The approach for using the ECAD tester requires that the circuit under test be logically organized as a set of two-wire configurations. For most circuits, the total number of combinations is manageable so that the time required to move the test lead connections between configurations is not significant. The test lead connection time does, however, become more significant as the number of two-wire configurations increases or if the number of similar circuits to be tested becomes large.
As an example, the testing sequence for a set of Westinghouse-designed Control Rod Drive Mechanism (CRDM) coils requires three (3) test configurations for the lift, moveable gripper and stationary gripper coils; a total of nine (9) tests per control rod. If the work scope is only a single set of coils, then the time required to move the test leads between the coil connections is not too burdensome with the total test time required being somewhere between 15 to 20 minutes.
But what happens if the work scope is larger than a single set of coils and all of the CRDM cables need to be tested? Most Westinghouse PWRs operating today have between 48 and 52 control rods which means approximately 430 to 470 individual ECAD tests are required to assess all of the CRDM circuits. How can the test connections be moved in the most efficient manner?
The key is automating the ECAD test sequence by using an additional switch matrix and by using test lead adapter cables that allow the tester to be connected to multiple test points at the same time.
CM Technologies offers a number of off-the-shelf and custom solutions. The form-factor of the solutions depends on the number of switching points (i.e., test connections) that are needed. As an example, CM Technologies offers PCI-form factor switch card that will allow the ECAD tester to be connected to 15 test points at one time. If more points are required, CM Technologies can provide a compact, external switch box which supports 128 test points with a single connection. Finally, if even more switch points are required, CM Technologies can provide an external switching matrix which is capable of testing up to 300 points with a single connection.
All of our switching solutions utilize wide bandwidth switches to minimize distortion and signal loss of the time domain reflectometer’s (TDR’s) high-frequency test pulse. Our switching circuits’ design also minimizes the “stub-length” of the matrix to reduce unwanted reflections in the TDR signature. And, lastly, our switch components also allow up to 500 VDC to be switched which minimizes the discharge time after performing an insulation resistance test.
If you would like to find out more information about our innovative switching solutions, please contact us with your questions.