To ensure that circuit breaker operation is guaranteed under the most onerous conditions placed on the substation tripping supply, circuit breaker trip coils are specified to work with a minimum tripping voltage much below the nominal battery voltage. The minimum trip voltage test is described in a number of international and national standards such as IEC 56, ANSI C37.09 etc.

Traditionally, this test was performed by tapping the main tripping battery. This method however should not by utilised as it presents a considerable risk to testing personnel, battery and breaker being tested.

POB30D, POB30AD, POB30DL and POB30ADL generate filtered DC voltage and it is developed for regular maintenance tests of power circuit breakers. It eliminates use of stationary batteries during testing. Output voltage is selectable from 10V to 300V DC (POB30D and POB30AD) or 1V to 50V DC (POB30DL and POB30ADL).

Procedure steps:

Manual

1. Make certain that the mains are de-energized on both sides of the breaker, safety grounded and that local safety regulations are followed.
2. Ground the test instrument.
3. Connect Power box to the breaker´s opening circuit and spring-charging motor.
4. Switch the test instrument on.
5. Set the desired test voltage.
6. Activate the trip pulse switch.
7. Repeat steps 3 and 4 at a higher voltage if the circuit breaker does not trip.

Automatic

1. Make certain that the mains are de-energized on both sides of the breaker, safety grounded and that local safety regulations are followed.
2. Ground the test instrument.
3. Connect Power box to the breaker´s opening circuit and spring-charging motor.
4. Switch the test instrument on.
5. Set the desired test voltages (minimal voltage, maximum voltage and step voltage).
6. Activate the trip pulse switch.
7. Wait until the coil is actuated. If the coil is not actuated, after 900msec of waiting time, voltage is automatically increased for a pre-selected step (value 1 to 19V), and the instrument repeats this procedure.

Test could have two possible outcomes:

• The coil is actuated; in which case the voltage and maximal current are registered,
• The maximum pre-selected test voltage is reached without coil actuation, which is indicated by "No activation" message at the display, and announced by sound and light alarm.

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