Protective relay apparatus

A protective relay apparatus having a transformer for outputting a detection signal in accordance with the varying current or voltage of a main circuit and a control unit for determining that said main circuit is in a predetermined state by using said detection signal and outputting a control signal for switching on/off said main circuit, said apparatus comprising:

• a first input circuit comprising a first operational amplifier for inputting said detection signals and an A/D converter for A/D converting an output signal from said first operational amplifier;
• and
• a second input circuit comprising a second operational amplifier for inputting said detection signal and an A/D converter for A/D converting an output signal from said second operational amplifier, said second operational amplifier having gain characteristics compatible with wide range detection permitting detection in a wide varying range of a current or a voltage, as compared with said first operational amplifier,
• wherein each of a plurality of input circuits comprises means for setting the detectable range thereof, each of said first and second circuits comprises means for setting the detectable range thereof, and said detectable range is figured out based on any error of said transformer and any detectable error of instrumentation.

A protective relay apparatus having a transformer for outputting a detection signal in accordance with the varying current or voltage of a main circuit and a control unit for determining that said main circuit is in a predetermined state by using said detection signal and outputting a control signal for switching on/off said main circuit, said apparatus comprising:

• a first input circuit comprising a first operational amplifier for inputting said detection signals and an A/D converter for A/D converting an output signal from said first operational amplifier;
• and
• a second input circuit comprising a second operational amplifier for inputting said detection signal and an A/D converter for A/D converting an output signal from said second operational amplifier, said second operational amplifier having gain characteristics compatible with wide range detection permitting detection in a wide varying range of a current or a voltage, as compared with said first operational amplifier,
• wherein each of said first and second circuits comprises means for setting the detectable range thereof, and said detectable ranges are figured out on the basis of the magnitude of the error of each of said first and second input circuits, resolving power of the A/D converter, and the tolerable detectable errors of said instrumentation by the following arithmetic expression,
• 23 IFS = 2 ( D - 1 ) ⁢ I ⁢ ⁢ e x ⁢ ( I ⁢ ⁢ g 2 + 2 ⁢ I ⁢ ⁢ g + 4 9 - 2 3 )
• where:
• Ig=Detected error,
• x=Magnitude of error of the current transformer input circuit (0, 5, 1, 2 . . . )
• D=Resolving power of the A/D converter,
• Ie=Effective amperage, and
• IFS=Full scale value.

A protective relay apparatus having a transformer for outputting a detection signal in accordance with the varying current or voltage of a main circuit and a control unit for determining that said main circuit is in a predetermined state by using said detection signal and outputting a control signal for switching on/off said main circuit, said apparatus comprising:

• a first input circuit comprising a first operational amplifier for inputting said detection signals and an A/D converter for A/D converting an output signal from said first operational amplifier;
• and
• a second input circuit comprising a second operational amplifier for inputting said detection signal and an A/D converter for A/D converting an output signal from said second operational amplifier, said second operational amplifier having gain characteristics compatible with wide range detection permitting detection in a wide varying range of a current or a voltage, as compared with said first operational amplifier,
• wherein said each of said first and second input circuits comprises means for setting the detectable range thereof, and said detectable ranges are figured out on the basis of the magnitude of the error of each of said first and second input circuits, resolving power of the A/D converter, and the tolerable detectable errors of instrumentation by the following arithmetic expression,
• 24 VFS = 2 ( D - 1 ) ⁢ V ⁢ ⁢ e x ⁢ ( V ⁢ ⁢ g 2 + 2 ⁢ V ⁢ ⁢ g + 4 9 - 2 3 )
• where:
• Vg=Detected error,
• x=Magnitude of error of the voltage transformer input circuit (0, 5, 1, 2 . . . )
• D=Resolving power of the A/D converter,
• Ve=Effective voltage, and
• VFS=Full scale value.