electrical insulation test - SailNet Community
 
LinkBack Thread Tools
post #1 of 7 Old 09-20-2007 Thread Starter
Junior Member
 
Join Date: Sep 2007
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
electrical insulation test

hi everybody,
can anyone here advice me of how to carry out the wiring insulation test?
thanks
rgds

jxing62
jxing62 is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 7 Old 09-20-2007
Seinor Member
 
capn_dave's Avatar
 
Join Date: Feb 2000
Location: Green Cove Springs, FL
Posts: 276
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 16
 
On What???

Do you just want to test the insulation of the wire on the boat? Insulation on motor windings? There are numerous ways to test insulation. Can you be more specific?

There is a device called a Megger. It produces high current and voltage that will blow a hole in a wire where the insulation is bad. You cannot use this method in an explosive atmosphere. It can also break down good insulation if you don't know what your doing.

Let me know what your want to do and I will try to help.

Fair Winds

Cap'n Dave
capn_dave is offline  
Quote Quick Reply Share with Facebook
post #3 of 7 Old 09-20-2007
Senior Member
 
Join Date: Jul 2001
Posts: 1,174
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 14
 
Quote:
Originally Posted by jxing62 View Post
hi everybody,
can anyone here advice me of how to carry out the wiring insulation test?
thanks
rgds

jxing62

kind of difficult to figure out what test you mean - test for electrical properties?, resistance to solvents?, elasticity test?, heat resistance?
k1vsk is offline  
Quote Quick Reply Share with Facebook
post #4 of 7 Old 09-21-2007 Thread Starter
Junior Member
 
Join Date: Sep 2007
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
thanks for replies .
i am trying to have this boat tested for its wiring insulation condition see if any replacement needed. Not the motor windings.

rgds
jxing62
jxing62 is offline  
Quote Quick Reply Share with Facebook
post #5 of 7 Old 09-21-2007
Seinor Member
 
capn_dave's Avatar
 
Join Date: Feb 2000
Location: Green Cove Springs, FL
Posts: 276
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 16
 
You asked for it

Basically, you're applying a voltage (specifically a highly regulated, stabilized DC voltage) across a dielectric, measuring the amount of current flowing through that dielectric and then calculating (using Ohm's Law) a resistance measurement. Let's clarify our use of the term "current." We're talking about leakage current. The resistance measurement is in megohms. You use this resistance measurement to evaluate insulation integrity.
Current flow through a dielectric may seem somewhat contradictory, but remember, no electrical insulation is perfect. So, some current will flow.

it's a good idea to have a basic familiarity with the item you're testing. Basically, you should know what is supposed to be insulated from what. The equipment you're testing will determine how you hook up your meghommeter.
After you make your connections, apply the test voltage for one minute. (This is a standard industry parameter that allows you to make relatively accurate comparisons of readings from past tests done by other technicians.)
During this interval, the resistance reading should drop or remain relatively steady. Larger insulation systems will show a steady decrease; smaller systems will remain steady because the capacitive and absorption currents drop to zero faster than on larger systems. After one minute, you should read and record the resistance value.
When performing insulation resistance testing, you must maintain consistency. Why? Because electrical insulation will exhibit dynamic behavior during the course of your test - whether the dielectric is "good" or "bad." To evaluate a number of test results on the same piece of equipment, you have to conduct the test the same way and under the relatively same environmental parameters - each and every time.
Your resistance measurement readings will also change with time. This is because electrical insulation materials exhibit capacitance and will charge during the course of the test. This can be somewhat frustrating to a novice. However, it becomes a useful tool to a seasoned technician.
As you gain more skills, you'll become familiar with this behavior and be able to make maximum use of it in evaluating your test results. This is one factor that generates the continued popularity of analog testers.
What affects insulation resistance readings? Insulation resistance is temperature-sensitive. When temperature increases, insulation resistance decreases, and vice versa. A common rule of thumb is insulation resistance changes by a factor of two for each 10???C change. So, to compare new readings with previous ones, you'll have to correct your readings to some base temperature. For example, suppose you measured 100 megohms with an insulation temperature of 30???C. A corrected measurement at 20???C would be 200 megohms (100 megohms times two).
Also, "acceptable" values of insulation resistance depend upon the equipment you're testing. Historically, many field electricians use the somewhat arbitrary standard of 1 megohm per kV. The interNational Electrical Testing Association (NETA) specification Maintenance Testing Specifications for Electrical Power Distribution Equipment and Systems provides much more realistic and useful values.
Remember, compare your test readings with others taken on similar equipment. Then, investigate any values below the NETS standard minimums or sudden departures from previous values.

Remember you will need you will need a meter that reads megaohms.
Fair Winds
Cap'n Dave
capn_dave is offline  
Quote Quick Reply Share with Facebook
post #6 of 7 Old 09-21-2007
SENIOR CHIEF
 
USCGRET1990's Avatar
 
Join Date: May 2007
Location: YORKTOWN, VA
Posts: 1,380
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 9
 
While Dave gave you a wonderful technological definition...another simple way is to take any wires you can get a hold of and bend them as much as possible (like around a finger) if the insulation cracks, it's no good and will require re-wiring.
USCGRET1990 is offline  
Quote Quick Reply Share with Facebook
post #7 of 7 Old 09-21-2007
Seinor Member
 
capn_dave's Avatar
 
Join Date: Feb 2000
Location: Green Cove Springs, FL
Posts: 276
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 16
 
Smile Ahoy USCGRET1990

Isn't that what I said. See what happens when you ask an engineer about something?
There are a couple of other test I could of given but these require a highly technical understanding of electrical properties. The Smoke Test comes to mind. You bypass all fuses and then load up a circuit until the smoke comes out. You then make note of the smoke location, repair the area and put the smoke back in.

NOTICE this test should only be performed by a highly trained and experienced person.

Fair Winds

Cap'n Dave
I sail therefore I ARRRRRRRRRRRR!!!!
capn_dave is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Troubleshooting Your Electrical System Tom Wood Gear and Maintenance Articles 0 06-23-2003 08:00 PM
Electrical Power on Board Kevin Jeffrey Gear and Maintenance Articles 0 02-11-2003 07:00 PM
Electrical Power on Board Kevin Jeffrey Her Sailnet Articles 0 02-11-2003 07:00 PM
Electrical Work Rules Don Casey Gear and Maintenance Articles 0 07-16-2000 08:00 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome