insulation resistance tester model: irb …userequip.com/files/specs/5995/irb10000_user...

INSULATION RESISTANCE TESTER

MODEL: IRB-10,000

OPERATING INSTRUCTIONS

Manual Version 1.0 July 2002

OPERATING INSTRUCTIONS MODEL: IRB-10000

ADWEL International Ltd.

HEAD OFFICE EUROPEAN OFFICE 50 Ironside Crescent, Unit 6 Scarborough, Ontario M1X 1G4 CANADA Telephone: 1- 416-321-1988 Toll Free: 1-800-463-9371 Fax: 1-416-321-1991 e-mail: [email protected] Website: http://www.adwel.com

Park House, Greenhill Crescent Watford Business Park Watford, Herts WD18 8PH UNITED KINGDOM Telephone: 44-(0) 1923-254433 Fax: 44-(0) 1923-218278 e-mail: [email protected]

2002 ADWEL International Limited, Canada

Copyright in this document is owned by ADWEL International Limited except for information supplied by other parties. No reproduction of the whole or any part is to be made without the authority of ADWEL International Limited

OPERATING INSTRUCTIONS MODEL: IRB-10000

TABLE OF CONTENTS

PAGE 1 DESCRIPTION PAGE 2 SPECIFICATIONS PAGE 3 INSULATION TESTING PAGE 4 MODE OF OPERATION AND DESIGN PAGE 6 FIGURE 1 - DIAGRAM OF IRB-10,000 PAGE 7 FIGURE 2 - VOLTAGE PLOT PAGE 8 SHOCK HAZARD PAGE 9 RESISTANCE OF CAPACITORS PAGE 10 CHARGING TIME OF CAPACITORS PAGE 11 OPERATING INSTRUCTIONS PAGE 14 FAULT DETECTION PAGE 15 TESTING WITH GUARD TERMINAL PAGE 16 FIGURE 3 - GUARD CIRCUIT PAGE 17 TRANSFORMER TEST GUIDE

1. DESCRIPTION

The Model IRB-10,000 is designed to indicate directly on a panel meter the resistance value of any "resistor" within the range of 0 to 10,000,000 megohms. The applied test voltage to the unknown resistance can be selected between 0 to 10,000 Volts DC continuously variable or in steps at 500, 1,000, 2,500, 5,000 and 10,000 Volts DC. Checking the insulation resistance of electric conductors, wire, cables, motors, transformers, capacitors, high voltage bushings and insulators, as well as complete installation, is one of the most important of all safety measures.

The pertinent safety regulations prescribe the permissible minimum values of insulation resistance for given operating conditions. The Model IRB-10,000 is a precision instrument incorporating the latest innovations in solid state technology with many decisive advantages over other more conventional but now outdated designs. The instrument is completely self-contained, portable, and can be battery or line operated. The absence of any handle to crank eliminates both bodily effort and vibration, permitting comfortable and accurate reading anywhere, independent of available line power. Tests can be performed accurately to CSA, IEEE, VDE, NETA, ANSI, ASTM, NEMA or MIL specifications. Up to 2,000 measurements can be made with the special large capacity Gel-Cell batteries which are rechargeable by means of the built-in charger. The instrument is supplied in a sturdy military style fibreglass case to withstand rough field use.

OPERATING INSTRUCTIONS MODEL: IRB-10000 1

2. SPECIFICATIONS

POWER INPUT 120V, 60 Hz (240V, 50 Hz available) TEST VOLTAGES 500/1,000/2,500/5,000/10,000 V regulated to ± .1% 0-10,000 VDC continuously variable. VOLTAGE SOURCE Solid state DC-DC inverter controlled and

stabilized by integrated circuit amplifiers. RANGE 0-500 Megohm on Scale I @ 500V current

limited to 200 microamperes maximum on short circuit.

