Do you think Earth leakage relay with only one tororid / CT input, and multiple toroid with relay switched automatically every millisecond by PLC can running properly ?, its similar to volt meter with selector, but this selection is automatically switched in every milliseconds by PLC, also its result is recorded by computer via modbus, do you think earth leakage relay can work properly by this way ?, is accuray is compromised ?

 

Really don't understand what you have.
Can you post a schematic?

 

Really don't understand what you have.
Can you post a schematic?

Lets assume
I have one earth leakage relay with only one CT
Then I use that relay with multiple CT, lets assume five CT
Then I connect all of five CT to only one earth leakage relay with contactor for each relay
Then I automatically switching between each five CT every milliseconds by PLC, and record earth leakage status for each five circuit with computer via modbus
Its my earth leakage relay still functioning properly this way ? and do you think accuracy is compromised ?
Are you understand my question ?

 

I understand your question but I don't understand what you have.

What is an earth leakage relay and how is it connected?
What is a CT?

Don't you have a schematic you can post?
I really don't like the game of 20 questions.

 

I understand your question but I don't understand what you have.

What is an earth leakage relay and how is it connected?
What is a CT?

Don't you have a schematic you can post?
I really don't like the game of 20 questions.

CT is current transformer, exactly ZCT for this case

 

I have five ZCT and only one earth leakage relay, that five ZCT is connected through contactor and then switched every milliseconds between five ZCT automatically

Do you understand ?

 

A millisecond sounds too slow since you would only be able to see the leakage current during a small part of a powerline cycle.

 

I have five ZCT and only one earth leakage relay, that five ZCT is connected through contactor and then switched every milliseconds between five ZCT automatically

Do you understand ?

Actually is switched through solid state relay not contactor, just avoid confusing for use two relay words (one for earth leakage, one for solid state)

 

A millisecond sounds too slow since you would only be able to see the leakage current during a small part of a powerline cycle.

Do you think 0.2 seconds is enough ?

 

First, one millisecond is faster than most PLCs can sense reliably, and now for the big question: WHAT ARE YOU ATTEMPTING TO ACHIEVE? Most earth leakage detection is done in GFCI devices to disconnect the voltage source before a dangerous amount of current flows. It seems that the TS is trying to monitor five different circuits with one interface device, which would be the "Earth Leakage Relay" device. That will not work. What will work is connecting all of the sensor outputs in parallel to the single "Earth Leakage Relay" device. The one problem is that when leakage is detected then which circuit is leaking will be unknown.

 

Further to what @MisterBill2 just said, and after reading your post #9 it is clear that you are trying to save some money by sharing one ground fault detection circuit over many circuits. The problem with that looks like you will not be able to sense a ground fault fast enough to save a life.

Put your engineer cap back on, find the relevant safety specification for the location or market you intend to serve and find out what the maximum response time is. From that you can decide whether you are likely to meet the specification. You may have noticed that the electromechanical part of a ground fault is a very fast circuit. Find the spec. then figure out whether or not you can meet it with the technique you have in mind, then carefully test according to the specification.

You sound like you are about to venture off into safety circuits, not something to go into lightly because if implemented people's lives will depend upon it working correctly. Every time.

 

UNFORTUNATELY, in many parts of the world, a GFCI device which mow sells for $24 USD may cost over $100 USD , and what may be available may be a trash-level-quality knock off, but with markings indicating that it is real quality.
Aside from sensitivity, response times of a GFCI are important. An interesting example is that on one job a few years back I kept getting sshocks that I never felt that were tripping the GFCI that was protecting the outlet that I was using. I never noticed those shocks from the electric drill that i was using, And my hands on the metal drill body were wet, making a good connection. So a good GFCI is fast, as well

 

Further to what @MisterBill2 just said, and after reading your post #9 it is clear that you are trying to save some money by sharing one ground fault detection circuit over many circuits. The problem with that looks like you will not be able to sense a ground fault fast enough to save a life.

Put your engineer cap back on, find the relevant safety specification for the location or market you intend to serve and find out what the maximum response time is. From that you can decide whether you are likely to meet the specification. You may have noticed that the electromechanical part of a ground fault is a very fast circuit. Find the spec. then figure out whether or not you can meet it with the technique you have in mind, then carefully test according to the specification.

You sound like you are about to venture off into safety circuits, not something to go into lightly because if implemented people's lives will depend upon it working correctly. Every time.

