How do you calculate relay settings in PDF?

How do you calculate relay settings in PDF?

Calculation of Over Current Relay Setting:

1. Over Load Current (In) = Feeder Load Current X Relay setting = 384 X 125% =480 Amp.
2. Required Over Load Relay Plug Setting= Over Load Current (In) / CT Primary Current.
3. Required Over Load Relay Plug Setting = 480 / 600 = 0.8.

What is Zone 4 in distance protection?

There is one more Zone in modern Distance Relay which is called Reverse Zone or Zone-4. As the name Reverse Zone implies it is back-up protection of the Substation where Distance Relay is installed, in our case to the substation A. The setting for zone is normally 10% of the impedance of protected line.

What is line angle in distance relay?

A is the relaying point and RAB is the angle by which the fault current lags the relay voltage for a fault on the line AB and RAC is the equivalent leading angle for a fault on line AC. Vector AB represents the impedance in front of the relay between the relaying point A and the end of line AB.

How is relay pickup current calculated?

From CT ratio, we first see the rated secondary current of CT. Say the CT ratio is 100 / 1 A, i.e. secondary current of CT is 1 A. From current setting we calculate the trick current of the relay. Say current setting of the relay is 150 % therefore pick up current of the relay is 1 × 150% = 1.5 A.

How is fault in transmission line calculated?

Fault current calculations are based on Ohm’s Law in which the current (I) equals the voltage (V) divided by the resistance (R). 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 3 zone distance relay?

Three-zone step distance relaying to protect 100% of a line and backup the neighboring line. Three-zone step distance relaying to protect 100% of a line and backup the neighboring line. For ground distance relays, the faulted phase voltage, and a compensated faulted phase current must be used.

What is the Zone 1 setting of a distance relay?

Zone-1 is meant for protection of the primary line. Typically, it is set to cover 80% of the line length. Zone-1 provides fastest protection because there is no intentional time delay associated with it.

What is Mho relay?

Mho relay is a voltage restrained directional relay. Important Points: Reactance relay is suitable for the protection of a short transmission line because its operation is independent of arc resistance. The relay which is selected for a long transmission line should be less affected due to power swings.

What is an offset Mho relay?

– Berdy or negative offset Mho relay characteristics: Negative Mho offset relay is a single-phase single element high speed distance relay. It is arranged to operate from the voltage between two phases, and the difference between the currents of the two phases, at the terminals of the generator to be protected.

What is the operating characteristic of the mho relay?

The operating characteristic of the mho relay is shown in the figure below. The diameter of the circle is practically independent of V and I, except at a very low magnitude of the voltage and current when the spring effect is considered, which causes the diameter to decrease.

How do you calculate the diameter of a circle relay?

The diameter of the circle is expressed by the equation as Z R = K 1 / K 2 = ohmic setting of the relay The relay operates when the impedance seen by the relay within the circle.

What is the impedance setting of an OHE relay?

Its impedance setting may be decided as follows: i. In the case of single-line sections, the impedance setting of the relay may correspond to 1.25 times the impedance of the OHE from the feeding post up to the adjoining feeding post. The factor 1.25 used here is to cater for errors in the relays, CT & PT.

What is the maximum torque angle of this relay?

The maximum torque angle of this relay is 75°. Its impedance setting may be decided as follows: i. In the case of single-line sections, the impedance setting of the relay may correspond to 1.25 times the impedance of the OHE from the feeding post up to the adjoining feeding post.

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