Page 8 - 2019 How-to-Specify E-Book
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test required for compliance with IEC 60512-4-1, which states that the test must last for one minute and no flashover or breakdown is allowed. Test voltage values represent the upper physical limit of a connector and are sometimes used as a basis to calculate operating levels when predefined safety factors are established.
In theory, test voltage may be stated as high as it is tested, provided the conditions of the standard are met. Practically, however, test voltage is usually set at 75% of the breakdown value (as defined, for example, in the EIA-364-20 and former MIL-STD-1344 Method 3001 standards).
Many connector suppliers, including Fischer Connectors, always apply the 75% ratio to ensure that the test voltage values cited are reliable even when breakdown values exhibit the large scatter typical in high-voltage testing.
 Breakdown voltage vs. test voltage
Operating Voltage
Operating voltage is the voltage under which a connector will actually work in the equipment, over the normal expected lifetime, and in typical environmental conditions, and is dependent upon both connector design and the specific operating environment.
Significant scatter is often observed in breakdown testing because the breakdown mechanism is naturally triggered by instabilities. Breakdown voltages determined in different locations with different equipment frequently vary by up to 10%, but are not indicative of differences between the test samples.
The overall performance of any electrical connector is typically determined by its contact spacing (i.e., clearance or air gap and creepage or the physical distance along insulating components) and its insulating material. In most general-purpose connector designs, short-term performance is driven by the insulating performance of the surrounding air. Over the long-term, the physical properties of the insulating material are important.
3. Best Practices for Determining Operating Voltage
The guidelines provided in the IEC 60664 specification are recommended for connectors in common applications because it uses creepage distance instead of test voltage as the basis for operating voltage calculations, taking into account the aforementioned long-term performance effects. It is also similar to the German VDE 0110 specification, in which typical applications are classified in insulation groups depending on their exposure to pollution.
Fischer Connectors recommends the use of IEC 60664 in general multipole connector specifications, unless other more specific standards or regulations are applicable to the design. IEC 60601, for example, provides

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