Its not my work, its engineer before me...
They use switching like that, and thats been for years until someone noticing, its get electric shock from isolation transformer in IT earthing system, but IMD is appear to be fine (all IMD and earth leakage relay is using multiple input and switching like I am describe)

 

Further to what @MisterBill2 just said, and after reading your post #9 it is clear that you are trying to save some money by sharing one ground fault detection circuit over many circuits. The problem with that looks like you will not be able to sense a ground fault fast enough to save a life.

Put your engineer cap back on, find the relevant safety specification for the location or market you intend to serve and find out what the maximum response time is. From that you can decide whether you are likely to meet the specification. You may have noticed that the electromechanical part of a ground fault is a very fast circuit. Find the spec. then figure out whether or not you can meet it with the technique you have in mind, then carefully test according to the specification.

You sound like you are about to venture off into safety circuits, not something to go into lightly because if implemented people's lives will depend upon it working correctly. Every time.

Do you think it is still unacceptable if earth leakage relay is just for secondary protection ?, when RCCB is also used

 

UNFORTUNATELY, in many parts of the world, a GFCI device which mow sells for $24 USD may cost over $100 USD , and what may be available may be a trash-level-quality knock off, but with markings indicating that it is real quality.
Aside from sensitivity, response times of a GFCI are important. An interesting example is that on one job a few years back I kept getting sshocks that I never felt that were tripping the GFCI that was protecting the outlet that I was using. I never noticed those shocks from the electric drill that i was using, And my hands on the metal drill body were wet, making a good connection. So a good GFCI is fast, as well

Do you think $35 ABB / Schneider RCCB its not good ?

 

Do you think it is still unacceptable if earth leakage relay is just for secondary protection ?, when RCCB is also used

Let me turn your question around:
If you have Residual Current Circuit Breaker (RCCB), why do you want to have an additional leakage current protection device?

Follow local codes and you will be alright, even though you may not yet know what the codes are.

 

OK, here are responses to several concerns. First, the Siemens RCCB is certainly a good part for it's intended purpose, if it is actually a Siemens part. In China I saw some fake parts eorsale in DongGuang City. So it seems that fake parts do exist.

Now there is a question about the comment in post #13:" until someone noticing, its get electric shock from isolation transformer in IT earthing system, but IMD is appear to be fine (all IMD and earth leakage relay is using multiple input and switching like I am describe) ". Usually an isolation transformer is able to eliminate the possible shock hazard by disconnecting and isolating the power circuit completely from "The Ground". But if it is instead a data line isolation transformer it may not provide mains power isolation.
And even the very best power supply isolation scheme can be thwarted by somebody connecting it's neutral side to "ground", either intentionally or accidentally. Grounding neutral is like a religious fixation with some people. The entire purpose of a power isolation transformer is to break the connection of the power circuit with ground.

In addition, the term "IMD" is not something I am familiar with by that name. What is "IMD" in this context??

 

OK, here are responses to several concerns. First, the Siemens RCCB is certainly a good part for it's intended purpose, if it is actually a Siemens part. In China I saw some fake parts eorsale in DongGuang City. So it seems that fake parts do exist.

Now there is a question about the comment in post #13:" until someone noticing, its get electric shock from isolation transformer in IT earthing system, but IMD is appear to be fine (all IMD and earth leakage relay is using multiple input and switching like I am describe) ". Usually an isolation transformer is able to eliminate the possible shock hazard by disconnecting and isolating the power circuit completely from "The Ground". But if it is instead a data line isolation transformer it may not provide mains power isolation.
And even the very best power supply isolation scheme can be thwarted by somebody connecting it's neutral side to "ground", either intentionally or accidentally. Grounding neutral is like a religious fixation with some people. The entire purpose of a power isolation transformer is to break the connection of the power circuit with ground.

In addition, the term "IMD" is not something I am familiar with by that name. What is "IMD" in this context??

IMD is for insulation monitoring devices...

 

OK, IMD= "Insulation Monitoring Device". That is a new one on me. IMD= InterModulationDistortion is what I am familiar with.

My experience has been quite different, in that using adequatequality insulation with reasonable standard voltasges provides a condition where the insulation will outlast the equipment that it is used in. That, along with reasonable construction practices, leads toward very long insulation life. But elsewhere in the world things may be different.