A comprehensive 64 page guide to electrical insulation testing containing helpful diagrams, value tables, product information and much more!. over a period of time, and the location and importance of the equipment megohmmeter is connected to the insulation to be tested and is operated for a short. The Dielectric Absorption (or Time-Resistance) test is an extension of the Megger, “A stitch in time – The Complete Guide to Electrical Insulation Testing”, a free.
|Published (Last):||23 October 2017|
|PDF File Size:||18.42 Mb|
|ePub File Size:||18.71 Mb|
|Price:||Free* [*Free Regsitration Required]|
Their presence could unpredictably affect your readings; they should be removed before tests are made.
Megger ‘A Stitch in Time’ Information Booklet on Insulation Testing
Current Leakage at Switches When apparatus is shut down for the insulation resistance test, make sure that the readings are not ni by leakage over or through switches or fuse blocks, etc. It is designed for other uses, too, but for insulation testing it provides: Intermittent Pilot Ignition Control. As explained in the Safety Precautions section, however, insulation testers should never be connected to energized lines or equipment when operated in any of the Insulation Test or Resistance Test modes.
In a series of lecture on basic electronics, learning by doing, we now. As explained previously, in DC testing, this current drops rapidly after the initial charging period. See Use of a Guard Terminal, page This may be considered as good housekeeping, and is essential in the maintenance of all types of electrical equipment. Best Methods for Safe Hipot Testing When working ln electrical safety test equipment, instruments that output potentially dangerous voltages and currents, it is always important to regular review and.
It can raise or lower the More information. Studies show, however, that dew will form in the cracks and crevices of insulation before it is visibly evident on the surface. Lugs should be fitted for attaching to the instrument terminals, and stout spring clips are recommended for connecting to the apparatus or tije under test.
Furthermore, manufacturers of wire, cable, motors, and so on have continually improved their insulations for services in industry.
For preventive maintenance, the motor winding should be cleaned, treated, and dried to restore winding flexibility. Explosion and Fire Hazard So far as is known, there is no fire hazard in the normal use of a Megger insulation tester. Cable fault location in power cables. The increase in resistance for clean and dry insulation occurs in the same manner whether a motor is large or small. Calculation of winding temperature. If you have a line-operated Megger instrument, you ll get best results by running the test 10 minutes, taking readings at 1- and at minutes, to get the polarization index.
With the DC test, you get a more qualitative picture; you can meter the leakage current as you increase the voltage and obtain specific values of insulation resistance. You can check this by insulation resistance tests, ih you have records of previous tests on the apparatus. Check for loose, missing, broken or corroded hardware, pivot pins, cotter pins, springs and other mechanical. Pay particular attention to conductors that lead away from the installation.
With good insulation, the conduction or ij current should build up to a steady value that is constant for the applied voltage, as shown in Fig.
Also you should make tests at about the same temperature, or correct them to the same temperature.
Employees performing cutting or welding must wear the. Make future tests with the same length of operating time.
A Stitch In Time | Megger Insights
The reference temperature for cable is given as 60 F Lecture 2 Power System Analysis Prof. Figure 9 Typical card plot of a time-resistance or double-reading test. It can raise or lower the. Wiring Installation Figure 13 Connections for testing to ground each circuit separately, working from the distribution panel.
Shock Megget from Test Voltage Observe the voltage rating of the Megger instrument and regard it with appropriate caution.
A general purpose motor for use in dry locations which are More information. We have seen that, essentially, good means a relatively high resistance to current. If a discharge function is not provided, a discharge stick should be used.
A Stitch In Time
AC frequently sttich used for high-potential testing; voltage is increased to some specified point to see if the insulation can stand that particular voltage. In some cases, or with certain equipment, drying out may not be necessary. On the other hand, if the pointer shows a gradual increase between the second and the second checks, then you re reasonably sure the windings are in good shape.