A Brief Guide To Primary Current Injection Test

A Brief Guide to Primary Current Injection Test

What is the Primary Current Injection Test?

A primary injection test is a system that incorporates the current sensors, wiring, and conduction route in the circuit breaker with the test. The primary current injection technique is generally the recommended test method. 

A primary injection test is helpful for substations or circuits with high voltage and current. It is just the flow of rated current in the circuit under test. If the rated current of the circuit is 2000 A, then 2000 A of current must flow through the circuit. This is necessary to verify overall equipment health and protection system performance.

A primary current injection test is performed on high voltage or high current circuits. Read on to learn more about the primary current injection test and primary current injection test kit.

Importance of Primary Injection Test


  • Reliability


Excellent maintenance is required for power circuit breakers to be reliable and safe. Maintenance plans must be tailored to the particular application, carefully planned, and executed by industry experience and manufacturer guidelines.


  • Protection


The primary injection testis the last commissioning check to verify that all equipment and protective systems are in good operating order. The polarity of connected CTs is verified using a Stability Test / Check. Hence, it is only performed with a primary injection test.

The primary current injection technique or the secondary current injection approach may conduct field-testing and calibrate solid-state trip devices. The primary current injection technique is often the recommended test method since it incorporates the circuit breaker’s current sensors, wiring, and conduction route into the test. 

What is done during the Primary Injection Test?  


  • Acceptance and Maintenance Tests 


In the field using a portable primary injection test kit, maintenance and Acceptance tests are carried out specially intended to be smaller than factory test equipment.

For proper operation Circuit breakers with electromechanical or thermal-magnetic trip devices may only be tested using the primary current injection technique. The secondary current injection may test circuit breakers equipped with solid-state trip mechanisms, saving time and money.


  • Primary Current Testing


A primary injection testis performed by passing a predetermined series of overload and fault magnitude currents. It is effected using a circuit breaker and recording how long it takes the trip unit to trigger. Electricity is continuously injected into all three poles of a circuit breaker when these tests are conducted in a repair facility or factory. 


  • Integration


In the test set fault current or simulated overload is supplied by an integrated high-current transformer. Test sets with current ratings ranging from 500 to 100,000 amperes are constructed. Acceptance and maintenance tests are carried out in the field using a portable primary injection test set specially intended to be smaller than factory test equipment. These smaller test sets are often incapable of concurrently injecting electricity into all three phases of a circuit breaker.

Properties of Primary Injection Testing

  • Done on thermal-magnetic and electronic breakers 
  • Time intensive 
  • It takes more expertise to run the test 
  • Equipment is heavy and less portable 
  • More expensive

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