11kV and 33kV Cables between Cores and Earth (As per ETSA Standard)
Q. What is the minimum insulation resistance value?
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.
Table of Contents
- Q. What is the minimum insulation resistance value?
- Q. What is a low insulation resistance reading?
- Q. How do you calculate the minimum insulation resistance of an engine?
- Q. What are the method improving insulation resistance?
- Q. What is the insulation resistance?
- Q. Why is my insulation resistance low?
- Q. What is difference between resistance and insulator?
- Q. Does insulation affect resistance?
- Q. What are the factors that affect insulation resistance?
- Q. What is the minimum insulation resistance for a 400v circuit?
Q. What is a low insulation resistance reading?
Testing the integrity of insulation requires measuring its resistance to current flow across it. A high level of resistance means that very little current is escaping through the insulation. Conversely, a low level of resistance indicates a significant amount of current may be leaking through and along the insulation.
| Application | Test Voltage | Min IR Value |
|---|---|---|
| 11KV New cables – Sheath | 5KV DC | 1000 MΩ |
| 11KV After repairs – Sheath | 5KV DC | 100 MΩ |
| 33KV no TF’s connected | 5KV DC | 1000 MΩ |
| 33KV with TF’s connected. | 5KV DC | 15MΩ |
Q. How do you calculate the minimum insulation resistance of an engine?
The minimum insulation resistance of new, cleaned or repaired windings with respect to ground is 10 Megohm or more. The minimum insulation resistance, R, is calculated by multiplying the rated voltage Un, with the constant factor 0.5 Megohm/kV.
Q. What are the method improving insulation resistance?
After the etching away of copper to selectively expose surface areas of insulating material in a printed circuit process based upon copper foil-clad insulating substrate material, the exposed surface areas of insulating material are contacted with an aqueous alkaline permanganate solution to remove from the areas …
Q. What is the insulation resistance?
An insulation resistance (IR) test measures the total resistance between any two points separated by electrical insulation. The test, therefore, determines how effective the dielectric (insulation) is in resisting the flow of electrical current.
Q. Why is my insulation resistance low?
Low insulation resistance may be due to the age of the installation, or alternatively it may be caused by an individual circuit, which would merit further investigation. In summary, insulation resistance testing should be undertaken at relevant times during and on completion of an installation.
Q. What is difference between resistance and insulator?
An insulator is a material which doesn’t conduct electricity, ie, it doesn’t allow the flow of electrons to flow through it. A resistor, however, is a device which simply provides resistance to the flow of electrons.
Q. Does insulation affect resistance?
Resistance and Thickness There is also a strong relationship between the resistance of a cable and the thickness of the insulator. Increase in thickness means increase in resistance, and the opposite is also true. If thickness is reduced, the resistance of the insulator also reduces.
Q. What are the factors that affect insulation resistance?
Factors that affect insulation resistance measurements include such things as temperature, humidity, previous conditioning, test voltage, charging current and duration of the test voltage (electrification time).
Q. What is the minimum insulation resistance for a 400v circuit?
Test voltage 500v for 230v or 400v installations or circuits with a minimum insulation resistance of 1 M ohm (1000,000 ohms). A combined resistance of 2 M ohm or less for all circuit should be investigated further to find the individual circuit(s) that may be causing the low reading.
