|
Subject - Fire re-construction
|
|
joepic
|
Can anyone tell me what to use and how to use test equipment to chect the extent of damage that wiring and devices have had due to fire and water damage. Thanks!
|
|
Ryan_J
| To really find the damage, you need to hire a company that can do a hi-pot test.
|
|
blackrd
| At the bare minninum, you should find an electrician that is a master on a meghometer. Steel mill and power plant electricians can tend to be very skilled in this area.
|
|
Ryan_J
| I got E-mails asking me about Hi-pot testing.
Here is an article: http://www.emersonprocess.com/home/library/articles/maintfacts/maintenancefacts0310_hipot-testing.pdf
Here is another: quote:
DIELECTRIC STRENGTH
Dielectric Strength (often called Hi-Pot or high potential) is commonly specified for production testing of electrical products. It is conducted by applying a high voltage between mutually insulated portions and ground. Normally the high voltage is applied to the current carrying wires holding the product's case (or exposed metal parts) at ground potential.
It is not intended to cause insulation breakdown or that it be used to detect corona. Rather it serves to determine whether insulating materials and spacings are adequate. When a product is faulty the application of test voltage will result in either a disruptive discharge or high fault currents. The results are a qualitative PASS or FAIL in lieu of measured values.
Some special care should be taken in the application and removal of the test voltage. If a simple switch or relay is used to control the voltage it will turn on the voltage at random points on the sine wave. This can cause unwanted high voltage spikes and breakdowns and can be a problem in products that contain inductive components such as large motors or transformers. The problem can be avoided by increasing and decreasing the voltage slowly. If the testing is being done on a production line the use of an automatic voltage ramp should be considered. Selecting a tester that uses a zero turn on switch can be a low cost and effective answer as well.
For products with large capacitors in the input., such as RFI filter, consider using a DC tester. Special precautions are required as in some cases DC testers can leave a charge on the product tested. A higher test voltage
is normally specified when DC is used to make up for the loss of the stress reversals that occur in AC testing.
|
