Directional overcurrent relay pdf

What is directional overcurrent relay?
What is 50N and 51N in relay?
What are the inputs to directional relay?
How does directional overcurrent protection work?
What is principle of directional over current protection?
What are the problems of directional relays?
What are the 3 types of overcurrent?
What is the maximum torque angle of a directional relay?
What is the difference between 50 51N and 50 51G?
What is o C and E F relay?
What are the 4 parts of a relay?
What does directional relay respond to?
What is the definition of directional relay?
What is difference between directional and non directional OC relay?
What is directional protection relay?
What is directional type relays?
What is the difference between reverse power relay and directional relay?
What are the disadvantages of directional relays?
What are the problems of directional relays?

What is directional overcurrent relay?

Directional overcurrent relays respond to excessive current flow in a particular direction in the power system. The relay typically consists of two elements. One is a directional element, which determines the direction of current flow with respect to a voltage reference.

What is 50N and 51N in relay?

2 device number 50N and 51N) that operates when the current exceeds a predetermined value. Relay 50N operates instantaneously. Relay 51N operates based on IEC 60255 Standard Normal Inverse IDMT (Inverse Definite Minimum Time) trip characteristic.

What are the inputs to directional relay?

Abstract: Conventionally, for power protective relay applications, overcurrent relaying is made directional by use of two inputs, the operating current and a reference or polarizing quantity (either voltage or current) that does not change with fault location.

How does directional overcurrent protection work?

Directional overcurrent protection devices can achieve this requirement, albeit at extra cost. Directional IEDs determine the direction of the fault current by measuring the voltage with a voltage transformer as well as the current with a current transformer, and establishing the phase difference.

What is principle of directional over current protection?

Directional overcurrent protection helps to protect the installation against phase-to-phase, phase-to-neutral, and phase-to-earth short circuits with total selectivity. The ANSI 67 - Directional overcurrent protection Digital Module is used to generate either an alarm or a trip.

What are the problems of directional relays?

Directional relays use voltage as the polarizing quantity. When three-phase faults occur close to the relay bus, the available voltage becomes nearly zero and this creates a problem in estimation of the fault direction. The capacitor coupling voltage transformer subsidence transients add to this problem.

What are the 3 types of overcurrent?

The three major categories or types of overcurrent are overload, short-circuit, and ground-fault.

What is the maximum torque angle of a directional relay?

The maximum torque angle of the relay is adjustable form I1 lag V1 between 0° and 90°. 45° is an appropriate setting for most applications.

What is the difference between 50 51N and 50 51G?

Type 50 is an "instantaneous off" relay, whereas type 51 has an inbuilt time delay. The N, G, etc depicts not what the relay is, but how it is wired up. In both systems the relays are the same - it is merely the arrangement of current transformers and where they get their feed from that changes.

What is o C and E F relay?

The combined overcurrent and earth-fault relay REJ 515 is a secondary relay which is connected to the current transformers of the object to be protected. The overcurrent unit and the earth-fault unit continuously measure the phase currents and the neutral current of the object.

What are the 4 parts of a relay?

A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core (a solenoid), an iron yoke which provides a low reluctance path for magnetic flux, a movable iron armature, and one or more sets of contacts (there are two contacts in the relay pictured).

What does directional relay respond to?

Directional relays can respond to positive sequence, negative sequence, or zero sequence inputs. This should be a consideration when applying directional relays at locations where zero-sequence voltage is minimal.

What is the definition of directional relay?

Definition: A protection relay in which the tripping decision is dependent in part upon the direction in which the measured quantity is flowing.

What is difference between directional and non directional OC relay?

Directional relays are designed to locate or sense the fault in a particular direction only, it will not sense fault if fault occurs in opposite direction. While non directional relays don't have directional features & will sense the fault in both directions.

What is directional protection relay?

(protection) Relay: equipment used to monitor one or more electrical variable (current or voltage), generally to detect a fault and to control the opening of a circuit breaker.

What is directional type relays?

Definition: A protection relay in which the tripping decision is dependent in part upon the direction in which the measured quantity is flowing.

What is the difference between reverse power relay and directional relay?

P RINCIPLE OF R EVERSE POWER R ELAY A reverse power relay is a directional relay that is used to monitor the power flow from generator (running in parallel with another generator or the utility) and in case of abnormal condition take appropriate action.

What are the disadvantages of directional relays?

Disadvantages or demerits:

The directional feature is absent in electromagnetic relays. Requires periodic maintenance and testing unlike static relays. Relay operation can be affected due to ageing of the components and dust, pollution resulting in spurious trips.