Is DSP really required for over current numerical relay. If we have processor with 16 bits ADC, frequency in MHz and some KB RAM, then also we can achieve over current protection with good accuracy for wide current range. So what is so special about DSP???

  • 1
    \$\begingroup\$ Find a processor with a 16-bit ADC (decent one) and 1 MHz rate (or better.) DSP or otherwise. The only one I know of is the C8051F061. Do you know of another? That said, I don't know of a reason (absent any specifications) why a DSP would be required. Or even a 16-bit ADC. Or even MHz rates of sampling. I think you need to write a lot more. (I referred to Types and Applications of Over Current Relays.) \$\endgroup\$
    – jonk
    Jan 3, 2018 at 18:22
  • \$\begingroup\$ As @jonk said, there is no need for a DSP for current monitoring. An opamp-driven low side sensing and a simple 12-bit ADC-equipped MCU would do the trick. \$\endgroup\$
    – altai
    Jan 3, 2018 at 19:14

1 Answer 1


DSP (Digital Signal Processing) could emulate the response of an existing mechanical overload protector, and thus conform to pre-existing standards. It could also allow thermal modelling of the device being protected.

For example, this paper describes a TMS320F2812-based overcurrent protection that meets the IEC 255-3 standard.

The benefit is to avoid false tripping or failure to trip under operating conditions. The cost is that the calculations are complex and have to be completed in a short time, so that's where DSP comes in rather than a general purpose micro. Some MCUs have DSP functionality.

  • \$\begingroup\$ How DSP can emulate the response of an existing mechanical overload protector?? \$\endgroup\$ Jan 4, 2018 at 17:55
  • \$\begingroup\$ Emulate the current-time trip curves. \$\endgroup\$ Jan 4, 2018 at 20:52
  • \$\begingroup\$ For emulating the current time trip curve, processor has to find the operating time based on iec or ieee curve .The processing time should be within margin, like within 1% of operation time calculated based on iec or ieee curve. This accuracy can be achieved with general purpose microprocessor. So why DSP is needed??? \$\endgroup\$ Jan 5, 2018 at 5:05
  • \$\begingroup\$ A general purpose processor (when equipped with appropriate peripherals) can do anything computationally that a DSP can do, but perhaps not fast enough. I doubt there any any necessity for a DSP over many modern processors in this particular application. \$\endgroup\$ Jan 5, 2018 at 5:25

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