DC Dielectric Test Sets

Dielectric test sets measure leakage current while applying a dc voltage at or above the insulation system’s operating level. This measurement aids in determining the insulation system’s ability to withstand over voltages such as lightning strikes and switching surges.

APPLICATIONS

Portable DC dielectric test sets check the electrical insulation quality of motors, power cables, switchgear, insulators, transformers and capacitors. Typical applications include acceptance and maintenance testing of critical equipment used by electrical utility substations and industrial plant distribution systems. Power apparatus manufacturers may also use the equipment to perform QA/QC production tests. The test sets can be used to perform step-voltage and proof tests which, when incorporated into a routine maintenance program, can aid in predicting potential failure before breakdown occurs.

Two models are available; a 5-kV unit for testing equipment rated 2.5 kV and below, and a 15-kV model for use on equipment rated 7.5 kV and below. Both are suitable for testing power cable, switchgear and rotating machinery in accordance with IEEE, ICEA, NEMA and ANSI guidelines.

Megger DC dielectric test sets act like full-wave rectified units, they also are suitable for applications involving vacuum bottles.

DC vs AC High-Potential Testing

Direct current high-potential testing provides several advantages over alternating current. Direct current test equipment uses far less power, provides fast charging of highly capacitive test samples, can be easily transported to the test site and costs less. Additionally, the dc test can detect incipient breakdown without the possibility of damage to good insulation.

FEATURES AND BENEFITS

_ Compact and portable

_ Air insulated, uses no oil

_ ±2% accuracy

_ Leakage current measurement as low as 0.1 mA

_ Continuously variable test voltage with zero-start safety interlock

_ Fast charging of high-capacitance samples

_ Current guard circuit for highly accurate measurements

_ Strip chart recorder for hard copies (optionally available)

Safety and Reliability

_ Input and output line circuit breaker

_ Output current overload relay

_ Zero-start interlock for high-voltage output

_ Pushbutton controls and indicating lights for high voltage ON/OFF

_ Full circuit breaker protection

_ Connection for external permissive and safety interlocks