10 - 10,000 Megohm @ 500 V on Scale II 20 - 20,000 Megohm @ 1,000 V on Scale II 50 - 50,000 Megohm @ 2,500 V on Scale II 100 - 100,000 Megohm @ 5,000 V on Scale II 100 -200,000 Megohm @ 10,000 V on Scale II

in addition, any scale can be increased by a factor of 10 by depressing expander button.

METERING 2 range Voltmeter 2 range Megohmmeter Direct reading battery condition indicator. Meters are fully protected against overload. ACCURACY Voltmeter - ± 1% of full scale Megohmmeter - ± 2% of midscale reading

± 10% at high end of scale CHECK Internal 100 Megohm ± 1% Standard SWITCHING Low Voltage Start interlocked range and test

voltage switch. Pushbutton Power Supply mode switch. HOLD-TEST lever type test actuator. TERMINALS UNKNOWN (+), GROUND (-) and GUARD

(unmeasured leakage). BATTERIES 2 sealed GEL-CELLS, 12 Volts, 4.5 AH each

BATTERY CHARGER Automatic current regulated voltage crossover

charger. CABINET Fibreglass Case (including lid) 38 x 38 x 24 cm 15 x 15 x 9 ½" WEIGHT 14 Kg. (30 lbs.)


3. INSULATION TESTING

In testing the insulation of electrical machinery, transformers, etc. the leakage resistance is only one of several parameters that have a bearing on the condition of the insulation. Routine measurements of capacitance and dissipation factor, as well as leakage resistance, provide useful data in monitoring the condition of the insulator and in guarding against incipient breakdown. A routine test that has been fairly widely adopted in the insulation testing field consists of measuring the apparent leakage resistance after a test voltage of 500 volts has been applied for one minute, and again for ten minutes. The ratio of the indicated resistances, sometimes referred to as the polarization index, can have some relation to the condition of the insulator. The results are a measure of the charging current at the two time intervals and can be much more dependent on the dielectric absorption of the insulator than on its true leakage resistance. To extend the usefulness of such information, complete charge-current vs time data should be obtained. The Model IRB-10,000 is useful in measuring the true leakage resistance by the method outlined in Section 8. and in measuring the apparent leakage at the end of one minute and ten minute intervals. The charge current is easily measured when the meter is on scale. The charge current is the applied voltage divided by the apparent resistance at any moment. The meter will be off scale at the start of the charge current vs time characteristic.



4. MODE OF OPERATION

A solid state control circuit maintains a test voltage constant to better than ± .1%, permitting the use of a simple sensitive moving coil meter movement instead of the traditional ratiometer movement or delicate high gain amplifiers which are generally used and subject to zero drifts.

AND DESIGN

The Model IRB-10,000 is a direct reading resistance meter in which the actual measured resistance is determined by the measurement of a current at a known fixed stabilized voltage.

Figure 1 (Page 6) shows a simplified diagram of the IRB-10,000. The heart of the instrument is the regulated power supply. Due to its stability to supply voltage fluctuations it is possible to achieve extremely accurate resistance readings even on a highly capacitive specimen without violent fluctuation of the Megohmmeter as is typical on conventional Insulation Resistance Testers. The regulated DC test voltage is programmed by a resistor network with trimmers for fine adjustment. The measuring voltage is pure DC with very low ripple superimposed AC voltage of less than 0.05% of the rated test voltage. The regulated supply derives its power either from the internal battery or from a regulated supply powered by the line. The line operated supply also acts as a regulated current battery charger. The battery is charged with about 250mA until its voltage reaches a carefully preset level. At this time, the automatic battery charger cuts the charging current to a low trickle level of about 25mA. When the line supply is used to power the high voltage supply it is programmed to a constant voltage supply with a current overload protection of about 500 mA. During line operation, the battery will be on a low trickle charge of approximately 20mA to maintain full capacity. A battery voltage meter will indicate the condition of the battery when the instrument is switched to the battery mode of operation. The instrument is equipped with two special sealed Gel-Cells. These batteries are extremely compact and lightweight. Their shelf-life is excellent and the self-discharge is about 3% per month. The test voltage and range can be selected by the large knob in the centre of the panel. It must be noted that the instrument has a unique interlocking feature, that allows the tester to be used only by starting in the lowest test voltage and lowest scale. This feature protects the instrument, the item under test and the operator. If on this low range any meter reading indicates less than 5 megohms or even zero (0), it is evident that the item under test is either short-circuited or has insulation resistance of very poor quality.


