Short-term voltage limitation

A short-term voltage limitation is specified in lEC 62067 Annex G (informative) as impulse levels [13]. Considering short-term voltage limitation, the following phenomena are studied ... 

As mentioned in the previous section, the limitation of the sheath voltage is an important factor that decides sheath bonding and other cable system designs related to the sheath. There are two types of limitations in the sheath voltage (1) the continuous voltage limitation and (2) the short-term voltage limitation. 

Generally, bias-stress instability refers to long-term changes in the transistor characteristics that do not saturate but continue without limit until the device is rendered useless. Hysteresis refers to short-term reversible shifts in the characteristics that lead to looping in the measured characteristics, depending on the direction in which the bias voltages are swept. There is no sharp distinction between bias-stress instability and hysteresis, and the two may arise from the same or similar physical causes. 

An electrochemical reaction is said to be polarized or retarded when it is limited by various physical and chemical factors. In other words, the reduction in potential difference in volts due to net current flow between the two electrodes of the corrosion cell is termed polarization. Thus, the corrosion cell is in a state of nonequilibrium due to this polarization. Figure 4-415 is a schematic illustration of a Daniel cell. The potential difference (emf) between zinc and copper electrodes is about one volt. Upon allowing current to flow through the external resistance, the potential difference falls below one volt. As the current is increased, the voltage continues to drop and upon completely short circuiting (R = 0, therefore maximum flow of current) the potential difference falls toward about zero. This phenomenon can be plotted as a polarization diagram shown in Figure 4-416. 

---