ANSI Design Tests

The AIS has been tested to rigorous specifications of the Standard for Deadfront Padmounted Switchgear, ANSI C37.72. Traditionally, switchgear was subjected to a variety of tests which imposed individual switches to the extremes of interrupting duty, momentary, make-and-latch, dielectric and mechanical tests. As a result of unanimous utility input to the Standards Committee, the design test requirements in the new standard were substantially changed. Now, a single switch must be subjected to a sequence which combines and expands all the rigors previously imposed on individual switches. The design test sequence consists of the following tests in the order indicated:

1. Interrupting Current Test
2. Momentary Current Test
3. Making Current Test
4. 60-Hertz Withstand Test
5. Thermal Runaway Test
6. Mechanical Operation Test

After completing the design test sequence, the switch must be capable of carrying rated current without thermal runaway. In addition, the design must pass a 60-Hertz, direct current and impulse test as well as one-second high current, corona and temperature rise tests. While the above tests in themselves are all very important, Chance does not stop at this point in their evaluation of new switch designs. Various other visual, mechanical, electrical and environmental tests are conducted to assure optimum performance.

Production Testing

After assembly, all switches are tested to ANSI Standards:

1. Voltage Drop Test (IR). Each line direction of the switch configuration is tested. The IR test is a current test where the voltage drop across the area tested is measured to indicate the impedance in the circuit which is tested. This test assures reliable electrical connections.
2. High Potential Testing. Each switch is tested phase-tophase and phase-to-ground across the insulation system with the switch in the open and closed positions.