Primary injection test set

Data records

• A battery-powered portable set with controlled electronic sources covers primary injection at lower currents, secondary injection and basic protection tests from one unit, generating alternating current over a wide frequency range and direct current with ramps, pulse ramps and sequences, and its inputs serve as binary or analog measuring channels. Source: OMICRON product page, web page edition. Verified 2026-10-27. Record instr.primary-injection-test-set.battery-portable-sets
• Injecting on the primary side proves the complete protection chain at once: the current transformer, the conductors and connection points, the relay and in some cases the circuit breaker, all working together under a current that stresses them as service does. Source: Megger application page, web page edition. Verified 2026-10-27. Record instr.primary-injection-test-set.complete-chain
• For a current transformer, current is injected into the primary winding and the resulting secondary current is measured, which gives the ratio, polarity and phase angle under real loading; the set reads the turns ratio directly and a switch box lets several secondary taps be measured in turn. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.primary-injection-test-set.ct-ratio-and-polarity
• The ground-fault function of a low-voltage breaker has a pickup current and a delay time like the long-time and short-time functions and is tested on its own; the ground-fault sensor is disabled while the long-time, short-time and instantaneous trips are tested so that it does not operate first. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.primary-injection-test-set.ground-fault-function
• For a low-voltage circuit breaker the current is injected through each pole in turn and the trip time is measured; injecting a high current is the only way to verify that a direct-acting breaker trips, and the long-time, short-time, instantaneous and ground-fault functions are each tested against the bands of the published time-current curve. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.primary-injection-test-set.low-voltage-breaker-trips
• Modern sets are modular: a control unit drives one or more current source modules, more modules being added when higher test currents are needed, and the output voltage can be raised at the expense of output current so that the test current is driven through a high-burden circuit; a long control cable lets the current source sit close to the test object so that the heavy current leads stay short. Source: Megger Electrical Tester article, December 2019 edition. Verified 2026-10-27. Record instr.primary-injection-test-set.modular-current-units
• Beyond breakers and current transformers, primary injection sets are used for heat runs with current applied continuously or in preset intervals, for testing reclosers and sectionalizers through a set number of operations before lockout, and for checking the integrity of ground grids and safety grounding devices. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.primary-injection-test-set.other-applications
• A primary injection test set drives a high current at low voltage directly through the primary circuit of a circuit breaker, current transformer or protection scheme, replicating the currents the circuit carries in service; it is most often used on low-voltage circuit breakers and current transformers, and the system under test is taken out of service. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.primary-injection-test-set.purpose
• The set measures the trip time from the start of injection to a stop condition, which is detected either internally, as the moment the current ceases when the breaker opens, or externally, from a contact that opens or closes or a voltage that appears or disappears; a hold function keeps a short-lived reading on the display. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.primary-injection-test-set.trip-time-stop-condition