This is a national standard used to evaluate the electrical performance stability of power connection fittings (such as strain clamps, connectors, etc.) under repeated power cycling and temperature variations. The core of the standard is to simulate the thermal expansion and contraction effects during long-term service by subjecting the fittings to a specified number of current heating and natural cooling cycles, while monitoring changes in their DC resistance and temperature rise. This test effectively reveals the risk of connection failure in fittings due to material aging or poor contact. During the test, it is typically necessary to use a high-current heating device and a thermal cycling test system capable of automatically collecting multi-channel temperature and current data. For example, certain models of line fitting thermal cycling test systems can provide the required current and simultaneously record temperature and loop resistance data.