Table of Contents
What does negative sequence mean?
What is negative sequence. Negative sequence is a balanced 3-phase system with the opposite phase sequence as the original sequence which means the set of the three pharos are equal in magnitude, spaced 120° apart from each other & having the phase sequence opposite to that of the original pharos.
What are the effect of negative sequence current on the rotor winding?
Performance of these induction motors is affected by the unbalance in bus voltage caused by negative sequence currents, which produces an air gap flux rotating opposite to the direction of rotor thereby heats up the rotor and generates a breaking torque.
What is negative sequence current protection?
Definition: A relay which protects the electrical system from negative sequence component is called a negative sequence relay or unbalance phase relay. The negative sequence relay protects the generator and motor from the unbalanced load which mainly occurs because of the phase-to-phase faults.
What is negative sequence overcurrent?
− Negative sequence overcurrent relays are used to detect unbalanced load on a generator which may cause exces- sive rotor heating. The relay is also used to detect unbal- anced load currents in motors.
What is negative sequence component?
Negative sequence: A balanced three-phase system with the opposite phase sequence as the original sequence. Zero Sequence: Three phasors that are equal in magnitude and phase.
What is the effect of negative phase sequence currents on wound equipment?
The flow of negative sequence currents in electrical machines (generators and motors) is undesirable as these currents can generate high and possibly dangerous temperatures in a very short period of time which can damage the insulation of the machines causing them to fail prematurely.
What are positive negative and zero sequences?
Positive Sequence: A balanced three-phase system with the same phase sequence as the original sequence. Negative sequence: A balanced three-phase system with the opposite phase sequence as the original sequence. Zero Sequence: Three phasors that are equal in magnitude and phase.
Which of the circuit given positive and negative sequence current will flow in primary?
2. In which of the circuit given positive and negative sequence currents will flow in primary? Explanation: The only positive and negative sequence currents flow in the lines on the delta side. This could also be achieved by star-connected primary provided the primary and secondary star points are grounded.
In which fault is the negative and zero sequence current absent?
Three phase symmetric fault: Therefore, in a symmetrical three-phase fault, both negative and zero sequence currents are zero.
What is positive and negative sequence impedance?
Positive Sequence Impedance – The impedance offered by the network to the flow of positive sequence current is called the positive sequence impedance. Negative Sequence Impedance – The negative sequence impedance means the impedance offered by the network to the flows of negative sequence current.
What is a positive sequence?
positive sequence. the sequence of the bases on the strand of a double-stranded nucleic acid that encodes the product. In DNA it is the strand that encodes the RNA, having thus the same base sequence except changing T for U in the RNA.
What is zero sequence impedance?
Zero Sequence Impedance – The impedance offered to zero sequence current is called the zero sequence impedance. The impedance of the positive, negative and zero sequence component is given by the ratio of the phase sequence voltage to the phase sequence current of the system. There is no mutual impedance between various symmetrical components.
What is negative phase current?
When a specific phase current is detected to be flowing reverse, a event for negative phase current is set for each phase individually. When the current direction in one phase is different from current direction of two other phases and all currents are above the current threshold parameter, meter starts a timer.
Negative sequence component:It indicates three equal phasors which are 120degrees apart and has opposite phase sequence as the original signal. If supply is RYB then these will be in RBY sequence. Zero sequence component: It indicates three phasors of equal magnitude with zero phase displacement that is in phase.