IEEE C62.37.1-2000 pdf free.IEEE Guide for the Application of Thyristor Surge Protective Devices.
IEEE C62.37.1 The off-state region is the high-resistance,low-current portion of the voltage-current characteristic.Thisregion extends from the origin to commencement of breakdown.The off-state current is the sum of junctionreverse current and any surface leakage current.Two measurements are typically made in this region: off-state current (Ip ), measured with the dc off-state voltage(Vp ) applied; and repetitive peak off-state current(1DRM ), measured with the rated repetitive peak off-state voltage (VDRM ) applied.
The breakdown region is the low-resistance, high-voltage portion of the voltage-current characteristic. Thisregion begins where the low-current portion of the voltage-current characteristic changes from a highdynamic resistance to a region of substantially lower dynamic resistance for an increasing magnitude ofcurrent. Finally, this region terminates when sufficient thyristor regeneration occurs to initiate switching.Depending on the thyristor design and temperature, the end of the breakdown region may be at a higher orlower voltage than at the start. The low-resistance characteristic of this region is the result of junctionbreakdown combined with transistor action. The maximum voltage that occurs in the breakdown region isdefined as the breakover voltage [V(Bo) ].Additional measurements may be made of the breakdown voltage[V(BR) ] at a given breakdown current[L(BR) ] and the voltage and current at the switching point [Vs, Is ].
The negative-resistance region represents the trajectory from the breakdown region switching point to theon-state condition. This region is a dynamic condition, where the thyristor regeneration (internal positivecurrent feedback) increases with time,causing an increased current demand that pulls down the voltageacross the thyristor until the on-state condition is reached.
In telecommunication applications, there are two classes of protector—primary and secondary. Primaryprotection is applied at the system location where it may prevent most of the stressful energy frompropagating beyond the designated interface. Secondary protection is applied subsequently to the primaryprotection and is subject to lower and better-defined stress levels.When a surge greatly exceeds thecapability of a thyristor SPD it fails catastrophically, it may be desirable that the primary protector fails shortcircuit and so prevents the surge from propagating further. Primary protectors are normally tested to ensuretheir failure mode is appropriate to their application.
The thyristor SPD should have an adequate service life, and a design life in excess of 20 years is typical.Most of this period would be under normal operating conditions, and the product would have to pass a seriesof aggressive environmental tests to verify life expectancy. Surge conditions are a small, but significant,proportion of the service life.Surge durability is typically evaluated by repetitively surging the protector atvarious current levels.IEEE C62.37.1 pdf download.