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Primary current injection test sets


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This product has now been discontinued.

  • Test relay protection systems and their current transformers together
  • Current level maintained though test circuit resistance may rise due to heating
  • Built-in timer to record protection relay operation

This Primary Current Injection Test Set is rugged, self-contained and designed for operation by one person.

The PCITS2000/2 is a two-wheeled unit (with a handle).

The test set has a separate hand-held controller connected by an expandable cable. This allows the operator to work close to a protective relay while controlling a test. The maximum output current is 2000 A a.c. at line frequency. By changing the range switch, half the rated output can be obtained at twice the voltage.

Additionally, a separate auxiliary voltage output of 250 V, 2 A a.c. or 125 V, 2 A a.c. is available for testing voltage operated relay coils or checking the magnetisation characteristics of current transformers. All outputs are fully variable and each test set has a nominal duty cycle when delivering full current and voltage. Continuous operation is possible at 40% of maximum current.


Primary current injection test sets have two main applications. The first of these is the testing of complete relay protection systems comprising the isolated high voltage conductor, the current transformer, the protection relay and the circuit breaker. Because of the inconvenience of breaking into the feeder circuit on the primary side of the current transformer, primary current injection is normally applied at the time of commissioning protection equipment or after major repair. Routine testing is carried out using secondary current injection with equipment such as the SCITS100 (100 A) or SCITS50D (50 A).

As many of the protection systems requiring testing have a critical performance in relation to time, the primary current injection test sets incorporate a time counter facility.

The second role of the primary current injection test set is in the testing of the current transformer in a protection system. Again, this test is normally applied prior to commissioning equipment or after repair.

In addition to these protection system applications, current injection test sets are ideal for any application where it is necessary to supply a low resistance load with a controlled and measured heavy current.

Primary or Secondary Testing, Which?

Primary injection testing

Most electricity supply protective equipment is fed from a current transformer on the supply cable or busbar. Primary current injection testing checks all the components of the protective system. A high test current, enough to cause the protection equipment to operate, in injected into the supply cable. Time taken for the protection relay to operate is then measured.

The primary current injection test is essential when commissioning new protection systems and after major repair and component replacement, since it tests the whole system. It will detect current transformers connected with incorrect polarity or relays that have been set in the wrong sequence in differential systems. However, the inconvenience of breaking the primary circuit means that the method is unsuitable for routine testing.

Secondary Injection Testing

Secondary current injection testing checks the operation of the protective relay etc. but does not test the overall system including the current transformer. Primary testing usually requires a high current (over 500 A). A secondary injection test is easier since there is not the need to break the primary circuit and it requires a lower current (up to 100 A) through the operating coil of the protective device. The time taken for the protection device to operate is then measured.

A test winding is sometimes provided on the current transformer through which the secondary testing can be carried out.

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