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Primary Current Injection instantenous Pickup

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    Primary Current Injection instantenous Pickup

    Hi guys,
    I need a help. In NETA ATS there is a sentence like "Determine instantaneous pickup by primary current injection."
    In my project some of the MCCB's are have 30000A. How can i perform this test? Also i need a current transformer to increase currents. Is it possible to find like 30000/5 A current transformer?

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    Quote Originally Posted by changeabilities View Post
    Hi guys,
    I need a help. In NETA ATS there is a sentence like "Determine instantaneous pickup by primary current injection."
    In my project some of the MCCB's are have 30000A. How can i perform this test? Also i need a current transformer to increase currents. Is it possible to find like 30000/5 A current transformer?
    You can test at a lower setting if the trip unit and job spec allows. For example a 4000A breaker dialed down to 2x will trip at 8000A opposed to 40000A at 10x.

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    Quote Originally Posted by changeabilities View Post
    Hi guys,
    I need a help. In NETA ATS there is a sentence like "Determine instantaneous pickup by primary current injection."
    In my project some of the MCCB's are have 30000A. How can i perform this test? Also i need a current transformer to increase currents. Is it possible to find like 30000/5 A current transformer?

    I've never heard of using a current transformer for increasing currents. In my experience CT are used for metering. If you are trying to increase currents it can be done with a power transformer or variac. If you use one of them you would already have a engendered core to couple primary and secondary.

    To perform a instantaneous pick up the method I use is to jog to pick up. If the PI tool cant handle the current I tell the customer, its never been a problem.

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    Quote Originally Posted by SecondGen View Post
    You can test at a lower setting if the trip unit and job spec allows. For example a 4000A breaker dialed down to 2x will trip at 8000A opposed to 40000A at 10x.
    I would absolutely recommend a dial down. Some customers don't like the idea of testing differently from study. However, you're beating the hell out of their equipment most of the time. It's not in the cubicle to help with the shock and you're definitely wearing out the contacts. You're testing if the breaker will function properly, not doing a current withstand test for UL listing.

    I've also seen breakers on skateboards(like a funiture dolly) jump out of test stabs at higher currents due to forces produced. So you could argue personnel safety as well.

    Bring these up to the customer when they object and usually they come around.

    One thing to note is that you should really pickup a manual for the particular trip unit. For example, I know some Eaton trip units have an instantaneous override making it impossible to test high settings in the field.

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    Quote Originally Posted by test11 View Post
    I would absolutely recommend a dial down. Some customers don't like the idea of testing differently from study. However, you're beating the hell out of their equipment most of the time. It's not in the cubicle to help with the shock and you're definitely wearing out the contacts. You're testing if the breaker will function properly, not doing a current withstand test for UL listing.

    I've also seen breakers on skateboards(like a funiture dolly) jump out of test stabs at higher currents due to forces produced. So you could argue personnel safety as well.

    Bring these up to the customer when they object and usually they come around.

    One thing to note is that you should really pickup a manual for the particular trip unit. For example, I know some Eaton trip units have an instantaneous override making it impossible to test high settings in the field.

    Usually when I explain that testing at the study setting (if it is fairly high) will most likely cause significant wear to the primary contacts, customers wont complain.
    Never ran into an end user who demands it tested at study setting, usually only asks why it is dialed down in the test report and is happy to hear I decided to spare their breakers life.

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    Quote Originally Posted by AaronCBI View Post
    Usually when I explain that testing at the study setting (if it is fairly high) will most likely cause significant wear to the primary contacts, customers wont complain.
    Never ran into an end user who demands it tested at study setting, usually only asks why it is dialed down in the test report and is happy to hear I decided to spare their breakers life.
    I see you haven't had the joy of testing breakers for data centers, where they want every test even if it doesn't make any sense (like IR of switchgear before energization). One center wants the breakers tested at the setting, and if the study changes at all they want all effected breakers fully retested. God forbid you try to explain any reason to these people.

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    Quote Originally Posted by RabbleRabble View Post
    I've never heard of using a current transformer for increasing currents. In my experience CT are used for metering. If you are trying to increase currents it can be done with a power transformer or variac. If you use one of them you would already have a engendered core to couple primary and secondary.

    To perform a instantaneous pick up the method I use is to jog to pick up. If the PI tool cant handle the current I tell the customer, its never been a problem.
    Minor point for educational purposes:
    CT's can be used both ways, to decrease current and to increase current (but normally only for decreasing current). They are normally used for metering as you say, but also very often, like in the above example for circuit protection.

    Some primary injection test sets like the SMC raptor uses a large CT to increase current. You run the heavy current cable through the hole and the system produces several thousand amps from a relatively small current (and higher voltage). You can also gang several of them together to further increase the current.
    https://www.protecequip.com/products...testing-system

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    Sorry, but primary injection test sets use a potential transformer. It is usually tapped at several different voltage levels. The load connected (circuit Breaker) contains resistance that with the applied voltage sets the level of current. Current Range of the tap is adjusted with the variac. With older TM breakers the current would need adjusting as the components heated up and added resistance during the test.

    A Current transformer used to pass current through a burden, if open circuited would have very bad things happen.

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    Quote Originally Posted by AaronCBI View Post
    Usually when I explain that testing at the study setting (if it is fairly high) will most likely cause significant wear to the primary contacts, customers wont complain.
    Never ran into an end user who demands it tested at study setting, usually only asks why it is dialed down in the test report and is happy to hear I decided to spare their breakers life.
    Just came across this while reading NEMA AB4, Section 6.5.4 INVERSE-TIME OVER CURRENT TRIP TEST

    NOTE 2—These tests should be conducted on individual circuit breaker poles using a test current of 300% of the circuit breaker's rated current. This test current has been chosen because it is relatively easy to attain and the wattage per pole is low enough that the transfer of heat into the adjacent poles is minor and does not appreciably affect the test results.
    NOTE 3—Circuit breakers equipped with electronic trip units typically are provided with more than one long-time trip curve. The tests in this clause should be performed with the circuit breaker set at the longest time setting or at the end use setting, as preferred.

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    Quote Originally Posted by Kalbi_Rob View Post
    Just came across this while reading NEMA AB4, Section 6.5.4 INVERSE-TIME OVER CURRENT TRIP TEST

    NOTE 2—These tests should be conducted on individual circuit breaker poles using a test current of 300% of the circuit breaker's rated current. This test current has been chosen because it is relatively easy to attain and the wattage per pole is low enough that the transfer of heat into the adjacent poles is minor and does not appreciably affect the test results.
    NOTE 3—Circuit breakers equipped with electronic trip units typically are provided with more than one long-time trip curve. The tests in this clause should be performed with the circuit breaker set at the longest time setting or at the end use setting, as preferred.
    This will be the death of all my specialty terminal connectors and bussing I have collected for primary injection testing if I am understanding correctly.

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