What is the purpose of 86 lockout relay?

Many utilities employ lockout relays (ANSI device number 86, electrically operated, hand or electrically reset) that function to shut down and hold equipment out of service on the occurrence of abnormal conditions.

How does a 87 differential relay work?

Current differential relays typically are equipped with restraint windings to which the CT inputs are to be connected. For electromechanical 87 current differential relays, the current through the restraint windings for each phase is summed and the sum is directed through an operating winding.

What are the requirements of protective relays?

Functional Requirements of Protection Relay

• Reliability. The most important requisite of protective relay is reliability.
• Selectivity. The relay must be operated in only those conditions for which relays are commissioned in the electrical power system.
• Sensitivity.
• Speed.
• Switchgear.
• Protective Gear.
• Station Battery.

When should a relay be sensitive to operate a protective system?

It is desirable that relay system should be sensitive so that it operates with low values of volt-ampere input. 4. Reliability: It is the ability of the Protective Relay system to operate under the pre-determined conditions.

How do lockout relays work?

Lock out relay is an electromechanical relay which latches its output contact. As the name suggests, this relay once operated locks out the circuit. Locking out means that circuit cannot be normalized until and unless this relay is reset. These relay have two types of coils: operating and resetting coil.

What are protective relays explain their operation?

In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. The need to act quickly to protect circuits and equipment often requires protective relays to respond and trip a breaker within a few thousandths of a second.

What is the need of power system protection?

The main objective of using power system protection is to detach the faulty section from the system to make the rest of the portion work without any disturbance. In addition to this, it is used for the protection of power system and prevent the flow of fault current.

What is protection relay in power system?

What is reliability of the relay?

Reliability means that relay operates only when there is a fault. Unreliable protection system will lead to spurious tripping of circuit breaker. Simplicity – Simplicity increases the reliability. The simpler the system, the greater will be its reliability.

What is the purpose of an 86 relay?

The purpose of an 86 relay is to serve as an intermediary element between one or more protective relays and one or more control devices, both expanding the number of control elements actuated by any one protective function and also providing a “latching” function which must be intentionally reset in order to resume normal operation of the system.

What is the function of a protective relay?

The fault can only be reduced if the protective relay is reliable, maintainable and sensitive enough to distinguish between normal and abnormal condition. The relay must come into action whenever there is a fault and must not operate if there is no fault. Some relays are used for the protection of the power system.

What are the reasons for the failure of the relay?

The relay failure is because of three reasons such as wrong setting, bad contacts and open circuit in the relay coil. In such cases, the second line of defence is provided by the backup relays.

What is the “normal” state of a latching relay?

When interpreting switch states in a latching relay such as this, the “reset” state is considered the “normal” state (i.e. the state where the relay is “at rest”).