De-energized maintenance uncovers problems that energized maintenance can miss. Don’t let today’s brewing problem become tomorrow’s lengthy shutdown. Schedule de-energized maintenance for a weekend or off-shift to ensure your installation stays up and running.
Definitions of Typical Tests
Contact Resistance Test commonly known as a Ductor Test measures resistance in micro-ohms between connections. This test helps find problems from corrosion or erosion of contact surfaces, failing construction of the contact assembly (loose connections), absent or contaminated lubricant in the contact assembly and improperly adjusted contacts.
An Insulation Integrity Test, commonly known as a Megger Test, measures the insulation reliability in megaohms of dry-type transformers and circuit breakers—that is, insulation of the moldings, inter-phase barriers and arc chutes. Comparing values from one test to the next can produce trends that identify insulation deterioration and help predict future circuit breaker and transformer failures.
A PIT or Primary Injection Test evaluates the ability of an electro-mechanical trip device or solid state trip system to open its associated circuit breaker. Current is injected through the circuit breaker at values that could be expected while the breaker is in service. The results of the test are then compared to the manufacturer’s curves to ensure that the overcurrent device is operating properly within the trip curve’s values.
A TTR or Transformer Turns Ratio Test detects shorts between turns of a given transformer coil, which would indicate insulation failure between the turns. A TTR test may uncover the need for an internal inspection or removal from service.