What is ANSI X R ratio?
First, X/R ratio is simply the ratio of the system reactance to the system resistance, looking back to the power source from any point in a power circuit, assuming that a short circuit is applied to the system at that point. It is another way of stating the power factor of the source system.
What is X R ratio of transformer?
The X/R ratio affects the dc component, and therefore, also the total current. The higher the X/R ratio of a circuit, the longer the dc component will take to decay (longer time constant). To illustrate, two circuits are shown in Figure 1.
What is r x ratio in distribution system?
x/r ratio is the ratio of reatance of the line and. resistance of the line. In distribution lines like 400 volt. three phase line, the resitance is far high than reactance. or we can say the reactance is negligible as compared to R.
What is a typical X R ratio for a transmission line?
For distribution circuits, X/R is lower, and, although data is limited, typical values are 10 (at source point) and 2-4 on a medium voltage overhead line.
What is ANSI C37?
IEEE C37.04-1999 – IEEE Standard Rating Structure for AC High-Voltage Circuit Breakers. This standard covers the rating structure for all high-voltage circuit breakers, which include all voltage ratings above 1000 V ac and comprise both indoor and outdoor types having the preferred ratings as listed in ANSI C37.
How do you calculate short circuit current?
The formula is I = V/R. When there is a short circuit the resistance becomes very small, and that means the current becomes very large.
What is the short circuit ratio of transformer?
Short circuit ratio or SCR is a measure of the stability of an electromechanical generator. It is the ratio of field current required to produce rated armature voltage at open circuit to the field current required to produce the rated armature current at short circuit.
What is MHO relay?
A mho Relay is a high-speed relay and is also known as the admittance relay. In this relay operating torque is obtained by the volt-amperes element and the controlling element is developed due to the voltage element. It means a mho relay is a voltage controlled directional relay.
What is X R ratio of distribution line?
In Transmission Lines the Deq which is the Geometric Mean distance among conductors is very larger than overhead distribution lines. So the X/R ratio in transmission lines is larger than distribution lines. In underground distribution networks (cables) the X/R ratio is very small and may be smaller than 1.
Why XR ratio is high in transmission lines?
The transmission line used to transmit electric power works at much higher voltage than the the distribution wire. There fore the distance between the wires is made much larger than the distribution line which leads to much higher magnetic energy storage and consequently its inductance per unit length will be higher.
What UL 1558?
UL 1558 – Standard for Metal-Enclosed Low-Voltage Power Circuit Breaker Switchgear defines safety tests for switchgear assemblies that service circuits operating at nominal ac voltages of not more than 1,000 volts. UL 1558 testing evaluates switchgear that is designed in accordance with ANSI C37.
What is the equation for resistance and reactance?
If the load on the secondary side of the transformer is purely resistive then ϕ = 0 and the equation (1) becomes. If the load on the secondary side of the transformer is capacitive then ϕ should be taken as negative, and the equation (1) becomes. Therefore this will be the load voltage.
How do you calculate reactance from impedance?
How do you calculate reactance from impedance? Ans- To calculate impedance, calculate resistance and reactance of a circuit, label resistance as R and reactance as X. Square both R and X, and sum the two products together. Take the square root of the sum of the squares of R and X to get impedance. Display the answer in ohms.
What’s the difference between reactance and resistance in a circuit?
The crucial difference between resistance and reactance is that resistance is the hindrance to the flow of electric current by only resistor. As against reactance is the opposition to the change in current by either inductor or capacitor. Basically the obstruction to the flow of electrical current in any circuit is defined as impedance.
How is resistance related to the power factor?
When current flows through a material having resistance, heat is transferred from the material to the surroundings. The resistance and reactance of a circuit establishes a power factor. The power factor ( p.f.) is given by the following equation: p.f. = cos(tan-1(X/R)) If the power factor is unity (1), then the impedance only has resistance.