Guide To Vacuum Circuit Breaker Testing Procedure

What Are The Steps In Vacuum Circuit Breaker Testing? Vacuum Circuit…

What Are The Steps In Vacuum Circuit Breaker Testing?

Vacuum Circuit Breakers (VCBs) play a pivotal role in ensuring the secure operation of switchgear systems. Regular testing is indispensable to uphold their reliability and performance. In this comprehensive guide, we will delve into the essential steps of Vacuum Circuit Breaker testing, covering visual inspection, contact resistance tests, vacuum interrupter integrity tests, high potential tests, MAC tests, and mechanism checks. Whether you’re engaged in medium voltage (mv) or high voltage (hv) VCB testing, this one-stop destination furnishes a detailed procedure to ensure the optimal functioning of these critical components in power systems.

How Is Vacuum Circuit Breaker Testing Performed?

Testing a Vacuum Circuit Breaker is a crucial activity before it is integrated into any power system. This test assesses the breaker’s operation, verifying that it will trip at the right high current. The test employs a comprehensive test set, including test leads and other necessary equipment.

The circuit breaker test encompasses timing tests, open and close operation tests, coil tests, contact resistance tests, and current-carrying capacity tests. These tests scrutinize all features, ensuring the circuit breaker functions correctly in its intended environment.

Additionally, these tests identify and rectify potential problems that could arise during the breaker’s use in a power system. After a successful vacuum circuit breaker testing, it can be safely deployed for its intended purpose in any power system.

Visual Inspection

The most basic and direct examination method is visual inspection. Elements such as drive insulators and molded pole unit support are observed for any dirt or damage. Control circuit components, including wiring and terminals, are checked to ensure their integrity.

A visual examination is conducted to detect dirt and debris in the machinery. In addition to visual inspection, a tactile assessment is performed to ascertain the tightness of hardware or moving parts.

Contact Resistance Test

A micro-ohmmeter is employed on the joined circuits of the vacuum interrupter (VI), and its resistance is logged. This value is then compared to the planned or normal values for other vacuum interrupters in that particular batch.

Vacuum Interrupter Integrity Test

The reliability of a vacuum circuit breaker hinges on the soundness of the vacuum and the built-in dielectric strength. To examine both, a vacuum interrupter test, also known as a hipot test, is conducted. This one-minute AC high potential test assesses the insulation quality from the primary circuit to ground, from the command circuit to ground, and between major circuit terminals.

A successful withstand indicates properly operating vacuum interrupters, while a breakdown implies a faulty interrupter or interrupters that require repair or replacement.

High Potential Testing

A high potential voltage is applied across the open contacts of the VI. The voltage is increased to the test value, and any leakage current is measured. Factory testing may be done with either AC or DC high-potential test sets.

Portable test sets from manufacturers are available for performing a high-potential test on open vacuum interrupters. The majority of these test sets are DC test sets, as they are more compact and portable than available AC high-potential test sets.

Leak-Rate Test (MAC Test)

This experiment, based on the Penning Discharge Theory, determines that when a strong voltage is applied to separate contacts in a gas and the contact design is surrounded by a magnetic field, the current flowing between the plates depends on the gas pressure, applied voltage, and strength of the magnetic field.

Mechanism Check

An analysis of the mechanism involves a visual examination of the instrument for any loose components like rings or screws. Other aspects of the check could include a measurement inspection, performance check, operational assessment, or a combination of these. The measurement evaluation is necessary to inspect vacuum interrupters for the presence of three contact corrosion indicators and contact wipe measurement.

To ensure the motor is working properly, a performance test needs to be conducted. Similarly, if there is any damage or distortion in the machinery, visual and operational assessments are carried out. Occasionally, certain components need to be tested for accurate and smooth running, including turning off the circuit breaker and manual loading.

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