Forums
New posts
Search forums
What's new
New posts
New media
New media comments
Latest activity
Media
New media
New comments
Search media
Members
Current visitors
Log in
Register
What's new
Search
Search
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Main Forums
Do-It-Yourself (DIY) Question & Answer Forum
Disconnection time 120 volts Uo vs 150 volts Uo
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Help Support Talk Electrician Forum:
This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Message
<blockquote data-quote="Sidewinder" data-source="post: 491319" data-attributes="member: 9512"><p>Firstly with faults. It is the U0 Voltage that we are concerned with.</p><p></p><p>How are you determining the disconnection time, is this a theoretical exercise, a design or calculation, or is it a measured value which when compare to the breaker impedance is giving these disconnection times?</p><p></p><p>At the instant of the fault the supply live conductor and the protective conductor act as a voltage divider.</p><p></p><p>To simplify things, lets allow them to be of equal value for a moment, this means at the instant of fault you are dropping half U0 in the line &amp; half U0 in the protective conductor.</p><p></p><p>The exact values will vary depending on the exact impedances, but for this model 50:50 will do.</p><p></p><p>So, with U0=120V this gives 60V at the point of the fault, with U0=150V you have 75V.</p><p></p><p>From this you can look back at the tables and data in IEC 61140 &amp; IEC 61479 and derive the allowable disconnection times.</p><p></p><p>These times are related to the physiology of the body, expected heart rate, body impedance etc. For the population based on statistical models.</p></blockquote><p></p>
[QUOTE="Sidewinder, post: 491319, member: 9512"] Firstly with faults. It is the U0 Voltage that we are concerned with. How are you determining the disconnection time, is this a theoretical exercise, a design or calculation, or is it a measured value which when compare to the breaker impedance is giving these disconnection times? At the instant of the fault the supply live conductor and the protective conductor act as a voltage divider. To simplify things, lets allow them to be of equal value for a moment, this means at the instant of fault you are dropping half U0 in the line & half U0 in the protective conductor. The exact values will vary depending on the exact impedances, but for this model 50:50 will do. So, with U0=120V this gives 60V at the point of the fault, with U0=150V you have 75V. From this you can look back at the tables and data in IEC 61140 & IEC 61479 and derive the allowable disconnection times. These times are related to the physiology of the body, expected heart rate, body impedance etc. For the population based on statistical models. [/QUOTE]
Insert quotes…
Verification
Post reply
Main Forums
Do-It-Yourself (DIY) Question & Answer Forum
Disconnection time 120 volts Uo vs 150 volts Uo
Top