Primary Current Injection instantenous Pickup

[changeabilities]

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?

[SecondGen]

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.

[RabbleRabble]

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.

[test11]

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.

[AaronCBI]

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.

[Kalbi_Rob]

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.

[gchoquette]

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/smc-raptor-c-05-primary-injection-testing-system

[southbury]

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.

[Kalbi_Rob]

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.

[AaronCBI]

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.

[anonymous]

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.

Inverse time means LT, not INST. Instantaneous is definite time (with partial exceptions for fancier trip units). NEMA is saying to test the long time delay at 3 x LTPU, with the LTD dial at either the highest setting or the specified setting (we always do the coordination study setting in my experience). This clause does not apply to instantaneous pickup tests. Instantaneous tests will be a pulsed ramp to the minimum pickup.

[AaronCBI]

Inverse time means LT, not INST. Instantaneous is definite time (with partial exceptions for fancier trip units). NEMA is saying to test the long time delay at 3 x LTPU, with the LTD dial at either the highest setting or the specified setting (we always do the coordination study setting in my experience). This clause does not apply to instantaneous pickup tests. Instantaneous tests will be a pulsed ramp to the minimum pickup.

Yes exactly.
My specialty circular connectors for RL type breakers will be melted doing maximum time on a 4000 A breaker at maximum delay setting.
Or SACE breakers. The longest setting on those with some of the electronic trips are 144s @ 6x I believe, and they come up to 5000A

[Kalbi_Rob]

Inverse time means LT, not INST. Instantaneous is definite time (with partial exceptions for fancier trip units). NEMA is saying to test the long time delay at 3 x LTPU, with the LTD dial at either the highest setting or the specified setting (we always do the coordination study setting in my experience). This clause does not apply to instantaneous pickup tests. Instantaneous tests will be a pulsed ramp to the minimum pickup.

You are correct, Inverse time means LT, not INST.

You are incorrect on how to perform Instantaneous test in accordance with NEMA AB4:

6.6.4.2.2 Apply a pulse of current, approximately 5 to 10 cycles in duration, and at a level approximately 5%
below the lower tolerance limit specified in Table 4 for the breaker setting. The breaker should not trip.
6.6.4.2.3 Apply a pulse of current, approximately 5 to 10 cycles in duration and at a level equivalent to the
high tolerance limit specified in Table 4. The breaker should trip.

What you are describing is similar to the Ramp up test, but not the same as NEMA calls for ramping current at a rate of 2-5 sec, which has been proven to damage rheostats on many test machines.

[anonymous]

Yes exactly.
My specialty circular connectors for RL type breakers will be melted doing maximum time on a 4000 A breaker at maximum delay setting.
Or SACE breakers. The longest setting on those with some of the electronic trips are 144s @ 6x I believe, and they come up to 5000A

Totally misunderstood you. I have no experience with RL breakers but we did do some SACE breakers last year with one of these adjustable stab sets, which worked great: http://www.newengland-tool.com/id22.html. But they were 3200A and the time dial was not all the way up. At 144s and 5000A the LTD test would be 15000A for about 2.5 minutes! That is some serious current and a PI-6000 would have trouble pushing that according to the spec sheet (max on time for 18kA @ 9V = 1.5 mins).


You are correct, Inverse time means LT, not INST.

You are incorrect on how to perform Instantaneous test in accordance with NEMA AB4:

6.6.4.2.2 Apply a pulse of current, approximately 5 to 10 cycles in duration, and at a level approximately 5%
below the lower tolerance limit specified in Table 4 for the breaker setting. The breaker should not trip.
6.6.4.2.3 Apply a pulse of current, approximately 5 to 10 cycles in duration and at a level equivalent to the
high tolerance limit specified in Table 4. The breaker should trip.

What you are describing is similar to the Ramp up test, but not the same as NEMA calls for ramping current at a rate of 2-5 sec, which has been proven to damage rheostats on many test machines.

I did not know that! I was taught to start just below the low tolerance, then inject higher and higher until the breaker trips, and then the trip current is the test result. What you/NEMA says makes sense, it's similar to how we test relays where they want to prove both sides of a tolerance. Thanks for the info, I guess I need to read the NEMA book some more.

[Kalbi_Rob]

Totally misunderstood you. I have no experience with RL breakers but we did do some SACE breakers last year with one of these adjustable stab sets, which worked great: http://www.newengland-tool.com/id22.html. But they were 3200A and the time dial was not all the way up. At 144s and 5000A the LTD test would be 15000A for about 2.5 minutes! That is some serious current and a PI-6000 would have trouble pushing that according to the spec sheet (max on time for 18kA @ 9V = 1.5 mins).



I did not know that! I was taught to start just below the low tolerance, then inject higher and higher until the breaker trips, and then the trip current is the test result. What you/NEMA says makes sense, it's similar to how we test relays where they want to prove both sides of a tolerance. Thanks for the info, I guess I need to read the NEMA book some more.

I personally have never met anybody test it per NEMA (nor would I test LT delay at max) in the 3 separate companies I have worked for, but I got into an argument with Siemens engineer rep over how to test. The Instantaneous failed to trip all the way up to 10x when set to 5x. He told the customer, Siemens would not validate the test results (for warranty replacement) since they were not performed 100% per NEMA AB4, and they would have to test it at their facility to verify operation.
Needless to say, this same Siemens engineer rep, gave me issues on another project when they had multiple breakers failing due to failed power supplies. He tried to convince the customer that my Withstand test on the Switchboard caused his 24Vdc power supply to fail through a open switch, pulled fuses, PT, and DC converter.

[RabbleRabble]

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/smc-raptor-c-05-primary-injection-testing-system


Thanks I’ve never seen that before. I wonder how the primary current is measured?