![]() The quantities are compared with the predetermined setting to decide whether the power system is experiencing faults or not. Then a relaying algorithm processed the discrete numbers. ![]() The analog interface sample the reduced level signals and convert their analog levels to equivalent numbers that are stored in memory. The outputs of the signal conditioner are applied to the analog interface. The low pass filter or anti-aliasing filter prevents the aliasing of the signal. Because the A/D converter only accepts only voltage signals. The I/V converter converts current signals into proportional voltage signals to make them accessible to the A/D converter. In the signal conditioner, the auxiliary transformer isolates the relay from the power system and reduces the levels of signals to make them suitable for use in the relays. Signal conditioner is a crucial part of DAS. ![]() The outputs of CT and VT are served to the signal conditioner. Therefore, the current and voltage levels are reduced by the current and voltage transformer. How does numerical relay work?Īt the power system, current and voltage levels are so high. If there is a fault in the protective zone, a trip signal is issued to the circuit breaker. Then the DAS (data acquisition system) acquires the sample of ac quantities in digital form and processes the data numerically using an algorithm to calculate fault and make a trip decision. Read more: How does a current transformer make it possible to measure high voltage current? These signals are sampled and conditioned at particular instants of time and then converted into a numeric form for displaying and recording. The numerical relay monitors the analog signals (current and voltage) through the current transformer and voltage transformer. The design and operation of both the electromechanical and static relay are different from this type of relay.
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