4. MODE OF OPERATION AND DESIGN (Continued)

For resistances below 5 Megohms on Scale I the voltage at the object to be measured will be well below the rated 500 volts. This range must not be considered a measuring range, it merely constitutes a range of indication for resistances falling below permissible minimum values or short circuits. The voltage at the terminals when using Scale I depends on the resistance of the specimen. Figure 2 (Page 7) plots the voltage against the indicated value. On all other ranges the series protection-current-limiting resistor will be shorted by RLV and the item under test will be subjected to the full test voltage as indicated on the Voltmeter. Should the item under test break down (arc-over) the meter will still be protected. Prolonged short circuits must be avoided on any range except when using Scale I. The calibration and full scale range on the Megohmmeter is automatically done by the range network coupled to the voltage selector switch. Test voltage may be applied momentarily or can be held for indefinite time lengths via the HOLD-TEST lever switch. The calibration of the instrument can be checked against a built-in 100 Megohm standard via R. The item under test and the instrument itself are always discharged when the test switch is not in the operating position, by RD. Care must be taken as described under "Shock Hazard". In addition to the GROUND and HIGH terminals for the 'UNKNOWN", a GUARD terminal is provided to permit measurements of objects with complicated operating grounding patterns.

B

W

G

+

HIGH

-

GROUND

GUARD

VV

RLV

RDRC

5M

100 M 1M

POWER-SUPPLYLINE

+

CHARGER

BATTERY

REGULATED

NETWORKRANGE

PROGRAMMER

VOLTAGE

SUPPLY

HIGH-VOLTAGE

REGULATED

E

N

I

L

R

FIGURE 1 - IRB-10,000 DIAGRAM


FIGURE 2

OPERATING INSTRUCTIONS 7 MODEL: IRB-10000


5. SHOCK HAZARD

Every precaution has been taken in the design of the Insulation Resistance Tester, Model IRB-10,000, to reduce the possibility of shock. However, the operator should be aware of the dangers involved because of the high voltages present. The resistance to current depends, of course, on humidity conditions. From arm to arm, leg to arm, leg to leg, it can be as low as 300 ohms but under some circumstances, it can be as high as 1 megohm. At low voltages the skin offers a fair protection but at higher voltages the skin is burned, its resistance is lowered and the low internal body resistance is the controlling factor. When the TEST-HOLD switch of the instrument is in an operating position, touching the HIGH terminal is painful and can cause a slight burn. When a large capacitor is connected to the UNKNOWN terminals, it should be treated with great caution because there can be high voltage at its terminals and it may have no appreciable inherent current-limiting series resistance. The current that will flow through the body upon connecting the "body resistance" to its terminals will at first be very great and the speed with which the current is damped depends on the capacitance as well as the resistance. A current-limiting resistor of 1 megohm should be connected as near as possible to the capacitor.


6. RESISTANCE OF CAPACITORS

The leakage resistance of capacitors is measured in exactly the same manner as the resistance of resistors, except that the charge and discharge currents involved require some precautions. Always short-circuit the capacitor for several seconds before connecting to the instrument to assure that is has no dangerous residual charge. Always start the test in the 500 Volt START position and leave the switch in the START position for a few seconds to assure rapid charge of the capacitor. To prevent damage to the meter do not set the range switch to higher values until the capacitor is well charged. When the measurement has been completed, the capacitor will automatically be discharged by a 1 Megohm resistor as the TEST-HOLD switch is returned to the centre OFF position. CAUTION:

Note that when testing large value capacitors the discharge time must be carefully watched.


