Voltage will be 0 to 100V and current may as high as 25 times of the rated current, that is 125A or 25A.
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The voltage and current are still too big for the AAF, S/H, MUX, ADC and other electronic circuit.
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Typical hardware structure
❖ The following Figure shows the general hardware outline of a numeric protection relay.
❖ It consists of: Galvanic Isolation Transformer Anti-Alias Filter S/H Amplifier Multiplexer ADC Micro-Processor Timer
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原理电路
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工作过程
❖ Sample mode:
S/H is high and AS is closed.
Vout=Vin
❖ Hold mode:
S/H is low and AS is opened.
Vout=VC= Vin (just before AS
open)
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波形
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基本要求:
多路切换开关
❖ Function :
In general case, relays need multichannel inputs
(3phase voltage, 3phase current, zero sequence current etc.)