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What is the difference between reverse current and overcurrent protection?
A reverse current relay senses Power in (uses both voltage and current, and looks at the phase angle between these), and operates if power is flowing in the reverse direction, and the current is above a set point. An overcurrent relay looks at only current, and operates if it is above a set point regardless of power flow direction. Reverse current relays are often referred to as reverse power relays.
What are current relays?
Current relays are the relay which sens the current passing in particular circuit and operates when this current exceed its set value.
How does the standby earth fault scheme work?
Restricted earth fault protection is used to protect a specific zone, and should not trip for a fault outside of that zone (usually limited to a transformer, and possibly extending to lowside, highside, and tertiary breakers). Stand by earth fault protection is a term I am not very familiar with, but I believe this would be protection that is meant for a specific zone as backup, and can operate for faults outside of this zone. An example might be a highside time overcurrent relay set looking into a transformer, where the transformer is protected by a differential (primary protection), and there is a lowside feeder with relays (primary protection). The highside overcurrent acts as a backup (secondary protection) for the transformer and the feeder, and is delayed due to the nature of a time overcurrent relay.
What are numerical relays?
As we know numerical relays use DIGITAL SIGNAL PROCESSOR as its computational hardware and based on microprocessor. WORKING: Analog input is feed into the anti aliasing filter which is a low pass filter.Output of this filter is feed into the sample and hold circuit , frequency of sampling should be twice of our highest frequency of interest(according to the nyquist criterion).if sampling frequency kept low than aliasing input may occur. after the sampling, signal are feed into the multiplexer,where all the signal get multiplexed and we have a single signal.this signal is feed into the analog to digital converter.this digital signal is feed into the microprocessor and microprocessor generates control signal according to its input. for example if you are using N.R. for over-current protection than you should set a value of current in your program.if the value of current passes through the circuit is greater than the set value..than N.R. enables the circuit breaker and hence our system is protected..
How do you calculate setting for over current earth fault relay setting?
An artificial neutral is crated in the CT of the line to be protected (for transmission lines) a CT is fixed in the neutral of the CT. if there is any imbalance in the 3 phase current then the relay will develop a difference in neutral.that can be sensed by the CT,then gives the trip command to relay
What is the difference between voltage restrained overcurrent protection and voltage controlled overcurrent protection?
The voltage-restrained overcurrent relay adjusts the pickup setting and characteristic curve of the overcurrent function based on the system voltage. The relay is set pickup greater than overload, and sensitivity increases as the voltage drops. The voltage-controlled overcurrent relay uses an undervoltage element to supervise the operation of the overcurrent element. When the voltage drops below a predetermined level, the undervoltage element permits the operation of the time overcurrent units. Voltage-restrained overcurrent relays can provide faster backup protection than voltagecontrolled overcurrent relays, particularly in cases where the generator voltage does not drop significantly below rated voltage during fault conditions. If the generator voltage always drops below a given voltage level for all faults in which operation is required, the voltage-controlled overcurrent unit may be set to provide faster overall clearing speed
What is the difference between reverse current and overcurrent protection?
A reverse current relay senses Power in (uses both voltage and current, and looks at the phase angle between these), and operates if power is flowing in the reverse direction, and the current is above a set point. An overcurrent relay looks at only current, and operates if it is above a set point regardless of power flow direction. Reverse current relays are often referred to as reverse power relays.
What are current relays?
Current relays are the relay which sens the current passing in particular circuit and operates when this current exceed its set value.
How does the standby earth fault scheme work?
Restricted earth fault protection is used to protect a specific zone, and should not trip for a fault outside of that zone (usually limited to a transformer, and possibly extending to lowside, highside, and tertiary breakers). Stand by earth fault protection is a term I am not very familiar with, but I believe this would be protection that is meant for a specific zone as backup, and can operate for faults outside of this zone. An example might be a highside time overcurrent relay set looking into a transformer, where the transformer is protected by a differential (primary protection), and there is a lowside feeder with relays (primary protection). The highside overcurrent acts as a backup (secondary protection) for the transformer and the feeder, and is delayed due to the nature of a time overcurrent relay.
What does instantaneous speed include?
Instantaneous speed is your speed in a given moment. The speedometer in your car and the radar gun that cops use both give a value in instantaneous speed. The disctinction here is to not confuse instantaneous speed with average speed, which is calculated over a set distance. To calculate average speed (V) you need to divide the distance travelled (D) by the time of travel (T). V= D/T
What does instantaneous speed?
Instantaneous speed is your speed in a given moment. The speedometer in your car and the radar gun that cops use both give a value in instantaneous speed. The disctinction here is to not confuse instantaneous speed with average speed, which is calculated over a set distance. To calculate average speed (V) you need to divide the distance travelled (D) by the time of travel (T). V= D/T
What is hinky pinky for a triple set of electrical contactors?
That would be: Three-phase relays
What is pick up of a relay?
The "pick up" of a relay is a setting at which the relay will begin to operate. Such as an overcurrent relay - if the pickup is set to 5A, when 5A is flowing through the relay, the relay will operate.
What does the constant control relay module do on 1999 Ford Escort?
The CCRM is a set of relays in the same box. The relays control the radiator cooling fan, the PCM, the fuel pump and the A/C compressor. Pre-97 Escorts had separate relays on the above functions. Starting in 97 continuing through 2002 they put all the relays in one box.
What information do you get from acceleration?
Distance travelled or time elapsed between set points, given the speed at the first point. Also instantaneous speed.
REF Protection how it will operate?
REF, or restricted earth fault protection is normally applied to transformers. The idea is to set a very sensitive overcurrent on the neutral of a Wye winding. For ground faults, current will flow up the neutral, triggering this overcurrent relay to operate very quickly. To prevent this relay from tripping for faults outside "the protected zone" (such as out on a line near the transformer), information is gathered from the high, low, and sometimes tertiary windings of the transformer to determine if the fault is inside the current transformers used to gather information for protecting the transformer (can be in the transformer bushings, but is often in the breakers that operate to protect the transformer) or outside them. If inside, the overcurrent is allowed to operate. If outside, the overcurrent is restrained from operating.
Why did Zen Buddhism appeal to Samurai Warriors?
Zen training in the instantaneous appreciation of a situation and the concurrent and equally instantaneous initiation of a response is the essence of the warrior skills. As a backup to this skill set the philosophy that actions are neither good or bad, but that they just "are" removed the expectation of remorse.
