Circuit Breaker Timer Calibration

Circuit breakers are critical elements in any power distribution system that provides safeguards for potentially damaging power system events and conditions, such as a short circuit, circuit overloads or equipment system failures.

Circuit breakers can be found in electrical panels in most residential and commercial buildings and they are routinely used in large high-voltage power substations. Circuit breakers are designed with the capabilities to open and close electrical circuits, carry load current with minimal losses and to direct current flow throughout the power system network. They will trip automatically if a circuit overload occurs or they can be manually operated when performing testing or maintenance.

It is important that circuit breakers are tested and analyzed regularly to ensure that they are performing under their strict performance specifications. The measurement of the timing of the opening and closing of the breaker contacts, the current consumption during operation, and the measurement of the contact resistance are the main tests necessary to determine the operating condition of the circuit breaker. These tests need to be performed under both normal operations and during fault conditions and they must be tested both individually and as a complete electro-mechanical system.

Circuit Breaker Timers

Circuit Breaker Timers are advanced, field-service instruments for circuit breaker testing and maintenance in medium and high voltage power substations used for the generation and distribution of electric power. Circuit Breaker Timers are also used in many other industrial environments and in the manufacturing facilities that produce circuit breakers.

Circuit Breaker Timers contain a microprocessor-controlled circuit that can test all of the required functions of the circuit breaker in one stand-alone unit to save significant man-hours and improve the testing productivity during maintenance events.

Circuit Breaker Timer Features

Circuit Breaker Timers can automatically test, capture and store the timing of all circuit breaker contact operations. They can measure the time between when a breaker coil is initially powered to when the circuit breaker’s contacts fully open or close, usually just a few hundred milliseconds.

Most Circuit Breaker Timers have a built-in micro-ohmmeter to provide an accurate four-wire contact resistance measurement of the main circuit and dynamic contact resistances to determine the condition of the arcing contacts in a single test.

The portability of the equipment allows the unit to be used in all indoor or outdoor testing conditions and makes it easier to connect the circuit breakers with the supplied testing cables. They contain an internal power supply to provide voltage and current outputs for testing circuit breakers in shut-down substations or when testing on a maintenance bench.

Circuit Breaker Timers can provide immediate test results with the built-in thermal printer so that the results can be analyzed on the spot. The printouts can be programmed to include additional testing information, such as circuit breaker and substation identification, type of test, and the testing date and time.

Circuit Breaker Timer Calibration

Regular calibration of the Circuit Breaker Timers is important to ensure that the instrument is measuring accurately and performing within the manufacturer’s specifications. The calibration of Circuit Breaker Timers is usually performed by simulating the measurement values with precision electronic standards and comparing the standard’s values with the display indications on the Circuit Breaker Timer.

The three main parameters that are calibrated for most Circuit Breaker Timers are the timing, current and contact resistance measurements. Other tests may need to be performed depending on the features of each individual model.

The timing measurements can be simulated by using a pulse generator or by using a switching circuit and measuring the switch timing with an electronic counter. The current measurement is made by using a power supply to generate the required current and using a characterized current shunt to accurately measure the current applied.

The contact resistance measurement is tested by using a variety of low-ohm resistors or decade resistor boxes for the standard resistance value. The exact value of the resistors can be obtained by characterizing the resistors by using Ohms law and a 4-wire measurement method to eliminate any lead resistance errors during the measurement.

If any of the values are found to be outside of the manufacturer’s specifications, most circuit breaker timers can be adjusted by the use of special calibration software, so that the equipment does not need to be opened for adjustments.

The accuracy of the Circuit Breaker Timers is typically 1% or less, so the standards used must be highly accurate to properly calibrate the equipment. is an accredited calibration laboratory and has the necessary standards to calibrate Circuit Breaker Timers and many other types of electronic, dimensional and physical measurement equipment.

For more information on our capabilities and how we can serve your calibration needs, contact e2b calibration.



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