what is insulation resistance, how it is measured, what is the ideal value?

Question

especially for instrumentaion & control panels

Answer 1

INSULATION RESISTANCE TEST :
The Insulation Resistance Test is the second test required by the electrical safety testing standards.

The Insulation Resistance Test consists in measuring the Insulation resistance of a device under test, while phase and neutral are short circuited together. The measured resistance has to be higher than the indicated limit from the international standards.

A megohmmeter (also called insulation resistance tester, teraohmmeter) is then used to measure the ohmic value of an insulator under a direct voltage of great stability.

To measure a high value resistance, techniques for measuring a low value current are used. A constant voltage source is applied to the resistance to be measured and the resulting current is read on a highly sensitive ammeter circuit that can display the resistance value.

Two types of ammeter circuits are used on our range of insulation resistance tester, each circuit being chosen depending on the resistance values to be measured.

Its objective is to measure the ohmmic value of the insulation under a direct voltage of great stability, generally 50, 100, 250, 500, or 1000 VDC. The ohmmic value of the insulation resistance is expressed in megohms (MΩ). To conform to specific standards, the insulation resistance test can be performed under voltages up to 1500VDC. Due to the stability of the voltage source, it is possible to adjust the test voltage by steps of 1 volt.

The stability of the voltage is critical; a non regulated voltage will drop sharply in presence of a bad insulation which will cause an erroneous measurement.

Click on following link for more understanding:
http://ecmweb.com/mag/electric_insulation_testing/

Answer 2

Insulation Resistance

Answer 3

Insulation Resistance or IR as the name suggests is the resistance of the insulation. IR actually protects electrical equipment from short circuit. IR values are generally very high in the range of Mega-ohm or Mohm.

IR is measured by meggar.

The value of IR for an equipment depends on its voltage rating.

For control panels as far as I remember the IR value should be more than 1 Mohm.

During rainy season the IR value of insulation drops.

Answer 4

Insulation resistance, as the name suggests, is the resistance in ohms between a conductor and ground. Ideally, the insulation resistance prevents short-circuits between conductors.
The ideal resistance value depends on the voltage level in the conductor. For example the minimum insulation resistance for a 220Vdc conductor should be 250000 ohms and that of a 440Vac conductor should be >1000000 ohms

Answer 5

Insulation Resistance, people might call its initials, I.R.
I.R.,one of the electrical properties, especially take one of the major roles of testing criteria for a object as insulation function. For example ceramic to electronics components needs to own high I.R. to resist thermal and electrical load.

In general nowadays you can easily find an instrument such as HP/Agilent portable facility to test the IR value through specific voltage and ampere.

As to ideal value, it's up to either your specific demand or EIA standard.

Answer 6

1) IR = The resistance between the Supply Terminals ( Shorted ) of Ele. Equipment w.r.t body, in terms of Meg Ohms.
2) It is measured with Meggar.
3) IR for Electrical Equipment is 5 Meg Ohms at 500 Volts.

Answer 7

electrical insulation resistance , is in ohms , how wel the material doesnot conduct electrical current.

ideal value : depends on usage , can be zero or infinity

good day