Portable Injection Tester, 5kA
High Current Injectors, Injection Testing

Testing and calibrating the direct-acting trip is arguably the most important safety test for circuit breakers. This particularly applies to the heavy-duty breakers used in railway traction but has equal importance elsewhere. Riker’s injection testing equipment operates on a very simple principle: Controlled current sources inject a current that increases steadily (under linear ramp control) until the circuit breaker trips out. The actual trip current of the breaker is then displayed on the control panel and enables breakers to be adjusted and calibrated at a precise safety trip point.

Without calibration, a 20% uncertainty in trip point is typical for traction supply protection so that a breaker must be set 20% below maximum safe current. Operating current must be held a further 20% below this if the risk of nuisance tripping is to be avoided. The net result is that, without testing and calibration, a traction supply can only be considered safe and reliable at or below 60% of its designed maximum safe output. This represents a considerable shortcoming on the power and revenue capacity available from a substantial infrastructure investment. Calibrated accurately, on the other hand, a breaker can be set to deliver 100% of a traction supply’s safe output and, typically, trip within 10A on a 7kA supply. In fact, correct adjustment and calibration can enable two trains to run concurrently on sections of track previously limited to one. Accurately calibrating the supply protection also ensures that cabling and connectors used in the traction supply do not suffer from the thermal effects of mechanical cycling and enhanced degradation if safe current levels are repetitively exceeded. Beyond the simple overload protection or emergency isolation there are, therefore, sound economic reasons for maintaining accurate calibration of the direct-acting trip.

Riker pioneered portable high current injectors with the modular 10kA BRECAT supplied to London Underground in 1996. Based on the efficiency of high frequency power conversion, the mass of the equipment is minimised to accommodate the thermal characteristics of a controlled test cycle. This enables lightweight equipment to replace the bulk of traditional fixed installations weighing several tons. Progressive development of the concept has now resulted in the CAT 5000, a 5kA module weighing less than 25kg and housed in a rugged and weatherproof plastic case. The CAT 5000 has now evolved into the definitive test apparatus for railway circuit breakers and guarantees precisely calibrated direct action tripping. The real advantage for railway networks comes from its mobility; systems can be readily transported in a small car or van and hand-carried into a substation or workshop.

Being current sources, output can be simply multiplied by parallel operation. The standard hand-held controller enables up to 20kA to be provided from 1-4 units. This spans the normal current range encountered from light railways through to heavier duties, traction rectifier equipment etc. With one unit or a multiple system, the Riker CAT 5000 provides a powerful and dependable tool for vital railway maintenance.