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IF answer is yes . please explain how we can measure in primary side ??
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Why the secondary terminals of ct's are shorted when not in use?
The current in the secondary side of a CT (Current Transformer) is induced by the current flowing in the primary circuit. If the current continues to flow in the primary circuit and the CT is left "Open Circuit" then dangerous voltages can build up and cause damage to equipment when reconnected or personal injury by electric shock. Therefore, shorting the secondary terminals of the CT allows current to circulate taking flux with, thus reducing the building up of flux; the higher the flux the higher the emf (voltage) induced; E = Blv.
What is cl PS current transformer?
CL of a CT is its accuracy class.. it is an approximate measure of the CT's accuracy. e.g. The ratio (primary to secondary current) error of a Class 1 (CL:1.0) CT is 1% at rated current
Can you saturate a CT with the secondarys shorted?
A CT becomes saturated when the induced secondary voltage is beyond the capabilities of the CT. Yes it is possible, if enough current is forced through the secondary to raise the voltage beyond the CT capability curve. Remember the CT has inherent resistance due to the secondary winding. That said, to saturate strictly based on the CT resistance is unlikely. But it is still theoretically possible.
Why secondary coil of ct is short?
A CT attempts to push a specific ratio of primary current through the secondary. If the secondary is open circuited, the resistance across the secondary will be very large. Following Ohm's law, V = I*R, so the secondary voltage will become very large, and will arc across the open, or damage the CT, or both.
Why a 5amp. rating ammeter is connected to secondary side of current transformer?
The maximum current output of a CT is 5 amps. Connected to a meter this will be full scale. What ever the ratio of the CT will dictate the scale face on the meter. A 500 amp CT's output will be 5 amps at 500 amps on the buss. 250 amps on the buss, the CT will output 2.5 amp or half scale on the meter face.
What happens when current transformer is replaced by a capacitor?
You will end up with no current output on the secondary side of the CT.
Why the CT secondary short circuited?
Current transformers produce a ratio of primary current in the secondary. If the secondary of a CT is open circuited, and primary current is flowing, the CT will try to push that same ratio of current through the secondary open circuit. This causes secondary voltage to climb until it the secondary open circuit flashes over. This can often damage the CT.
Is it necessary to connect a fuse at the secondary side of a current transformer?
Definitely NOT! An open circuit (across a melted fuse for example) on the secondary side of a current transformer is subject to a dangerously-high voltage, so a fuse must not be fitted. The secondary side of a CT must never be open circuited.
Why the secondary terminals of ct's are shorted when not in use?
The current in the secondary side of a CT (Current Transformer) is induced by the current flowing in the primary circuit. If the current continues to flow in the primary circuit and the CT is left "Open Circuit" then dangerous voltages can build up and cause damage to equipment when reconnected or personal injury by electric shock. Therefore, shorting the secondary terminals of the CT allows current to circulate taking flux with, thus reducing the building up of flux; the higher the flux the higher the emf (voltage) induced; E = Blv.
How do you check ct ratio test?
ct ratio test is the current between the primary to secondary
How do you calculate burden resistor fo current transformer?
The method I have seen employed is to estimate the maximum current that will flow in the secondary side of the CT due to fault currents on the primary side, and calculate the total load (resistance) on the secondary side, including the CT resistance, cable resistance (2 way for ground faults, 1 way for three phase and L-L), resistance of any meters/relays connected to the CT. Once this is known, the voltage rise in the CT can be determined to see if the CT is likely to saturate.Alternately, you can determine the VA burden by the above, VA = V*I = (I*R)*I, using Ohm's law.The above answers the question of how to calculate the VA burdon on a current transformer. The VA burden of a CT is determined by the resistivity of the CT, multiplied by the current squared through the secondary. In general, this will be provided by the manufacturer in the form of a CT burden characteristic, developed through testing of the CT in question, not through calculations.
What is CT ratio?
CT ratio is the ratio of primary (input) current to secondary (output) current. A CT with a listed ratio of 4000:1 would provide 1A of output current, when the primary current was 4000A.
How do you test over current relay?
Normally the Over current relay is connected using a suitable CT (Current Transformer). Say the CT ratio is 100/5 Amps. (secondary is normally 5 or 1 amps). 100 Amps in the primary induces 5 amps in secondary which flows through over current relay circuit. Secondary current is proportional to the primary current. To test the OCR , inject the current into relay circuit ranging from 0 to 5 amps in steps (which represents upto full load current on primary). Relay will operate accordingly operate the trip contacts. These relays are normally with a time factor setting as well.
What is knee poit volt and what is c t saturation?
It is the maximum voltage across the secondary terminals beyond which a CT will saturate when it is loaded.If the CT gets saturated,the ratio of primary current to the secondary current will not be to the designed value.
What is cl PS current transformer?
CL of a CT is its accuracy class.. it is an approximate measure of the CT's accuracy. e.g. The ratio (primary to secondary current) error of a Class 1 (CL:1.0) CT is 1% at rated current
What does CL of a current transformer signifies?
CL of a CT is its accuracy class.. it is an approximate measure of the CT's accuracy. e.g. The ratio (primary to secondary current) error of a Class 1 (CL:1.0) CT is 1% at rated current
Why can a CT be shorted and a Pt cannot?
A current transformer pushes a ratio of primary current in the secondary. A potential transformer pushes a ratio of primary voltage in the secondary. Shorting a CT allows the full current the CT wants to push to flow. Shorting a PT makes it very difficult for the PT to produce rated voltage. To keep the voltage at rated value, the PT would have to push ~infinite secondary current.
