage together with the selected electrode gap. Assuming that the 2,5mm key was operated, the display would appear similar to figure 19.

Repeated pressing of the centre key marked STIR MODE changes the choice of stirring through MAGNETIC, IMPELLER or NONE. Pressing QUIT returns to the previous sub menu.

Figure 17. BS5730a Equipment Category selection display screen.

Figure 18. BS5730a electrode gap selection display screen.

Figure 19. BS5730a Test start display screen.

BS 5730a: A, D

QUIT

2.5mm

4.0mm

SELECT GAP

BS 5730a: A, D

QUIT

VOLTAGE: 30kV

START STIR MODE

STIRRING: MAGNETIC

2.5

BS5730a:1979

SELECT

EQUIPMENT

CATEGORY

A, D

B, C, E, F

6. On pressing the START key, the automatic test sequence is initiated, and the voltage is displayed ramping up to the withstand voltage level. Pressing the right hand key labelled STOP will abort the test, and return to the original display. On successfully attaining the upper voltage limit, the display will appear similar to figure 10. Elapsing time (in seconds) is indicated, until 1 minute has elapsed, or breakdown has occurred.

. The sequence of events now depends on the results of the first test. If the test was successful

no further testing takes place. The display appears similar to figure 20.

8. If the first test fails the requirements of BS 5730a, two further consecutive successful tests mustbe performed. Prior to the repeat withstand voltage application, a 1 minute stir followed by a 1 minute stand period is automatically performed.

9. The second application of the withstand voltage will automatically occur next, with the sequence repeating step (6) above. The display will indicate the actual test number in progress.

10. The sequence of events now depends on the result of the second test. If the second test is unsuccessful, no further testing takes place.The display appears similar to figure 21.

Pressing the left hand key labelled VIEW changes the top half of the display to show the break down voltages, together with the pass limit voltage. The display appears similar to figure 22.

If the automatic print out option is pre-selected, the results will be automatically printed. If not, press the centre key labelled PRINT

to obtain a print out of the results. When the printer is in

operation, the display shows ‘PLEASE WAIT PRINTING’.

If the second test was successful, a third test must be performed. Prior to the repeat withstand voltage application, a 1 minute stir followed by a 1 minute stand period is automatically performed.

12. A third application of the withstand voltage will occur next, with the sequence repeating step (9) above.

The display indicates the actual test number in progress.

13. If the third test was successful, the display will appear similar to figure 20. An unsuccessful third test will prompt a display similar to figure 21, and no further testing takes place.

Figure 20. BS5730a PASS-FAIL display screens. Figure 21.

Figure 22. BS5730a Results display screen.

Operation

PASS LIMIT: 30kV

PASS

GAP: 2.5mm

BS 5730a: A, D

VIEW

NEW

TEST 1: 28.6kV TEST 2: 26.3kV

PASS LIMIT: 30kV

BS 5730a: A, D

VIEW

NEW

PASS LIMIT: 30kV

FAIL

GAP: 2.5mm

BS 5730a:A, D

VIEW

NEW

14. On completion of the test(s) (1, 2 or 3 may have been performed), the appropriate PASS or FAIL message is displayed. Pressing the right hand key labelled NEW returns to the EQUIPMENT CATEGORY selection display screen. Pressing the left hand key labelled VIEWchanges the top half of the display to list the breakdown voltage(s), together with the pass limit voltage. The display appears similar to figure 22.

f the automatic print out option is pre-selected, the results will be automatically printed. If not, press the centre key labelled PRINT to obtain a print out of the results. When the printer is in operation, the display shows ‘PLEASE WAIT PRINTING’.

Note:- At any time during a test sequence, pressing the right hand key labelled STOP will end a test

and return to EQUIPMENTCATEGORY selection display. Similarly during printing the left hand key labelled STOP can be used to stop the print function and return to the test result display.

SELF CHECK Tests

The SELF CHECK option enables the following parts of the circuit to be checked:-

NOVRAM (Non Volatile Random Access Memory) KEYBOARD DISPLAY CONTRAST DISPLAY BACKLIGHT TIME / DATE PRINTER (Internal and External) STIR RISING VOLTAGE WATCHDOG TIMER

Note:- It is not necessary to have the oil test vessel filled with sample oil for the SELF CHECK tests,

but a vessel with a stirrer is necessary.

1. From the main menu select the SELF CHECK option. The first display to appear gives a warning that a NOVRAM test will clear the memory. The option keys take the labels YES; NO and QUIT. Pressing the QUIT key returns you to the main menu.

Caution:- If the YES button is pressed, the NOVRAM memory will be cleared. This will

include the parameters set up for CUSTOM and WITHSTAND tests as well as any results data. If this information is needed then the YES button must NOT be pressed.

