Voltage protection level (UP) is a maximum voltage to be expected at the SPD terminals due to an impulse stress with defined voltage steepness and an impulse stress with a discharge current with given amplitude and waveshape.
The voltage protection level is given by the manufacturer and may not be exceeded by:
- the measured limiting voltage determined for front-of-wave sparkover (if applicable) and the measured limiting voltage determined from the residual voltage measurements at amplitudes corresponding to In and/or Iimp respectively for test classes II and/or I;
- the measured limiting voltage at the open circuit voltage of the combination wave generator (UOC), determined for the combination wave for test class III.
The measured limiting voltage of the SPDs shall not exceed the voltage protection level that is specified by the manufacturer.
Preferred values of voltage protection level Up: 0,08; 0,09; 0,10; 0,12; 0,15; 0,22; 0,33; 0,4; 0,5; 0,6; 0,7; 0,8; 0,9; 1,0; 1,2; 1,5; 1,8; 2,0; 2,5; 3,0; 4,0; 5,0; 6,0; 8,0 and 10 kV.
When a surge or transient overvoltage occurs, the SPD’s voltage protection level is critical in determining when it activates to provide protection. The lower the Up value, the better the SPD can protect against high voltage surges. The Up value is usually expressed in kilovolts (kV) and is specified by the manufacturer for a particular SPD.
For instance, if an SPD has an Up rating of 1.5 kV, it means that the device will start to conduct and divert surge currents when the voltage across its terminals exceeds 1.5 kilovolts. It is important to select SPDs with appropriate Up values based on the equipment being protected and the level of surge protection required. Different types of equipment may have different voltage tolerance levels, so the Up value of the surge protection device should be chosen to ensure adequate protection for the specific application.
The tests on the different SPD types to determine their measured limiting voltages shall be performed according to the flow chart in Figure 1.
Figure 1 – Flow chart of testing to check the voltage protection level Up [based on figure 5 of IEC 61643-11:2011]
- IEC 61643-11:2011
- IEC 60364-5-53-2020