7. CHARGING TIME OF CAPACITORS

Since the panel meter reading of the instrument depends on the current through the unknown resistor, the leakage resistance of the capacitor or of the insulator cannot be correctly indicated until the charging current due to the capacitive component is negligible. When the capacitor has very little dielectric absorption the charging current is limited mainly by the resistance standard in the instrument. In the START position this resistance is 5 Megohms and for large capacitance values the charging time is in the order of five seconds. Should this time be too long for production testing proceed as follows:

Insert a 1 Megohm resistor in series with the capacitor under test. Start the instrument in the START position and switch to the next position in about 1 second.

The total charge time R will now be reduced by a factor of 5, namely 1 second per microfarad. Many capacitors and most insulators (especially those of laminated structure) exhibit appreciable dielectric absorption (dipole and interfacial polarization). When a voltage is applied, the charge slowly diffuses throughout the volume and it may require minutes or hours (even days in some special cases) before equilibrium is established and the charging current is small compared to the true leakage current. Using the time constant formula R, the discharge time to 37% of the applied voltage can be easily calculated. Since the discharge resistor R is 1 Megohm, simply multiply the capacitance value C by 1 to get the time constant.

On a 10 MFD Capacitor this time will be 10 seconds. As an extra safety precaution it is advisable to discharge the capacitor with a test lead before touching.


8. OPERATING INSTRUCTIONS

8.1 SAFETY

8.1.1 Main selector switch must be in the OFF position.

8.1.2 HOLD-TEST switch should be in the centre OFF position.

8.1.3 Voltmeter should read "0".

8.2 CHECKING MECHANICAL ZERO

8.2.1 Place the instrument in the operating position either horizontal or vertical.

8.2.2 The pointer on the Voltmeter should indicate "0".

8.2.3 The pointer on the Megohmmeter should indicate

infinity. 8.3 CALIBRATION OF INSTRUMENT

The Model IRB-10,000 is factory calibrated and due to the use of ultrastable components will rarely require recalibration.

TO CHECK CALIBRATION PROCEED AS FOLLOWS:

8.3.1 If battery operation is desired, depress the BATT. pushbutton. The Battery meter should now indicate approximately 24 volts.

8.3.2 If line operation is desired, depress the LINE

pushbutton. The instrument must, of course, be connected to a suitable 120 volt, 60 Hz. properly grounded outlet.

8.3.3 Ensure that nothing is connected to the test terminals.

8.3.4 Advance the main selector switch to START – 500

Volts.

8.3.5 Move the HOLD-TEST lever switch to TEST and keep depressed.

8.3.6 While keeping the HOLD-TEST lever switch depressed,

advance the selector switch to the other voltage ranges. The Voltmeter should always indicate the voltage corresponding to the switch position. The Megohmmeter should always indicate infinity in any of the above tests.


8. OPERATING INSTRUCTIONS (Continued)

8.3.7 Ensure the FAULT switch is in the OFF position.

8.3.8 Set the main selector switch to 500 volts START. While keeping the HOLD-TEST lever switch depressed, push the 100 MEG-CHECK pushbutton. The Megohmmeter should indicate 100 Meg on Scale I.

8.3.9 Set the main selector switch to 500 Volt Scale II. While

keeping the HOLD-TEST lever switch depressed, push the 100 MEG-check pushbutton. The Megohmmeter should indicate 100 Meg. on Scale II.

8.3.10 The IRB-10,000 is now ready for operation.

8.4 TESTING OF SPECIMEN CAUTION ....................

Before connecting anything to the instrument terminals make sure the specimen is not energized and no potential of any kind appears across its terminals.

8.4.1 If battery operation is desired depress the BATT. pushbutton. The Battery meter should now indicate about 24 Volts but not less than 20 Volts.

8.4.2 If line operation is desired, or if the battery is below

20V depress the line pushbutton. The instrument must, of course, be connected to a suitable 120 volt, 60 Hz. properly grounded outlet.

8.4.3 Connect the grounded side of the object to be tested

to the nickel plated bare binding post marked Ground. Connect the other side to the terminal marked HIGH.

