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<p style="text-align:justify"><span style="font-size:14px">The relay, presented in this section, can be used to provide any kind of inverse time-current characteristic. As such definite time characteristic can also be obtained. Figure 6.20 shows the block diagram of generalized overcurrent relay. Voltage proportional to current (from C. T. secondary) is first rectified. The output of this rectifier is converted into logarithmic value using the log circuit. The output of this log circuit is amplified n times. (As per requirements of the characteristic. n = 0 gives the definite time characteristic, n = 1 gives IT = K curve and n = 2 gives I<sup>2</sup> t = K curve). In the next stage, there is antilog circuit. The output of antilog circuit is integrated. Op-amp can be used as an integrator circuit. Another form of integrating circuit can be as shown in figure 6.21. The output of integrating circuit is a ramp signal as shown in figure 6.21. The output of integrator is compared with a reference voltage as shown in figure 6.22. When the voltage of the integrator output crosses the reference voltage (which decides the TMS), the level detector gives the output signal which can be given to an output unit for finally generating a trip signal. The charging process in the integrator unit is allowed only if the current is higher than a pre-set threshold (plug-setting). Otherwise, the charging process is suitably blocked.</span></p>