How do you find polarity index?
An initial reading of insulation resistance is recorded at one minute and a second reading is taken at 10 minutes. The resistance is measured consecutively and it is not necessary to take further readings beyond 10 minutes. The ratio between the 10-minute and the one-minute measurements provides the Polarization Index.
What is Pi in Megger?
Polarisation index is the ratio of megger value taken for 10 minutes to the megger value taken for 1 minute.
What is the purpose of PI test?
A Predictive Index (PI) Test allows recruiters to evaluate the cognitive abilities, personality traits and behavioral tendencies of a potential employee, to determine if they are the right fit.
Is a Megger AC or DC?
RE: Difference between AC and DC megger All meggers output only DC. What the manual means that it is a ac power operated megger (could be ac motor operated or eletronic) as against the hand-cranked one.
What is a bad reading on a Megger?
What is a bad Megger reading? If the megger reads a resistance under 1 (1,000 ohms) on your meter after the initial 60-second interval, the cable has failed and the cable should be removed. If the megger reads a resistance between 1-1.25 on your meter, then the cable passes.
What is considered a bad Megger reading?
Turn on and read the meter. Anything reading between 2 megohms and 1000 megohms is usually considered a good reading, unless other problems have been noted. Anything less than 2 megohms indicates an insulation problem.
How do you read Megger results?
If the megger reads a resistance under 1 (1,000 ohms) on your meter after the initial 60-second interval, the cable has failed and the cable should be removed. If the megger reads a resistance between 1-1.25 on your meter, then the cable passes. Any reading above 1.25 is considered excellent.
What is the minimum insulation resistance?
Insulation resistance should be approximately one megohm for each 1,000 volts of operating voltage, with a minimum value of one megohm. For example, a motor rated at 2,400 volts should have a minimum insulation resistance of 2.4 megohms.
How do you Megger a circuit?
If you are testing insulation resistance to ground, place the positive probe on the ground wire or the grounded metal junction box and the negative probe on the conductor or terminal. Energize the Megger for 1 minute. Read the value of the resistance at the end of the minute test and note it in your table.
What is a good insulation resistance value?
A general rule-of-thumb is 10 Megohm or more.
| Insulation resistance value | Insulation level |
|---|---|
| 5-10 Megohm | Abnormal |
| 10-50 Megohm | Good |
| 50-100 Megohm | Very good |
| 100 Megohm or more | Excellent |
Which is the best choice for measuring high resistance?
Solution: The Megger method is used for the measurement of the high value of resistance. And this is best suitable for the measurement of insulation resistance of cables. To measure High resistance Three(3) terminals are required.
What is the range of high resistance?
High Resistance: Resistance of the order of 0.1 MΩ and above is classified as High resistance.
What is the most popular method for measuring low resistance?
Which is the most popular method for measuring low resistance? Explanation: Kelvin’s double bridge is used for the measurement of low resistances of the order of 1ῼ or less. Ammeter voltmeter method is used for the measurement of current flowing through and the voltage across the circuit.
Which is the most popular method for measuring medium resistance?
Wheatstone bridge
How do you measure high resistance?
Two methods are used to measure high resistance, the constant voltage method and the constant current method. In the constant- voltage method, a known voltage is sourced and a picoammeter or electrometer ammeter is used to measure the resulting current.