Safe isolation procedure

[lyledunn]

We have an industry recognised safe isolation procedure in the UK for circuits up to 400v. It requires that a test lamp is prooved on a known live source, isolate the circuit, proove the circuit dead with the test lamp, re-proove the test lamp. Lock off as required and place appropriate notices.
I am interested in such safe isolation procedures in other countries.

 

[ongchazira]

Sorry lyledunn, I am putting up another question to you and I will answer your question after you answer my question. My question is "What is the safety procedure for system of more than 400v?".

 

[busbar]

For places of employment in the US, “OSHA” regulations apply. From:

http://www.osha-slc.gov/OshStd_data/1910_0333.html

:

(b)(2)(iv) Verification of deenergized condition. The requirements of this paragraph shall be met before any circuits or equipment can be considered and worked as deenergized.

(b)(2)(iv)(A) A qualified person shall operate the equipment operating controls or otherwise verify that the equipment cannot be restarted.

(b)(2)(iv)(B) A qualified person shall use test equipment to test the circuit elements and electrical parts of equipment to which employees will be exposed and shall verify that the circuit elements and equipment parts are deenergized. The test shall also determine if any energized condition exists as a result of inadvertently induced voltage or unrelated voltage backfeed even though specific parts of the circuit have been deenergized and presumed to be safe. If the circuit to be tested is over 600 volts, nominal, the test equipment shall be checked for proper operation immediately after this test.


The use of the word "shall" means mandatory. §1910.269 generally addresses conditions in an electric-utility setting. The cited text does not specifically call for testing of the voltage-detecting device before use, and only seems to mandate testing after use for circuits over 600 volts. I, and most others I know would never trust electrical safety to an immediate before-and-after verification. Similarly, corresponding §1910.147 lockout/tagout [LOTO] rules apply.

 

[peterb]

In addition to testing the circuit, a program for shorting and grounding out the primary circuit is implemented in many industrial as well as utility systems. This is a good supplement to the lockout/tagout procedure, providing an extra layer of personnel safety.

 

[busbar]

peterb, that’s an excellent point. Over 600 volts, “it’s not dead until it’s grounded.” The grounding jumpers must also be rated for current withstand in excess of the fault duty where applied on the circuit, and for the time interval that it takes for the upstream overcurrent device to operate.