2. Pressing the NO key bypasses the NOVRAM test and moves straight to the KEYBOARD test. Press the left arrow key and then the right hand key

. When pressed, each key displays its

number to indicate that it is active.

3. The DISPLAY CONTRAST test is now presented, and a grid appears on the display. The left and centre arrow keys can be used to increase or decrease the display contrast. Press SELECT to move on to the DISPLAY BACKLIGHT test. Use the left and centre arrow keys to turn the light ‘On’

and ‘Of

’.

4. Press the SELECT key and the current TIME and DATE will be displayed and checked. If all is in order, the message ‘TESTPASSED’ will be displayed.

Pressing the NEXT

key brings into effect a PRINTERS test. The internal printer is checked, and

then the external printer (if fitted).

The option to ST

the test is given.

6. Pressing the NEXT key starts the STIRRING TEST which lasts for one minute, and is

automatically followed by the RISING VOL

AGE test. (Options to RETEST or NEXT are given).

7. Before the screen automatically returns to the main menu, a WATCHDOG test is performed. The WATCHDOG TIMER ensures that the microprocessor is constantly running.

Calibration Check

The optional OTS/VCM100 calibrator provides the means to carry out a quick calibration check of the test set high voltage output. The calibrator fits onto the test chamber cradle terminals in place of a test vessel, and voltage indication is viewed on an analogue meter marked from 0 to 100kV in 2kV divisions (accuracy 3%).The scale also shows pass tolerance bands to enable a quick assessment of the a

ccuracy to be made. The design ensures that the load to the test set transformer is similar to the load

during an oil dielectric strength test.

Using the OTS/ VCM100

1. Place the VCM100 on the cradle terminals at the top of the support horns.

2. From the main menu select CHECK CALIBRATION. The display will appear similar to figure 24.

3. If a hard copy of the test results is required, press the centre key marked PRINT to obtain a calibration check list. This enables the user to manually record the calibrator readings as the test proceeds. When the printer is in operation, the display shows ‘PRINTING PLEASE WAIT’.

4. On pressing START, the check sequence is initiated. The voltage ramps up from 0kV to the maximum voltage value, pausing at each 10kV point for a period of 10 seconds. This enables the oil test set indicated voltage to be verified against the calibrator.

Note:- At any time during a test sequence the right hand control key labelled ST

can be used to

enda test and return to the first screen display

5. If required, write down each analogue reading on the print out check list.

6. Press the right hand key marked MENU to return to the main menu.

Figure 23. OTS/VCM100 Calibrator.

Figure 24. OTS/VCM100 Calibrator.

Operation

CHECK CALIBRATION

START

USE OTS/VCM 100

Printer Facilities

Paper feed key

The printer paper feed key, situated adjacent to the On/Off switch, may be pressed at any time (when the test set is switched on) to advance the paper roll.

Replacing a printer paper roll

Do not replace the printer paper roll while a test is being conducted.

1. Remove the printer cover by releasing its two fasteners, by giving them each a 1/4 turn.

2. Remove what remains of the old paper roll, noting where the paper feeds into the printer head, and place a new roll into the roll tray.

3. Keeping the edge of the paper ‘sharp’ and straight, feed the end of the paper through the printer head. It slots in at the bottom just behind the ribbon carrier. Use the paper feed key to advance the paper through the printer head.

4. Feed the paper through the slot in the printer cover then replace the cover and secure its fasteners by giving them a 1/4 turn.

Connecting an external printer

Connect the external printer to the 9 way ‘D’ type plug on the mains input panel at the rear of the test set.

Lead connections are as shown in figure 25.

Oil test set Typical Printer 9-way ‘D’ type plug 25-way ‘D’ type socket

pin 3 data from oil test set to pin 3 pin 5 signal ground to pin 7 pin 6 printer busy line to pin 20

pins 1, 7, 8 not connected pins 2, 4, 9 reserved

Figure 25. Typical 9 & 25 Way ‘D’ type plug and socket connections to external printer.

Downloading Results to a PC

o transfer test results to a PC, connect a suitable cable (see below) between the RS232 socket on the

OTS and a serial port on the PC. A suitable communications program is required on the PC.

When the OTS is set to print to an external printer, text will appear on the PC display, which may be copied to other programs for storage or calculation.

RS232 Cable

he following shows the cable connections which has been found to work with Microsoft

erminal and

Hyperterminal programs:-

PC: ‘D’ type socket OTSAF/2 9 pin ‘D’ type socket

Function 25 Pin 9 Pin Pin Function

RXD (i/p) 3 2 3 TXD (o/p)

GND 7 5 5 GND

RTS (o/p) 4 7 6 Busy (i/p)

DCD (i/p) 8 1

DTR (o/p) 20 4 Joined together

DSR (i/p) 6 6

1, 7, 8 Not connected. 2, 4, 9 Reserved - Do not connect.

Shell Braid Shell

(Screen)

Configuring the OTS

From the main menu, choose OPTIONS and then PRINTER CONTROL. Verify the following settings:-

Baud Rate - 9600

Ext. Printer - ON

It may be useful to set AUTOPRINT to

On, which will cause the OTS to output data automatically after

each test sequence.

Refer to page13 ‘

Setting the Printer options‘

for further information on how to do this.

Configuring the PC Communication Program

The following settings have been found to work with Microsoft®Terminal and Hyperterminal programs.

Baud Rate - 9600

Data Bits - 8

Parity

- None

Stop Bits - 1

Flow Control

Hardware

Operation

Print Out Information

Each print out provides all information related to the specific test carried out. Headings are also provided for insertion of sample identification and ambient temperature. Where a standard oil test specification allows different electrode shape and/or gap, these will be shown on the printout so that the user can indicate which were used.

Fuse Replacement

Three fuses are fitted in holders mounted on the mains input panel at the rear of the instrument. Ensure that the test set is disconnected from the supply before fuses are replaced. To replace a fuse unscrew and remove the cap in the centre of the holder. Remove the fuse, replace with a new one of the correct size and rating, and refit the cap.

It is important that fuses of the correct rating and type are fitted, (see Specification for details). FS1 is the mains power supply fuse, 2A rating for a 220 V/240 V supply and 4 A rating for a 110V/120V supply. FS2 and FS3 are internal power supply fuses of 6,3 A rating.

Figure 26.

ypical test sequence print-out.

The following notes are mainly intended for the guidance of those whose experience in the subject may be limited. The notes should be read in conjunction with the relevant oil testing specifications.

Causes of Bad Oil

Transformers and switchgear oil may be rendered unsuitable for further use due to four main reasons:-

1. Low dielectric strength. 2

. High acidity.

3. High sludge content.

4. Excessive free water content.

Low dielectric strength may result from many causes, the most common of which is foreign particles or fibres and water in combination. Individually their effect may be relatively small, but together a contamination of only a few parts in a million can cause considerable lowering of the breakdown voltage of the oil. High acidity, sludge and free water should not be tolerated, but will not necessarily reduce the dielectric strength below acceptable or specified levels.

Appearance of the Sample

Only an experienced person can judge the condition of an insulating oil from its appearance, but a general guide may be obtained from the following observations:-

1. A cloudy appearance may indicate that sludge has been formed.

2. A dark yellow colour could be a sign of overheating.

3. A blackish colour often results from an arc having taken place with either carbonisation of the oil or of the insulation within the equipment.

4. A green colour may be due to copper salts dissolving in the oil.

Cleanliness of the Apparatus

The necessity for scrupulous cleanliness in the apparatus and during the process of sampling, cannot be over emphasised. The measurement of the dielectric strength of the sample is as dependent on the cleanliness of the test cell and the sampling apparatus as the condition of the oil itself.

After cleaning the apparatus, it should under no circumstances be wiped, dried or even handled with a dusty or fibrous cloth as loose dust or fibres are liable to cause contamination.

Precautions Necessary During Sampling

Since the oil taken from a drain cock will inevitably contain an excess of settled out solid impurities, and will not necessarily be representative of the bulk of the oil, it should be run to waste until clear.

Always run off a quantity of oil into a glass bottle or a test tube for an initial check on the appearance of the oil. Attention to this point may prevent contamination of a clean test vessel.

If necessary, thoroughly clean and dry the sample point using a suitable solvent. Any cloth used should be lint free. Open the sample cock and drain to waste enough oil to ensure that the sample cock is fully flushed and the sample is representative of the bulk of oil to be tested. This quantity will depend upon the size of the transformer or main container. About 2 litres is usually suitable.

When sampling from a drum or supply container, the oil should flow at a steady rate into the test vessel and after being swilled around the sides it should be discarded. Without altering the rate of flow of the oil the quantity required for the test should then be run of

f while taking extreme care to prevent the ingress of atmospheric dust, cloth fibres or moisture. Do not use a syphon. In the absence of a useable sample point, use a ‘thief’.

Shield the sample from direct light until ready to be tested.

urbulence and air bubbles should be avoided when pouring the oil. Relevant national specifications

should be observed.

Particular care to prevent contamination is necessary when a test is to be made on a bulk delivery tanker, and on all occasions when a high value of dielectric strength is anticipated. The procedure suggested above should be rigorously applied.

Sampling and Testing Oil for Dielectric Strength

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