NOTE: The HIGH terminal is positive.

8.4.4 Advance the main selector switch to 500 V - START.

8.4.5 Depress the HOLD-TEST lever switch to the TEST position.


8. OPERATING INSTRUCTIONS (Continued)

8.4.6 If the reading on the Megohmmeter is above 10 Megohms on Scale I advance the selector switch to the next 500 V position and read the insulation resistance on Scale II.

8.4.7 While keeping the TEST-HOLD switch depressed,

advance the selector switch to the test voltage range desired and read the insulation resistance on Scale II and multiply the reading by the factor indicated on the switch position used.

If it is undesirable to increase the test voltage an increase in range can be achieved by depressing "SCALE II x 10" button. The multiplication factor is 10 times that shown on the switch position as long as the button is depressed.

8.4.8 The TEST-HOLD switch can be let in the HOLD position

if long-time tests are made. For safety reasons it is advisable to use the momentary TEST position.

8.4.9 After completion of test, release the TEST-HOLD

switch, return the main selector switch to OFF and depress the OFF pushbutton.

8.4.10 As the TEST-HOLD switch is released the test voltage

is disconnected and the terminals are shorted by a 1 Megohm resistor to discharge the specimen.

NOTE: See Section 5 SHOCK HAZARD


9. FAULT DETECTION

9.1 To automatically disconnect the instrument under

fault conditions select the FAULT-ON position. (This will cause a shutdown if current exceeds twice the full scale reading at any time.)

9.2 After connecting the specimen as before, rotate

counter-clockwise to START 500 V.

9.3 Rotate 0-10000V ADJUST counter-clockwise to about 1/2 turn from the end.

9.4 Move HOLD-TEST lever to HOLD.

9.5 Rotate VOLTAGE/SCALE TO 0-10,000V.

9.6 Rotate the 0-10,000V ADJUST slowly until the desired

test voltage is reached.

9.7 If a fault is indicated press RESET and start again. Use more gradual voltage increases to ensure sample charge-up transients are not to blame.


10. TESTING WITH GUARD TERMINAL

10.1 The black GUARD terminal provides a means for directing the unwanted current of multiconductor cables, terminals or bushings around the meter an measuring only the desired current or leakage of one conductor by the Megohmmeter.

10.1.1 Connect the return or ground side of the specimen to

be tested to the bare GROUND binding post of the instrument.

10.1.2 Connect all other isolated leads or terminals not under

test to the black GUARD terminal.

Any leakage from the high voltage point to these parts will now be directed around the metering circuit.

10.1.3 Proceed testing as in Sec. 7.4.

See Figure 3 (Page 16) for schematic of Guard Circuit.

HIGH


HIGH-VOLTAGE

SUPPLY GUARD GROUND

FIGURE 3 GUARD CIRCUIT

For Transformers, see Transformer Test Guide

MEGOHM METER CABLE

UNDERTEST

17 OPERATING INSTRUCTIONS MODEL: IRB-10000

Transformer Test Guide In the IRB-10000 the black terminal is the “Guard” terminal. High to Ground: To test the insulation resistance between the High winding of a transformer and ground; ♦ Connect the High winding to red terminal. ♦ Connect the Low winding to black GUARD terminal. ♦ Connect tank to bare GROUND terminal. Low to Ground: To test the insulation resistance between the Low winding of a transformer and ground; ♦ Connect the Low winding to red terminal. ♦ Connect the High winding to black GUARD terminal. ♦ Connect tank to bare GROUND terminal. High to Low: To test the insulation resistance between the High and Low windings of a transformer; ♦ Connect the High winding to the red terminal. ♦ Connect the Low winding to the bare GROUND terminal. This will measure the insulation resistance between High and Low windings but includes the insulation resistance of High to Ground plus Ground to Low. If the influence of High to Ground plus Ground to Low is to be eliminated, the transformer tank must be isolated from ground and connect to the black GUARD terminal.

insulation resistance tester model: irb …userequip.com/files/specs/5995/irb10000_user...

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