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In symmetrical components, there are three types of impedances - positive sequence (balanced), negative sequence (unbalanced), and zero sequence (ground).
In a transformer, positive and negative are equal. Ground impedance is determined by the (same factors as the) positive sequence and is based on the flux paths available through the transformer core that can induce ground current.
Wiki User
∙ 14y ago
Wiki User
∙ 13y agoThe zero sequence impedance in a transmission line is the sum of the positive sequence impedance and three times the impedance of the ground return. That is Z0 = Z1 + 3ZE where
Z0 = Zero sequence impedance
Z1 = Positive sequence (or actual) impedance of transmission line conductor.
ZE = Impedance of ground return (may include actual earth, aerial earth wires and counterpoise).
Hope it helps
Kind regards
Terence Tambatamba
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Relation between kva and fault level?
There isn't enough information here. Available short circuit fault level can be given as a KVA value for different types of faults, but I assume the questioner is looking for a relationshiop between (transformer?) KVA and available short circuit current - If my assumption is correct, there is no direct correlation without knowing the transformer positive and zero sequence impedances. If these are known, you can assume the source impedance is infinite, and calculate the maximum short circuit current through the transformer as follows: lowside fault current for a 3 phase fault on the lowside of the transformer: lowside kV (line to line) / (1.732 x per unit positive sequence impedance x scalar to real impedance), where scalar to real impedance is equivalent to lowside kV (line to line) ^2 / base kVA. For a L-G fault, do the same with zero sequence impedance.
Does ideal amplifer has zero output impedance?
Yes
Is a voltage source a zero or infinite impedance?
Obviously it's not infinite impedance--that would mean it soaks up all the voltage. It can't be zero impedance either...that would be a superconductor, and there aren't many of those around. Voltage sources have impedance, but it's not infinite. Sometimes the impedance of the source is critical--radio frequency amplifiers have to be impedance matched to their transmitting antennas if you don't want to burn them out.
What is the impedance reactance 22 mva power transformer?
A transformer this size will usually come with a test report which will give this information. Depending on the configuration, it may give zero seqence and positive sequence impedances.
What should be real and reactive power flow through the transmission line when the sending end and receiving end voltages are of same magnitudes and phase angles?
The power transfer equation is this:P = V1*V2*sin(phi)/Xt,V1 = source 1 voltageV2 = source 2 voltagephi = angle between the two sourcesXt = transfer impedance, the impedance of the line + both source impedancesFrom this you can see that if the angle between the two sources is 0, then the power transferred would be zero as well.Reactive power flow *should* be zero if perfectly matched as well, although there will be a small amount of reactive power usage due to line charging (charging current).
What is the practical values of zero sequence impedance?
zero sequence value of 110 kv XLPE is more than its reference value what is the cause
What is zero sequence impedence?
Zero sequence impedance indicates a homopolar symmetrical component. It is a term used in electrical engineering within a three-phase system of linear combinations.
Relation between kva and fault level?
There isn't enough information here. Available short circuit fault level can be given as a KVA value for different types of faults, but I assume the questioner is looking for a relationshiop between (transformer?) KVA and available short circuit current - If my assumption is correct, there is no direct correlation without knowing the transformer positive and zero sequence impedances. If these are known, you can assume the source impedance is infinite, and calculate the maximum short circuit current through the transformer as follows: lowside fault current for a 3 phase fault on the lowside of the transformer: lowside kV (line to line) / (1.732 x per unit positive sequence impedance x scalar to real impedance), where scalar to real impedance is equivalent to lowside kV (line to line) ^2 / base kVA. For a L-G fault, do the same with zero sequence impedance.
How do you derive negative sequence impedance of an earthing transformer for 11 KV delta connected 10 MVA source transformer?
Negative sequence and positive sequence are the same for a transformer. You would derive using the same connections as done to calculate the positive sequence impedance. Usually the test report will give positive, and often zero sequence impedances (sometimes left off, depending on the type of transformer as the zero sequence sometimes is the same as the positive sequence). The negative sequence is never given to my knowledge, because it is redundant and unnecessary test.
How calculate zero phase sequence capacitance of transformer?
In my experience, the zero sequence of transformers is not calculated, it is directly tested following ANSII/IEEE guidlines for Z1no, Z2no, and Z1ns tests (for three phase, three winding transformers). Rough estimations of zero sequence impedance can be determined based on the positive sequence and core form of the transformer. A Shell type core will have a zero sequence of ~100% the positive sequence because the flux stays in the core / follows the same path as it does for positive sequence currents. For a core type, the zero sequence will be ~80-90% typically, because the flux must travel outside the core. This is for three winding transformer.
Which device has its characteristics very close to that of an ideal current source?
A: A current source can be defined as a zero impedance source. A battery is essentially a zero impedance since it can provide lots of current with zero volts out
Does ideal amplifer has zero output impedance?
Yes
When VSWR taken as infinity?
VSWR on a line is infinite when the far end of the line is perfectly open or perfectly shorted,i.e. the line is terminated in an impedance of exactly zero or exactly infinite, AND the lineis perfectly lossless.Under those conditions, the reflection coefficient is 1.0 and the return loss is zero.
Is a voltage source a zero or infinite impedance?
Obviously it's not infinite impedance--that would mean it soaks up all the voltage. It can't be zero impedance either...that would be a superconductor, and there aren't many of those around. Voltage sources have impedance, but it's not infinite. Sometimes the impedance of the source is critical--radio frequency amplifiers have to be impedance matched to their transmitting antennas if you don't want to burn them out.
What are symmetrical and unsymmetrical faults?
the fault in electrical transmission line which give rise to symmetrical fault current is called symmetric fault. e.g; L-L-L-G fault. the fault in transmission line which give rise to unsymmetrical fault current is called unsymmetrical fault.e.g; L-L , L-L-G , L-G fault to solve the unsymmetrical fault, the fault current can be represented by sum of the sequences--zero phase sequence , +ve phase sequence , -ve phase sequence. where L:line G:ground
What is the impedance reactance 22 mva power transformer?
A transformer this size will usually come with a test report which will give this information. Depending on the configuration, it may give zero seqence and positive sequence impedances.
Why the resistance of a current source is zero?
It isn't. The internal impedance of a current source is high. In an ideal one it would be infinite. A voltage source, however, has a low internal impedance, ideally zero ohms.
